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  • FLUID MECHANICS AND HEAT TRANSFER  (2,457)
  • 1985-1989  (2,457)
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Year
  • 101
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    Direct simulation of AFE forebody and wake flow with thermal radiation (1988)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Calculated results for the flowfield structure and surface quantities are presented for an axisymmetric representation of an aeroassist flight experiment vehicle. The direct simulation Monte Carlo (DSMC) method is used to perform the calculations, since the flow is highly nonequilibrium about the vehicle during both the compression and expansion phases. The body configuration is an elliptically blunt nose followed by a skirt with a circular radius and an afterbody. Freestream conditions correspond to a single point along the entry trajectory at an altitude of 90 km and a velocity of 9.9 km/s. The calculations account for nonequilibrium in the translational and internal modes, dissociation, ionization, and thermal radiation. The degree of dissociation is large, but the maximum ionization is only about 2 percent by mole fraction. The bluntforebody flow experiences a high degree of thermal nonequilibrium in which the translational temperature is generally greater than the internal temperature. However, as the flow expands about the aerobrake skirt and afterbody, the internal temperature is generally greater than the translational temperature.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-TM-100673 , NAS 1.15:100673 , International Symposium on Rarefied Gas Dynamics; Jul 10, 1988 - Jul 16, 1988; Pasadena, CA; United States
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  • 102
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    Navier-Stokes calculations of transonic flows past cavities (1989)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: A computational investigation of subsonic and transonic flows past 3-D deep transitional cavities is presented. Computational simulations of these self-induced oscillatory flows were generated through time-accurate solutions of the Reynolds averaged full Navier-Stokes equations, using the explicit MacCormack scheme. The Reynolds stresses were included through the Baldwin-Lomax algebraic turbulence model with certain modifications. Two cases were computed to demonstrate the capability of the numerical scheme in modeling the complex 3-D flow features inside a cavity. The results from an experimental investigation were used not only to benchmark the computations, but also to widen the database used for the discussions and conclusions. The computational results include instantaneous and time averaged flow properties everywhere in the computational zone. Time series analyses were performed for the instantaneous pressure values on the cavity floor. The features of deep and transitional cavity flows, and the effect of the sidewall on the cavity flow flowfield are illustrated through computational graphics.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-CR-4210 , NAS 1.26:4210
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  • 103
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    Effects of core turbulence on jet excitability (1989)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The effects of varying freestream core turbulence on the evolution of a circular jet with and without tonal excitation are examined. Measurements are made on an 8.8 cm diameter jet at a Mach number of 0.3. The jet is excitated by plane waves at Strouhal number 0.5. For the excited and unexcited cases the turbulence level is varied by screens and grids placed upstream of the nozzle exit. The experiment results are compared with a theoretical model which incorporates a variable core turbulence and considers the energy interactions between the mean flow, the turbulence and the forced component. Both data and theory indicate that increasing the freestream turbulence diminishes the excitability of the jet and reduces the effect of excitation on the spreading rate of the jet.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-TM-101405 , ICOMP-88-21 , E-4497 , NAS 1.15:101405 , AIAA PAPER 89-0966 , Shear Flow Control Conference; Mar 13, 1989 - Mar 16, 1989; Tempe, AZ; United States
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  • 104
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    Axisymmetric confined turbulent jet directed towards the liquid surface from below (1988)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: A numerical simulation is presented of an axisymmetric turbulent jet discharging axially from below into a cylindrical tank and directed towards the liquid vapor interface. The liquid vapor interface is assumed to be flat and shear free. The k-epsilon turbulence model is used to calculate the eddy viscosity. The turbulence intensity distribution and the length scale associated with the k-epsilon model are calculated as functions of jet flow rates and systems parameters. Numerical results are compared with appropriate experimental data. The problems associated with the free surface boundary conditions for the turbulent quantities are discussed.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-TM-101409 , E-4499 , NAS 1.15:101409 , AIAA PAPER 89-0172 , Aerospace Sciences Meeting; Jan 09, 1989 - Jan 12, 1989; Reno, NV; United States
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  • 105
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    Rarefied flow past a flat plate at incidence (1988)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Results of a numerical study using the direct simulation Monte Carlo (DSMC) method are presented for the transitional flow about a flat plate at 40 deg incidence. The plate has zero thickness and a length of 1.0 m. The flow conditions simulated are those experienced by the Shuttle Orbiter during reentry at 7.5 km/s. The range of freestream conditions are such that the freestream Knudsen number values are between 0.02 and 8.4, i.e., conditions that encompass most of the transitional flow regime. The DSMC simulations show that transitional effects are evident when compared with free molecule results for all cases considered. The calculated results demonstrate clearly the necessity of having a means of identifying the effects of transitional flow when making aerodynamic flight measurements as are currently being made with the Space Shuttle Orbiter vehicles. Previous flight data analyses have relied exclusively on adjustments in the gas-surface interaction models without accounting for the transitional effect which can be comparable in magnitude. The present calculations show that the transitional effect at 175 km would increase the Space Shuttle Orbiter lift-drag ratio by 90 percent over the free molecule value.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-TM-101493 , NAS 1.15:101493 , International Symposium on Rarefied Gas Dynamics; Jul 10, 1988 - Jul 16, 1988; Pasadena, CA; United States
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  • 106
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    Direct simulation of three-dimensional flow about the AFE vehicle at high altitudes (1988)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Three-dimensional hypersonic rarefied flow about the Aeroassist Flight Experiment (AFE) vehicle was studied using the direct simulation Monte Carlo (DSMC) technique. Results are presented for the transitional flow regime encountered between 120 and 200 km altitudes with a reentry velocity of 9.92 km/s. In the simulations, a five-species reacting real-gas model that accounts for internal energies (rotational and vibrational) is used. The results indicate that the transitional effects are significant even at an altitude of 200 km and influence the overall vehicle aerodynamics. For the cases considered, the aerodynamic coefficients, surface pressures, convective heating, and flow field structure variations with rarefaction effects are presented.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-TM-101492 , NAS 1.15:101492 , International Symposium on Rarefied Gas Dynamics; Jul 10, 1988 - Jul 16, 1988; Pasadena, CA; United States
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  • 107
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    Fluid spray simulation with two-fluid nozzles (1988)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Two-phase interacting flow inside a two-fluid fuel atomizer was investigated and a correction of aerodynamic and liquid-surface forces with characteristic drop diameter was obtained for liquid-jet breakup in Mach 1 gas flow. Nitrogen gas mass-flux was varied from 6 to 50 g/sq cm sec by using four differently sized two-fluid atomizers with nozzle diameters varyig from 0.32 to 0.56 cm. The correlation was derived by using the acoustic gas velocity, V sub c, as a basic parameter in defining and evaluating the dimensionless product of the Weber (We) and Reynolds (Re) numbers. By using the definition of WeRe, it was found that the ratio of orifice diameter to Sauter mean drop diameter could be correlated with the dimensionless ratio WeRe and the gas to liquid density ratio.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-TM-101367 , E-4406 , NAS 1.15:101367 , AIAA PAPER 89-0053 , Aerospace Sciences Meeting; Jan 09, 1989 - Jan 12, 1989; Reno, NV; United States
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  • 108
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    A high heat flux experiment for verification of thermostructural analysis (1988)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: A major concern in advancing the state of the art technologies for hypersonic vehicles is the development of an aeropropulsion system capable of handling the high heat fluxes during flight. The leading edges of such systems must not only tolerate the maximum heating rates, but must also minimize distortions to the flow field due to excessive blunting and/or thermal warping of the compression surface to achieve the high inlet performance required. A combined analytical and experimental effort to study the aerothermodynamic loads on actively cooled structures for hypersonic applications was established. A hydrogen/oxygen rocket engine was modified to establish a high enthalpy high heat flux environment. The facility provides heat flux levels from about 200 up to 10000 Btu/sq ft/sec. Cross flow and parallel flow regeneratively cooled model can be tested and analyzed by using cooling fluids of water and hydrogen. Results are presented of the experiment and the characteristics of the Hot Gas Test Facility. The predicted temperature results of the cross flow model are compared with the experimental data on the first monolithic specimens and are found to be in good agreement. Thermal stress analysis results are also presented.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-TM-100931 , E-4202 , NAS 1.15:100931 , Winter Annual Meeting of the ASME; Nov 28, 1988 - Dec 02, 1988; Chicago, IL; United States
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  • 109
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    Higher order turbulence closure models (1988)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Theoretical models are developed and numerical studies conducted on various types of flows including both elliptic and parabolic. The purpose of this study is to find better higher order closure models for the computations of complex flows. This report summarizes three new achievements: (1) completion of the Reynolds-stress closure by developing a new pressure-strain correlation; (2) development of a parabolic code to compute jets and wakes; and, (3) application to a flow through a 180 deg turnaround duct by adopting a boundary fitted coordinate system. In the above mentioned models near-wall models are developed for pressure-strain correlation and third-moment, and incorporated into the transport equations. This addition improved the results considerably and is recommended for future computations. A new parabolic code to solve shear flows without coordinate tranformations is developed and incorporated in this study. This code uses the structure of the finite volume method to solve the governing equations implicitly. The code was validated with the experimental results available in the literature.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-CR-183236 , NAS 1.26:183236
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  • 110
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    Mixing and Demixing Processes in Multiphase Flows With Application to Propulsion Systems (1988)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: A workshop on transport processes in multiphase flow was held at the Marshall Space Flight Center on February 25 and 26, 1988. The program, abstracts and text of the presentations at this workshop are presented. The objective of the workshop was to enhance our understanding of mass, momentum, and energy transport processes in laminar and turbulent multiphase shear flows in combustion and propulsion environments.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-CP-3006 , M-591 , NAS 1.55:3006 , Feb 25, 1988 - Feb 26, 1988; Huntsville, AL; United States
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  • 111
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    Discretization formulas for unstructured grids (1988)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The Galerkin weighted residual technique using linear triangular weight functions is employed to develop finite difference formula in cartesian coordinates for the Laplacian operator, first derivative operators and the function for unstructured triangular grids. The weighted residual coefficients associated with the weak formulation of the Laplacian operator are shown to agree with the Taylor series approach on a global average. In addition, a simple algorithm is presented to determine the Voronoi (finite difference) area of an unstructured grid.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-TM-101298 , E-4094 , NAS 1.15:101298 , International Conference on Numerical Grid Generation in Computational Fluid Dynamics; Dec 05, 1988 - Dec 08, 1988; Miami Beach, FL; United States
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  • 112
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    High-resolution heat-transfer-coefficient maps applicable to compound-curve surfaces using liquid crystals in a transient wind tunnel (1988)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Tests were performed in a transient heat transfer tunnel in which the model under test was preheated prior to allowing room temperature air to be suddenly drawn over the model. The resulting movement of isothermal contours on the model is revealed using a surface coating of thermochromic liquid crystals that display distinctive colors at particular temperatures. A video record is obtained of a temperature and time data pair for all points on the model during a single test. Experiments on a duct model are reported in which the model was preheated using a hot air stream. A manner in which initial model temperature nonuniformities could be taken into account was investigated. The duct model was also tested with a steady-state measurement technique and results were compared with the transient measurements, but recognizing that differences existed between the upstream thermal boundary conditions. The steady-state and transient measurements were shown to be consistent with predicted values. The main advantage of this transient heat transfer technique using liquid crystals is that since the test model need not be actively heated, high-resolution measurements on surfaces with complex shapes may be obtained.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-TM-89855 , E-3269 , NAS 1.15:89855 , ASME National Heat Transfer Conference; Aug 09, 1987 - Aug 12, 1987; Pittsburgh, PA; United States
