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  • FLUID MECHANICS AND HEAT TRANSFER
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  • 1
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    Effect of shear stress on cell cultures and other reactor problems (1981)
    In:  CASI
    Details
    Publikationsdatum: 2006-02-14
    Beschreibung: Anchorage dependent cell cultures in fluidized beds are tested. Feasibility calculations indicate the allowed parameters and estimate the shear stresses therein. In addition, the diffusion equation with first order reaction is solved for the spherical shell (double bubble) reactor with various constraints.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Houston Univ. The 1981 NASA ASEE Summer Fac. Fellowship Program, Vol. 2; 19 p
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  • 2
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    Capillary priming characteristics of a dual passage heat pipe in zero-g (1981)
    In:  CASI
    Details
    Publikationsdatum: 2006-02-14
    Beschreibung: Technical improvements of a long life heat rejection system, suitable for long duration high power missions, that can be constructed and deployed in orbit is discussed. A mathematical model is formulated and a computer program developed which describes the transient priming characteristics of a dual passage heat pipe. An experimental test package is described for flight in the KC-135 Zero-g Aircraft, to be used to verify the modeling predictions.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Houston Univ. The 1981 NASA ASEE Summer Fac. Fellowship Program, Vol. 2; 50 p
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  • 3
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    Two-phase flow and heat transfer under low gravity (1981)
    In:  CASI
    Details
    Publikationsdatum: 2006-02-14
    Beschreibung: Spacelab experiment to investigate two-phase flow patterns under gravity uses a water-air mixture experiment. Air and water are circulated through the system. The quality or the mixture or air-water is controlled. Photographs of the test section are made and at the same time pressure drop across the test section is measured. The data establishes a flow regime map under reduced gravity conditions with corresponding pressure drop correlations. The test section is also equipped with an electrical resistance heater in order to allow a flow boiling experiment to be carried out using Freon II. High-speed photographs of the test section are used to determine flow patterns. The temperature gradient and pressure drop along the duct can be measured. Thus, quality change can be measured, and heat transfer calculated.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: NASA. Marshall Space Flight Center Spacecraft Dyn. as Related to Lab. Expt. in Space; p 43-57
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  • 4
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    Effects of spacecraft motions on fluids experiments (1981)
    In:  CASI
    Details
    Publikationsdatum: 2006-02-14
    Beschreibung: The equations of motion governing an incompressible fluid contained in an orbiting laboratory were examined to isolate various fictitious forces and their relative influence on the fluid. The forces are divided into those arising from the orbital motions and those arising from small local motions of the spacecraft about its center of mass. The latter dominate the nonrotating experiments. Both are important for rotating experiments. A brief discussion of the onset of time-dependence and violent instability in earth-based rotating and processing systems is given.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: NASA. Marshall Space Flight Center Spacecraft Dyn. as Related to Lab. Expt. in Space; p 96-102
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  • 5
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    Convection in fluids at reduced gravity (1981)
    In:  CASI
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    Publikationsdatum: 2006-02-14
    Beschreibung: Natural convection is not always harmful and, therefore, to be avoided. In some situations it may be desirable to have fluid flows in space processes, e.g., to stir the fluid phase for mixing and cooling or to help maintain concentration gradients. In may event, it is important to know the extent and nature of convection in space and the factors on which it depends, in order either to minimize the effects to convection, or to utilize the convection to advantage. The information needed to assess both conventional and unstable convection includes: (1) the magnitude and direction of accelerations; (2) geometric configuration; (3) imposed boundary conditions; and (4) material properties.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: NASA. Marshall Space Flight Center Spacecraft Dyn. as Related to Lab. Expt. in Space; p 69-95
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  • 6
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    Geophysical fluid dynamics (1981)
    In:  CASI
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    Publikationsdatum: 2006-02-14
    Beschreibung: Systematic scaling or dimensional analysis reveals that certain scales of geophysical fluid flows (such as stellar, ocean, and planetary atmosphere circulations) can be accurately modeled in the laboratory using a procedure which differs from conventional engineering modeling. Rather than building a model to obtain numbers for a specific design problem, the relative effects of the significant forces are systematically varied in an attempt to deepen understanding of the effects of these forces. Topics covered include: (1) modeling a large-scale planetary atmospheric flow in a rotating cylindrical annulus; (2) achieving a radial dielectric body force; (3) spherical geophysical fluid dynamics experiments for Spacelab flights; (4) measuring flow and temperature; and (5) the possible effect of rotational or precessional disturbances on the flow in the rotating spherical containers.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Spacecraft Dyn. as Related to Lab. Expt. in Space; p 25-31
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  • 7
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    Analysis of low-g heat transfer for a cryogenic oxygen pressurization heater (1981)
    In:  CASI
    Details
    Publikationsdatum: 2006-02-14
    Beschreibung: After the external tank separates from the Orbiter about 2000 pounds of residual liquid oxygen remain in the main propulsion system lines. The pressurization of liquid oxygen from a subcritical to a supercritical state by the use of the heaters of the PRSA tanks while in a low-g environment is investigated. The performance of the heaters while bringing the state of the substance from the subcritical state to the supercritical one is studied, with particular emphasis on the time the pressurization process takes, and the temperature of the heater as the process proceeds.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Houston Univ. The 1981 NASA ASEE Summer Fac. Fellowship Program, Vol. 2; 38 p
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  • 8
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    A direct interaction approximation treatment of turbulence in a compressible fluid. I - Formalism (1988)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: The direct interaction approximation is used to treat turbulence in a compressible medium with constant mean gradients. The set of coupled nonlinear integrodifferential equations is derived that is satisfied by the transverse and longitudinal energy spectral functions, Q(T) and Q(L) and by the transverse and longitudinal response functions, G(T) and G(L). Finally, expressions for the average of the product of pairs of physically relevant fluctuating quantities (velocity, temperature, density) are derived in terms of Q(T) and Q(L).
