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  • FLUID MECHANICS AND HEAT TRANSFER  (2,457)
  • 1985-1989  (2,457)
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  • 1
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    Characteristic features of the operation of high-temperature heat pipes with a noncondesable gas (1987)
    In:  CASI
    Details
    Publication Date: 2019-08-28
    Description: The principal concepts related to the nature of the processes occurring in high-temperature heat pipes with a noncondensable gas are examined, and guidelines for the development of such heat pipes are presented. The discussion is illustrated by experimental results obtained for a horizontal sodium heat pipe (diameter, 18/1 mm; length, 710 mm). In particular, attention is given to the starting dynamics and mechanisms, the shape of the vapor-gas front, and the vapor-gas front velocity.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-TT-20015 , NAS 1.77:20015
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  • 2
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    Analysis method for the production of Reynolds stresses in compressible turbulent flow (fluid mechanics) (1988)
    In:  CASI
    Details
    Publication Date: 2019-08-28
    Description: A geometrical interpretation of the grouping and variation rate terms of Reynolds stresses in compressible turbulent flow is presented. Examples of applications of the method are also given.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-TT-20330 , NAS 1.77:20330
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  • 3
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    Studies on pressure response of gas bubbles contributions of condensed droplets in bubbles generated by a uniform nucleation (1988)
    In:  CASI
    Details
    Publication Date: 2019-08-28
    Description: The response of a tiny gas bubble under reduced pressure is investigated in its relation to cavitation. Equations of motion are formulated for gas mixtures inside the bubble and numerical calculations performed for several examples. The conclusions are as follows: (1) at the onset of bubble growth, the gas mixture inside it adiabatically expands and the temperature decreases. Condensed droplets appear inside the gas mixture due to a uniform nucleation and the temperature recovers, thus the motion of the bubble is apparently isothermal; (2) the evaporation and condensation coefficient largely affects bubble motions (maximum radius, period and rate of attenuation of the bubble oscillation) including the uniform contraction; (3) the oscillation period of the bubble is longer as the equilibrium bubble radius is larger when the surrounding pressure decreases stepwise. In this circumstance the temperature inside the bubble is kept constant due to condensation evaporation phenomena and is nearly isothermal; and (4) when the surrounding pressure decreases in a stepwise fashion, the critical pressure bubble radius relation becomes closer to that for the isothermal process if the bubble radius is larger than 8 microns.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-TT-20343 , NAS 1.77:20343
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  • 4
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    Heat transfer during the boiling of liquids in heat pipe wicks (1987)
    In:  CASI
    Details
    Publication Date: 2019-08-28
    Description: Data in the literature on heat transfer in the case of nucleate boiling of various liquids in the wicks of heat pipes are reviewed. It is shown that none of the known analytical relationships can be used to generalize, with sufficient accuracy, the experimental data found in the literature. It is further shown that the exponent of the specific heat flux in the heat transfer law changes as a function of the liquid and wick properties. A relationship is obtained which generalizes experimental data for heat transfer agents of moderate temperatures (water, acetone, ethanol, and R-11 and R-113 coolants) and ammonia.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-TT-20108 , NAS 1.77:20108
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  • 5
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    Transitional Boundary Layers Under the Influence of High Free Stream Turbulence, Intensive Wall Cooling and High Pressure Gradients in Hot Gas Circulation (1987)
    In:  CASI
    Details
    Publication Date: 2019-08-28
    Description: The requirements for fundamental experimental studies of the influence of free stream turbulence, pressure gradients and wall cooling are discussed. Under turbine-like free stream conditions, comprehensive tests of transitional boundary layers with laminar, reversing and turbulent flow increments were performed to decouple the effects of the parameters and to determine the effects during mutual interaction.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-TM-88524 , NAS 1.15:88524
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  • 6
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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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  • 7
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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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  • 8
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    Laminar boundary layer in conditions of natural transition to turbulent flow (1986)
    In:  CASI
    Details
    Publication Date: 2019-08-28
    Description: Results of experimental study of regularities of a natural transition of a laminar boundary layer to a turbulent layer at low subsonic air flow velocities are presented, analyzed and compared with theory and model experiments.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-TM-77985 , NAS 1.15:77985
