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  • FLUID MECHANICS AND HEAT TRANSFER
  • 1985-1989  (391)
  • 1985  (391)
  • 1
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    Hypersonic aerothermodynamics status report (1985)
    In:  Other Sources
    Details
    Publication Date: 2019-08-28
    Description: This survey paper gives an overview of NASA's Aerothermodynamics program. The purpose is to present the elements of, example results from, and projected technology needs for hypersonic fluid and thermal physics. The NASA program is focused on improving the fundamental understanding of aerodynamic and aerothermodynamic flow phenomena over hypersonic vehicles operating in the continuum, transitional, and free molecule flow regime. Vehicle design capabilities, computational fluid dynamics, computational chemistry, turbulence modeling, aerothermal loading, Shuttle Orbiter flight data analysis, and aerothermal facilities are discussed.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
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  • 2
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    Propagation of detonations in hydrazine vapor (1985)
    In:  CASI
    Details
    Publication Date: 2019-08-28
    Description: In the range of greater hydrazine vapor pressure, detonation speed depends exclusively on the extent of the ammonia decomposition in the second reaction stage. As vapor pressure decreases, the ammonia disintegration speed becomes increasingly slower and the reaction reached in the reaction zone increasingly decreases until finally, in the vapor pressure range between 53 and 16 Torr, the contribution of the second stage to detonation propagation disappears, and only the first stage remains active. Since the disintegration speed of the hydrazine in this pressure range has decreased markedly as well, no level, but rather only spinning, detonations occur. Temporary separations of the impact front and the reaction zone in the process lead to fluctuations of the detonation speed.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-TM-77922 , NAS 1.15:77922
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  • 3
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    Heat transfer in pipes (1985)
    In:  CASI
    Details
    Publication Date: 2019-08-28
    Description: The heat transfer from hot water to a cold copper pipe in laminar and turbulent flow condition is determined. The mean flow through velocity in the pipe, relative test length and initial temperature in the vessel were varied extensively during tests. Measurements confirm Nusselt's theory for large test lengths in laminar range. A new equation is derived for heat transfer for large starting lengths which agrees satisfactorily with measurements for large starting lengths. Test results are compared with the new Prandtl equation for heat transfer and correlated well. Test material for 200- and to 400-diameter test length is represented at four different vessel temperatures.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-TM-77838 , NAS 1.15:77838
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  • 4
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    Generation and development of small-amplitude disturbances in a laminar boundary layer in the presence of an acoustic field (1985)
    In:  CASI
    Details
    Publication Date: 2019-08-28
    Description: A low-turbulence subsonic wind tunnel was used to study the influence of acoustic disturbances on the development of small sinusoidal oscillations (Tollmien-Schlichting waves) which constitute the initial phase of turbulent transition. It is found that acoustic waves propagating opposite to the flow generate vibrations of the model (plate) in the flow. Neither the plate vibrations nor the acoustic field itself have any appreciable influence on the stability of the laminar boundary layer. The influence of an acoustic field on laminar boundary layer disturbances is limited to the generation of Tollmien-Schlichting waves at the leading-edge of the plate.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-TM-77826 , NAS 1.15:77826
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  • 5
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    Numerical simulation of vortex breakdown (1985)
    In:  CASI
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    Publication Date: 2019-08-27
    Description: The breakdown of an isolated axisymmetric vortex embedded in an unbounded uniform flow is examined by numerical integration of the complete Navier-Stokes equations for unsteady axisymmetric flow. Results show that if the vortex strength is small, the solution approaches a steady flow and the vortex is stable. If the strength is large enough, the solution remains unsteady and a recirculating zone will appear near the axis, its form and internal structure resembling those of the axisymmetric breakdown bubbles with multi-cells observed by Faler and Leibovich (1978). For apppropriate combinations of flow parameters, the flow reveals quasi-periodicity. Parallel calculations with the quasi-cylindrical approximation indicate that so far as predicting of breakdown is concerned, its results coincide quite well with the results mentioned above. Both show that the vortex breakdown has little concern with the Reynolds number or with the critical classification of the upstream flow, at least for the lower range of Reynolds numbers.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-TM-77951 , NAS 1.15:77951
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  • 6
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    A device for generating motive force through the expansion of a non-elastic dense fluid (1985)
    In:  CASI
    Details
    Publication Date: 2019-08-27
    Description: A device for generating motive force through the expansion of a dense, nonelastic fluid is described. It consists of an exterior block of a material with a low expansion coefficient, the interior of which is equipped with two circular cavities, both of which are equipped with rotors having blades constantly stressed outward by springs, so that they make contact with the cavity walls. One cavity is heated externally, and both have an exterior wall made of a friction ring which keeps the volume constant when their length varies. These cavities are interconnected by ducts which, at the inlet, are a prolongation of a peripheral groove made in the friction ring. The excess fluid produced by expansion flows through the groove, subsequently entering the cavity again after passing through a cooler located in the exterior part of the block. Both rotors are connected to gears with appropriate ratios which are equipped with a blocking device to guarantee that they always rotate in the same direction.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-TM-77664 , NAS 1.15:77664
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  • 7
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    Characteristics of heat exchange in the region of injection into a supersonic high-temperature flow (1985)
    In:  CASI
    Details
    Publication Date: 2019-08-27
    Description: An experimental investigation of the local heat transfer coefficient distribution during gas injection into the supersonic-flow portion of a Laval nozzle is discussed. The controlling dimensionless parameters of the investigated process are presented in terms of a generalized relation for the maximum value of the heat transfer coefficient in the nozzle cross section behind the injection hole. Data on the heat transfer coefficient variation along the nozzle length as a function of gas injection rate are also presented, along with the heat transfer coefficient distribution over a cross section of the nozzle.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-TM-77833 , NAS 1.15:77833
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  • 8
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    Contribution to the theory of stationary separation areas (1985)
    In:  CASI
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    Publication Date: 2019-08-27
    Description: An attempt is made to determine the region of existence of possible steady flows with a closed separation area in a range of Reynolds numbers such that flow in the viscous mixing area can be described by the Prandtl's equations. The boundary conditions for the flow in the separation region are selected so as to simplify the flow pattern in this region, making it possible to use the methods of hydrodynamic analysis. A rule for determining stable steady flows with separation areas is formulated which is well suited for analyzing laminar flows and can be applied to turbulent flows in some areas.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-TM-77825 , NAS 1.15:77825
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  • 9
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    Stability of an oscillating boundary layer (1985)
    In:  CASI
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    Publication Date: 2019-08-27
    Description: Levchenko and Solov'ev (1972, 1974) have developed a stability theory for space periodic flows, assuming that the Floquet theory is applicable to partial differential equations. In the present paper, this approach is extended to unsteady periodic flows. A complete unsteady formulation of the stability problem is obtained, and the stability characteristics over an oscillating period are determined from the solution of the problem. Calculations carried out for an oscillating incompressible boundary layer on a plate showed that the boundary layer flow may be regarded as a locally parallel flow.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-TM-77827 , NAS 1.15:77827
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  • 10
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    A New Finite Element Approach for Prediction of Aerothermal Loads: Progress in Inviscid Flow Computations (1985)
    In:  CASI
    Details
    Publication Date: 2019-08-14
    Description: Recent progress in the development of finite element methodology for the prediction of aerothermal loads is described. Two dimensional, inviscid computations are presented, but emphasis is placed on development of an approach extendable to three dimensional viscous flows. Research progress is described for: (1) utilization of a commerically available program to construct flow solution domains and display computational results, (2) development of an explicit Taylor-Galerkin solution algorithm, (3) closed form evaluation of finite element matrices, (4) vector computer programming strategies, and (5) validation of solutions. Two test problems of interest to NASA Langley aerothermal research are studied. Comparisons of finite element solutions for Mach 6 flow with other solution methods and experimental data validate fundamental capabilities of the approach for analyzing high speed inviscid compressible flows.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-TM-86434 , NAS 1.15:86434 , AIAA PAPER 85-1533-CP
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  • 11
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    The volume change during solidification (1985)
    In:  CASI
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    Publication Date: 2019-08-13