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Physics of Fluids (ISSN 0031-9171); 31; 1034-105
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  • 9
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    Generalized energy and potential enstrophy conserving finite difference schemes for the shallow water equations (1988)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: The conditions under which finite difference schemes for the shallow water equations can conserve both total energy and potential enstrophy are considered. A method of deriving such schemes using operator formalism is developed. Several such schemes are derived for the A-, B- and C-grids. The derived schemes include second-order schemes and pseudo-fourth-order schemes. The simplest B-grid pseudo-fourth-order schemes are presented.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Monthly Weather Review (ISSN 0027-0644); 116; 650-662
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  • 10
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    Renormalization-group theory for the eddy viscosity in subgrid modeling (1988)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: Renormalization-group theory is applied to incompressible three-dimensional Navier-Stokes turbulence so as to eliminate unresolvable small scales. The renormalized Navier-Stokes equation now includes a triple nonlinearity with the eddy viscosity exhibiting a mild cusp behavior, in qualitative agreement with the test-field model results of Kraichnan. For the cusp behavior to arise, not only is the triple nonlinearity necessary but the effects of pressure must be incorporated in the triple term. The renormalized eddy viscosity will not exhibit a cusp behavior if it is assumed that a spectral gap exists between the large and small scales.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Physical Review A - General Physics, 3rd Series (ISSN 0556-2791); 37; 2590-259
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  • 11
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    The centring dynamics of a thin liquid shell in capillary oscillations (1988)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: The physical mechanism governing the centring of a hollow liquid shell in capillary oscillations, which has been observed in experiments, is investigated theoretically. First, the shell is assumed to be inviscid and to have a thickness that is much less than its spherical radius. A system of one-dimensional nonlinear equations of motion is derived using a thin-sheet model. From a numerical study the nonlinear effects of the wave are found to cause the core to oscillate slowly relative to the shell while the centre of mass of the whole system remains stationary. The effects of small viscosity are then considered in an approximation. Finally the strength of the centring mechanism is compared with that of the decentring effect due to buoyancy. The findings are consistent with the limited experimental information available.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Journal of Fluid Mechanics (ISSN 0022-1120); 188; 411-435
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  • 12
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    Developing fluid flow in a curved duct of square cross-section and its fully developed dual solutions (1988)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: Developing fluid flow in a curved duct of square cross-section is studied numerically by a factored ADI finite-difference method on a staggered grid. A central-difference scheme with primitive variables is used inside the computational domain to reduce numerical diffusion. Two Reynolds numbers, 574 and 790, based upon a bulk velocity and hydraulic diameter are chosen for curvature ratios of 1/6.45 and 1/2.3, respectively. It is found that the secondary flow is far more complicated than expected, with the appearance of at least two pairs of vortices. Main-flow separation is also observed for the higher curvature ratio. Furthermore, it is observed that the flow develops into two quite different states downstream, depending upon the inlet conditions. Solutions of the fully developed Navier-Stokes equations is shown to be not unique beyond a certain critical Reynolds number. Developing flow seems to evolve into the fully developed state along a particular branch into which the fully developed solution bifurcates.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Journal of Fluid Mechanics (ISSN 0022-1120); 188; 337-361
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  • 13
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    Multiphase flow in porous media (1988)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: A development history and current status evaluation are presented for the theory of permeability and percolation. The microscale phenomena treated in this field have proven difficult to analyze due both to their tortuous geometry and the influence of capilarity. Capilary effects may be not only important but predominant, and are differentiated into those at the fluid-fluid interface, and those involving the existence of a contact line between the solid substrate and this interface. Percolation theory has been borrowed from physics and adapted to the two-phase engineering context.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