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  • 113
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    Dynamics of two fluids under periodic acceleration (1988)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: The evolution of the interface between two fluids confined in a rectangular cavity is investigated numerically to predict its transient behavior. These computations address mixing characteristics of fluids under microgravity conditions, particularly g-jitter conditions resulting from aircraft vibration or crew motion, and have applications in solution crystal growth. The two-dimensional formulation employs the Boussinesq approximation and treats the mixing of two fluids as an initial value problem with a prescribed concentration field. For fluid mixing of practical applications inside a cavity, it is shown that nonlinear convective transport can dominate over both viscous and molecular diffusion. However, viscous diffusion can become important for low Reynolds number or certain cavity sizes. A stacking phenomenon is shown to occur for aspect ratios (Ar) approximately between 5 to 10. For aspect ratios in the neighborhood of 0.1 to 0.2, inner cells evolve at the interface with increasing time. For a square cavity of Ar = 1, chaotic mixing of the fluid appears to occur for a Stokes-Reynolds number greater than about 5.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: AIAA PAPER 88-3728 , AIAA, ASME, SIAM, and APS, National Fluid Dynamics Congress; Jul 25, 1988 - Jul 28, 1988; Cincinnati, OH; United States
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  • 114
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    Solutal convection during directional solidification (1988)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: During directional solidification of a binary alloy at constant velocity, buoyancy-driven fluid flow may occur due to the solute gradients generated by the solidification process. Numerical calculations of the solute and fluid flow fields in the melt have been carried out using finite differences in a two-dimensional, time-dependent model that assumes a planar crystal-melt interface and allows time-dependent gravitational accelerations. The container walls are rigid and perfectly insulating for solute. For constant vertical gravitational accelerations, as the solutal Rayleigh number is varied, multiple steady states and time-dependent states may occur. The bifurcation from the quiescent state may be subcritical or transcritical, depending on the aspect ratio of the container. Calculations have also been performed for a gravitational acceleration that is assumed to be uniform in magnitude with its direction rotating uniformly. Numerical results have been obtained for a Schmidt number of 10 and a gravitational acceleration of 0.0001 G. The maximum variation in the solute concentration at the crystal-melt interface is calculated for various values of the rotation rate of the gravitational acceleration.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: AIAA PAPER 88-3635 , AIAA, ASME, SIAM, and APS, National Fluid Dynamics Congress; Jul 25, 1988 - Jul 28, 1988; Cincinnati, OH; United States
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  • 115
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    Microgravity bubble migration in rotating flows (1988)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: The NASA KC-135 microgravity-environment aircraft was used to gather experimental data on the migration of bubbles in rotating liquid fields under reduced gravity conditions. The data thus obtained were compared to those of an analysis for the prediction of fluid particle trajectories in the presence of both gravitational and rotational fields at the limit of quasi-steady creeping flow. Reasonable agreement with experimental results was achieved, despite the large size of the bubbles, their close proximity to a bounding surface over significant portions of their migration time, and their rather nonspherical geometry.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: AIAA PAPER 88-3555 , AIAA, ASME, SIAM, and APS, National Fluid Dynamics Congress; Jul 25, 1988 - Jul 28, 1988; Cincinnati, OH; United States
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  • 116
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    Extrema principles of entropy production and energy dissipation in fluid mechanics (1988)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: A survey is presented of several extrema principles of energy dissipation as applied to problems in fluid mechanics. An exact equation is derived for the dissipation function of a homogeneous, isotropic, Newtonian fluid, with terms associated with irreversible compression or expansion, wave radiation, and the square of the vorticity. By using entropy extrema principles, simple flows such as the incompressible channel flow and the cylindrical vortex are identified as minimal dissipative distributions. The principal notions of stability of parallel shear flows appear to be associated with a maximum dissipation condition. These different conditions are consistent with Prigogine's classification of thermodynamic states into categories of equilibrium, linear nonequilibrium, and nonlinear nonequilibrium thermodynamics; vortices and acoustic waves appear as examples of dissipative structures. The measurements of a typical periodic shear flow, the rectangular wall jet, show that direct measurements of the dissipative terms are possible.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: AIAA PAPER 88-3830 , AIAA, ASME, SIAM, and APS, National Fluid Dynamics Congress; Jul 25, 1988 - Jul 28, 1988; Cincinnati, OH; United States
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  • 117
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    The development of flux-split algorithms for flows with non-equilibrium thermodynamics and chemical reactions (1988)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: A finite-volume method for the numerical computation of flows with nonequilibrium thermodynamics and chemistry is presented. A thermodynamic model is described which simplifies the coupling between the chemistry and thermodynamics and also results in the retention of the homogeneity property of the Euler equations (including all the species continuity and vibrational energy conservation equations). Flux-splitting procedures are developed for the fully coupled equations involving fluid dynamics, chemical production and thermodynamic relaxation processes. New forms of flux-vector split and flux-difference split algorithms are embodied in a fully coupled, implicit, large-block structure, including all the species conservation and energy production equations. Several numerical examples are presented, including high-temperature shock tube and nozzle flows. The methodology is compared to other existing techniques, including spectral and central-differenced procedures, and favorable comparisons are shown regarding accuracy, shock-capturing and convergence rates.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: AIAA PAPER 88-3595 , AIAA, ASME, SIAM, and APS, National Fluid Dynamics Congress; Jul 25, 1988 - Jul 28, 1988; Cincinnati, OH; United States
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  • 118
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    Effect of surface tension on the dynamical behavior of bubble in rotating fluids under low gravity environment (1988)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: Time dependent evolutions of the profile of free surface (bubble shapes) for a cylindrical container partially filled with a Newtonian fluid of constant density, rotating about its axis of symmetry, have been studied. Numerical computations of the dynamics of bubble shapes have been carried out with the following situations: (1) linear functions of spin-up and spin-down in low and microgravity environments, (2) linear functions of increasing and decreasing gravity enviroment in high and low rotating cylidner speeds, (3) step functions of spin-up and spin-down in a low gravity environment, and (4) sinusoidal function oscillation of gravity environment in high and low rotating cylinder speeds. The initial condition of bubble profiles was adopted from the steady-state formulations in which the computer algorithms have been developed by Hung and Leslie (1988), and Hung et al. (1988).
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: AIAA PAPER 88-3554 , AIAA, ASME, SIAM, and APS, National Fluid Dynamics Congress; Jul 25, 1988 - Jul 28, 1988; Cincinnati, OH; United States
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  • 119
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    Reduced gravity boiling and condensing experiments simulated with the COBRA/TRAC computer code (1988)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: A series of reduced-gravity two-phase flow experiments has been conducted with a boiler/condenser apparatus in the NASA KC-135 aircraft in order to obtain basic thermal-hydraulic data applicable to analytical design tools. Several test points from the KC-135 tests were selected for simulation by means of the COBRA/TRAC two-fluid, three-field thermal-hydraulic computer code; the points were chosen for a 25-90 percent void-fraction range. The possible causes for the lack of agreement noted between simulations and experiments are explored, with attention to the physical characteristics of two-phase flow in one-G and near-zero-G conditions.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: AIAA PAPER 88-3634 , AIAA, ASME, SIAM, and APS, National Fluid Dynamics Congress; Jul 25, 1988 - Jul 28, 1988; Cincinnati, OH; United States
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  • 120
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    Electrohydrodynamic migration of charged droplets in an insulating fluid (1988)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: The motion of charged, conducting droplets present in an insulating fluid medium is analyzed under the action of an electric field, in microgravity. Previous analyses of this problem have considered the Maxwell stresses as the only driving force. In the present study, arguments from macroscopic thermodynamics and the molecular theory of surface tension are used to show that the surface tension gradients can be induced due to the variation of the electric potential on the interface. In the limit of Reynolds numbers small compared to unity, the terminal velocity of migration of the droplet is calculated under the combined action of the Maxwell stresses and the surface tension gradients. The results show that there are no surface tension gradients (i.e., no electric potential variation at the interface) in a case that is due to the convection of the surface charges, surface tension gradients do exist and tend to reduce the terminal velocity of the droplet. The shape of the droplet altered by the motion was also calculated, when the deformations from the speherical shape are small.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: AIAA PAPER 88-3557 , AIAA, ASME, SIAM, and APS, National Fluid Dynamics Congress; Jul 25, 1988 - Jul 28, 1988; Cincinnati, OH; United States
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  • 121
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    Effects of free-stream turbulence on turbulent boundary layers with mild adverse pressure gradients (1988)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: The influence of near isotropic free-stream turbulence on the shape factors and skin friction coefficients of turbulent boundary layers is presented for the cases of zero and mild adverse pressure gradients. With free-stream turbulence, improved fluid mixing occurs in boundary layers with adverse pressure gradients relative to the zero pressure gradient condition, with the same free-stream turbulence intensity and length scale. Stronger boundary layers with lower shape factors occur as a result of a lower ratio of the integral scale of turbulence to the boundary layer thickness, and to vortex stretching of the turbulent eddies in the free-stream, both of which act to improve the transmission of momentum from the free-stream to the boundary layers.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: AIAA PAPER 88-3757 , AIAA, ASME, SIAM, and APS, National Fluid Dynamics Congress; Jul 25, 1988 - Jul 28, 1988; Cincinnati, OH; United States
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  • 122
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    Some effects of finite spatial resolution on skin friction measurements in turbulent boundary layers (1988)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: The effects of finite spatial resolution often cause serious errors in measurements in turbulent boundary layers, with particularly large effects for measurements of fluctuating skin friction and velocities within the sublayer. However, classical analyses of finite spatial resolution effects have generally not accounted for the substantial inhomogeneity and anisotropy of near-wall turbulence. The present study has made use of results from recent computational simulations of wall-bounded turbulent flows to examine spatial resolution effects for measurements made at a wall using both single-sensor probes and those employing two sensing volumes in a V shape. Results are presented to show the effects of finite spatial resolution on a variety of quantitites deduced from the skin friction field.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: AIAA PAPER 88-3753 , AIAA, ASME, SIAM, and APS, National Fluid Dynamics Congress; Jul 25, 1988 - Jul 28, 1988; Cincinnati, OH; United States
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  • 123
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    Three-dimensional viscous flow computations of a circular jet in subsonic and supersonic cross flow (1988)
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    Publication Date: 2019-07-13
    Description: Three-dimensional viscous flow computations are presented for 90 deg. injection angle jets in subsonic and supersonic crossflow. Comparisons with experimental data include jet centerline and vortex trajectories for the subsonic crossflow, and surface pressure measurement for the supersonic crossflow case. The vortices induced in the jet/freestream interaction are computed and illustrated. The vortices persist in subsonic flow and die out quickly in supersonic flow. The structure of the shocks in the unconfined supersonic flow is illustrated.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: AIAA PAPER 88-3703 , AIAA, ASME, SIAM, and APS, National Fluid Dynamics Congress; Jul 25, 1988 - Jul 28, 1988; Cincinnati, OH; United States
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  • 124
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    Initial conditional effect on pressure waves in an axisymmetric jet (1988)
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    Publication Date: 2019-07-13
    Description: A pair of microphones (separated axially by 5.08 cm and laterally by 1.3 cm) are placed on either side of the jet centerline to investigate coherent pressure fluctuations in an axisymmetric jet at Strouhal numbers less than unity. Auto-spectra, transfer-function, and coherence measurements are made for a tripped and untripped boundary layer initial condition. It was found that coherent acoustic pressure waves originating in the upstream plenum chamber propagate a greater distance downstream for the tripped initial condition than for the untripped initial condition. In addition, for the untripped initial condition the developmet of the coherent hydrodynamic pressure waves shifts downstream.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: AIAA PAPER 88-3702 , AIAA, ASME, SIAM, and APS, National Fluid Dynamics Congress; Jul 25, 1988 - Jul 28, 1988; Cincinnati, OH; United States