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  • 9
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    Semiempirical methods for computing turbulent flows (1986)
    In:  CASI
    Details
    Publication Date: 2019-08-28
    Description: Two semiempirical theories which provide a basis for determining the turbulent friction and heat exchange near a wall are presented: (1) the Prandtl-Karman theory, and (2) the theory utilizing an equation for the energy of turbulent pulsations. A comparison is made between exact numerical methods and approximate integral methods for computing the turbulent boundary layers in the presence of pressure, blowing, or suction gradients. Using the turbulent flow around a plate as an example, it is shown that, when computing turbulent flows with external turbulence, it is preferable to construct a turbulence model based on the equation for energy of turbulent pulsations.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-TM-77996 , NAS 1.15:77996
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  • 10
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    Measurement of heat-transfer coefficients in shock wave-turbulent boundary layer interaction regions with a multi-layered thin film heat transfer gauge (1986)
    In:  CASI
    Details
    Publication Date: 2019-08-28
    Description: A thin film heat transfer gauge is applied to the measurement of heat transfer coefficients in the interaction regions of incident shock waves and fully developed turbulent boundary layers. It was developed to measure heat flux with high spatial resolution and fast response for wind tunnels with long flow duration. To measure the heat transfer coefficients in the interaction region in detail, experiments were performed under the conditions of Mach number = 4, total pressure = 1.2 MPa, 0.59 to approximately 0.65. Reynolds number = 1.3 to approximately 1.5 x 10 to the 7th power and incident shock angles from 17.8 to 22.8 degrees. The results show that the heat transfer coefficient changes complicatedly in the interaction region. At the beginning the interaction region, the heat transfer coefficient decreases at first, reaches its minimum value at the point where the pressure begins to increase, and then increases sharply. When the boundary layer begins to separate, even a small separation bubble causes significant changes in the heat transfer coefficient, while the pressure does not show any changes which suggests that the boundary layer begins to separate.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-TM-77958 , NAS 1.15:77958
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  • 11
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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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  • 12
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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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  • 13
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    Determination of the specific area of liquid gas and the velocity of weak pressure waves in aqueous foams (1988)
    In:  CASI
    Details
    Publication Date: 2019-08-27
    Description: The specific area of an aqueous foam contained in a tube is obtained by determining the fraction of the quantity of light emitted by a source and diffused by the specific area of the column of the foam. The velocity of the waves of weak pressure (which propagate in the air with the velocity of sound) is measured by noticing the moment when the wave penetrates the column and the moment when, having reached the opposite side, it determines a variation of the light diffused by the area of the latter.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-TT-20347 , NAS 1.77:20347
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  • 14
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    Conservative boundary conditions for 3D gas dynamics problems (1986)
    In:  CASI
    Details
    Publication Date: 2019-08-27
    Description: A method is described for 3D-gas dynamics computer simulation in regions of complicated shape by means of nonadjusted rectangular grids providing unified treatment of various problems. Some test problem computation results are given.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-TM-88487 , NAS 1.15:88487
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  • 15
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    Heat and mass transfer in a dissociated laminar boundary layer of air with consideration of the finite rate of chemical reaction (1986)
    In:  CASI
    Details
    Publication Date: 2019-08-27
    Description: A numerical investigation of heat and mass transfer in a dissociated laminar boundary layer of air on an isothermal flat plate is carried out for different degrees of cooling of the wall. A finite-difference chemical model is used to study elementary reactions involving NO2 and N2O. The analysis is based on equations of continuity, momentum, energy, conservation and state for the two-dimensional viscous flow of a reacting multicomponent mixtures. Attention is given to the effects of both catalyticity and noncatalyticity of the wall.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-TM-78001 , NAS 1.15:78001 , Heat and Mass Transfer All-Union Conference, Minsk; May 17, 1976 - May 20, 1976; Belorussian; USSR
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  • 16
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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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  • 17