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  • 14
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    Condensation heat transfer in a microgravity environment (1988)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Journal of Thermophysics and Heat Transfer (ISSN 0887-8722); 2; 82-84
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  • 15
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    Flow-induced morphological instabilities - The rotating disc (1988)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: The morphological stability of a rotating and solidifying disk is investigated under the assumption that delta, the thickness of the viscous boundary layer, is much larger than delta(c), the thickness of the solute boundary layer. It is found that axisymmetric disturbances with wavelengths comparable to delta respond to nonparallel flow effects and have stability characteristics quite different from disturbances in a parallel flow. These long waves are unstable because of the nonparallel flow and would decay without it. This analysis thus identifies a new mechanism of morphological change induced by flow.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Journal of Crystal Growth (ISSN 0022-0248); 87; 4, Ma; 385-396
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  • 16
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    On the receptivity of free shear layers to two-dimensional external excitation (1988)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: In this paper, the receptivity of a typical free shear layer to pulse-type and periodic excitation is studied. This is done by solving the initial-value problem completely and studing its long-time behavior. This leads to a wave packet for the pulse. By the superposition of many wave packets, a spatial instability mode when the flow is convectively unstable is generated. This establishes a general and simple relationship between the receptivities for pulse-type and sinusoidal excitations. It is found that a shear layer is very receptive to high-frequency disturbances that are generated near the centerline of the layer.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Journal of Fluid Mechanics (ISSN 0022-1120); 187; 155-177
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  • 17
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    Direct simulation of a turbulent boundary layer up to R sub theta = 1410 (1988)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: The turbulent boundary layer on a flat plate, with zero pressure gradient, is simulated numerically at four stations between R sub theta = 225 and R sub theta = 1410. The three-dimensional time-dependent Navier-Stokes equations are solved using a spectral method with up to about 10 to the 7th grid points. Periodic spanwise and streamwise conditions are applied, and a multiple-scale procedure is applied to approximate the slow streamwise growth of the boundary layer. The flow is studied, primarily, from a statistical point of view. The solutions are compared with experimental results. The scaling of the mean and turbulent quantities with Reynolds number is compared with accepted laws, and the significant deviations are documented. The turbulence at the highest Reynolds number is studied in detail. The spectra are compared with various theoretical models. Reynolds-stress budget data are provided for turbulence-model testing.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Journal of Fluid Mechanics (ISSN 0022-1120); 187; 61-98
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  • 18
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    A direct interaction approximation treatment of high Rayleigh number convective turbulence and comparison with experiment (1988)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: A method is proposed for treating steady-state, thermally driven convection using the full direct interaction approximation to treat the nonlinear energy transfer and a prescribed instability function to model the eenrgy input. The instability function used is the growth rate of the mechanism generating the turbulence. This methodology can be easily generalized and applied to other driving mechanisms. The 1/3 power law form of the N vs. R relation for water is duplicated here and the coefficient is computed, using a two-point closure, to be less than about 0.08.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Physics of Fluids (ISSN 0031-9171); 31; 256-262
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  • 19
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    Velocity spectra in the irrotational flow outside a turbulent shear layer (1988)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: The relationship between the spectra of the three normal stresses near a turbulent shear layer is derived from the constraint of irrotationality. The relationship implies that the common practice of determining time scales of the turbulence from spectra in the near field is not valid. This implication is reinforced by a discussion of the scaling of irrotational spectra that follows from the formulation of Phillips (1975).