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  • 125
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    Primitive numerical simulation of circular Couette flow - Carrousel wind tunnel nonturbulent solutions (1988)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: The azimuthal-invariant, three-dimensional cylindrical, incompressible Navier-Stokes equations are solved to steady state for a finite-length, physically realistic model. The numerical method relies on an alternating-direction implicit scheme that is formally second-order accurate in space and first-order accurate in time. The equations are linearized and uncoupled by evaluating variable coefficients at the previous time iteration. Wall grid clustering is provided by a Roberts transformation in radial and axial directions. A vorticity-velocity formulation is found to be preferable to a vorticity-streamfunction approach. Subject to no-slip, Dirichlet boundary conditions, except for the inner cylinder rotation velocity (impulsive start-up) and zero-flow initial conditions, nonturbulent solutions are obtained for sub- and supercritical Reynolds numbers of 100 to 400 for a finite geometry where R(outer)/R(inner) = 1.5, H/R(inner) = 0.73, and H/Delta-R = 1.5. An axially-stretched model solution is shown to asymptotically approach the one-dimensional analytic Couette solution at the cylinder midheight. Flowfield change from laminar to Taylor-vortex flow is discussed as a function of Reynolds number. Three-dimensional velocities, vorticity, and streamfunction are presented via two-dimensional graphs and three-dimensional surface and contour plots.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: AIAA PAPER 88-2520 , AIAA Applied Aerodynamics Conference; Jun 06, 1988 - Jun 08, 1988; Williamsburg, VA; United States
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  • 126
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    A numerical simulation of vortex breakdown (1987)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: A numerical simulation of vortex breakdown using the time-dependent Navier-Stokes equations is performed. Unlike previous studies, the numerical algorithm, formulated in terms of the velocity and vorticity, is not restricted by axisymmetry conditions. The vortex is parameterized in terms of the Reynolds number and Rossby number. The resulting breakdown structure is analyzed using contour plots of velocity, vorticity and pressure as well as axial, radial, and swirl velocity profiles at various streamwise locations. The relationship of these results to experimentally observed structures and previous numerical results is discussed.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Forum on Unsteady Flow Separation; Jun 14, 1987 - Jun 17, 1987; Cincinnati, OH; United States
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  • 127
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    Measurements of turbulence moments in boundary layers over transversely grooved surfaces (1987)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: Wind tunnel measurements of second, third, and fourth order turbulence moments in turbulent boundary layers over d-types and k-types of grooved and smooth surfaces are discussed. The near-wall turbulence structure is found to vary with the spanwise aspect ratio. For decreasing height, the third moment of the normal velocity fluctuations is shown to become negative over crop canopies and model plant canopies, although not in smooth, two-dimensional, sandgrain or gravel roughness. The instantaneous motions related to the flux of shear stress near the wall in smooth and transversely grooved surfaces are shown to be opposite in sign to those in three-dimensional roughness.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Forum on Turbulent Flows - 1987; Jun 14, 1987; Cincinnati, OH; United States
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  • 128
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    Corona anemometry for qualitative measurement of reversing surface flow with application to separation control by external excitation (1987)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: An corona anemometer which detects gas flow by the displacement of an ion beam is described, and experiments are performed using the anemometer to investigate the active control of diffusor separation by periodic forcing. The apparatus is applied to the separated flow over a rearward facing ramp. An oscillating vane is attached to the surface near the separation point. It is suggested that the enhancement in turbulent energy produced by the oscillating vane is due to drastic modification of the wake shear flow, and not to vane-produced turbulence.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Forum on Unsteady Flow Separation; Jun 14, 1987 - Jun 17, 1987; Cincinnati, OH; United States
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  • 129
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    Coherent motion induced fluctuations in the primary transition region of a plane shear layer (1987)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: The naturally occurring large scale motions in a single stream shear layer (that is initiated from a fully turbulent boundary layer) are made evident by the induced velocities in the entrainment region beyond the active shear layer. The distinctive attributes of these induced motions are particularly evident in the Michigan State Univerity Free Shear Flow Facility since the total test section length (3m) is nominally the same as the location of the first, fully formed, coherent motion, ca/x theta (0) = 400 (or 2.5 m). Hence, detailed studies of the induced motions can be executed. Individual coherent motions are identified by the induced velocity signatures and conditional-ensemble statistics are used to represent the irrotational field properties. Clusters of such motions exist; some of their properties are substantially different from the unconditionally averaged values.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Forum on Turbulent Flows - 1987; Jun 14, 1987; Cincinnati, OH; United States
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  • 130
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    Performance characteristics of moving belt radiators (1987)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: A design features and performance capabilities evaluation is made for a novel, 'hybrid belt radiator' spacecraft heat rejection system, which retains the excellent heat transfer capacity of liquid belt radiators but does not require the direct exposure of a free liquid surface to the space environment. Attention is given to the preliminary results of a computer model analyzing the dynamic behavior of the flexible belt structure due to spacecraft accelerations, as well as to the results of system studies determining size constraints on the radiator. Over the 300-700 K range of operating temperatures, Space Shuttle-stowable radiators with 10-200 MW thermal capacities can be designed.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: IECEC ''87; Aug 10, 1987 - Aug 14, 1987; Philadelphia, PA; United States
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  • 131
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    Radiator selection for Space Station Solar Dynamic Power Systems (1987)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: A study was conducted to define the best radiator for heat rejection of the Space Station Solar Dynamic Power System. Included in the study were radiators for both the Organic Rankine Cycle and Closed Brayton Cycle heat engines. A number of potential approaches were considered for the Organic Rankine Cycle and a constructable radiator was chosen. Detailed optimizations of this concept were conducted resulting in a baseline for inclusion into the ORC Preliminary Design. A number of approaches were also considered for the CBC radiator. For this application a deployed pumped liquid radiator was selected which was also refined resulting in a baseline for the CBC preliminary design. This paper reports the results and methodology of these studies and describes the preliminary designs of the Space Station Solar Dynamic Power System radiators for both of the candidate heat engine cycles.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: IECEC ''87; Aug 10, 1987 - Aug 14, 1987; Philadelphia, PA; United States
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  • 132
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    Adaptive computational methods for aerothermal heating analysis (1988)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The development of adaptive gridding techniques for finite-element analysis of fluid dynamics equations is described. The developmental work was done with the Euler equations with concentration on shock and inviscid flow field capturing. Ultimately this methodology is to be applied to a viscous analysis for the purpose of predicting accurate aerothermal loads on complex shapes subjected to high speed flow environments. The development of local error estimate strategies as a basis for refinement strategies is discussed, as well as the refinement strategies themselves. The application of the strategies to triangular elements and a finite-element flux-corrected-transport numerical scheme are presented. The implementation of these strategies in the GIM/PAGE code for 2-D and 3-D applications is documented and demonstrated.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-CR-181636 , NAS 1.26:181636 , LMSC-HEC-TR-F225772
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  • 133
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    Improved 3-D turbomachinery CFD algorithm (1988)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The building blocks of a computer algorithm developed for the time-accurate flow analysis of rotating machines are described. The flow model is a finite volume method utilizing a high resolution approximate Riemann solver for interface flux definitions. This block LU implicit numerical scheme possesses apparent unconditional stability. Multi-block composite gridding is used to orderly partition the field into a specified arrangement. Block interfaces, including dynamic interfaces, are treated such as to mimic interior block communication. Special attention is given to the reduction of in-core memory requirements by placing the burden on secondary storage media. Broad applicability is implied, although the results presented are restricted to that of an even blade count configuration. Several other configurations are presently under investigation, the results of which will appear in subsequent publications.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-CR-179364 , NAS 1.26:179364
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  • 134
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    Reynold stress closure in jet flows using wave models (1988)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Research program efforts have continued to concentrate on the development of the numerical methods that will form the computational part of the turbulence closure scheme. Studies have continued on the wave model for the two dimensional shear layer. This configuration is being used as a test case for the closure schemes. Several numerical schemes for the solution of the non-separable Rayleigh equation were developed. This solution is required for the closure scheme in more complex geometries. The most efficient method found is a Hybrid scheme that combines both pseudospectral and finite difference techniques. In addition, conformal transformation techniques were developed to transform the arbitrary geometry of the jet to a simple computational domain. The study of the shock structure in arbitrary geometry jets and multiple jets. These developments are described briefly.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-CR-182662 , NAS 1.26:182662
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  • 135
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    Interior impedance wedge diffraction with surface waves (1988)
    In:  CASI
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    Publication Date: 2019-07-13
    Description: The exact impedance wedge solution is evaluated asymptotically using the method of steepest descents for plane wave illumination at normal incidence. Uniform but different impedances on each face are considered for both soft and hard polarizations. The asymptotic solution isolates the incident, singly reflected, multiply reflected, diffracted, and surface wave fields. Multiply reflected fields of any order are permitted. The multiply reflected fields from the exact solution are written as ratios of auxiliary Maliuzhinets functions, whereas a geometrical analysis gives the reflected fields as products of reflection coefficients. These two representations are shown to be identical in magnitude, phase and the angular range over which they exist. The diffracted field includes four Fresnel transition functions as in the perfect conductor case, and the expressions for the appropriate discontinuities at the shadow boundaries are presented. The surface wave exists over a finite angular range and only for certain surface impedances. A surface wave transition field is included to retain continuity. Computations are presented for interior wedge diffractions although the formulation is valid for both exterior and interior wedges.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-CR-182405 , NAS 1.26:182405
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  • 136
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    Advanced radiator concepts utilizing honeycomb panel heat pipes (1987)
    In:  CASI
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    Publication Date: 2019-07-13
    Description: The feasibility of fabricating and processing moderate temperature range vapor chamber type heat pipes in a low mass honeycomb panel configuration for highly efficient radiator fins for potential use on the space station was investigated. A variety of honeycomb panel facesheet and core-ribbon wick concepts were evaluated within constraints dictated by existing manufacturing technology and equipment. Concepts evaluated include type of material, material and panel thickness, wick type and manufacturability, liquid and vapor communication among honeycomb cells, and liquid flow return from condenser to evaporator facesheet areas. A thin-wall all-welded stainless steel design with methanol as the working fluid was the initial prototype unit. It was found that an aluminum panel could not be fabricated in the same manner as a stainless steel panel due to diffusion bonding and resistance welding considerations. Therefore, a formed and welded design was developed. The prototype consists of ten panels welded together into a large panel 122 by 24 by 0.15 in., with a heat rejection capability of 1000 watts and a fin efficiency of essentially 1.0.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-CR-172017 , NAS 1.26:172017
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  • 137