    Description: The liquid-solid phase transformation of solidifying metallic melts is accompanied by a volume change Delta-Vm. This volume change produces a gravity-independent microscopic flow near the solidification front. In a ground-based laboratory, solidification processes are also affected by convection due to temperature and concentration gradients. A quantitative evaluation of the effects of these flows on the formation of structure requires reproducible values of Delta-Vm. Alloys with Delta-Vm = 0 would be best suited for such an evaluation, while alloys with a constant value for Delta-Vm are still usable. Another requirement is related to a solidus-liquidus interval which is as small as possible. One-phase alloys, which would be particularly well suited, could not be found. For these reasons, alloys which solidify in two phases, as for example eutectics, have been considered, taking into account the Al-Ge system. Attention is given to the volume change at the melting point, the measurement of this change, the volume change at solidification, and applications to terrestrial technology.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-TM-77817 , NAS 1.15:77817 , Spacelab Utilization: Mater. Res. and Technol. in Space; Seminar on Current Status; Oct 04, 1982 - Oct 06, 1982; Bonn; Germany
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  • 12
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    Surface-slip equations for multicomponent, nonequilibrium air flow (1985)
    In:  CASI
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    Publication Date: 2019-07-20
    Description: Equations are presented for the surface slip (or jump) values of species concentration, pressure, velocity, and temperature in the low-Reynolds-number, high-altitude flight regime of a space vehicle. These are obtained from closed-form solutions of the mass, momentum, and energy flux equations using the Chapman-Enskog velocity distribution function. This function represents a solution of the Boltzmann equation in the Navier-Stokes approximation. The analysis, obtained for nonequilibrium multicomponent air flow, includes the finite-rate surface catalytic recombination and changes in the internal energy during reflection from the surface. Expressions for the various slip quantities have been obtained in a form which can readily be employed in flow-field computations. A consistent set of equations is provided for multicomponent, binary, and single species mixtures. Expression is also provided for the finite-rate species-concentration boundary condition for a multicomponent mixture in absence of slip.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-CR-181252 , NAS 1.26:181252
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  • 13
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    Experimental studies on Taylor-Goertler vortices (1985)
    In:  CASI
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    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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  • 14
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    Nonlinear acoustic wave propagation in atmosphere. Absorbing boundary conditions for exterior problems (1985)
    In:  CASI
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    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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  • 15
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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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  • 16
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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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  • 17
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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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  • 18
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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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  • 19
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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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  • 20
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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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  • 21
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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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  • 22
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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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  • 23
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    Recent applications of spectral methods in fluid dynamics (1985)
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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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  • 24
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    Application of TVD schemes for the Euler equations of gas dynamics (1985)
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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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  • 25
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    A nonoscillatory shock capturing scheme using flux limited dissipation (1985)
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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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  • 26
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    Numerical simulation in three space dimensions of time-dependent thermal convection in a rotating fluid (1985)
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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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  • 27
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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)
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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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  • 28
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    Finite element methods for high speed flows (1985)
    In:  Other Sources
    Details
    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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    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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  • 30
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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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    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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  • 32
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    Conducting a thermal conductivity survey (1985)
    In:  CASI
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    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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    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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    The influence of jet-grid turbulence on heat transfer from the stagnation region of a cylinder in crossflow (1985)
    In:  CASI
    Details
    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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  • 35
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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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  • 36
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    Measurements in liquid fuel sprays (1985)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: A ground test facility is being established at NASA Lewis Research Center to simulate the environmental and flight conditions needed to study adverse weather effects. One of the most important components is the water spray system which consists of many nozzles fitted on spray bars. Water is injected through air-assisted atomizers to generate uniform size drops to simulate icing in clouds. The primary objective is to provide experimental data on drop size distribution over a wide range of operating conditions. Correlation equations for mean drop size and initial injection parameters are being determined to assist in the design and modification of the Altitude Wind Tunnel. Special emphasis is being placed on the study of the aerodynamic structure of the air-assisted atomizer sprays. Detailed measurements of the variation of drop size distribution and velocity as a function of time and space are being made. Accurate initial and boundary conditions are being provided for computer model evaluation.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-CR-177088 , NAS 1.26:177088
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  • 37
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    Vortex boundary-layer interactions (1985)
    In:  CASI
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    Publication Date: 2019-07-13
    Description: The interaction of a turbulent boundary layer on a flat plate with a strong artificially generated longitudinal vortex which may or may not actually enter the boundary layer is studied. The vortices are generated by a delta wing suspended ahead of the test plate, so that the configuration is approximately that of a close coupled carnard with zero main-wing sweep and an invisible body. All necessary configuration and parametric checks are completed, and data acquisition and analysis on the first configuration chosen for detailed study, in which the vortex starts to merge with the boundary layer a short distance downstream of the leading edge of the test plate, are nearly complete.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-CR-176192 , NAS 1.26:176192
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  • 38
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    A theoretical study of non-adiabatic surface effects for a model in the NTF cryogenic wind tunnel (1985)
    In:  CASI
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    Publication Date: 2019-07-13
    Description: A theoretical analysis was made of the severity and effect of nonadiabatic surface conditions for a model in the NTF cryogenic wind tunnel. The nonadiabatic condition arises from heaters that are used to maintain a constant thermal environment for instrumentation internal to the model. The analysis was made for several axi-symmetric representations of a fuselage cavity, using a finite element heat conduction code. Potential flow and boundary layer codes were used to calculate the convection condition for the exterior surface of the model. The results of the steady state analysis show that it is possible to maintain the surface temperature very near the adiabatic value, with the judicious use of insulating material. Even for the most severe nonadiabatic condition studied, the effects on skin friction drag and displacement thickness were only marginally significant. The thermal analysis also provided an estimate of the power required to maintain a specified cavity temperature.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-CR-3924 , NAS 1.26:3924 , TR-83-4975-02