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Physics of Fluids (ISSN 0031-9171); 31; 1807
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  • 20
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    Ejection mechanisms in the sublayer of a turbulent channel (1988)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: The structure of the vorticity field in the viscous wall layer of a turbulent channel is studied by examining the results of a fully resolved direct numerical simulation. It is shown that this region is dominated by intense three-dimensional shear layers in which the dominant vorticity component is spanwise. The advection and reproduction processes of these structures are examined and shown to be consistent with the classical generation mechanism for two-dimensional Tollmien-Schlichting waves. This process is fundamentally different from the usually accepted mechanism involving hairpin vortices.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Physics of Fluids (ISSN 0031-9171); 31; 1311-131
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  • 21
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    A finite element computation of turbulent boundary layer flows with an algebraic stress turbulence model (1988)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: An algebraic stress turbulence model and a computational procedure for turbulent boundary layer flows which is based on the semidiscrete Galerkin FEM are discussed. In the algebraic stress turbulence model, the eddy viscosity expression is obtained from the Reynolds stress turbulence model, and the turbulent kinetic energy dissipation rate equation is improved by including a production range time scale. Good agreement with experimental data is found for the examples of a fully developed channel flow, a fully developed pipe flow, a flat plate boundary layer flow, a plane jet exhausting into a moving stream, a circular jet exhausting into a moving stream, and a wall jet flow.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Computer Methods in Applied Mechanics and Engineering (ISSN 0045-7825); 66; 45-63
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  • 22
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    Free-streamline analysis of deformation and dislodging by wind force of drops on a surface (1988)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: Free-streamline theory is used to analyze the deformation and dislodging by wind pressure of drops of liquid adhered by surface tension to a solid surface. The critical Weber number for droplets to be dislodged is determined as a function of advancing and receding contact angle. Graphical results for drop shape are in good agreement with observation.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Physics of Fluids (ISSN 0031-9171); 31; 43-48
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  • 23
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    Considerations on the moving contact-line singularity, with application to frictional drag on a slender drop (1988)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: It has previously been shown that the no-slip boundary conditions leads to a singularity at a moving contact line and that this presumes some form of slip. Present considerations on the energetics of slip due to shear stress lead to a yield stress boundary condition. A model for the distortion of the liquid state near solid boundaries gives a physical basis for this boundary condition. The yield stress condition is illustrated by an analysis of a slender drop rolling down an incline. That analysis provides a formula for the frictional drag resisting the drop movement. With the present boundary condition, the length of the slip region becomes a property of the fluid flow.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Journal of Fluid Mechanics (ISSN 0022-1120); 197; 157-169
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  • 24
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    Lower-upper Symmetric-Gauss-Seidel method for the Euler and Navier-Stokes equations (1988)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: AIAA Journal (ISSN 0001-1452); 26; 1025
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  • 25
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    Numerical study of the interactions between droplets at intermediate Reynolds numbers (1988)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Journal of Propulsion and Power (ISSN 0748-4658); 4; 481-489
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  • 26
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    Unsteady solution of incompressible Navier-Stokes equations (1988)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: The numerical scheme used by the present time-accurate FEM numerical method for incompressible Navier-Stokes equations, using primitive variables as the unknowns, is a Crank-Nicholson implicit treatment of all equation terms with central differencing for space derivatives. The introduction of a continuous auxilliary system in pseudo-time, with artificial compressibility, yields the incompressible solution at the advanced time level; time-accurate solutions are thereby obtained for two-dimensional fluid flows in a square cavity, in the cases of both an impulsively starting lid and an oscillating lid.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Journal of Computational Physics (ISSN 0021-9991); 79; 113-134
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  • 27
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    Measurements of the free-stream fluctuations above a turbulent boundary layer (1988)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: The paper describes an investigation of the velocity fluctuations in the free stream above an incompressible turbulent boundary layer developing at constant pressure. Measurements were performed in a wind tunnel with an rms level of axial velocity fluctuations of about 0.2 percent. The possibility of assessing the contributions to the rms level of the velocity fluctuations without using the high-pass filtering technique is demonstrated.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Physics of Fluids (ISSN 0031-9171); 31; 2834-284
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  • 28
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    Model consistency in large eddy simulation of turbulent channel flows (1988)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: Combinations of filters and subgrid scale stress models for large eddy simulation of the Navier-Stokes equations are examined by a priori tests and numerical simulations. The structure of the subgrid scales is found to depend strongly on the type of filter used, and consistency between model and filter is essential to ensure accurate results. The implementation of consistent combinations of filter and model gives more accurate turbulence statistics than those obtained in previous investigations in which the models were chosen independently from the filter. Results and limitations of the a priori test are discussed. The effect of grid refinement is also examined.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Physics of Fluids (ISSN 0031-9171); 31; 1884-189
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  • 29
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    Structure of rough-wall turbulent boundary layers (1988)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: Recent experiments have shown that, in rough-wall turbulent boundary layers, drag varies systematically with the spanwise aspect ratio lambda(z) (span/height) of roughness elements. In this paper, the effect of lambda(z) on turbulence structure has been examined. Based on lambda(z), the roughness in a transversely grooved surface with lambda(z) much greater than 1 is the opposite extreme of model plant canopies with lambda(z) much less than 1, studied in wind tunnels, whereas sandgrain is an intermediate type. Second-, third-, and fourth-order turbulence moments have been measured in turbulent boundary layers over transversely grooved and smooth surfaces and compared with available turbulence structure measurements over other types of surfaces. The near-wall turbulence structure is found to vary with lambda(z). The instantaneous motions involved in the flux of shear stress near the wall in smooth and transversely grooved surfaces are opposite in sign to those in three-dimensional roughness. The former is explained in terms of hairpin vortices alone, while the latter group is modeled to have an additional vortex (the so-called necklace vortex which straddles a three-dimensional roughness element near its base).