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    Designs of profiles for cascades (1988)
    In:  CASI
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    Publication Date: 2019-08-27
    Description: Optimized cascade profiles for arbitrary applications were designed. The influence of Mach number, Reynolds number, and degree of turbulence were taken into account. The optimization aimed at maximum pressure increase, minimum pressure loss, low Reynolds number dependence, or large angle-of-attack range. Starting from the boundary layer form parameter distribution (by which transition point and separation point can be controlled) the velocity distribition and the contour were calculated. The profile characteristics were tested off-design and were improved. Interferometric measurements were performed in the transonic cascade channel.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-TT-20161 , NAS 1.77:20161
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  • 18
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    Some problems of the theory of bubble growth and condensation in bubble chambers (1988)
    In:  CASI
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    Publication Date: 2019-08-27
    Description: This work is an attempt to explain the reasons for the discrepancies between the theoretical and experimental values of bubble growth rate in an overheated liquid, and to provide a brief formulation of the main premises of the theory on bubble growth in liquid before making a critical analysis. To simplify the problem, the floating upward of bubbles is not discussed; moreover, the study is based on the results of the theory of the behavior of fixed bubbles.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-TT-20232 , NAS 1.77:20232 , JINR-P-13-3726
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  • 19
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    A device for generating motive force through the expansion of a non-elastic dense fluid (1985)
    In:  CASI
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    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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  • 20
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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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  • 21
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    Self-adaptive difference method for the effective solution of computationally complex problems of boundary layer theory (1986)
    In:  CASI
    Details
    Publication Date: 2019-08-27
    Description: An implicit difference procedure for the solution of equations for a chemically reacting hypersonic boundary layer is described. Difference forms of arbitrary error order in the x and y coordinate plane were used to derive estimates for discretization error. Computational complexity and time were minimized by the use of this difference method and the iteration of the nonlinear boundary layer equations was regulated by discretization error. Velocity and temperature profiles are presented for Mach 20.14 and Mach 18.5; variables are velocity profiles, temperature profiles, mass flow factor, Stanton number, and friction drag coefficient; three figures include numeric data.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-TM-88440 , NAS 1.15:88440 , DGLR-76-185 , Sep 14, 1976 - Sep 16, 1976; Munich; Germany
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  • 22
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    Development of perturbations in the boundary layer (1986)
    In:  CASI
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    Publication Date: 2019-08-27
    Description: The transition of laminar flows into turbulent flows in a boundary layer is discussed. The individual aspects of the transition process, observed under controllable model conditions are examined. The aspect of this problem, namely the development or excitation of the natural oscillations in the boundary layer, the so-called Tollmin-Schlichting waves is covered. Three types of excitation of these waves are considered: (1) distributed generation throughout the boundary layer; (2) generation in the vicinity of the forward edge of a model, having either a sharp edge or an edge with a large radius or curvature, and (3) generation in a developed boundary layer by means of a focused effect.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-TM-77986 , NAS 1.15:77986
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  • 23
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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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  • 24
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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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  • 25
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    A Study of Flow Separation in Transonic Flow Using Inviscid and Viscous Computational Fluid Dynamics (CFD) Schemes (1988)
    In:  CASI
    Details
    Publication Date: 2019-08-14
    Description: A comparison of flow separation in transonic flows is made using various computational schemes which solve the Euler and the Navier-Stokes equations of fluid mechanics. The flows examined are computed using several simple two-dimensional configurations including a backward facing step and a bump in a channel. Comparison of the results obtained using shock fitting and flux vector splitting methods are presented and the results obtained using the Euler codes are compared to results on the same configurations using a code which solves the Navier-Stokes equations.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-CR-183119 , NAS 1.26:183119 , ODU/ICAM-88-102