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  • 39
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    Vapor-liquid phase separator studies (1985)
    In:  CASI
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    Publication Date: 2019-07-13
    Description: A study of porous plug use for vapor-liquid phase seperation in spaceborne cryogenic systems was conducted. The three main topics addressed were: (1) the usefulness of porous media in designs that call for variable areas and flow rates; (2) the possibility of prediction of main parameters of porous plugs for a given material; and (3) prediction of all parameters of the plug, including secondary parameters.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-CR-166545 , T-6624 , NAS 1.26:166545
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  • 40
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    Application of computational fluid dynamics to complex inlet ducts (1985)
    In:  CASI
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    Publication Date: 2019-07-13
    Description: A three-dimensional parabolic Navier-Stokes code, PEPSIG, was used to analyze the flow in the subsonic diffuser section of a typical modern inlet design. The effect of curvature of the diffuser centerline and transitioning cross sections was studied to determine the primary cause of flow distortion in the duct. Total pressure values at the engine compressor face are reported.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-TM-87060 , E-2629 , NAS 1.15:87060 , AIAA PAPER 85-1213 , Joint Propulsion Conf.; Jul 08, 1985 - Jul 10, 1985; Monterey, CA; United States
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  • 41
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    Fast approach for calculating film thicknesses and pressures in elastohydrodynamically lubricated contacts at high loads (1985)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The film thicknesses and pressures in elastohydrodynamically lubricated contacts have been calculated for a line contact by using an improved version of Okamura's approach. The new approach allows for lubricant compressibility, the use of Roelands' viscosity, a general mesh (nonconstant step), and accurate calculations of the elastic deformation. The new approach is described, and the effects on film thickness, pressure, and pressure spike of each of the improvements are discussed. Successful runs have been obtained at high pressure (to 4.8 GPa) with low CPU times.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-TM-87032 , E-2581 , NAS 1.15:87032 , Joint Lubrication Conf.,; Oct 08, 1985 - Oct 10, 1985; Atlanta, GA; United States
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  • 42
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    A three-dimensional turbulent separated flow and related mesurements (1985)
    In:  CASI
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    Publication Date: 2019-07-13
    Description: The applicability of and the limits on the applicability of 11 near wall similarity laws characterizing three-dimensional turbulent boundary layer flows were determined. A direct force sensing local wall shear stress meter was used in both pressure-driven and shear-driven three-dimensional turbulent boundary layers, together with extensive mean velocity field and wall pressure field data. This resulted in a relatively large number of graphical comparisons of the predictive ability of 10 of these 11 similarity models relative to measured data over a wide range of flow conditions. Documentation of a complex, separated three-dimensional turbulent flow as a standard test case for evaluating the predictive ability of numerical codes solving such flows is presented.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-CR-175913 , NAS 1.26:175913
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  • 43
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    Analysis of physical-chemical processes governing SSME internal fluid flows (1985)
    In:  CASI
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    Publication Date: 2019-07-13
    Description: The basic issues concerning the physical chemical processes of the Space Shuttle Main Engine are discussed. The objectives being to supply the general purpose CFD code PHOENICS and the associated interactive graphics package - GRAFFIC; to demonstrate code usage on SSME related problems; to perform computations and analyses of problems relevant to current and future SSME's; and to participate in the development of new physical models of various processes present in SSME components. These objectives are discussed in detail.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-CR-175893 , NAS 1.26:175893 , CHAM-4045/22
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  • 44
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    Modeling of transient heat pipe operation (1985)
    In:  CASI
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    Publication Date: 2019-07-13
    Description: The overall goal is to gain a better understanding of the transient behavior of heat pipes operating under both normal and adverse conditions. Normal operation refers to cases where the capillary structure remains fully wetted. Adverse operation occurs when drying, re-wetting, choking, noncontinuum flow, freezing, thawing etc., occur within the heat pipe. The work was redirected towards developing the capability to predict operational behavior of liquid metal heat pipes used for cooling aerodynamic structures. Of particular interest is the startup of such heat pipes from an initially frozen state such as might occur during re-entry of a space vehicle into the Earth's atmosphere or during flight of hypersonic aircraft.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-CR-175496 , NAS 1.26:175496
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  • 45
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    Analysis of experimental shaft seal data for high-performance turbomachines, as for Space Shuttle main engines (1985)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: High-pressure, high-temperature seal flow (leakage) data for nonrotating and rotating Raleigh-step and convergent-tapered-bore seals were characterized in terms of a normalized flow coefficient. The data for normalized Rayleigh-steip and nonrotating tapered-bore seals were in reasonable agreement with theory, but data for the rotating tapered-bore seals were not. The tapered-bore-seal operational clearances estimated from the flow data were significantly larger than calculated. Although clearances are influenced by wear from conical to cylindrical geometry and errors in clearance corrections, the problem was isolated to the shaft temperature - rotational speed clearance correction. The geometric changes support the use of some conical convergence in any seal. Under these conditions rotation reduced the normalized flow coefficiently by nearly 10 percent.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-TM-86928 , E-2430 , NAS 1.15:86928 , Symp. on Transport Phenomena in Rotating Machinery; Apr 28, 1985 - May 03, 1985; Honolulu, HI; United States
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  • 46
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    A three-dimensional spectral algorithm for simulations of transition and turbulence (1985)
    In:  CASI
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    Publication Date: 2019-07-13
    Description: A spectral algorithm for simulating three dimensional, incompressible, parallel shear flows is described. It applies to the channel, to the parallel boundary layer, and to other shear flows with one wall bounded and two periodic directions. Representative applications to the channel and to the heated boundary layer are presented.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-CR-172561 , ICASE-85-19 , NAS 1.26:172561 , AIAA Aerospace Sci. Meeting; Jan 14, 1985 - Jan 17, 1985; Reno, NV; United States
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  • 47
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    Surface-slip equations for multicomponent nonequilibrium air flow (1985)
    In:  CASI
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    Publication Date: 2019-07-13
    Description: Equations are presented for the surface-slip (or jump) values of species concentration, pressure, velocity, and temperature in the low-Reynolds number, high-altitude flight regime of a space vehicle. The equations are obtained from closed form solutions of the mass, momentum, and energy flux equations using the Chapman-Enskog velocity distribution function. This function represents a solution of the Boltzmann equation in the Navier-Stokes approximation. The analysis, obtained for nonequilibrium multicomponent air flow, includes the finite-rate surface catalytic recombination and changes in the internal energy during reflection from the surface. Expressions for the various slip quantities were obtained in a form which can be employed in flowfield computations. A consistent set of equations is provided for multicomponent, binary, and single species mixtures. Expression is also provided for the finite-rate, species-concentration boundary condition for a multicomponent mixture in absence of slip.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-TM-85820 , NAS 1.15:85820 , AIAA PAPER 84-1732 , AIAA Thermophys. Conf.; Jun 25, 1984 - Jun 28, 1984; Snowmass, CO; United States
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  • 48
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    Liquid fuel spray processes in high-pressure gas flow (1985)
    In:  CASI
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    Publication Date: 2019-07-13
    Description: Atomization of single liquid jets injected downstream in high pressure and high velocity airflow was investigated to determine the effect of airstream pressure on mean drop size as measured with a scanning radiometer. For aerodynamic - wave breakup of liquid jets, the ratio of orifice diameter D sub o to measured mean drop diameter D sub m which is assumed equal to D sub 32 or Sauter mean diameter, was correlated with the product of the Weber and Reynolds numbers WeRe and the dimensionless group G1/square root of c, where G is the gravitational acceleration, 1 the mean free molecular path, and square root of C the root mean square velocity, as follows; D sub o/D sub 32 = 1.2 (WeRe) to the 0.4 (G1/square root of c) to the 0.15 for values of WeRe 1 million and an airstream pressure range of 0.10 to 2.10 MPa.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-TM-86944 , E-2463 , NAS 1.15:86944 , Intern. Conf. on Liquid Atomization and Spray Systems; Jul 08, 1985 - Jul 10, 1985; London
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    Flow visualization study of the effect of injection hole geometry on an inclined jet in crossflow (1985)
    In:  CASI
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    Publication Date: 2019-07-13