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Physics of Fluids (ISSN 0031-9171); 31; 1877-188
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    Stability of swirling gas flows (1988)
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    Publikationsdatum: 2011-08-19
    Beschreibung: The stability of inviscid swirling gas flows to small nonaxisymmetric perturbations is considered. For small Brunt-Vaisala frequencies, the problem reduces to the classical Sturm-Liouville form and the oscillation theorem can be applied. The resulting necessary and sufficient stability condition is compared to various criteria in the literature and a limited numerical study of isothermal rigidly rotating Poiseuille flow. For given azimuthal and axial wavenumbers, it is found numerically that the higher inertial modes become unstable for successively lower Rossby numbers and that this sequence of critical values approaches the theoretical value from above.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Physics of Fluids (ISSN 0031-9171); 31; 1872-187
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    Weak solutions of the three-dimensional vorticity equation with vortex singularities (1988)
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    Publikationsdatum: 2011-08-19
    Beschreibung: The extension of the concept of vortex singularities, developed by Saffman and Meiron (1986) for the case of two-dimensional point vortices in an incompressible vortical flow, to the three-dimensional case of vortex sticks (vortons) is investigated analytically. The derivation of the governing equations is explained, and it is demonstrated that the formulation obtained conserves total vorticity and is a weak solution of the vorticity equation, making it an appropriate means for representing three-dimensional vortical flows with limited numbers of vortex singularities.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Physics of Fluids (ISSN 0031-9171); 31; 1838
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    Rain simulation studies for high-intensity acoustic nose cavities (1988)
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    Publikationsdatum: 2011-08-19
    Beschreibung: Unarmed plastic projectiles can be equipped with small axisymmetric cavities for the generation of intense tones that are useful in training maneuvers. Attention is presently given to the simulation of rainfall in an airstream and the effect of rain droplet impingement on the nose of projectiles, and especially to any penetration or accumulation of water at the base of the cavity that might increase the fundamental cavity frequency and/or reduce the intensity of sound production during rain conditions.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Journal of Aircraft (ISSN 0021-8669); 25; 281-283
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    Equilibrium shapes of rotating spheroids and drop shape oscillations (1988)
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    Publikationsdatum: 2011-08-19
    Beschreibung: Recent work on the equilibrium shapes of a rotating spheroid and drop shape oscillations is reviewed. The related theoretical aspects of the equilibrium shapes of a rotating drop, the stability, shape oscillations, gravitational forces, and drop fission are examined. Experimental findings on figures of a rotating drop in an immiscible system, drop oscillations in an immiscible system, oscillations of a rotating drop, compound drop oscillations, and drop dynamics in space are addressed.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
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    Oxygen plasma effects on several liquid droplet radiator fluids (1988)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Journal of Spacecraft and Rockets (ISSN 0022-4650); 25; 99-101
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    Solutions of one-dimensional steady nozzle flow revisited (1988)
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    Publikationsdatum: 2011-08-19
    Beschreibung: A formulation is presented by which any iteration process for obtaining the entropy increase in the flow of a one-dimensional steady nozzle is eliminated, and the simple solution of a quadratic equation is obtained. The proper parameters are then explicitly seen in the equation, and their effects on the solution are easily determined. Since only one root of the equation is physically admissible, entropy production, and therefore the shock wave, are uniquely determined by this set of parameters.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: AIAA Journal (ISSN 0001-1452); 26; 625-628
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    Karhunen-Loeve expansion of Burgers' model of turbulence (1988)
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    Publikationsdatum: 2011-08-19
    Beschreibung: The properties of the Karhunen-Loeve expansion of a strongly inhomogeneous random process are examined with emphasis on applications to turbulent flow fields. The ability of the KL expansion to represent functions that have both slow and rapid variations in a relatively small number of expansion terms is tested on a one-dimensional model based on the forced Burgers' equation. The rate of the convergence of the expansion is evaluated, and its dependence on the Reynolds number is determined. It is shown that the KL eigenfunctions possess wall boundary layers attached to outer structures that are independent of the Reynolds number (at high Reynolds numbers). It is also shown that the spectrum of eigenvalues is broad at large Reynolds numbers, requiring many terms to represent higher-order derivatives of the function.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Physics of Fluids (ISSN 0031-9171); 31; 2573-258
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    On the nonlinear interaction of Goertler vortices and Tollmien-Schlichting waves in curved channel flows at finite Reynolds numbers (1988)
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    Publikationsdatum: 2011-08-19