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    Finite element solver for 3-D compressible viscous flows (1986)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The space shuttle main engine (SSME) has extremely complex internal flow structure. The geometry of the flow domain is three-dimensional with complicated topology. The flow is compressible, viscous, and turbulent with large gradients in flow quantities and regions of recirculations. The analysis of the flow field in SSME involves several tedious steps. One is the geometrical modeling of the particular zone of the SSME being studied. Accessing the geometry definition, digitalizing it, and developing surface interpolations suitable for an interior grid generator require considerable amount of manual labor. There are several types of grid generators available with some general-purpose finite element programs. An efficient and robust computational scheme for solving 3D Navier-Stokes equations has to be implemented. Post processing software has to be adapted to visualize and analyze the computed 3D flow field. The progress made in a project to develop software for the analysis of the flow is discussed. The technical approach to the development of the finite element scheme and the relaxation procedure are discussed. The three dimensional finite element code for the compressible Navier-Stokes equations is listed.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-CR-179182 , NAS 1.26:179182
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    Experimental test of liquid droplet radiator performance (1987)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: The liquid droplet radiator (LDR) is a heat rejection system for space power systems wherein an array of heated liquid droplets radiates energy directly to space. The use of submillimeter droplets provides large radiating area-to-mass ratio, resulting in radiator systems which are several times lighter than conventional solid surface radiators. An experiment is described in which the power radiated by an array of 2300 streams of silicone oil droplets is measured to test a previously developed theory of the LDR radiation process. This system would be capable of rejecting several kW of heat in space. Furthermore, it would be suitable as a modular unit of an LDR designed for 100-kW power levels. The experiment provided confirmation of the theoretical dependence of droplet array emissivity on optical depth. It also demonstrated the ability to create an array of more than 1000 droplet streams having a divergence less than 1 degree.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Space nuclear power systems 1986; Jan 13, 1986; Albuquerque, MN; United States
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  • 139
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    Radiation heat transfer shapefactors for combustion systems (1987)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: The computation of radiation heat transfer through absorbing media is commonly done through the zoning method which relies upon values of the geometric mean transmittance and absorptance. The computation of these values is difficult and expensive, particularly if many spectral bands are used. This paper describes the extension of a scan line algorithm, based upon surface-surface radiation, to the computation of surface-gas and gas-gas radiation transmittances.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Fundamentals and applications of radiation heat transfer; Aug 09, 1987 - Aug 12, 1987; Pittsburgh, PA; United States
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  • 140
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    High-resolution heat-transfer-coefficient maps applicable to compound-curve surfaces using liquid crystals in a transient wind tunnel (1987)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: Tests were performed in a transient heat transfer tunnel in which the model under test was preheated prior to allowing room temperature air to be suddenly drawn over the model. The resulting movement of isothermal contours on the model is revealed using a surface coating of thermochromic liquid crystals that display distinctive colors at particular temperatures. A video record is obtained of a temperature and time data pair for all points on the model during a single test. Experiments on a duct model are reported in which the model was preheated using a hot air stream. A manner in which initial model temperature nonuniformities could be taken into account was investigated. The duct model was also tested with a steady-state measurement technique and results were compared with the transient measurements, but recognizing that differences existed between the upstream thermal boundary conditions. The steady-state and transient measurements were shown to be consistent with predicted values. The main advantage of this transient heat transfer technique using liquid crystals is that since the test model need not be actively heated, high-resolution measurements on surfaces with complex shapes may be obtained.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Developments in experimental techniques in heat transfer and combustion; Aug 09, 1987 - Aug 12, 1987; Pittsburgh, PA; United States
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  • 141
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    Experimental studies on Taylor-Goertler vortices (1985)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Taylor-Goertler vortices arise in boundary layer along concave surfaces due to centrifugal effects. These counter-rotating streamwise vortices are one of three known flow instabilities which lead to boundary layer transition. Coupled with Tollmien-Schlichting waves and cross flow vortices, Taylor-Goertler vortices can triggerr early transition to turbulence. The flow field patterns were studied by flow visualization using a sublimating chemical technique and a three component laser velocimeter was used to study the flow field in the test region. Results from these studies are given and briefly discussed.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-CR-181254 , NAS 1.26:181254
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  • 142
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    Nonlinear acoustic wave propagation in atmosphere. Absorbing boundary conditions for exterior problems (1985)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Elliptic and hyperbolic problems in unbounded regions are considered. These problems, when one wants to solve them numerically, have the difficulty of prescribing boundary conditions at infinity. Computationally, one needs a finite region in which to solve these problems. The corresponding conditions at infinity imposed on the finite distance boundaries should dictate the boundary conditions at infinity and be accurate with respect to the interior numerical scheme. The treatment of these boundary conditions for wave-like equations is discussed.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-CR-181260 , NAS 1.26:181260
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  • 143
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    Numerical solutions of Navier-Stokes equations for a Butler wing (1987)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The flow field is simulated on the surface of a Butler wing in a uniform stream. Results are presented for the Mach number 3.5 and Reynolds number of 2,000,000. The simulation is done by integrating the viscous Navier-Stokes equations. These equations govern the unsteady, viscous, compressible and heat conducting flow of an ideal gas. The equations are written in curvilinear coordinates so that the wing surface is represented accurately. O-type and H-type grids have been used for this study, and results are compared. The governing equations are solved by the McCormack time-split method, and the results are compared with other theoretical and experimental results. The codes are written in FORTRAN, vectorized and currently run on the CDC Vector Processing System (VPS-32) computer.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-CR-180331 , NAS 1.26:180331
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  • 144
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    Modeling of transient heat pipe operation (1987)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The use of heat pipes is being considered as a means of reducing the peak temperature and large thermal gradients at the leading edges of reentry vehicles and hypersonic aircraft and in nuclear reactors. In the basic cooling concept, the heat pipe covers the leading edge, a portion of the lower wing surface, and a portion of the upper wing surface. Aerodynamic heat is mainly absorbed at the leading edge and transported through the heat pipe to the upper and lower wing surface, where it is rejected by thermal radiation and convection. Basic governing equations are written to determine the startup, transient, and steady state performance of a haet pipe which has initially frozen alkali-metal as the working fluid.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-CR-180280 , NAS 1.26:180280
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  • 145
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    Computational fluid dynamics and aerothermodynamics (1987)
    In:  CASI
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    Publication Date: 2019-07-13
    Description: At the present time the efforts on this project are organized into two areas: the development of an approximate stagnation point solution and approximate flowfield studies which can be used to develop and investigate shock jump, electron temperature, radiation, vibration-dissociation coupling, and chemistry models. Progress in each area is discussed.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-CR-181111 , NAS 1.26:181111 , TAMRF-5671-87-01
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  • 146
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    Research in computational fluid dynamics (1987)
    In:  CASI
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    Publication Date: 2019-07-13
    Description: The numerical integration of quasi-one-dimensional unsteady flow problems which involve finite rate chemistry are discussed, and are expressed in terms of conservative form Euler and species conservation equations. Hypersonic viscous calculations for delta wing geometries is also examined. The conical Navier-Stokes equations model was selected in order to investigate the effects of viscous-inviscid interations. The more complete three-dimensional model is beyond the available computing resources. The flux vector splitting method with van Leer's MUSCL differencing is being used. Preliminary results were computed for several conditions.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-CR-180542 , NAS 1.26:180542 , MIT-OSP-95315
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  • 147
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    Computational methods for vortex dominated compressible flows (1987)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The principal objectives were to: understand the mechanisms by which Euler equation computations model leading edge vortex flows; understand the vortical and shock wave structures that may exist for different wing shapes, angles of incidence, and Mach numbers; and compare calculations with experiments in order to ascertain the limitations and advantages of Euler equation models. The initial approach utilized the cell centered finite volume Jameson scheme. The final calculation utilized a cell vertex finite volume method on an unstructured grid. Both methods used Runge-Kutta four stage schemes for integrating the equations. The principal findings are briefly summarized.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-CR-181144 , NAS 1.26:181144 , MIT-OSP-93666
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    An experimental study of the properties of surface pressure fluctuations for separating turbulent boundary layers (1986)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Noise generated by helicopter and turbomachine rotors is a nuisance that designers would like to predict and to minimize within other design constraints. A key element for the noise calculation procedure is knowledge relating the flowfield structure to the surface pressure fluctuation structure. Surface pressure fluctuation data for zero-pressure-gradient and accelerating turbulent boundary layers were obtained. The zero-pressure-gradient turbulent boundary layers were examined with freestream velocities of 72 and 105 fps. Mean and fluctuation velocity profiles and streamwise velocity spectra and wavespeeds were obtained for momentum thickness Reynolds numbers up to 18000 for the zero-pressure-gradient case and up to 4000 for the favorable-pressure-gradient case. The wall shearing stress was estimated from a Clauser plot of the near wall data. It is clear that turbulent pressure fluctuations are produced by turbulent velocity fluctuations. Detailed simultaneous measurements of all of these fluctuations are needed to determine in more detail the structural relationships between velocity and pressure fields. Although some measurements were made for unseparated flows, none were made for separated flows.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-CR-180295 , NAS 1.26:180295
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  • 149
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    Boundary layer simulation improvement (1987)
    In:  CASI
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    Publication Date: 2019-07-13
    Description: The current Boundary Layer Integral Matrix Procedure - Version J (BLIMPJ) is advanced with regard to the previously modeled calculation methods accounting for surface roughness, relaminarization, condensed phase, and thick boundary layer effects. Current analytical limitations will be relaxed to permit more realistic wall and flow conditions and to use appropriate turbulence models with specific emphasis for the projected Orbit Transfer Vehicle (OTV) engine application. The updates will be incorporated into the BLIMPJ computer program, and the modified program will be made operational on the MSFC CRAY computer system. Experimental feasibility studies were conducted to find out how to obtain quality test data with advanced instrumentation for concept verification purposes.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-CR-178845 , NAS 1.26:178845 , RPR-161-04
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    Numerical solutions of the complete Navier-Stokes equations (1986)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Using ideas from the kinetic theory, the Navier-Stokes equations are modified in such a way that they can be cast as a set of first order hyperbolic equations. This is achieved by incorporating time dependent terms into the definition of the stress tensor and the heat flux vectors. The boundary conditions are then determined from the theory of characteristics. Because the resulting equations reduce to the traditional Navier-Stokes equations when the steady state is reached, the present approach provides a straightforward scheme for the determination of inflow and outflow boundary conditions. The method is validated by comparing its predictions with known exact solutions of the steady Navier-Stokes equations.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-CR-180627 , NAS 1.26:180627 , PR-10
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    Development of computer models for correlating data of film cooling of nose cone under hypersonic flow (1987)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: A 12.5 degree half cone with tangential slot injection at Mach 6.95 was studied to determine the heating rates to the surface of the body near and far downstream of the slot. The cone had a zero degree angle of attack. The heating rates were obtained using a computer program that was developed at NASA-Langley Research Center. The concentration of nitrogen from the slot into the boundary layer was also determined. The ratio of slot to freestream was varied to determine its effect on heating. The numerical heating rates were compared to other correlations obtained from experimental studies as well as theoretical laminar and turbulent results.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-CR-180673 , NAS 1.26:180673