    Description: A flow visualization was studied by using neutrally buoyant, helium-filled soap bubbles, to determine the effect of injection hole geometry on the trajectory of an air jet in a crossflow and to investigate the mechanisms involved in jet deflection. Experimental variables were the blowing rate, and the injection hole geometry cusp facing upstream (CUS), cusp facing downstream (CDS), round, swirl passage, and oblong. It is indicated that jet deflection is governed by both the pressure drag forces and the entrainment of free-stream fluid into the jet flow. For injection hole geometries with similar cross-sectional areas and similar mass flow rates, the jet configuration with the larger aspect ratio experienced a greater deflection. Entrainment arises from lateral shearing forces on the sides of the jet, which set up a dual vortex motion within the jet and thereby cause some of the main-stream fluid momentum to be swept into the jet flow. This additional momentum forces the jet nearer the surface. Of the jet configurations, the oblong, CDS, and CUS configutations exhibited the largest deflections. The results correlate well with film cooling effectiveness data, which suggests a need to determine the jet exit configuration of optimum aspect ratio to provide maximum film cooling effectiveness.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-TM-86936 , E-2450 , NAS 1.15:86936 , Symp. on Transport Phenomena in Rotating Machinery,; Apr 28, 1985 - May 03, 1985; Honolulu, HI; United States
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  • 50
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    Ribbon burner simulation of T-700 turbine shroud for ceramic lined seals research (1985)
    In:  CASI
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    Publication Date: 2019-07-13
    Description: Experimental and analytical studies were conducted to determine the acceptability of a ribbon-burner simulation of engine conditions for testing ceramic-lined turbine tip shrouds. The calculated values reveal that the ribbon burner establishes at least as harsh a thermal environment as is present at any time within the turbine shroud. Comparisons were made with ceramic components in a turboshaft engine.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-TM-86940 , E-2458 , NAS 1.15:86940 , Ann. Conf. on Composites and Advan. Ceram. Mater.; Jan 20, 1985 - Jan 24, 1985; Cocoa Beach, FL; United States
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    Heat transfer results and operational characteristics of the NASA Lewis Research Center Hot Section Cascade Test Facility (1985)
    In:  CASI
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    Publication Date: 2019-07-13
    Description: The NASA Lewis Research Center gas turbine hot section test facility has been developed to provide a real-engine environment with well known boundary conditions for the aerothermal performance evaluation/verification of computer design codes. The initial aerothermal research data obtained are presented and the operational characteristics of the facility are discussed. This facility is capable of testing at temperatures and pressures up to 1600 K and 18 atm which corresponds to a vane exit Reynolds number range of 0.5x10(6) to 2.5x10(6) based on vane chord. The component cooling air temperature can be independently modulated between 330 and 700 K providing gas-to-coolant temperature ratios similar to current engine application. Research instrumentation of the test components provide conventional pressure and temperature measurements as well as metal temperatures measured by IR-photography. The primary data acquisition mode is steady state through a 704 channel multiplexer/digitizer. The test facility was configured as an annular cascade of full coverage filmcooled vanes for the initial series of research tests.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-TM-86890 , E-2357 , NAS 1.15:86890 , Intern. Gas Turbine Conf. and Exhibit; Mar 17, 1985 - Mar 21, 1985; Houston, TX; United States
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  • 52
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    Piezoviscous effects in nonconformal contacts lubricated hydrodynamically (1985)
    In:  CASI
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    Publication Date: 2019-07-13
    Description: The analysis is concerned with the piezoviscous-rigid regime of lubrication for the general case of elliptical contacts. In this regime several formulas of the lubricant film thickness have been proposed by Hamrock and Dowson, by Dowson et al., and more recently by Houpert. However, either they do not include the load parameter W, which has a strong effect on film thickness, or they overestimate the film thickness by using the Barus formula for pressure-viscosity characteristics. The Roelands formula was used for the pressure-viscosity relationship. The effects of the dimensionless load, speed, and materials parameters, the radius ratio, and the lubricant entrainment direction were investigated. The dimensionless load parameter was varied over a range of one order of magnitude. The dimensionless speed parameter was varied by 5.6 times the lowest value. Conditions corresponding to the use of solid materials of steel, bronze, and silicon nitride and lubricants of paraffinic and naphthenic mineral oil were considered in obtaining the exponent in the dimensionless materials parameter. The radius ratio was varied from 0.2 to 64 (a configuration approaching a line contact). Forty-one cases were used in obtaining a minimum film thickness formula. Contour plots indicate in detail the pressure developed between the contacting solids.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-TM-87141 , E-2767 , NAS 1.15:87141 , USAAVSCOM-TR-86-C-1 , Annual Meeting of the American Society of Lubrication Engineers; May 05, 1985 - May 09, 1985; Las Vegas, NV; United States
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  • 53
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    Two-fluid models of turbulence (1985)
    In:  CASI
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    Publication Date: 2019-07-13
    Description: The defects of turbulence models are summarized and the importance of so-called nongradient diffusion in turbulent fluxes is discussed. The mathematical theory of the flow of two interpenetrating continua is reviewed, and the mathematical formulation of the two fluid model is outlined. Results from plane wake, axisymmetric jet, and combustion studies are shown.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-CR-176419 , NAS 1.26:176419 , CFD/85/4 , NASA Langley Workshop on Theoretical Approaches to Turbulence; Oct 10, 1984 - Oct 12, 1984; Hampton, VA; United States
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    Study of journal bearing dynamics using 3-dimensional motion picture graphics (1985)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Computer generated motion pictures of three dimensional graphics are being used to analyze journal bearings under dynamically loaded conditions. The motion pictures simultaneously present the motion of the journal and the pressures predicted within the fluid film of the bearing as they evolve in time. The correct prediction of these fluid film pressures can be complicated by the development of cavitation within the fluid. The numerical model that is used predicts the formation of the cavitation bubble and its growth, downstream movement, and subsequent collapse. A complete physical picture is created in the motion picture as the journal traverses through the entire dynamic cycle.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-TM-87205 , E-2862 , NAS 1.15:87205 , USAAVSCOM-TR-86-C-3 , ASEE Engineering Design Graphics Division Midyear Meeting; Nov 24, 1985 - Nov 26, 1985; West Lafayette, IN; United States
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    Experimental study of ceramic coated tip seals for turbojet engines (1985)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Ceramic gas-path seals were fabricated and successfully operated over 1000 cycles from flight idle to maximum power in a small turboshaft engine. The seals were fabricated by plasma spraying zirconia over a NiCoCrAlX bond boat on the Haynes 25 substrate. Coolant-side substrate temperatures and related engine parameters were recorded. Post-test inspection revealed mudflat surface cracking with penetration to the ceramic bond-coat interface.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-TM-86939 , E-2457 , NAS 1.15:86939 , USAAVSCOM-TM-84-C-2 , Ann. Conf. on Composites and Advan. Ceram. Mater.; Jan 20, 1985 - Jan 24, 1985; Cocoa Beach, FL; United States
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  • 56
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    Flow through very porous inclined screens (1985)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The steady, inviscid flow through and around a screen inclined at a uniform angle to the incoming flow was investigated. For a screen placed in an infinite flow field, an asymptotic analysis for small resistance coefficients was performed, and the effects of inclination were determined. The velocity at first order in the asymptotic expansion was nonuniform along the screen. This nonuniformity caused the wake behind the screen to contain distributed vorticity at second order. These effects therefore occurred at one order lower than for normal screens.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-TM-86979 , E-2517 , NAS 1.15:86979 , Fluid Dyn. and Plasmadyn. and Lasers Conf.,; Jul 16, 1985 - Jul 18, 1985; Cincinnati, OH; United States
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  • 57
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    Computations and turbulent flow modeling in support of helicopter rotor technology (1985)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The angle of attack (AOA) tandem cavity wind tunnel experiment was prepared. Actual wind tunnel testing started shortly after the beginning of 1985. A multi-probe aerodynamic rake was designed and installed for use in surveying the shear layers present over the open cavity on the Kuiper Airborne Observatory (KAO). The nature of the behavior of the thermal environment within the KAO cavity at operational altitudes was determined. Assistance was given in the design of the cavity for the University of Denver radiometer. Attempts to distinguish between the optical terms of blur circle size (or image size) and the term due to jitter were discussed.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-CR-177095 , NAS 1.26:177095
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    Advanced radiator concepts (1985)
    In:  CASI
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    Publication Date: 2019-07-13
    Description: The liquid droplet radiator and the liquid belt radiator currently under study by the NASA LeRC are discussed. These advanced concepts offer benefits in reduced mass, compact stowage, and ease of deployment. Operation and components of the radiators are described, heat transfer characteristics are discussed, and critical technologies are identified. The impact of the radiators on large power systems is also assessed.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-TM-87008 , E-2552 , NAS 1.15:87008 , Soc. of Women Engr. Natl. Convention; Jun 27, 1985 - Jun 30, 1985; Minneapolis, MN; United States