    Beschreibung: The flow in a two-dimensional curved channel driven by an azimuthal pressure gradient can become linearly unstable due to axisymmetric perturbations and/or nonaxisymmetric perturbations depending on the curvature of the channel and the Reynolds number. For a particular small value of curvature, the critical neighborhood of this curvature value and critical Reynolds number, nonlinear interactions occur between these perturbations. The Stuart-Watson approach is used to derive two coupled Landau equations for the amplitudes of these perturbations. The stability of the various possible states of these perturbations is shown through bifurcation diagrams. Emphasis is given to those cases which have relevance to external flows.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Journal of Fluid Mechanics (ISSN 0022-1120); 193; 569-595
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    Experimental and theoretical effects of nitrogen gas flow rate on liquid-jet atomization (1988)
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    Publikationsdatum: 2011-08-19
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Journal of Propulsion and Power (ISSN 0748-4658); 4; 406-411
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    Experimental study of thermocapillary flows in a thin liquid layer with heat fluxes imposed on the free surface (1988)
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    Publikationsdatum: 2011-08-19
    Beschreibung: To study thermocapillary flows in a two-dimensional thin liquid layer with heat fluxes imposed on the free surface experimentally, a long tray configuration was employed to simulate the infinite layer. The surface temperature distribution due to thermocapillary convection for different flow regimes was measured and compared with theorectical predictions. A short tray configuration was also employed to study the end wall effects (insulating or conducting). The results show that, for a strong convection flow with an insulating wall as the boundary, the surface temperature distribution became quite uniform. Consequently, the thermocapillary driving force was greatly reduced. On the other hand, a strong fluid motion always existed adjacent to the conducting wall because of the large surface temperature gradient near the wall.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Metallurgical Transactions A - Physical Metallurgy and Materials Science (ISSN 0360-2133); 19A; 1895-189
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    Transfinite element methodology for nonlinear/linear transient thermal modelling/analysis - Progress and recent advances (1988)
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    Publikationsdatum: 2011-08-19
    Beschreibung: The 'transfinite element method' (TFEM) proposed by Tamma and Railkar (1987 and 1988) for the analysis of linear and nonlinear heat-transfer problems is described and demonstrated. The TFEM combines classical Galerkin and transform approaches with state-of-the-art FEMs to obtain a flexible hybrid modeling scheme. The fundamental principles of the TFEM and the derivation of the governing equations are reviewed, and numerical results for sample problems are presented in extensive graphs and briefly characterized. Problems analyzed include a square plate with a hole, a rectangular plate with natural and essential boundary conditions and varying thermal conductivity, the Space Shuttle thermal protection system, a bimaterial plate subjected to step temperature variations, and solidification in a semiinfinite liquid slab.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: International Journal for Numerical Methods in Engineering (ISSN 0029-5981); 25; 475-494
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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 (1988)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: ASME, Transactions, Journal of Heat Transfer (ISSN 0022-1481); 110; 449-455
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  • 42
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    Reynolds-stress and dissipation-rate budgets in a turbulent channel flow (1988)
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    Publikationsdatum: 2011-08-19
    Beschreibung: The budgets for the Reynolds stresses and for the dissipation rate of the turbulence kinetic energy are computed using direct simulation data of a turbulent channel flow. The budget data reveal that all the terms in the budget become important close to the wall. For inhomogeneous pressure boundary conditions, the pressure-strain term is split into a return term, a rapid term, and a Stokes term. The Stokes term is important close to the wall. The rapid and return terms play different roles depending on the component of the term. A split of the velocity pressure-gradient term into a redistributive term and a diffusion term is proposed, which should be simpler to model. The budget data is used to test existing closure models for the pressure-strain term, the dissipation rate, and the transport rate. In general, further work is needed to improve the models.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Journal of Fluid Mechanics (ISSN 0022-1120); 194; 15-44
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    Transient radiative cooling of an absorbing and scattering cylinder - A separable solution (1988)
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    Publikationsdatum: 2011-08-19
    Beschreibung: A cylindrical region filled with absorbing-emitting material is cooled by radiation to surroundings at a much lower temperature. A solution is found showing that, for each set of parameters, the transient radial temperature distribution reaches a fixed shape, although the temperatures are decreasing with time. This 'fully developed' transient region is characterized by having a constant emittance based on instantaneous values of the cylinder heat loss and mean temperature. This emittance depends only on the optical radius of the cylinder and the scattering albedo. The emittance is lower than that for a cylinder at uniform temperature. This arises from the larger local cooling and, hence, reduced temperatures of the outer layers of the cylinder. An examination of this transient emittance provides the ranges of parameters within which the simplification can be made that the cylinder has uniform radial temperature distribution throughout the cooling process.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Journal of Thermophysics and Heat Transfer (ISSN 0887-8722); 2; 110-117
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    Nonlinear vortex trail dynamics (1988)
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    Publikationsdatum: 2011-08-19