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    Thermodynamic evaluation of transonic compressor rotors using the finite volume approach (1986)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The development of a computational capability to handle viscous flow with an explicit time-marching method based on the finite volume approach is summarized. Emphasis is placed on the extensions to the computational procedure which allow the handling of shock induced separation and large regions of strong backflow. Appendices contain abstracts of papers and whole reports generated during the contract period.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-CR-180587 , NAS 1.26:180587 , JM/87-4
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    A transport model of the turbulent scalar-velocity (1987)
    In:  CASI
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    Publication Date: 2019-07-13
    Description: Performance tests of the third-order turbulence closure for predictions of separating and recirculating flows in backward-facing steps were studied. Computations of the momentum and temperature fields in the flow domain being considered entail the solution of time-averaged transport equations containing the second-order turbulent fluctuating products. The triple products, which are responsible for the diffusive transport of the second-order products, attain greater significance in separating and reattaching flows. The computations are compared with several algebraic models and with the experimental data. The prediction was improved considerably, particularly in the separated shear layer. Computations are further made for the temperature-velocity double products and triple products. Finally, several advantages were observed in the usage of the transport equations for the evaluation of the turbulence triple products; one of the most important features is that the transport model can always take the effects of convection and diffusion into account in strong convective shear flows such as reattaching separated layers while conventional algebraic models cannot account for these effects in the evaluation of turbulence variables.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-CR-180605 , NAS 1.26:180605 , REPT-332E/3389E
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  • 154
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    Turbulence control on an airborne laser platform (1987)
    In:  CASI
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    Publication Date: 2019-07-13
    Description: An active flow control device to generate large-scale, periodic structures in a turbulent shear flow is developed. Together with adaptive optics, the device may be used on airborne laser platforms to reduce or eliminate optical distortion caused by the turbulence in the aircraft's boundary layer. A cyclic jet issuing from a spanwise slot is used to collect the turbulent boundary layer for a finite time and then release all of the flow instantaneously in one large eddy that convects downstream. Flow visualization and hot-film probe measurements are used together with pattern recognition algorithms to demonstrate the viability of the flow control method. A flat plate towed in a water channel is used as a test bed. The instantaneous velocity signal is used to compute important statistical quantities of the random velocity field, such as the mean, the root-mean-square, the spectral distribution, and the probability density function. When optimized for a given boundary layer, it is shown that the cyclic jet will produce periodic structures that are similar to the random, naturally occurring ones. These structures seem to trigger the onset of bursting events near the wall of the plate. Thus, the present device generates periodic structures in both the outer and inner regions of a turbulent boundary layer.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-CR-178249 , NAS 1.26:178249 , REPT-365
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  • 155
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    Vortex/boundary layer interaction (1987)
    In:  CASI
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    Publication Date: 2019-07-13
    Description: The second test case (longitudinal vortex above, but not merging with, a turbulent boundary layer) was investigated with flow visualization studies, and photographs selected. The results of quantitative data acquisition for the non-merging test case are presented. Other work in progress includes further flow visualization of the delta-wing wake. Considerable effort is being devoted to the development of graphical output routines.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-CR-180255 , NAS 1.26:180255
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  • 156
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    Feasibility analysis of reciprocating magnetic heat pumps (1986)
    In:  CASI
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    Publication Date: 2019-07-13
    Description: The conceptual design selected for detailed system analysis and optimization is the reciprocating gadolinium core in a regenerative fluid column within the bore of a superconducting magnet. The thermodynamic properties of gadolinium are given. A computerized literature search for relevant papers was conducted and is being analyzed. Contact was made with suppliers of superconducting magnets and accessories, magnetic materials, and various types of hardware. A description of the model for the thermal analysis of the core and regenerator fluids is included.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-CR-180262 , NAS 1.26:180262
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  • 157
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    Selection principles and pattern formation in fluid mechanics and nonlinear shell theory (1987)
    In:  CASI
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    Publication Date: 2019-07-13
    Description: Wave theories of vortex breakdown were studied. A setting which involved dynamical systems and bifurcations of homoclinic and heteroclinic orbits in infinite-dimensional spaces was investigated. The determination of axisymmetric inviscid flows bifurcating from the primary flow lead to the study of a system of ordinary differential equations. The problem of rotating plane Couette flow was solved by means of the structure parameter approach.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-CR-180159 , NAS 1.26:180159
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  • 158
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    Near field pressure fluctuations in a circular jet (1985)
    In:  CASI
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    Publication Date: 2019-07-13
    Description: The vortical structures in shear layers govern many dynamic aspects of the jet, including entrainment of mass, transfer of momentum and noise generation. These structures develop from instability waves and undergo a merging process. Vortex merging reduces the time scale and increases the length scale of the shear layer. At the same time pressure fluctuations are induced by the unsteady motion. These pressure perturbations can exert high level dynamic loading on nearby structures, and radiate to the far field as noise. In this study, the generation mechanism of the pressure fluctuations and the radiation process are examined.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-CR-179847 , NAS 1.26:179847
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  • 159
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    Incipient transition phenomena in compressible flows over a flat plate (1986)
    In:  CASI
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    Publication Date: 2019-07-13
    Description: The full three-dimensional time-dependent compressible Navier-Stokes equations are solved by a Fourier-Chebyshev method to study the stability of compressible flows over a flat plate. After the code is validated in the linear regime, it is applied to study the existence of the secondary instability mechanism in the supersonic regime.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-CR-178111 , NAS 1.26:178111 , ICASE-86-39 , International Conference on Numerical Methods in Fluid Dynamics; Jan 01, 1986; Hampton, VA; United States
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  • 160
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    Optical diagnostics of gas-dynamic flows using advanced laser measurement techniques (1985)
    In:  CASI
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    Publication Date: 2019-07-13
    Description: Using laser-induced fluorescence to probe nitrogen flows seeded with small amounts of nitric oxide, simultaneous measurements of all three thermodynamic scalar quantities temperature, density, and pressure, were demonstrated in a supersonic turbulent boundary layer. Instrumental uncertainty is 1% for temperature and 2% for density and pressure, making the techniques suitable for measurements of turbulent fluctuations. This technology is currently being transferred to an experimental program designed to use these optical techniques in conjunction with traditional methods to make measurements in turbulent flowfields that were not possible before. A detailed descritpion of the research progress and pertinent results are presented.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-CR-176950 , NAS 1.26:176950
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  • 161
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    Flow direction measurement criteria and techniques planned for the 40- by 80-/80- x 120-foot wind tunnel integrated systems tests (1985)
    In:  CASI
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    Publication Date: 2019-07-13
    Description: A study was performed in order to develop the criteria for the selection of flow direction indicators for use in the Integrated Systems Tests (ISTs) of the 40 by 80/80 by 120 Foot Wind Tunnel System. The problems, requirements, and limitations of flow direction measurement in the wind tunnel were investigated. The locations and types of flow direction measurements planned in the facility were discussed. A review of current methods of flow direction measurement was made and the most suitable technique for each location was chosen. A flow direction vane for each location was chosen. A flow direction vane that employs a Hall Effect Transducer was then developed and evaluated for application during the ISTs.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-CR-176969 , NAS 1.26:176969
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  • 162
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    Diffusion flame extinction in slow convenctive flow under microgravity environment (1986)
    In:  CASI
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    Publication Date: 2019-07-13
    Description: A theoretical analysis is presented to study the extinction characteristics of a diffusion flame near the leading edge of a thin fuel plate in slow, forced convective flows in a microgravity environment. The mathematical model includes two-dimensional Navier-Stokes momentum, energy and species equations with one-step overall chemical reaction using second-order finite rate Arrhenius kinetics. Radiant heat loss on the fuel plate is applied in the model as it is the dominant mechanism for flame extinguishment in the small convective flow regime. A parametric study based on the variation of convective flow velocity, which varies the Damkohler number (Da), and the surface radiant heat loss parameter (S) simultaneously, is given. An extinction limit is found in the regime of slow convective flow when the rate of radiant heat loss from fuel surface outweighs the rate of heat generation due to combustion. The transition from existent envelope flame to extinguishment consists of gradual flame contraction in the opposed flow direction together with flame temperature reduction as the convective flow velocity decreases continuously until the extinction limit is reached. A case of flame structure subjected to surface radiant heat loss is also presented and discussed.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-TM-88799 , E-3137 , NAS 1.15:88799 , Microgravity Fluid Mechanics Symposium; Dec 10, 1986 - Dec 11, 1986; Anaheim, CA; United States
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  • 163
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    Thermomechanical design criteria for ceramic-coated surfaces (1986)
    In:  CASI
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    Publication Date: 2019-07-13
    Description: Some early history of ceramic applications is presented. Finite element modeling of components to determine service and fabrication loads found inelastic behavior and residual stresses to be significant to component life. Inelastic behavior mitigates peak strains but enhances residual strains. Results of furnace, Mach 0.3 burner, and engine tests are discussed and categorized into design criteria (loading, geometry, fabrication, materials, analysis, and testing). These design rules and finite element analyses are brought to bear on two test cases: turboshaft engine seals, and rocket thrust chambers.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-TM-87328 , E-3002 , NAS 1.15:87328 , CIMTEC World Congress on High Tech Ceramics; Jun 23, 1986 - Jun 28, 1986; Milan; Italy
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  • 164
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    Simulation of the turbulent Rayleigh-Benard problem using a spectral/finite difference technique (1986)
    In:  CASI
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    Publication Date: 2019-07-13
    Description: The three-dimensional, incompressible Navier-Stokes and energy equations with the Bousinesq assumption have been directly simulated at a Rayleigh number of 3.8 x 10 to the 5th power and a Prandtl number of 0.76. In the vertical direction, wall boundaries were used and in the horizontal, periodic boundary conditions were used. A spectral/finite difference numerical method was used to simulate the flow. The flow at these conditions is turbulent and a sufficiently fine mesh was used to capture all relevant flow scales. The results of the simulation are compared to experimental data to justify the conclusion that the small scale motion is adequately resolved.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-CR-178027 , ICASE-86-6 , NAS 1.26:178027 , EUROMECH 199 Direct and Large Eddy Simulation of Turbulent Flows; Sep 30, 1985 - Oct 02, 1985; Munich; Germany
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  • 165
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    Non-reflecting boundary conditions for the compressible Navier-Stokes equations (1986)
    In:  CASI
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    Publication Date: 2019-07-13
    Description: A small perturbation analysis, in the long wavelength regime, is used to obtain the downstream boundary condition for the pressure for the flow over a flat plate. The methodology is extendable to other geometries. Numerical results for high Reynolds number laminar flows show great improvement in convergence rate to steady state as well as the quality of the results.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-CR-178068 , ICASE-86-9 , NAS 1.26:178068 , International Conference on Computing Methods in Applied Sciences and Engineering; Dec 09, 1985 - Dec 13, 1985; Versailles; France
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  • 166
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    Coupling between fluid dynamics and energy addition in arcjet and microwave thrusters (1986)
    In:  CASI
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    Publication Date: 2019-07-13