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    Nested subcritical flows within supercritical systems (1985)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: In supercritical systems the design inlet and outlet pressures are maintained above the thermaodynamic critical pressure P sub C. Designers rely on this simple rule of thumb to circumvent problems associated with a subcritical pressure regime nested within the supercritical pressure system along with the uncertainties in heat transfer, fluid mechanics, and thermophysical property variations. The simple rule of thumb is adequate in many low-power designs but is inadequate for high-performance turbomachines and linear systems, where nested two-phase regions can exist. Examples for a free-jet expansion with backpressure greater than P sub C and a rotor (bearing) with ambient pressure greater than P sub C illustrate the existence of subcritical pressure regimes nested within supercritical systems.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-TM-86980 , E-2518 , NAS 1.15:86980 , Ann. Cavitation and Multiphase Flow Forum; Jun 24, 1985 - Jun 26, 1985; Albuquerque, NM; United States
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  • 60
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    Computational analysis of scramjet dual mode operation (1985)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: One critical element in the design of a Scramjet is the detailed understanding of the complex flow field in the engine during various phases of operation. One area of interest is the computation of chemically reacting flows in the vicinity of flame holders. The characteristics of a method for solving the Navier-Stokes equations with chemical reactions are proposed. Also of interest are the flame holding characteristics of simple ramp and rearward facing steps. Both of these configurations are considered candidates for Scramjet flame holders.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-CR-174250 , NAS 1.26:174250
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    Viscous dissipation effects on thermophoretically augmented aerosol particle transport across laminar boundary layers (1985)
    In:  Other Sources
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    Publication Date: 2019-07-12
    Description: The effect of viscous dissipation on mass transport across nonisothermal low-mass-loading laminar boundary layers of dusty gas is investigated theoretically by means of numerical simulations. The derivation of the model is outlined, and numerical results are presented in extensive graphs and characterized in detail. The dissipation effects are found to be significant, increasing total particle-deposition rates; the intensity of the effects depends on the ratio of wall temperature to mainstream static temperature.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: International Journal of Heat and Fluid Flow (ISSN 0142-727X); 6; 293-297
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  • 62
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    Finite-amplitude steady waves in plane viscous shear flows (1985)
    In:  Other Sources
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    Publication Date: 2019-07-12
    Description: Computations of two-dimensional solutions of the Navier-Stokes equations are carried out for finite-amplitude waves on steady unidirectional flow. Several cases are considered. The numerical method employs pseudospectral techniques in the streamwise direction and finite differences on a stretched grid in the transverse direction, with matching to asymptotic solutions when unbounded. Earlier results for Poiseuille flow in a channel are re-obtained, except that attention is drawn to the dependence of the minimum Reynolds number on the physical constraint of constant flux or constant pressure gradient. Attempts to calculate waves in Couette flow by continuation in the velocity of a channel wall fail. The asymptotic suction boundary layer is shown to possess finite-amplitude waves at Reynolds numbers orders of magnitude less than the critical Reynolds number for linear instability. Waves in the Blasius boundary layer and unsteady Rayleigh profile are calculated by employing the artifice of adding a body force to cancel the spatial or temporal growth. The results are verified by comparison with perturbation analysis in the vicinity of the linear-instability critical Reynolds numbers.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: AD-A165461 , Journal of Fluid Mechanics (ISSN 0022-1120); 160; 281-295
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    High Marangoni number convection in a square cavity (1985)
    In:  Other Sources
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    Publication Date: 2019-07-12
    Description: Steady thermocapillary flows in a square cavity are computed using a finite difference procedure. Accurate numerical solutions are obtained for as high a Reynolds number as possible, in order to characterize the nature of strongly convective flows of this general class. Only the case of capillary number going to zero is considered, so that the free surface is assumed flat at the leading order. Surface deflections are computed by domain perturbation. Boundary layer formation at different values of the Prandtl number is observed at large values of the Marangoni number and Re. The numerical results are used to infer the relevant scalings of a consistent boundary layer picture of the flow, valid asymptotically as Re goes to infinity.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Physics of Fluids (ISSN 0031-9171); 28; 3467-347
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  • 64
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    Local heat-transfer measurements on a large scale-model turbine blade airfoil using a composite of a heater element and liquid crystals (1985)
    In:  Other Sources
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    Publication Date: 2019-07-12
    Description: Local heat transfer coefficients were experimentally mapped along the midchord of a five-time-size turbine blade airfoil in a static cascade operated at room temperature over a range of Reynolds numbers. The test surface consisted of a composite of commercially available materials: a mylar sheet with a layer of cholesteric liquid crystals, that change color with temperature, and a heater sheet made of a carbon-impregnated paper, that produces uniform heat flux. After the initial selection and calibration of the composite sheet, accurate, quantitative, and continuous heat transfer coefficients were mapped over the airfoil surface. The local heat transfer coefficients are presented for Reynolds numbers from 2.8 x 10 to the 5th power to 7.6 x 10 to the 5th power. Comparisons are made with analytical values of heat transfer coefficients obtained from the STANS boundary layer code. Also, a leading edge separation bubble was revealed by thermal and flow visualization.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: ASME PAPER 85-GT-59 , ASME, Transactions, Journal of Engineering for Gas Turbines and Power (ISSN 0022-0825); 107; 953-960
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    Structure of nonevaporating sprays. II - Drop and turbulence properties (1985)
    In:  Other Sources
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    Publication Date: 2019-07-12
    Description: This is the second part of a study reporting structure measurements in the dilute portion of axisymmetric nonevaporating sprays. Measurements are compared with predictions of three typical methods for analyzing sprays: (1) locally homogeneous flow (LHF) analysis, where slip between the phases is neglected; (2) deterministic separated flow (DSF) analysis, where slip is considered but effects of drop interactions with turbulence are ignored; and (3) stochastic separated flow (SSF) analysis, where both slip and effects of drop interactions with turbulence are considered. This part of the study reports measurements of mean and fluctuating drop velocities, the variation of Sauter mean diameter, and gas-phase turbulence properties in the dilute portion of the sprays. Best agreement between predictions and measurements was obtained with the SSF analysis. For present measurements in the dilute region (void fraction greater than 99.1 percent), effects of drops on gas-phase turbulence properties (turbulence modulation) were small. However, as the dense spray regions near the injector were approached, the measurements indicated modification of turbulence properties by drop motion.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: AIAA Journal (ISSN 0001-1452); 23; 1724-173
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    Observations of complex oscillations in a closed thermosyphon (1985)
    In:  Other Sources
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    Publication Date: 2019-07-12
    Description: Observations have been made of thermal oscillations in a slightly inclined closed thermosyphon. The thermosyphon is made up of two isothermal tubes, capped at the outer ends, and joined along their axes by an insulating section. The tube assembly is filled with liquid and inclined slightly with respect to the vertical. The lower isothermal section is hotter than the upper one and convection is driven across the insulating region. Between the applied temperature difference at which simple steady convection occurs, and that required for persistent turbulent motions, there is a wide range over which thermal oscillations are observed. These oscillations reflect quasi-periodic flows as well as a type of periodic chaos.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: ASME, Transactions, Journal of Heat Transfer (ISSN 0022-1481); 107; 833-839
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    A spectral collocation method for the Navier-Stokes equations (1985)
    In:  Other Sources
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    Publication Date: 2019-07-12
    Description: A Fourier-Chebyshev spectral method for the incompressible Navier-Stokes equations is described. It is applicable to a variety of problems including some with fluid properties which vary strongly both in the normal direction and in time. In this fully spectral algorithm, a preconditioned iterative technique is used for solving the implicit equations arising from semi-implicit treatment of pressure, mean advection and vertical diffusion terms. The algorithm is tested by applying it to hydrodynamic stability problems in channel flow and in external boundary layers with both constant and variable viscosity.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Journal of Computational Physics (ISSN 0021-9991); 61; 64-88
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  • 68
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    Tone excited jets. III - Flow measurements (1985)
    In:  Other Sources
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    Publication Date: 2019-07-12
    Description: This paper describes the effects of upstream excitation on the flow characteristics of tone-excited jet under static as well as simulated forward velocity conditions. The data presented include axial and radial distributions of mean velocities and turbulence intensities as functions of excitation conditions. Results for both unheated and heated jets are presented. The measured distributions of pressures associated with the large-scale turbulence are also presented for some test conditions.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Journal of Sound and Vibration (ISSN 0022-460X); 102; 71-91