    Beschreibung: The nonlinear evolution of periodic disturbances on vortex trails is considered. In addition to following small initial perturbations, large amplitude initial disturbances of the vortex trails are also studied. It is shown that the equations support a rich variety of essentially nonlinear solutions including unbounded and quasisteady ones. These solutions are found to correspond to various modes of vortex clustering in the physical plane. At the close of the paper, comparisons of these results with recent numerical and experimental findings on the wakes behind stationary cylinders, and also transversely oscillating bluff objects, are made.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Physics of Fluids (ISSN 0031-9171); 31; 991-998
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  • 45
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    Computation of the velocity field of an excited shear layer (1988)
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    Publikationsdatum: 2011-08-19
    Beschreibung: An infinitely thin shear layer emanating from a semi-infinite flat plate subjected to acoustic excitation is considered. The flow field outside the excited shear layer is computed employing a source distribution approach. Results are given for the region of the velocity field that cannot easily be obtained by analytical approximations.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Communications in Applied Numerical Methods (ISSN 0748-8025); 4; 85-89
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    Vibration of a liquid with a free surface in a spinning spherical tank (1981)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: The problem of forced fluid vibrations in a partially filled spinning spherical tank is solved numerically by using the finite element method. The governing equations include Coriolis acceleration and spatially homogeneous vorticity. An exponential instability is detected in the present simulation for fill ratios below 0.5 and centrifugal acceleration to thrust ratios less than 1.7. This fictitious instability appears in the model as a result of the homogeneous vortex assumption since the free slosh equations are neutrally stable in the Liapunov sense.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Journal of Sound and Vibration; 76; May 8
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    Heat transfer in cooled porous region with curved boundary (1981)
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    Publikationsdatum: 2011-08-18
    Beschreibung: Heat transfer characteristics are analyzed for a cooled two-dimensional porous medium having a curved boundary. A general analytical procedure is given in combination with a numerical conformal mapping method used to transform the porous region into an upper half plane. To illustrate the method, results are evaluated for a cosine shaped boundary subjected to uniform external heating. The results show the effects of coolant starvation in the thick regions of the medium, and the extent that internal heat conduction causes the heated surface to have a more uniform temperature.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
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    Interactive method for computation of viscous flow with recirculation (1981)
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    Publikationsdatum: 2011-08-18
    Beschreibung: An interactive method is proposed for the solution of two-dimensional, laminar flow fields with identifiable regions of recirculation, such as the shear-layer-driven cavity flow. The method treats the flow field as composed of two regions, with an appropriate mathematical model adopted for each region. The shear layer is computed by the compressible boundary layer equations, and the slowly recirculating flow by the incompressible Navier-Stokes equations. The flow field is solved iteratively by matching the local solutions in the two regions. For this purpose a new matching method utilizing an overlap between the two computational regions is developed, and shown to be most satisfactory. Matching of the two velocity components, as well as the change in velocity with respect to depth is amply accomplished using the present approach, and the stagnation points corresponding to separation and reattachment of the dividing streamline are computed as part of the interactive solution. The interactive method is applied to the test problem of a shear layer driven cavity. The computational results are used to show the validity and applicability of the present approach.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Journal of Computational Physics; 40; Apr. 198
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    Large-eddy simulation of the shear-free turbulent boundary layer (1981)
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    Publikationsdatum: 2011-08-18
    Beschreibung: The shear-free turbulent boundary layer is calculated by the large-eddy simulation technique. The filtered Navier-Stokes equations are used; the method of integration employs Fourier expansions in the homogeneous directions and finite differences in the cross-stream direction. Results indicate that the simulation is capable of predicting the primary Reynolds-number effects.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Journal of Fluid Mechanics; 103; Feb. 198
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    A molecular model for ice nucleation and growth, attachment 1 (1981)
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    Publikationsdatum: 2011-08-18
    Beschreibung: The quantum mechanical technique is used to study ionic, configurational, and impurity defects in the ice surface. In addition to static calculations of the energetics of the water monomer-ice surface interactions, molecular dynamics studies were initiated. The calculations of the monomer-ice surface interaction, molecular dynamics studies were initiated. The calculations of monomer-ice surface interactions indicate that many adsorption sites exist on the ice surfaces and that the barriers between bonding sites are relatively low. Bonding on the prism face of ice is preferentially above lattice sites.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: A Mol. Model for Ice Nucleation and Growth; 27 p
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    A molecular model for ice nucleation and growth, attachment 2 (1981)
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    Publikationsdatum: 2011-08-18