    Description: A new approach to numerically solving the problem of the constricted electric arcjet is presented. An Euler Implicit finite difference scheme is used to solve the full compressible Navier Stokes equations in two dimensions. The boundary and initial conditions represent the constrictor section of the arcjet, and hydrogen is used as a propellant. The arc is modeled as a Gaussian distribution across the centerline of the constrictor. Temperature, pressure and velocity profiles for steady state converged solutions show both axial and radial changes in distributions resulting from their interaction with the arc energy source for specific input conditions. The temperature rise is largest at the centerline where there is a the greatest concentration arc energy. The solution does not converge for all initial inputs and the limitations in the range of obtainable solutions are discussed.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-CR-176690 , NAS 1.26:176690
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  • 167
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    Hydrodynamic aspects of shark scales (1986)
    In:  CASI
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    Publication Date: 2019-07-13
    Description: Ridge morphometrices on placoid scales from 12 galeoid shark species were examined in order to evaluate their potential value for frictional drag reduction. The geometry of the shark scales is similar to longitudinal grooved surfaces (riblets) that have been previously shown to give 8 percent skin-friction reduction for turbulent boundary layers. The present study of the shark scales was undertaken to determine if the physical dimensions of the ridges on the shark scales are of the right magnitude to be used by the sharks for drag reduction based on previous riblet work. The results indicate that the ridge heights and spacings are normally maintained between the predicted optimal values proposed for voluntary and burst swimming speeds throughout the individual's ontogeny. Moreover, the species which might be considered to be the faster posses smaller and more closely spaced ridges that based on the riblet work would suggest a greater frictional drag reduction value at the high swimming speeds, as compared to their more sluggish counterparts.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-CR-3963 , NAS 1.26:3963
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  • 168
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    Effect of a rotor wake on the local heat transfer on the forward half of a circular cylinder (1986)
    In:  CASI
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    Publication Date: 2019-07-13
    Description: Turbine rotor-stator wake dynamics was simulated by a spoked wheel rotating in annular flow, generating rotor wakes. Spanwise averaged circumferentially local heat transfer in the circular cylindrical leading edge region of a turbine airfoil was obtained. Reynolds numbers ranged from 35,000 to 175,000. Strouhal numbers ranged from 0.63 to 2.50. Wakes were generated by 2 sets of circular cylindrical bars, 1.59 and 3.18 mm in diameter. The rotor could be rotated either clockwise or counterclockwise. Grid turbulence was introduced upstream yielding freestream turbulence of 1.0 to 2.5% at the stator. Data represented an extensive body of local heat transfer coefficients, which can be used to model the leading edge region of a turbine airfoil. In the presence of rotor wakes, an asymmetry from the leeward to windward side was noted. Windward side levels were 30 to 40% higher than the corresponding leeward side.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-TM-87234 , E-2751 , NAS 1.15:87234 , International Heat Transfer Conference; Aug 17, 1986 - Aug 22, 1986; San Francisco, CA; United States
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  • 169
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    Two-phase flows and heat transfer within systems with ambient pressure above the thermodynamic critical pressure (1986)
    In:  CASI
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    Publication Date: 2019-07-13
    Description: In systems where the design inlet and outlet pressures P sub amb are maintained above the thermodynamic critical pressure P sub c, it is often assumed that heat and mass transfer are governed by single-phase relations and that two-phase flows cannot occur. This simple rule of thumb is adequate in many low-power designs but is inadequate for high-performance turbomachines, boilers, and other systems where two-phase regions can exist even though P sub amb P sub c. Heat and mass transfer and rotordynamic-fluid-mechanic restoring forces depend on momentum differences, and those for a two-phase zone can differ significantly from those for a single-phase zone. By using a laminar, variable-property bearing code and a rotating boiler code, pressure and temperature surfaces were determined that illustrate nesting of a two-phase region within a supercritical pressure region. The method of corresponding states is applied to bearings with reasonable rapport.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-TM-87228 , E-2897 , NAS 1.15:87228 , International Heat Transfer Conference; Aug 17, 1986 - Aug 22, 1986; San Francisco, CA; United States
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  • 170
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    Improvement of the second- and third-moment modeling of turbulence: A study of Reynolds-stress closure model (1986)
    In:  CASI
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    Publication Date: 2019-07-13
    Description: Four parts of the Reynolds-stress closure modeling are reported: (1) improvement of the k and epsilon equaitons; (2) development of the third-moment transport equation; (3) formulation of the diffusion coefficient of the momentum equation by using the algebraic-stress model of turbulence; and (4) the application of the Reynolds-stress model to a heat exchanger problem. It was demonstrated that the third-moment transport model improved the prediction of the triple-velocity products in the recirculating and reattaching flow regions in comparison with the existing algebraic models for the triple-velocity products. Optimum values for empirical coefficients are obtained for the prediction of the backward-facing step flows. A functional expression is derived for the coefficient of the momentum diffusion by employing the algebraic-stress model. The second-moment closure is applied to a heat transfer problem. The computations for the flow in a corrugated-wall channel show that the second-moment closure improves the prediction of the heat transfer rates by 30% over the k - epsilon model.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-CR-176478 , NAS 1.26:176478 , REPT-94E/2623E , TF/86/1
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  • 171
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    Mean velocity and turbulence measurements in a 90 deg curved duct with thin inlet boundary layer (1985)
    In:  CASI
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    Publication Date: 2019-07-13
    Description: The experimental database established by this investigation of the flow in a large rectangular turning duct is of benchmark quality. The experimental Reynolds numbers, Deans numbers and boundary layer characteristics are significantly different from previous benchmark curved-duct experimental parameters. This investigation extends the experimental database to higher Reynolds number and thinner entrance boundary layers. The 5% to 10% thick boundary layers, based on duct half-width, results in a large region of near-potential flow in the duct core surrounded by developing boundary layers with large crossflows. The turbulent entrance boundary layer case at R sub ed = 328,000 provides an incompressible flowfield which approaches real turbine blade cascade characteristics. The results of this investigation provide a challenging benchmark database for computational fluid dynamics code development.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-CR-174811 , NAS 1.26:174811 , UTSI/85-08
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  • 172
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    Determination of convective diffusion heat/mass transfer rates to burner rig test targets comparable in size to cross-stream jet diameter (1985)
    In:  CASI
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    Publication Date: 2019-07-13
    Description: Two sets of experiments have been performed to be able to predict the convective diffusion heat/mass transfer rates to a cylindrical target whose height and diameter are comparable to, but less than, the diameter of the circular cross-stream jet, thereby simulating the same geometric configuration as a typical burner rig test specimen located in the cross-stream of the combustor exit nozzle. The first set exploits the naphthalene sublimation technique to determine the heat/mass transfer coefficient under isothermal conditions for various flow rates (Reynolds numbers). The second set, conducted at various combustion temperatures and Reynolds numbers, utilized the temperature variation along the surface of the above-mentioned target under steady-state conditions to estimate the effect of cooling (dilution) due to the entrainment of stagnant room temperature air. The experimental information obtained is used to predict high temperature, high velocity corrosive salt vapor deposition rates in burner rigs on collectors that are geometrically the same. The agreement with preliminary data obtained from Na2SO4 vapor deposition experiments is found to be excellent.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-TM-87176 , E-2722 , NAS 1.15:87176 , International Gas Turbine Conference,; Jun 08, 1986 - Jun 12, 1986; Dusseldorf; Germany
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  • 173
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    Multiple-scale turbulence closure modeling of confined recirculating flows (1985)
    In:  CASI
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    Publication Date: 2019-07-13
    Description: A multiple-scale turbulence closure scheme is developed for the numerical predictions of confined recirculating flows. This model is based on the multiple-time-scale concepts of Hanjalic et al. (1980) and takes into account the non-equilibrium spectra energy transfer mechanism. Problems concerning new formulation of energy transfer rate equations and subsequent model coefficient redefinition and energy spectrum partition are discussed. Comparisons are made with several experiments of internal recirculating flows for the purpose of model validation. Numerical results using the present model show significant improvement of predictive capability over that obtained with the single-scale k-epsilon model and show promising potential for complex turbulent flow predictions.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-CR-178536 , NAS 1.26:178536 , Midwestern Mech. Conf.; Sep 01, 1985; Columbus, OH; United States
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  • 174
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    Theoretical and experimental comparison of vapor cavitation in dynamically loaded journal bearings (1985)
    In:  CASI
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    Publication Date: 2019-07-13
    Description: Vapor cavitation for a submerged journal bearing under dynamically loaded conditions was investigated. The observation of vapor cavitation in the laboratory was done by high-speed photography. It was found that vapor cavitation occurs when the tensile stress applied to the oil exceeded the tensile strength of the oil or the binding of the oil to the surface. The theoretical solution to the Reynolds equation is determined numerically using a moving boundary algorithm. This algorithm conserves mass throughout the computational domain including the region of cavitation and its boundaries. An alternating direction implicit (MDI) method is used to effect the time march. A rotor undergoing circular whirl was studied. Predicted cavitation behavior was analyzed by three-dimensional computer graphic movies. The formation, growth, and collapse of the bubble in response to the dynamic conditions is shown. For the same conditions of dynamic loading, the cavitation bubble was studied in the laboratory using high-speed photography.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-TM-87121 , E-2729 , NAS 1.15:87121 , USAAVSCOM-TR-85-C-19 , Intern. Symp. on Cavitation; Apr 16, 1986 - Apr 19, 1986; Sendai; Japan
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  • 175
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    Theoretical modeling of the vapor cavitation in dynamically loaded journal bearings (1985)
    In:  CASI
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    Publication Date: 2019-07-13
    Description: A theoretical investigation is made of the evolution of a vapor-bubble for a submerged journal bearing under dynamically loaded conditions using the Elrod algorithm. This method conserves mass throughout the computational domain. A comparison study is performed to determine some of the consequences of applying a nonconservative theory (pseudo-Gumbel BC) to a dynamic problem. A complete dynamic cycle of a journal whirling in a circular path is chosen for the basis of comparison. Significant differences are observed in the load components near the end of the cycle. Further, good agreement with experiment is found for stationary and nonstationary cavitation.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-TM-87076 , E-2651 , USAAVSCOM-TR-85-C-15 , NAS 1.15:87076 , Tribology Conf.,; Oct 08, 1985 - Oct 10, 1985; Atlanta, GA; United States
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  • 176
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    Recent applications of spectral methods in fluid dynamics (1985)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: Origins of spectral methods, especially their relation to the method of weighted residuals, are surveyed. Basic Fourier and Chebyshev spectral concepts are reviewed and demonstrated through application to simple model problems. Both collocation and tau methods are considered. These techniques are then applied to a number of difficult, nonlinear problems of hyperbolic, parabolic, elliptic and mixzed type. Fluid dynamical applications are emphasized.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Large-scale computations in fluid mechanics; Jun 27, 1983 - Jul 08, 1983; La Jolla, CA
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  • 177
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    Application of TVD schemes for the Euler equations of gas dynamics (1985)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: Highly accurate and yet stable shock-capturing finite difference schemes have been designed for the computation of the Euler equations of gas dynamics. Four different principles for the construction of high resolution total variation diminishing (TVD) schemes are available, including hybrid schemes, a second-order extension of Godunov's scheme by van Leer (1979), the modified flux approach of Harten (1983, 1984), and the numerical fluctuation approach of Roe (1985). The present paper has the objective to review the class of second-order TVD schemes via the modified flux approach. Attention is given to first-order TVD schemes, a second-order accurate explicit TVD scheme, the global order of accuracy of the second-order TVD scheme, extensions to systems and two-dimensional conservation laws, numerical experiments with a second-order explicit TVD scheme, implicit TVD schemes, and second-order implicit TVD schemes.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Large-scale computations in fluid mechanics; Jun 27, 1983 - Jul 08, 1983; La Jolla, CA