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    An experimental study of organized motions in the turbulent plane mixing layer (1985)
    In:  Other Sources
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    Publication Date: 2019-07-12
    Description: Recent investigations suggest that turbulent shear flows are generally characterized by large-scale coherent structures. Little is currently known regarding the detailed characteristics and dynamical roles of these structures. The present study has been motivated by a number of questions which arise in connection with such structures, taking into account the education procedure, the topological characteristics, and the mechanics of the large-scale structures in a high-Reynolds-number plane mixing layer, originating from an initially fully turbulent boundary layer. Attention is given to the experimental apparatus, the initial conditions, the education scheme, and the coherent-structure properties.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Journal of Fluid Mechanics (ISSN 0022-1120); 159; 85-104
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  • 70
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    Correlations and droplet growth (1985)
    In:  Other Sources
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    Publication Date: 2019-07-12
    Description: Consideration is given to the time development of a system in which small spheres of a stable phase grow out of a supersaturated melt. The spheres then grow and shrink in a manner similar to Ostwald ripening. The growth process of pairs of particles in an effective background accounts for can be used to explain the long time correlations which develop in the system. The correlations broaden the distribution of particles sizes, even for relatively dilute systems.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Physical Review Letters (ISSN 0031-9007); 55; 2953-295
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  • 71
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    Incipient singularities in the Navier-Stokes equations (1985)
    In:  Other Sources
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    Publication Date: 2019-07-12
    Description: Infinite pointwise stretching in a finite time for general initial conditions is found in a simulation of the Biot-Savart equation for a slender vortex tube in three dimensions. Viscosity is ineffective in limiting the divergence in the vorticity as long as it remains concentrated in tubes. Stability has not been shown.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Physical Review Letters (ISSN 0031-9007); 55; 1749-175
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  • 72
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    Algorithmic and theoretical results on computation of incompressible viscous flows by finite element methods (1985)
    In:  Other Sources
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    Publication Date: 2019-07-12
    Description: Primitive variable as well as streamfunction-vorticity and pure streamfunction formulations are discussed. For the primitive variable case alternative choices of the viscous stress term are shown to produce natural boundary conditions which are well suited for matching to various far field conditions. For the other cases recent analytical results, including error estimates are described, and an optical algorithm for pressure recovery as well as treatment for multiply connected domains are given.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Computers and Fluids (ISSN 0045-7930); 13; 3 19
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  • 73
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    The Stokes force on a droplet in an unbounded fluid medium due to capillary effects (1985)
    In:  Other Sources
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    Publication Date: 2019-07-12
    Description: The Stokes force on a fluid droplet is obtained when the droplet is placed in an unbounded fluid medium and motion ensues due to an arbitrary interfacial-tension gradient on the droplet surface. The force, derived here for a spherical droplet, is proportional to the integral of the interfacial-tension gradient over the droplet surface. When the interfacial-tension gradients are caused by temperature or concentration variations, the result for the force may be further specialized when convective transport effects are negligible. In this case, it is possible to express the force in terms of the gradient of the undisturbed temperature (or concentration) field evaluated at the location of the droplet center in a form analogous to Faxen's force law.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Journal of Fluid Mechanics (ISSN 0022-1120); 153; 389-400
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  • 74
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    Flow and atomization in flashing injectors (1985)
    In:  Other Sources
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    Publication Date: 2019-07-12
    Description: Flashing injection involves expanding a fluid through an injector until a supersaturated state is reached, causing a portion of the fluid to flash to a vapor. This investigation considered the flow, atomization and spreading properties of flashing injectors with flowing liquids containing dissolved gases (Jet A/air) as well as superheated liquids (Freon-11). The use of a two-stage expansion process, separated by an expansion chamber, was found to be beneficial for good atomization properties of flashing injection - particularly for dissolved gas systems. Both locally homogeneous and separated flow models provided good predictions of injector flow properties. Conventional correlations for drop sizes from pressure and airblast injectors were successfully modified, using the separated flow model to prescribe injector exit conditions, and to correlate drop size measurements. Additional experimental results are provided for spray angles of sprays from flashing injectors.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Atomisation and Spray Technology (ISSN 0266-3481); 1; 53-76
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  • 75
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    Three-dimensional convection in horizontal cylinders - Numerical solutions and comparison with experimental and analytical results (1985)
    In:  Other Sources
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    Publication Date: 2019-07-12
    Description: The results of a three-dimensional numerical simulation of Boussinesq free convection in a horizontal differentially heated cylinder are presented. The computation was based on a Samarskii-Andreyev scheme (described by Leong, 1981) and a false-transient advancement in time, with vorticity, velocity, and temperature as dependent variables. Solutions for velocity and temperature distributions were obtained for Rayleigh numbers (based on the radius) Ra = 74-18,700, thus covering the core- and boundary-layer-driven regimes. Numerical solutions are compared with asymptotic analytical solutions and experimental data. The numerical results well represent the complex three-dimensional flows found experimentally.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Numerical Heat Transfer (ISSN 0149-5720); 8; 5 19; 613-631
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    Heat transfer and fluid mechanics measurements in transitional boundary layer flows (1985)
    In:  Other Sources
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    Publication Date: 2019-07-12
    Description: Experimental results are presented to document hydrodynamic and thermal development of flat-plate boundary layers undergoing natural transition. Local heat transfer coefficients, skin friction coefficients and profiles of velocity, temperature and Reynolds normal and shear stresses are presented. A case with no transition and transitional cases with 0.68 percent and 2.0 percent free-stream disturbance intensities were investigated. The locations of transition are consistent with earlier data. A late-laminar state with significant levels of turbulence is documented. In late-transitional and early-turbulent flows, turbulent Prandtl number and conduction layer thickness values exceed, and the Reynolds analogy factor is less than, values previously measured in fully turbulent flows.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: ASME PAPER 85-GT-113 , ASME, Transactions, Journal of Engineering for Gas Turbines and Power (ISSN 0022-0825); 107; 1007-101
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  • 77
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    Review of some vortex relations (1985)
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    Publication Date: 2019-07-12
    Description: The evaluation of the circulation from numerical solutions of the momentum and energy equations is discussed for incompressible and compressible flows. It is shown how artificial damping directly influences the time rate of change of the circulation.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Computers and Fluids (ISSN 0045-7930); 13; 4 19; 513-515
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    Effect of rotation on isotropic turbulence - Computation and modelling (1985)
    In:  Other Sources
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    Publication Date: 2019-07-12
    Description: This paper uses numerical simulation to analyse the effects of uniform rotation on homogeneous turbulence. Both large-eddy and full simulations were made. The results indicate that the predominant effect of rotation is to decrease the rate of dissipation of the turbulence and increase the lengthscales, especially those along the axis of rotation. These effects are a consequence of the reduction, due to the generation of inertial waves, of the net energy transfer from large eddies to small ones. Experiments are also influenced by a more complicated interaction between the rotation and the wakes of the turbulence-generating grid which modifies the nominal initial conditions in the experiment. The latter effect is accounted for in simulations by modifying the initial conditions. Finally, a two-equation model is proposed that accounts for the effects of rotation and is able to reproduce the experimental decay of the turbulent kinetic energy.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Journal of Fluid Mechanics (ISSN 0022-1120); 154; 321-336
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    The effect of contraction on a homogeneous turbulent shear flow (1985)
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    Publication Date: 2019-07-12
    Description: In the present study, a homogeneous flow was generated and allowed to reach its asymptotic state. A two-dimensional contraction was inserted a short distance downstream. Both mean velocity and turbulence-stress profiles (normal and shear) were measured at several points along the flow direction. The pressure-strain terms were evaluated from the energy balance made along the wind-tunnel axis. On the basis of the obtained results, it is concluded that a uniformly sheared turbulent flow with approximate transverse homogeneity remains in its condition at all stages of its development through a two-dimensional contraction. Small deviations from homogeneity observed upstream of contraction become much less visible towards the end of contraction. The mean-flow development can be predicted adequately by the Bernoulli equation.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Journal of Fluid Mechanics (ISSN 0022-1120); 154; 187-213