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  • 26
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    Numerical Solution of the Incompressible Navier-Stokes Equations in Three-dimensional Generalized Curvilinear Coordinates (1986)
    In:  CASI
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    Publication Date: 2019-08-14
    Description: Numerically solving the incompressible Navier-Stokes equations is known to be time consuming and expensive. Testing of the INS3D computers code, which solves these equations with the use of the pseudocompressibility method, shows this method to be an efficient way to obtain the steady state solution. The effects of the waves introduced by the pseudocompressibility method are analyzed and criteria are set and tested for the choice of the pseudocompressibility parameter which governs the artificial sound speed. The code is tested using laminar flow over a two dimensional backward-facing step, and laminar flow over a two dimensional circular cylinder. The results of the computations over the backward-facing step are in excellent agreement with experimental results. The transient solution of the flow over the cylinder impulsively started from rest is in good agreement with experimental results. However, the computed frequency of periodic shedding of vortices behind the cylinder is not in agreement with the experimental value. For a three dimensional test case, computations were conducted for a cylinder end wall junction. The saddle point separation and horseshoe vortex system appear in the computed field. The solution also shows secondary vortex filaments which wrap around the cylinder and spiral up in the wake.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-TM-86840 , A-85413 , NAS 1.15:86840
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  • 27
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    A New Finite Element Approach for Prediction of Aerothermal Loads: Progress in Inviscid Flow Computations (1985)
    In:  CASI
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    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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  • 28
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    Further Improvements to Nozzle Boundary Layer Calculations in BLIMPJ (1989)
    In:  CASI
    Details
    Publication Date: 2019-08-13
    Description: Further improvements made to advance the current Boundary Layer Integral Matrix Procedure - Version J (BLIMPJ) containing previously modeled simplified calculation methods by accounting for condensed phase, thick boundary layer and free stream turbulence effects are discussed. The condensed phase effects were included through species composition effect considered via input to the code and through particle damping effect considered via a turbulence model. The thrust loss calculation procedure for thick boundary layer effects was improved and the optimization of net thrust with respect to nozzle length was performed. The effects of free stream turbulence were approximately modeled in the turbulence model.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: JHU, The 26th JANNAF Combustion Meeting, Volume 2; p 311-325|26th JANNAF Combustion Meeting; Oct 23, 1989 - Oct 27, 1989; Pasadena, CA; United States
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  • 29
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    Liquid Behavior at Critical and Supercritical Conditions (1989)
    In:  CASI
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    Publication Date: 2019-08-13
    Description: At a JANNAF workshop, the issue of fluids at and above the critical point was discussed to obtain a better understanding of similar conditions in combustion chambers of rocket engines. Invited experts from academic, industrial, and government institutions presented the most recent physical, numerical, and experimental advances. During the final discussion period, it was agreed that: (1) no analytical capability exists to simulate subject conditions; (2) mechanisms reflected by opalescence, the solubility of gases, other interfacial phenomena listed, and fluorescence diagnostics are new and important; (3) multicomponent mixtures, radiation, critical fluctuation, and other recorded ones pose unknown effects; and (4) various identified analytical and experimental actions must be initiated in a mutually supporting sequence.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: 26th JANNAF Combustion Meeting; Oct 23, 1989 - Oct 27, 1989; Pasadena, CA; United States|JHU, The 26th JANNAF Combustion Meeting, Volume 2; p 335-342
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  • 30
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    The theory of flotation (1988)
    In:  CASI
    Details
    Publication Date: 2019-08-13
    Description: A brief summary of the fundamentals of the Linear theory of flotation is given. The theory by no means contradicts the previous Laminar theory or even the thermodynamics (Wark-Siedler), rather it is a refinement of the known Hardy-Langmuir-Harkin conceptions for the case when there are not two phases and phase boundaries, but rather three phases and corresponding phase boundary edges. The appearance of such three-phase boundaries (ore, water, air) is characteristic for modern flotation methods.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-TT-20278 , NAS 1.77:20278
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    Experimental studies on the stability and transition of 3-dimensional boundary layers (1987)
    In:  CASI
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    Publication Date: 2019-08-13