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  • 178
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    A nonoscillatory shock capturing scheme using flux limited dissipation (1985)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: A method for modifying the third order dissipative terms by the introduction of flux limiters is proposed. The first order dissipative terms can then be eliminated entirely, and in the case of a scalar conservation law the scheme is converted into a total variation diminishing scheme provided that an appropriate value is chosen for the dissipative coefficient. Particular attention is given to: (1) the treatment of the scalar conservation law; (2) the treatment of the Euler equations for inviscid compressible flow; (3) the boundary conditions; and (4) multistage time stepping and multigrid schemes. Numerical results for transonic flows suggest that a central difference scheme augmented by flux limited dissipative terms can lead to an effective nonoscillatory shock capturing method.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Large-scale computations in fluid mechanics; Jun 27, 1983 - Jul 08, 1983; La Jolla, CA
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  • 179
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    Numerical simulation in three space dimensions of time-dependent thermal convection in a rotating fluid (1985)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: Three-dimensional time-dependent convection in a plane layer of fluid, uniformly heated from below and subject to vertical shear and to rotation about an axis tilted from the vertical, was simulated by the numerical solution of the Boussinesq equations, including all Coriolis terms. Rotation about a vertical axis produces smaller convection cells with diminished heat fluxes and considerable vorticity. When the rotation axis is tilted from the vertical to represent tropical latitudes, the convection cells become elongated in a N-S direction. Imposed flows with constant vertical shear produce convective rolls aligned with the mean flow. When the rotation vector is tilted from the vertical, the competing effects due to rotation and shear can stabilize the convective motions.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Large-scale computations in fluid mechanics; Jun 27, 1983 - Jul 08, 1983; La Jolla, CA
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  • 180
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    Large-scale computations in fluid mechanics; Proceedings of the Fifteenth Summer Seminar on Applied Mathematics, University of California, La Jolla, CA, June 27-July 8, 1983. Parts 1 & 2 (1985)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: Papers are presented on such topics as the use of semi-Lagrangian advective schemes in meteorological modeling; computation with high-resolution upwind schemes for hyperbolic equations; dynamics of flame propagation in a turbulent field; a modified finite element method for solving the incompressible Navier-Stokes equations; computational fusion magnetohydrodynamics; and a nonoscillatory shock capturing scheme using flux-limited dissipation. Consideration is also given to the use of spectral techniques in numerical weather prediction; numerical methods for the incorporation of mountains in atmospheric models; techniques for the numerical simulation of large-scale eddies in geophysical fluid dynamics; high-resolution TVD schemes using flux limiters; upwind-difference methods for aerodynamic problems governed by the Euler equations; and an MHD model of the earth's magnetosphere.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Large-scale computations in fluid mechanics; Jun 27, 1983 - Jul 08, 1983; La Jolla, CA
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  • 181
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    Finite element methods for high speed flows (1985)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: An explicit finite element based solution procedure for solving the equations of compressible viscous high speed flow is presented. The method uses domain splitting to advance the solution with different timesteps on different portions of the mesh. For steady inviscid flows, adaptive mesh refinement procedures are successfully employed to enhance the definition of discontinuities. Preliminary ideas on the application of adaptive mesh refinement to the solution of problems involving steady viscous flow are presented. Sample timings are given for the performance of the finite element code on modern supercomputers.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: AIAA PAPER 85-1531 , Computational Fluid Dynamics Conference; Jul 15, 1985 - Jul 17, 1985; Cincinnati, OH
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  • 182
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    Development of a boundary-layer-type solver based on simultaneous iteration technique for axisymmetric separated flows (1985)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: A boundary-layer-type solver is developed for the numerical solution of axisymmetric separated flows. A new fully implicit coupling scheme for the viscous and inviscid regions is demonstrated. This fully implicit coupling technique is similar to the work of Carter, Veldman, and an extension of an earlier work of Halim and Hafez. A comparison is made for the convergence rate using this new fully implicit coupling technique and the semiimplicit coupling of Halim and Hafez. Numerical results using the fully implicit coupling are obtained for laminar incompressible separated flows, including a boattail and a series of trough geometries. Also, the near-wake flow problem is considered using the present formulation. A clear conclusion of this investigation is that the present scheme using the fully implicit coupling method converges at a faster rate than the semiimplicit coupling and the partially parabolized Navier-Stokes (PPNS) procedures.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: AIAA PAPER 85-1505 , Computational Fluid Dynamics Conference; Jul 15, 1985 - Jul 17, 1985; Cincinnati, OH
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  • 183
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    Upwind relaxation algorithms for the Navier Stokes equations (1985)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: The development of upwind relaxation algorithms for obtaining efficient steady-state solutions to the compressible Navier-Stokes equations is described. The method is second-order accurate spatially and naturally disipative, using third-order flux splitting of the pressure and convective terms and second-order central differencing for shear and heat flux terms. A line Gauss-Seidel relaxation approach, shown to be unconditionally stable for model convection and diffusion equations, is used. The algorithm is demonstrated for several flows using the thin-layer form of the equations, including the problem of shock-induced separation over a flat plate.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: AIAA PAPER 85-1501 , Computational Fluid Dynamics Conference; Jul 15, 1985 - Jul 17, 1985; Cincinnati, OH
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  • 184
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    An implicit time-marching method for studying unsteady flow with massive separation (1985)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: A fully implicit time-marching method is developed such that all spatial derivatives are approximated using central differences, but no use is made of any artificial dissipation. The numerical method solves the discretized equations using Alternating Direction Implicit-Block Gaussian Elimination technique. The method is implemented in the unsteady analysis, which solves the incompressible Navier-Stokes equations in terms of vorticity and stream function in generalized orthogonal coordinates. A clustered conformal C-grid is employed, and every effort is made to resolve the various length scales in the flow problem. The metric discontinuity at the branch-cut is treated appropriately using analytic continuation. Introduction of the BGE reordering permits implicit treatment of the branch cut in the numerical method. The vorticity singularity at the cusped trailing edge is also appropriately treated. This accurate and efficient implicit method is used to study flow at Re = 1000, past a 12-percent thick symmetric Joukowski airfoil at high angle of attack 30 and 53 deg.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: AIAA PAPER 85-1489 , Computational Fluid Dynamics Conference; Jul 15, 1985 - Jul 17, 1985; Cincinnati, OH
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  • 185
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    Conducting a thermal conductivity survey (1985)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: A physically transparent approximate theory of phonon decay rates is presented starting from a pair potential model of the interatomic forces in an insulator or semiconductor. The theory applies in the classical regime and relates the 3-phonon decay rate to the third derivative of the pair potential. Phonon dispersion relations do not need to be calculated, as sum rules relate all the needed quantities directly to the pair potential. The Brillouin zone averaged phonon lifetime turns out to involve a dimensionless measure of the anharmonicity multiplied by an effective density of states for 3-phonon decay. Results are given for rare gas and alkali halide crystals. For rare gases, the results are in good agreement with more elaborate perturbation calculations. Comparison to experimental data on phonon linewidths and thermal conductivity are made.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-CR-175792 , JPL-9950-1088 , NAS 1.26:175792
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  • 186
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    A study of Reynolds-stress closure model (1985)
    In:  CASI
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    Publication Date: 2019-07-13
    Description: A hybrid model of the Reynolds stress closure was developed. This model was tested for various sizes of step flow, and the computed Reynolds stress behavior was compared with experimental data. The third order closure model was reviewed. Transport equations for the triple velocity correlation were developed and implemented in a numerical code to evaluate the behavior of the triple velocity products in various regions of the flow field including recirculating, reattaching, and redeveloping flow domains.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-CR-174342 , NAS 1.26:174342
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  • 187
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    The influence of jet-grid turbulence on heat transfer from the stagnation region of a cylinder in crossflow (1985)
    In:  CASI
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    Publication Date: 2019-07-13
    Description: The effect of high-intensity turbulence on heat transfer from the stagnation region of a circular cylinder in crossflow was studied. The work was motivated by the desire to be able to more fully understand and predict the heat transfer to the leading edge of a turbine airfoil. In order to achieve high levels of turbulence with a reasonable degree of isotropy and homogeneity, a jet-injection turbulence grid was used. The jet grid provided turbulence intensities of 10 to 12 percent, measured at the test cylinder location, for downstream blowing with the blowing rate adjusted to an optimal value for flow uniformity. Heat transfer augmentation above the zeroturbulence case ranged from 37 to 53 percent for the test cylinder behind the jet grid for a cylinder Reynolds number range of 48,000 to 180,000, respectively. The level of heat transfer augmentation was found to be fairly uniform with respect to circumferential distance from the stagnation line. Stagnation point heat transfer results (expressed in terms of the Frossling number) were found to be somewhat low with respect to previous studies, when compared on the basis of equal values of the parameter Tu Re(1/2), indicating an additional Reynolds number effect as observed by previous investigators. Consequently, for a specified value of Tu Re(1/2), data obtained with a relatively high turbulence intensity will have a lower value of the Frossling number.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-TM-87011 , E-2555 , NAS 1.15:87011 , Natl. Heat Transfer Conf.,; Aug 04, 1985 - Aug 07, 1985; Denver, CO; United States
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  • 188
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    Reduction of crossflow shock-induced separation with a porous cavity at supersonic speeds (1988)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: The effectiveness of wing surface porosity in reducing boundary-layer separation induced by a cross flow shock on a conical wing in a supersonic flow was investigated in tests conducted in the NASA Langley Research Center Unitary Plan Wind Tunnel, at a Reynolds number of 2 mln/ft at Mach numbers 1.62, 1.70, 1.86, and 2.00 and with the angle of attack varying between -2 and 10 deg. A porous cavity was installed in a 57 deg swept conical wing at a location where a cross flow shock had been observed in previous tests. The porosity was varied from 11 to 22 percent, the pore hole diameter was varied from 0.025 to 0.050 in., and the cavity depth varied from 0.067 to 0.255 in. It was found that a hole of 0.025 in. in diameter is more effective than a 0.050-in. hole. However, the effectiveness of the larger holes could be increased by reducing the cavity depth, causing a closed-cavity type flow condition.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: AIAA PAPER 88-2567 , ; 8 p.|AIAA, Applied Aerodynamics Conference; Jun 06, 1988 - Jun 08, 1988; Williamsburg, VA; United States
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  • 189
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    Heat pipes for low-humidity applications (1989)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: A novel application of an air-to-air heat pipe heat exchanger (HPHX) in a cooling and dehumidification process of an air-conditioning system is described which provides significant energy savings in applications requiring reheat of cold supply air to maintain low humidity. The efficiency of the system has been demonstrated in an application requiring a humidity of 40 percent. The use of the HPHX and fine tuning of the air-conditioning system and controls has resulted in significant energy savings. The technology can be advantageously used in many low-humidity applications commonly encountered in high-tech and aerospace facilities.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Space Congress; Apr 25, 1989 - Apr 28, 1989; Cocoa Beach, FL; United States
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  • 190
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    Topology of three-dimensional, variable density flows (1989)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: This paper is concerned with the interpretation of unsteady, variable-density flow fields. The topology of the flow is determined by finding critical points and identifying the character of local solution trajectories. The time evolution of the flow is studied by following the paths of the critical points in the three-dimensional space of invariants of the local deformations tensor. The methodology can be applied to any smooth vector field and its associated gradient tensor including the vorticity and pressure gradient fields. This approach provides a framework for describing the geometry of complex flow patterns. Concisely summarizing that geometry in the space of invariants of the local gradient tensor may be a useful way of gaining insight into time-dependent processes described by large computational data bases. Applications to the descriptions of a flickering diffusion flame and a compressible wake are discussed.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Australasian Fluid Mechanics Conference; Dec 11, 1989 - Dec 15, 1989; Melbourne; Australia