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  • 80
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    Solution algorithms for nonlinear transient heat conduction analysis employing element-by-element iterative strategies (1985)
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    Publication Date: 2019-07-12
    Description: The particular problems investigated in the present study arise from nonlinear transient heat conduction. One of two types of nonlinearities considered is related to a material temperature dependence which is frequently needed to accurately model behavior over the range of temperature of engineering interest. The second nonlinearity is introduced by radiation boundary conditions. The finite element equations arising from the solution of nonlinear transient heat conduction problems are formulated. The finite element matrix equations are temporally discretized, and a nonlinear iterative solution algorithm is proposed. Algorithms for solving the linear problem are discussed, taking into account the form of the matrix equations, Gaussian elimination, cost, and iterative techniques. Attention is also given to approximate factorization, implementational aspects, and numerical results.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Computer Methods in Applied Mechanics and Engineering (ISSN 0045-7825); 52; 711-815
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    An adaptive finite element procedure for compressible high speed flows (1985)
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    Publication Date: 2019-07-12
    Description: A practical finite element-based solution procedure for high-speed inviscid compressible flow problems is described. The method provides time-accurate solutions to the coompressible Euler equations, and is computationally more efficient than the one-step Taylor-Galerkin approach and better suited for implementation on the modern generation of vector computers. The method is coupled to an adaptive mesh refinement process that enables steady state solutions of improved quality to be obtained.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Computer Methods in Applied Mechanics and Engineering (ISSN 0045-7825); 51; 441-465
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    Numerical schemes for a model for nonlinear dispersive waves (1985)
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    Publication Date: 2019-07-12
    Description: A description is given of a number of numerical schemes to solve an evolution equation (Korteweg-deVries) that arises when modelling the propagation of water waves in a channel. The discussion also includes the results of numerical experiments made with each of the schemes. It is suggested, on the basis of these experiments, that one of the schemes may have (discrete) solitary-wave solutions.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Journal of Computational Physics (ISSN 0021-9991); 60; 167-186
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    A model of flow in a closed-loop thermosyphon including the Soret effect (1985)
    In:  Other Sources
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    Publication Date: 2019-07-12
    Description: This theoretical study addresses the nature of convective motions in a toroidal loop of binary fluid oriented in the vertical plane and heated from below. The boundaries of the loop are impermeable, but gradients of the solute can be set up by Soret diffusion in the direction around the loop. The existence and stability of steady solutions are discussed over the Rayleigh number-Soret coefficient parameter plane. When the Soret coefficient is negative, periodic and chaotic oscillations analogous to those of thermohaline convection are predicted. When the Soret coefficient is positive, relaxation oscillations and low Rayleigh number chaotic motions are found. Both sets of phenomena are predicted to occur for realistic thermosyphon parameters.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: ASME, Transactions, Journal of Heat Transfer (ISSN 0022-1481); 107; 840-849
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  • 84
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    A multilevel-multigrid technique for recirculating flows (1985)
    In:  Other Sources
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    Publication Date: 2019-07-12
    Description: A solution algorithm has been developed for the prediction of recirculating flows. Brandt's multilevel acceleration technique is used with Leonard's QUICK differencing scheme and a modified pressure implicit operator splitting scheme. Intermediate calculations enable a tau error distribution to be used for the identification of regions for local grid refinement, i.e., multigrid. The algorithm was tested for the prediction of laminar flow in a shear-driven and a buoyancy-driven cavity.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Numerical Heat Transfer (ISSN 0149-5720); 8; 5 19
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  • 85
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    Oscillatory thermocapillary flows (1985)
    In:  Other Sources
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    Publication Date: 2019-07-12
    Description: Experimental and theoretical research conducted to understand the physical mechanism of oscillatory thermocapillary convection is discussed. A physical model that plausibly describes the cause of thermocapillary flow oscillations and to yield the proper parameters for identifying their onset is considered. Strong convection indicated by a large Marangoni number, as well as free surface deformation, appear to be important factors for the onset of the convection.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: PCH/PhysicoChemical Hydrodynamics (ISSN 0191-9059); 6; 5-6
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  • 86
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    Simplex finite element analysis of viscous incompressible flow with penalty function formulation (1985)
    In:  Other Sources
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    Publication Date: 2019-07-12
    Description: Viscous flow calculations are important for the determination of separated flows, recirculating flows, secondary flows and so on. This paper presents a penalty function approach for the finite element analysis of steady incompressible viscous flow. A simplex element is used with linear velocity and constant pressure in contrast to other works which usually employ higher order elements. Simplex elements yield analytical expressions for the element matrices which in turn lead to efficient solutions. Earlier works have partially indicated how constraint and lock-up problems might be avoided for simplex elements. This paper extends the earlier works by indicating the approach in detail and verifying that it is successful for several applications not discussed in the literature so far. Solution times and accuracy considerations are discussed for Couette flow, plane Poiseuille flow, a driven cavity problem, and laminar and turbulent flow over a step.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Finite Elements in Analysis and Design (ISSN 0168-874X); 1; 71-88
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  • 87
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    Numerical study of Reynolds stress in compressible flows (1985)
    In:  Other Sources
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    Publication Date: 2019-07-12
    Description: A second order closure has been implemented in an implicit Navier-Stokes solver to study the behavior of the Reynolds stresses under the influence of severe pressure gradients. In the boundary layer zone, the strongly sheared character of the mean flow dominates the turbulence generation mechanisms. However, the pressure gradients also play a very important role for these processes, but at different locations within the boundary layer.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: PCH/PhysicoChemical Hydrodynamics (ISSN 0191-9059); 6; 5-6
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  • 88
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    Instability of capillary jets with thermocapillarity (1985)
    In:  Other Sources
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    Publication Date: 2019-07-12
    Description: Long axisymmetric liquid zones are subject to axial temperature gradients which induce steady viscous flows driven by thermocapillarity. The approximately parallel flow in a cylindrical zone is examined for linearized instabilities. Capillary, surface-wave and thermal modes are found. Capillary breakup can be retarded or even suppressed for small Prandtl number and large Biot number B, which measures heat transfer from the liquid to the surrounding atmosphere. In the limiting case B approaches infinity the zone becomes an isothermal jet subject to axial 'wind stress' on its interface. It is then possible to suppress capillary breakup entirely so that one can maintain long coherent jets.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Journal of Fluid Mechanics (ISSN 0022-1120); 161; 1-25
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  • 89
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    Thermal fields in the Bridgman-Stockbarger technique (1985)
    In:  Other Sources
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    Publication Date: 2019-07-12
    Description: Temperature measurements were made throughout a naphthalene melt and solid in a simulated Bridgman-Stockbarger apparatus. Heating and cooling were provided by agitated baths separated by a polymer diaphragm. While agitation was sufficient to give uniform temperatures in the baths, the level of agitation in the heater strongly influenced the results. Unlike theoretical results for high thermal conductivity materials, natural convection in the melt had a strong influence on interface position and on the temperature distribution. Isotherms were relatively flat in the solid and both curved and erratic in the melt. The interface became more convex as it was moved higher into the heating bath by raising either the heating bath or cooling bath temperatures. Using a one-dimensional model, the Biot number in the cooler was determined to be 0.03, that for the solid in the heater 0.008, and for the molten region in the heater 0.3. Biot numbers for two or three dimensional models would be significantly different.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Journal of Crystal Growth (ISSN 0022-0248); 73; 350-358
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  • 90
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    Thermophoretically enhanced mass transport rates to solid and transpiration-cooled walls across turbulent (law-of-the-wall) boundary layers (1985)
    In:  Other Sources
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    Publication Date: 2019-07-12