    Description: Three-dimensional unstable boundary layers were investigated as to their characteristic instabilities, leading to turbulence. Standing cross-flow instabilities and traveling waves preceding the transition were visualized with the hydrogen bubble technique in the boundary layer above the wall of a swept cylinder. With the sublimation method and hot film technique, a model consisting of a swept flat plate with a pressure-inducing displacement body in the 1 m wind tunnel was studied. Standing waves and traveling waves in a broad frequency are observed. The boundary layer of this model is close to the assumptions of the theory.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-TM-88539 , NAS 1.15:88539 , DFVLR-FB-86-24
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    Spacelab 3 Mission Science Review (1987)
    In:  CASI
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    Publication Date: 2019-08-13
    Description: Papers and abstracts of the presentations made at the symposium are given as the scientific report for the Spacelab 3 mission. Spacelab 3, the second flight of the National Aeronautics and Space Administration's (NASA) orbital laboratory, signified a new era of research in space. The primary objective of the mission was to conduct applications, science, and technology experiments requiring the low-gravity environment of Earth orbit and stable vehicle attitude over an extended period (e.g., 6 days) with emphasis on materials processing. The mission was launched on April 29, 1985, aboard the Space Shuttle Challenger which landed a week later on May 6. The multidisciplinary payload included 15 investigations in five scientific fields: material science, fluid dynamics, life sciences, astrophysics, and atmospheric science.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-CP-2429 , M-547 , NAS 1.55:2429
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  • 33
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    Studies of acoustic effects on a flow boundary layer in air (1986)
    In:  CASI
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    Publication Date: 2019-08-13
    Description: Effects of sound fields on the flow boundary layer on a flat plate subjected to a parallel flow are studied. The boundary layer is influenced by controlling the stagnation point flow at the front edge of the plate. Depending on the Reynolds number and sound frequency, excitation or suppression of turbulent is observed. Measurements were taken at wind velocities between 10 and 30 m/sec and sound frequencies between 0.2 and 3.0 kHz.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-TM-77981 , NAS 1.15:77981
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  • 34
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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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  • 35
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    Comparison between pressure gradient method and MAC method on high Re calculation (1989)
    In:  Other Sources
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    Publication Date: 2019-07-27
    Description: A cavity flow driven by shear and buoyancy forces is used as a test problem in the application of a nonstaggered pressure gradient (PG) method in solving the two-dimensional incompressible Navier-Stokes equations. Twelve finite differencing schemes are used to solve the cavity flow problem. The schemes consist of various combinations of grid arrangements, upwinding treatments, and conservativeness of convection terms. An artificial source term is introduced, and the solutions are compared with those obtained by the conventional marker-and-cell (MAC) method. The comparisons favor the PG method. Numerical results obtained by the twelve schemes are compared with exact solutions in order to assess the stability and accuracy of each scheme.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: International Symposium on Numerical Methods in Engineering; Sept. 11-15, 1989; Lausanne; Switzerland
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    A spectral multi-domain technique applied to stability and transition of incompressible and compressible flows (1989)
    In:  Other Sources
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    Publication Date: 2019-07-27
    Description: Techniques for the numerical simulation of compressible and incompressible viscous flows are described and demonstrated. The focus is on a multidomain spectral method based on the flux-balance domain-interface scheme of Macaraeg and Streett (1986). The fundamental principles of the method are reviewed, and it is shown that the multidomain spectral approach facilitates the treatment of instability and the transition to turbulence. Typical numerical results for the Taylor-Couette problem and for bounded compressible high-speed mixing layers are presented in graphs and briefly characterized.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: International Symposium on Numerical Methods in Engineering; Sept. 11-15, 1989; Lausanne; Switzerland
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  • 37
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    Advanced computational techniques for hypersonic propulsion (1989)
    In:  Other Sources
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    Publication Date: 2019-07-27
    Description: Computational Fluid Dynamics (CFD) has played a major role in the resurgence of hypersonic flight, on the premise that numerical methods will allow performance of simulations at conditions for which no ground test capability exists. Validation of CFD methods is being established using the experimental data base available, which is below Mach 8. It is important, however, to realize the limitations involved in the extrapolation process as well as the deficiencies that exist in numerical methods at the present time. Current features of CFD codes are examined for application to propulsion system components. The shortcomings in simulation and modeling are identified and discussed.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: International Symposium on Air Breathing Engines; Sept. 3-8, 1989; Athens; Greece