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  • 191
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    Characterization of flow in a scroll duct (1985)
    In:  CASI
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    Publication Date: 2019-07-13
    Description: A quantitative, flow visualization study was made of a partially elliptic cross section, inward curving duct (scroll duct), with an axial outflow through a vaneless annular cutlet. The working fluid was water, with a Re(d) of 40,000 at the inlet to the scroll duct, this Reynolds number being representative of the conditions in an actual gas turbine scroll. Both still and high speed moving pictures of fluorescein dye injected into the flow and illuminated by an argon ion laser were used to document the flow. Strong secondary flow, similar to the secondary flow in a pipe bend, was found in the bottom half of the scroll within the first 180 degs of turning. The pressure field set up by the turning duct was strong enough to affect the inlet flow condition. At 90 degs downstream, the large scale secondary flow was found to be oscillatory in nature. The exit flow was nonuniform in the annular exit. By 270 degs downstream, the flow appeared unorganized with no distinctive secondary flow pattern. Large scale structures from the upstream core region appeared by 90 degs and continued through the duct to reenter at the inlet section.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-CR-188612 , NAS 1.26:188612
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  • 192
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    Discussion of turbulence modelling: Past and future (1989)
    In:  CASI
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    Publication Date: 2019-07-13
    Description: The full text of a paper presented at the Whither Turbulence Workshop (Cornell University, March 22-24, 1989) on past and future trends in turbulence modeling is provided. It is argued that Reynolds stress models are likely to remain the preferred approach for technological applications for at least the next few decades. In general agreement with the Launder position paper, it is further argued that among the variety of Reynolds stress models in use, second-order closures constitute by far the most promising approach. However, some needed improvements in the specification of the turbulent length scale are emphasized. The central points of the paper are illustrated by examples from homogeneous turbulence.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-CR-181884 , ICASE-89-58 , NAS 1.26:181884 , Whither Turbulence Workshop; Mar 22, 1989 - Mar 24, 1989; Ithaca, NY; United States
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  • 193
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    Experience with advanced instrumentation in a hot section cascade (1989)
    In:  CASI
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    Publication Date: 2019-07-13
    Description: The Lewis Research Center gas turbine Hot Section Test Facility was developed to provide a real engine environment with known boundary conditions for the aerothermal performance evaluation and verification of computer design codes. This verification process requires experimental measurements in a hostile environment. The research instruments used in this facility are presented, and their characteristics and how they perform in this environment are discussed. The research instrumentation consisted of conventional pressure and temperature sensors, as well as thin-film thermocouples and heat flux gages. The hot gas temperature was measured by an aspirated temperature probe and by a dual-element, fast-response temperature probe. The data acquisition mode was both steady state and time dependent. These experiments were conducted over a wide range of gas Reynolds numbers, exit gas Mach numbers, and heat flux levels. This facility was capable of testing at temperatures up to 1600 K, and at pressures up to 18 atm. These corresponded to an airfoil exit Reynolds number range of 0.5 x 10(6) to 2.5 x 10(6) based on the airfoil chord of 5.55 cm. The results characterize the performance capability and the durability of the instrumentation. The challenge of making measurements in hostile environments is also discussed. The instruments exhibited more than adequate durability to achieve the measurement profile. About 70 percent of the thin-film thermocouples and the dual-element temperature probe survived several hundred thermal cycles and more than 35 hr at gas temperatures up to 1600 K. Within the experimental uncertainty, the steady-state and transient heat flux measurements were comparable and consistent over the range of Reynolds numbers tested.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-TM-102294 , E-4962 , NAS 1.15:102294 , Winter Annual Meeting of the American Society of Mechanical Engineers; Dec 10, 1989 - Dec 15, 1989; San Francisco, CA; United States
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  • 194
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    Navier-Stokes analysis of cold scramjet-afterbody flows (1989)
    In:  CASI
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    Publication Date: 2019-07-13
    Description: The progress of two efforts in coding solutions of Navier-Stokes equations is summarized. The first effort concerns a 3-D space marching parabolized Navier-Stokes (PNS) code being modified to compute the supersonic mixing flow through an internal/external expansion nozzle with multicomponent gases. The 3-D PNS equations, coupled with a set of species continuity equations, are solved using an implicit finite difference scheme. The completed work is summarized and includes code modifications for four chemical species, computing the flow upstream of the upper cowl for a theoretical air mixture, developing an initial plane solution for the inner nozzle region, and computing the flow inside the nozzle for both a N2/O2 mixture and a Freon-12/Ar mixture, and plotting density-pressure contours for the inner nozzle region. The second effort concerns a full Navier-Stokes code. The species continuity equations account for the diffusion of multiple gases. This 3-D explicit afterbody code has the ability to use high order numerical integration schemes such as the 4th order MacCormack, and the Gottlieb-MacCormack schemes. Changes to the work are listed and include, but are not limited to: (1) internal/external flow capability; (2) new treatments of the cowl wall boundary conditions and relaxed computations around the cowl region and cowl tip; (3) the entering of the thermodynamic and transport properties of Freon-12, Ar, O, and N; (4) modification to the Baldwin-Lomax turbulence model to account for turbulent eddies generated by cowl walls inside and external to the nozzle; and (5) adopting a relaxation formula to account for the turbulence in the mixing shear layer.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-CR-184949 , NAS 1.26:184949
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  • 195
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    Studying Turbulence Using Numerical Simulation Databases, 2. Proceedings of the 1988 Summer Program (1988)
    In:  CASI
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    Publication Date: 2019-07-13
    Description: The focus of the program was on the use of direct numerical simulations of turbulent flow for study of turbulence physics and modeling. A special interest was placed on turbulent mixing layers. The required data for these investigations were generated from four newly developed codes for simulation of time and spatially developing incompressible and compressible mixing layers. Also of interest were the structure of wall bounded turbulent and transitional flows, evaluation of diagnostic techniques for detection of organized motions, energy transfer in isotropic turbulence, optical propagation through turbulent media, and detailed analysis of the interaction of vortical structures.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-CR-184905 , NAS 1.26:184905 , SU-CTR-S88 , Jun 27, 1988 - Jul 22, 1988; Stanford, CA; United States
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  • 196
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    Some characteristics of bypass transition in a heated boundary layer (1989)
    In:  CASI
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    Publication Date: 2019-07-13
    Description: Experimental measurements of both mean and conditionally sampled characteristics of laminar, transitional and low Reynolds number turbulent boundary layers on a heated flat plate are presented. Measurements were obtained in air over a range of freestream turbulence intensities from 0.3 percent to 6 percent with a freestream velocity of 30.5 m/s and zero pressure gradient. Conditional sampling performed in the transitional boundary layers indicate the existence of a near-wall drop in intermittency, especially pronounced at low intermittencies. Nonturbulent intervals were observed to possess large levels of low-frequency unsteadiness, and turbulent intervals had peak intensities as much as 50 percent higher than were measured at fully turbulent stations. Heat transfer results were consistent with results of previous researchers and Reynolds analogy factors were found to be well predicted by laminar and turbulent correlations which accounted for unheated starting length. A small dependence of the turbulent Reynolds analogy factors on freestream turbulence level was observed. Laminar boundary layer spectra indicated selective amplification of unstable frequencies. These instabilities appear to play a dominant role in the transition process only for the lowest freestream turbulence level studied, however.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-TM-102126 , E-4912 , NAS 1.15:102126 , Symposium on Turbulent Shear Flows; Aug 21, 1989 - Aug 23, 1989; Stanford, CA; United States
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  • 197
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    Two-dimensional numerical simulation of a Stirling engine heat exchanger (1989)
    In:  CASI
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    Publication Date: 2019-07-13
    Description: The first phase of an effort to develop multidimensional models of Stirling engine components is described; the ultimate goal is to model an entire engine working space. More specifically, parallel plate and tubular heat exchanger models with emphasis on the central part of the channel (i.e., ignoring hydrodynamic and thermal end effects) are described. The model assumes: laminar, incompressible flow with constant thermophysical properties. In addition, a constant axial temperature gradient is imposed. The governing equations, describing the model, were solved using Crank-Nicloson finite-difference scheme. Model predictions were compared with analytical solutions for oscillating/reversing flow and heat transfer in order to check numerical accuracy. Excellent agreement was obtained for the model predictions with analytical solutions available for both flow in circular tubes and between parallel plates. Also the heat transfer computational results are in good agreement with the heat transfer analytical results for parallel plates.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-TM-102057 , E-4815 , NAS 1.15:102057 , Intersociety Energy Conversion Engineering Conference; Aug 06, 1989 - Aug 11, 1989; Washington, DC; United States
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  • 198
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    Advanced computational techniques for hypersonic propulsion (1989)
    In:  CASI
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    Publication Date: 2019-07-13
    Description: Computational Fluid Dynamics (CFD) has played a major role in the resurgence of hypersonic flight, on the premise that numerical methods will allow performance of simulations at conditions for which no ground test capability exists. Validation of CFD methods is being established using the experimental data base available, which is below Mach 8. It is important, however, to realize the limitations involved in the extrapolation process as well as the deficiencies that exist in numerical methods at the present time. Current features of CFD codes are examined for application to propulsion system components. The shortcomings in simulation and modeling are identified and discussed.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-TM-102005 , E-4711 , NAS 1.15:102005 , International Symposium on Air Breathing Engines; Sep 04, 1989 - Sep 09, 1989; Athens; Greece
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  • 199
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    Gas density effect on dropsize of simulated fuel sprays (1989)
    In:  CASI
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    Publication Date: 2019-07-13
    Description: Two-phase flow in pneumatic two-fluid fuel nozzles was investigated experimentally to determine the effect of atomizing-gas density and gas mass-flux on liquid-jet breakup in sonic-velocity gas-flow. Dropsize data were obtained for the following atomizing-gases: nitrogen; argon; carbon dioxide; and helium. They were selected to cover a gas molecular-weight range of 4 to 44. Atomizing-gas mass-flux ranged from 6 to 50 g/sq cm-sec and four differently sized two-fluid fuel nozzles were used having orifice diameters that varied from 0.32 to 0.56 cm. The ratio of liquid-jet diameter to SMD, D sub o/D sub 32, was correlated with aerodynamic and liquid-surface forces based on the product of the Weber and Reynolds number, We*Re, and gas-to-liquid density ratio, rho sub g/rho sub l. To correlate spray dropsize with breakup forces produced by using different atomizing-gases, a new molecular-scale dimensionless group was derived. The derived dimensionless group was used to obtain an expression for the ratio of liquid-jet diameter to SMD, D sub o/D sub 32. The mathematical expression of this phenomenon incorporates the product of the Weber and Reynolds number, liquid viscosity, surface tension, acoustic gas velocity, the RMS velocity of gas molecules, the acceleration of gas molecules due to gravity, and gas viscosity. The mathematical expression encompassing these parameters agrees well with the atomization theory for liquid-jet breakup in high velocity gas flow. Also, it was found that at the same gas mass-flux, helium was considerably more effective than nitrogen in producing small droplet sprays with SMD's in the order of 5 micrometers.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-TM-102013 , E-4725 , NAS 1.15:102013 , Joint Propulsion Conference; Jul 10, 1989 - Jul 12, 1989; Monterey, CA; United States
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  • 200
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    Computational fluid dynamics and aerothermodynamics (1989)
    In:  CASI
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    Publication Date: 2019-07-13
    Description: The primary objective was the development of nonequilibrium radiation and chemistry models suitable for engineering applications associated with the flow fields about aeroassisted orbital transfer vehicles (AOTVs), the aero-assisted flight experiment vehicle (AFE), and other vehicles operating at superorbital velocities and very high attitudes.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-CR-180079 , NAS 1.26:180079 , TAMRF-5671-89-01
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