    Description: Convective-diffusion mass transfer rate predictions are made for both solid wall and transpiration-cooled 'law-of-the-wall' nonisothermal turbulent boundary layers (TBLs), including the mechanism of thermophoresis, i.e., small particle mass transport 'down a temperature gradient'. The present calculations are confined to low mass-loading situations but span the entire particle size range from vapor molecules to particles near the onset of inertial ('eddy') impaction. It is shown that, when Sc is much greater than 1, thermophoresis greatly increases particle deposition rates to internally cooled solid walls, but only partially offsets the appreciable reduction in deposition rates associated with dust-free gas-transpiration-cooled surfaces. Thus, efficient particle sampling from hot dusty gases can be carried out using transpiration 'shielded' probe surfaces.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: I & EC - Industrial and Engineering Chemistry, Fundamentals (ISSN 0196-4313); 24; 208-214
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  • 91
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    Flux limiters (1985)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: It is well known that first order accurate difference schemes for the numerical solution of conservation laws produce results which suffer from excessive numerical diffusion, classical second order schemes, although giving better resolution, suffer from spurious oscillations. Recently much effect has been put into achieving high resolution without these oscillations, using a variety of techniques. Here one class of such methods, that of flux limiting, is outlined together with the TVD constraint used to ensure oscillation free solutions. Brief numerical comparisons of different limiting functions are also presented.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
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  • 92
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    Numerical solution of the unsteady Navier-Stokes equation (1985)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The construction and the analysis of nonoscillatory shock capturing methods for the approximation of hyperbolic conservation laws are discussed. These schemes share many desirable properties with total variation diminishing schemes, but TVD schemes have at most first-order accuracy, in the sense of truncation error, at extrema of the solution. In this paper a uniformly second-order approximation is constructed, which is nonoscillatory in the sense that the number of extrema of the discrete solution is not increasing in time. This is achieved via a nonoscillatory piecewise linear reconstruction of the solution from its cell averages, time evolution through an approximate solution of the resulting initial value problem, and averaging of this approximate solution over each cell.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-CR-181173 , NAS 1.26:181173
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    Advanced radiator concepts utilizing honeycomb panel heat pipes (stainless steel) (1985)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The feasibility of fabricating and processing moderate temperature range heat pipes in a low mass honeycomb sandwich panel configuration for highly efficient radiator fins for the NASA 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 thicknesses, wick type and manufacturability, liquid and vapor communication among honeycomb cells, and liquid flow return from condenser to evaporator facesheet areas. In addition, the overall performance of the honeycomb panel heat pipe was evaluated analytically.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-CR-171977 , NAS 1.26:171977 , W-30746
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    Algorithms for the Euler and Navier-Stokes equations for supercomputers (1985)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: The steady state Euler and Navier-Stokes equations are considered for both compressible and incompressible flow. Methods are found for accelerating the convergence to a steady state. This acceleration is based on preconditioning the system so that it is no longer time consistent. In order that the acceleration technique be scheme-independent, this preconditioning is done at the differential equation level. Applications are presented for very slow flows and also for the incompressible equations.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
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  • 95
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    Pattern formation by particles settling in viscous flows (1985)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: Results are reported of several simulations of the motions of small objects in two-dimensional cellular flows performed to study the evolution of the distributions of particle flows over time in processes such as sedimentation. Stream functions are defined in the form of a Hamiltonian system for the particle motions, with inertial and particle acceleration being neglected. Conditions are found for which the particles will become trapped in an oscillatory motion or the particle orbits attain an oscillary motion. Various simulation images are provided to illustrate the usefulness of the technique for modeling fractal swarms.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
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  • 96
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    Surface temperature distribution along a thin liquid layer due to thermocapillary convection (1985)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: The surface temperature distributions due to thermocapillary convections in a thin liquid layer with heat fluxes imposed on the free surface were investigated. The nondimensional analysis predicts that, when convection is important, the characteristics length scale in the flow direction L, and the characteristic temperature difference delta T sub o can be represented by L and delta T sub o approx. (A2Ma)/1/4 delta T sub R, respectively, where L sub R and delta sub R are the reference scales used in the conduction dominant situations with A denoting the aspect ratio and Ma the Marangoni number. Having L and delta sub o defined, the global surface temperature gradient delta sub o/L, the global thermocapillary driving force, and other interesting features can be determined. Numerical calculations involving a Gaussian heat flux distribution are presented to justify these two relations.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: IAF PAPER 85-282
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  • 97
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    Near field pressure fluctuations of a circular jet (1985)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: The relationship between the evolution of vortices in a circular jet and the generation of fluctuating pressure was studied, using an apparatus consisting of a jet nozzle connected to a stagnation chamber with a fifth-order polynomial contraction. The data were digitized and computer-processed. The constant pressure contours near the jet shoow that the evolution of coherent structures is the source of pressure perturbations. The data obtained in the vicinity of the jet indicate that two length scales govern the decay of the fluctuating pressure. A thin hydrodynamic near-field extends about 1 instability wavelength from the jet edge, and pressure decays exponentially. A thick acoustic near-field takes about ten acoustic wavelengths to reach the far field. The pressure disturbances decay algebraically in this region.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
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  • 98
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    The non-Newtonian heat and mass transport of He 2 in porous media used for vapor-liquid phase separation (1985)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: This investigation of vapor-liquid phase separation (VLPS) of He 2 is related to long-term storage of cryogenic liquid. The VLPS system utilizes porous plugs in order to generate thermomechanical (thermo-osmotic) force which in turn prevents liquid from flowing out of the cryo-vessel (e.g., Infrared Astronomical Satellite). An apparatus was built and VLPS data were collected for a 2 and a 10 micrometer sintered stainless steel plug and a 5 to 15 micrometer sintered bronze plug. The VLPS data obtained at high temperature were in the nonlinear turbulent regime. At low temperature, the Stokes regime was approached. A turbulent flow model was developed, which provides a phenomenological description of the VLPS data. According to the model, most of the phase separation data are in the turbulent regime. The model is based on concepts of the Gorter-Mellink transport involving the mutual friction known from the zero net mass flow (ZNMF) studies. The latter had to be modified to obtain agreement with the present experimental VLPS evidence. In contrast to the well-known ZNMF mode, the VLPS results require a geometry dependent constant (Gorter-Mellink constant). A theoretical interpretation of the phenomenological equation for the VLPS data obtained, is based on modelling of the dynamics of quantized vortices proposed by Vinen. In extending Vinen's model to the VLPS transport of He 2 in porous media, a correlation between the K*(GM) and K(p) was obtained which permits an interpretation of the present findings. As K(p) is crucial, various methods were introduced to measure the permeability of the porous media at low temperatures. Good agreement was found between the room temperature and the low temperature K(p)-value of the plugs.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-CR-177075 , NAS 1.26:177075
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    Adapting a Navier-Stokes code to the ICL-DAP (1985)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The results of an experiment are reported, i.c., to adapt a Navier-Stokes code, originally developed on a serial computer, to concurrent processing on the CL Distributed Array Processor (DAP). The algorithm used in solving the Navier-Stokes equations is briefly described. The architecture of the DAP and DAP FORTRAN are also described. The modifications of the algorithm so as to fit the DAP are given and discussed. Finally, performance results are given and conclusions are drawn.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-CR-178034 , ICASE-85-61 , NAS 1.26:178034
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    Active control of compressible flows on a curved surface (1985)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The effect of localized, time periodic surface heating and cooling over a curved surface is studied. This is a mechanism for the active control of unstable disturbances by phase cancellation and reinforcement. It is shown that the pressure gradient induced by the curvature significantly enhances the effectiveness of this form of active control. In particular, by appropriate choice of phase, active surface heating can completely stabilize and unstable wave.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-CR-178018 , ICASE-85-52 , NAS 1.26:178018
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