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  • 38
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    Near wall flow parameters in the blade end-wall corner region (1989)
    In:  Other Sources
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    Publication Date: 2019-07-27
    Description: The effects of secondary end-wall corner flows on near wall flow parameters in turbomachinary are studied. Important near wall flow parameters such as the wall shear stress vector, the mean wall pressure, the wall pressure fluctuations, and the correlation of the wall pressure fluctuation with the velocity fluctuation in three-dimensional turbulent flows are first experimentally investigated. The blade end-wall corner region is simulated by mounting airfoil section of symmetric blades on both sides of the flat plate with semicircular leading edge. Observed changes in the maximum values of the wall shear stress and its location from the corner line could be associated with the streching and attenuation of the horseshoe vortex. The values of wall pressure fluctuation intensity in the blade end-wall corner region are found to be influenced by the changes of the strength of the horseshoe vortex. The correlation of the wall pressure fluctuation with the velocity fluctuation indicated higher values of correlation coefficient in the inner region as compared to the outer region of the shear layer. The values of wall pressure-velocity correlation coefficient in the blade end-wall corner region also decrease in the streamwise direction while increasing in the presence of favorable and adverse pressure gradients.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: International Symposium on Air Breathing Engines; Sept. 3-8, 1989; Athens; Greece
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  • 39
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    Finite element solution of the Euler equations in two and three dimensions (1988)
    In:  Other Sources
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    Publication Date: 2019-07-27
    Description: The paper presents a finite element procedure for solving the equations of compressible flow over bodies of arbitrary geometry. The numerical solution algorithm employed is an explicit two-step version of a second order Taylor-Galerkin scheme. The discretization of the computational domain into unstructured meshes of triangles in two dimensions and tetrahedra in three dimensions is performed by an automatic mesh generator. In the approach, the mesh generator is coupled to the finite element solver to produce an adaptive remeshing procedure.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: GAMM-Conference on Numerical Methods in Fluid Mechanics; Sept. 9-11, 1987; Louvain-la-Neuve; Belgium
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  • 40
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    Comparative study of high-resolution shock-capturing schemes for a real gas (1988)
    In:  Other Sources
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    Publication Date: 2019-07-27
    Description: Recently developed second-order explicit shock-capturing methods, in conjunction with generalized flux-vector splittings, and a generalized approximate Riemann solver for a real gas are studied. The comparisons are made on different one-dimensional Riemann (shock-tube) problems for equilibrium air with various ranges of Mach numbers, densities and pressures. Six different Riemann problems are considered. These tests provide a check on the validity of the generalized formulas, since theoretical prediction of their properties appears to be difficult because of the non-analytical form of the state equation. The numerical results in the supersonic and low-hypersonic regimes indicate that these produce good shock-capturing capability and that the shock resolution is only slightly affected by the state equation of equilibrium air. The difference in shock resolution between the various methods varies slightly from one Riemann problem to the other, but the overall accuracy is very similar. For the one-dimensional case, the relative efficiency in terms of operation count for the different methods is within 30 percent. The main difference between the methods lies in their versatility in being extended to multidimensional problems with efficient implicit solution procedures.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: GAMM-Conference on Numerical Methods in Fluid Mechanics; Sept. 9-11, 1987; Louvain-la-Neuve; Belgium
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  • 41
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    What happens to the large eddies when net drag reduction is achieved by outer flow manipulators? (1987)
    In:  Other Sources
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    Publication Date: 2019-07-27
    Description: The tandem-arranged parallel plate manipulator (TAPPM) presently used to generate a flow with net drag reduction is conditionally sampled and found to exhibit significant changes of the boundary layer's large-scale motions at 20 delta(0), where delta(0) is the boundary layer thickness at the upstream plate of the TAPPM. Flow fields in the 'valleys' are equally affected. Both turbulent and irrotational flows then reestablish themselves by 50 delta(0). Flow visualization indicates that the TAPPM wake is very coherent at 20 delta(0), and has not yet spread into the wall region, while large scale motions and the ambient response flow continue to exhibit dynamic changes. This indicates that the shielding effect of the TAPPM's wake prolongs suppression of large-scale motions, thereby reducing skin friction over a sufficiently long extent of the boundary layer to overcome device drag and yield net drag reductions.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Turbulent drag reduction by passive means; Sept. 15-17, 1987; London
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  • 42
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    Turbulence structure at high shear rate (1987)
    In:  Other Sources
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    Publication Date: 2019-07-27
    Description: The structure of homogeneous turbulence in the presence of a high shear rate is studied using results obtained from three-dimensional time-dependent numerical simulations of the Navier-Stokes equations on a grid of 512 x 128 x 128 node points. It is shown that high shear rate enhances the streamwise fluctuating motion to such an extent that a highly anisotropic turbulence state with a one-dimensional velocity field and two-dimensional small-scale turbulence develops asymptotically as total shear increases. Instantaneous velocity fields show that high shear rate in homogeneous turbulent shear flow produces structures which are similar to the streaks present in the viscous sublayer of turbulent boundary layers.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Symposium on Turbulent Shear Flows; Sept. 7-9, 1987; Toulouse; France
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  • 43
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    Rotordynamic forces on centrifugal pump impellers (1987)
    In:  Other Sources
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    Publication Date: 2019-07-27
    Description: The asymmetric flow around an impeller in a volute exerts a force upon the impeller. To study the rotordynamic force on an impeller which is vibrating around its machine axis of rotation, the impeller, mounted on a dynamometer, is made to whirl in a circular orbit within the volute. The measured force is expressed as the sum of a steady radial force and an unsteady force due to the eccentric motion of the impeller. These forces were measured in separate tests on a centrifugal pump with radically increased shroud clearance, a two-dimensional impeller, and an impeller with an inducer, the impeller of the HPOTP (High Pressure Oxygen Turbopump) of the SSME (Space Shuttle Main Engine). In each case, a destabilizing force was observed over a region of positive whirl.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Conference on Fluid Machinery; Sept. 1987; Budapest; Hungary
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  • 44
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    Near-wall k-epsilon turbulence modeling (1987)
    In:  Other Sources
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    Publication Date: 2019-07-27
    Description: The flow fields from a turbulent channel simulation are used to compute the budgets for the turbulent kinetic energy (k) and its dissipation rate (epsilon). Data from boundary layer simulations are used to analyze the dependence of the eddy-viscosity damping-function on the Reynolds number and the distance from the wall. The computed budgets are used to test existing near-wall turbulence models of the k-epsilon type. It was found that the turbulent transport models should be modified in the vicinity of the wall. It was also found that existing models for the different terms in the epsilon-budget are adequate in the region from the wall, but need modification near the wall. The channel flow is computed using a k-epsilon model with an eddy-viscosity damping function from the data and no damping functions in the epsilon-equation. These computations show that the k-profile can be adequately predicted, but to correctly predict the epsilon-profile, damping functions in the epsilon-equation are needed.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Symposium on Turbulent Shear Flows; Sept. 7-9, 1987; Toulouse; France
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  • 45
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    Stochastic estimation of organized structures in turbulent channel flow (1987)
    In:  Other Sources
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    Publication Date: 2019-07-27
    Description: Linear stochastic estimation is used to approximate the conditional vector fields associated with high Reynolds stress producing events in numerically simulated turbulent channel flow. Joint probability density distributions of u-v are presented for y(+) between 1.35 and 180, and at each position the u-v values that make the greatest contributions to the average uv3 are used to define conditional ejection- and sweep-type events. In the y-z plane the conditional fields appear to be pairs of counter-rotating vortices. When the conditional event defined by the weighted probability density function is specified at a point close to the wall, the spacing and size of these eddies are consistent with the accepted wall streak spacing. As this point moves outwards, the eddy size increases significantly. An abrupt change in the flow angle occurs in the buffer layer and may indicate transition from streamwise oriented wall layer structures to hairpin vortices characterizing the outer layer.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Symposium on Turbulent Shear Flows; Sept. 7-9, 1987; Toulouse; France
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  • 46
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    Unsteady motion and transition to turbulence in developing curved duct flow (1987)
    In:  Other Sources
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    Publication Date: 2019-07-27
    Description: An experiment was performed to further the understanding of developing flows in curved ducts of square cross-section. Unlike most earlier works, attention was paid to investigating the time-dependent character of the motion. Mean and unsteady flow characteristics were determined using flow visualization and a laser-Doppler velocimeter. Only one velocity component, that aligned in the longitudinal (streamwise) coordinate direction, was measured. Notwithstanding, the time histories, autocorrelations and spectra derived reveal a time-periodic motion that becomes turbulent with increasing Reynolds number. The results are of intrinsic fundamental value and also illustrate the danger of imposing symmetry of the conservation equations on numerical solutions of this flow.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Symposium on Turbulent Shear Flows; Sept. 7-9, 1987; Toulouse; France
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    An orthogonal decomposition of the axisymmetric jet mixing layer utilizing cross-wire velocity measurements (1987)
    In:  Other Sources
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    Publication Date: 2019-07-27
    Description: The structure of the mixing layer of the axisymmetric turbulent jet was investigated using cross-wire velocity measurements, which generated radial and streamwise cross-spectral data at eight radial positions and 25 azimuthal positions. The results show the existence of an azimuthal coherent ringlike structure dominated by axisymmetric mode near the potential core; however, from the center of the mixing layer out toward its low-speed side, the fourth, fifth, and sixth modes are dominating. A mechanism for the life cycle of coherent structures and for turbulence production in the axisymmetric jet mixing layer is proposed, which accounts for the observed phenomena and is amenable to dynamical analysis using the equations of motion.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Symposium on Turbulent Shear Flows; Sept. 7-9, 1987; Toulouse; France
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    Unsteady diffuser vane pressure and impeller wake measurements in a centrifugal pump (1987)
    In:  Other Sources
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    Publication Date: 2019-07-27
    Description: Unsteady surface pressure measurements on a vaned diffuser of a centrifugal pump, and wake measurements of the flow exiting a centrifugal impeller into a vaneless diffuser are presented. Frequency spectra and ensemble averages are given for the unsteady measurements. Two different impellers were used, the pump impeller of the HPOTP (High Pressure Oxygen Turbopump) of the SSME (Space Shuttle Main Engine) and a two-dimensional impeller. The magnitude of the unsteady total pressure measured in the stationary frame at the impeller exit was found to be of the same order of magnitude as the total pressure rise across the pump. The magnitude of the unsteady diffuser vane pressures was observed to be significantly different on suction and pressure side of the vane, attaining its largest value on the suction side the leading edge while decreasing along the vane.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Conference on Fluid Machinery; Sept. 1987; Budapest; Hungary
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  • 49
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    Direct simulation of a turbulent oscillating boundary layer (1987)
    In:  Other Sources
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    Publication Date: 2019-07-27
    Description: The turbulent boundary layer driven by a freestream velocity that varies sinusoidally in time around a zero mean is considered. The flow has a rich behavior including strong pressure gradients, inflection points, and reversal. A theory for the velocity and stress profiles at high Reynolds number is formulated. Well-resolved direct Navier-Stokes simulations are conducted over a narrow range of Reynolds numbers, and the results are compared with the theoretical predictions. The flow is also computed over a wide range of Reynolds numbers using a new algebraic turbulence model; the results are compared with the direct simulations and the theory.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Symposium on Turbulent Shear Flows; Sept. 7-9, 1987; Toulouse; France
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    Transport of passive scalars in a turbulent channel flow (1987)
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    Publication Date: 2019-07-27
    Description: A direct numerical simulation of a turbulent channel flow with three passive scalars at different molecular Prandtl numbers is performed. Computed statistics including the turbulent Prandtl numbers are compared with existing experimental data. The computed fields are also examined to investigate the spatial structure of the scalar fields. The scalar fields are highly correlated with the streamwise velocity; the correlation coefficient between the temperature and the streamwise velocity is as high as 0.95 in the wall region. The joint probability distributions between the temperature and velocity fluctuations are also examined; they suggest that it might be possible to model the scalar fluxes in the wall region in a manner similar to the Reynolds stresses.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Symposium on Turbulent Shear Flows; Sept. 7-9, 1987; Toulouse; France
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