    Beschreibung: The central field empirical pair potential model is applied to studying the effects of kinks, ledges, and vacancies on the absorption of water molecules from the vapor. Molecular dynamics simulations indicate that cluster and/or surface modes play a primary role in the absorption process, the flexibility of the hydrogen bond serves to decrease the energy required for structural interconversion, and the rapid distribution of added energy in a hydrogen bonded system lead to aggregate stability which greatly exceeds that predicted by static energy calculations.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: A Mol. Model for Ice Nucleation and Growth; 22 p
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    Report of the panel on fluid dynamics (1981)
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    Publikationsdatum: 2011-08-18
    Beschreibung: Areas of investigation in fluid dynamics, recommended experiments, and use of the facility for theory evaluation are discussed. Tunnel flow quality and calibration of the NTF are considered. Recent technological advances affecting tunnel design are surveyed.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: High Reynolds Number Res. - 1980; p 169-195
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    Flux vector splitting of the inviscid gasdynamic equations with application to finite-difference methods (1981)
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    Publikationsdatum: 2011-08-18
    Beschreibung: The conservation-law form of the inviscid gasdynamic equations has the remarkable property that the nonlinear flux vectors are homogeneous functions of degree one. This property readily permits the splitting of flux vectors into subvectors by similarity transformations so that each subvector has associated with it a specified eigenvalue spectrum. As a consequence of flux vector splitting, new explicit and implicit dissipative finite-difference schemes are developed for first-order hyperbolic systems of equations. Appropriate one-sided spatial differences for each split flux vector are used throughout the computational field even if the flow is locally subsonic. The results of some preliminary numerical computations are included.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Journal of Computational Physics; 40; Apr. 198
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    Spectral energy transfer for inhomogeneous turbulence (1981)
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    Publikationsdatum: 2011-08-18
    Beschreibung: It is noted that several terms in the two-point spectral equation for homogeneous turbulence can be interpreted as spectral-transfer terms; that is, they represent the net rate of energy transfer into a wavenumber region from all other wavenumbers. This holds for terms associated with both turbulence and self-interaction and interaction between turbulence and mean gradients. It is not seen as obvious, however, that similar interpretations apply when the turbulence is not homogeneous. In particular, one might question the interpretation for the terms associated with turbulence self-interaction because the condition of homegeneity is generally used in making the interpretation. It is the purpose here to consider whether terms interpretable as transfer terms exist in the equations for inhomogeneous turbulence. It is found that certain terms in the two-point spectral equation can be interpreted as transfer terms.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Physics of Fluids; 24; Oct. 198
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    Distorted turbulence in axisymmetric flow (1981)
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    Publikationsdatum: 2011-08-18
    Beschreibung: A solution to the rapid-distortion theory for small-scale turbulence in flow round an axisymmetric obstacle is derived. General formulae for velocity covariances and Eulerian time scales are obtained and are evaluated for the particular case of flow round a sphere. The large-scale limit for this flow is also discussed.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Quarterly Journal of Mechanics and Applied Mathematics; 34; Nov. 198
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    Overlapping grids for flow field calculations (1988)
    In:  CASI
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    Publikationsdatum: 2013-08-31
    Beschreibung: Many problems in computational fluid dynamics (CFD) involve the calculation of flow fields within or around complex geometric configurations. The flow solution is computed on a computational grid. The construction of the grid is one of the major difficulties in the application of CFD to the analysis of flow about actual aircraft configurations. Due to geometric complexity, the grid has to be constructed in simple subregions and then all of these subgrids have to be pieced together to form a complete grid for the entire flow field. The entire grid, which is called a composite grid because it is formed from many parts, may have common regions. In either case, the computation of the flow field, using any numerical algorithm, will require the transfer of information between individual subgrids. The transfer of information is more difficult with overlapping grids. Algorithms have been developed and tested for automating the transfer of information between two overlapping grids.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Hampton Inst., NASA/American Society for Engineering Educ; Hampton Inst., NASA(
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    Modeling of transitional flows (1988)
    In:  CASI
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    Publikationsdatum: 2013-08-31
    Beschreibung: An effort directed at developing improved transitional models was initiated. The focus of this work was concentrated on the critical assessment of a popular existing transitional model developed by McDonald and Fish in 1972. The objective of this effort was to identify the shortcomings of the McDonald-Fish model and to use the insights gained to suggest modifications or alterations of the basic model. In order to evaluate the transitional model, a compressible boundary layer code was required. Accordingly, a two-dimensional compressible boundary layer code was developed. The program was based on a three-point fully implicit finite difference algorithm where the equations were solved in an uncoupled manner with second order extrapolation used to evaluate the non-linear coefficients. Iteration was offered as an option if the extrapolation error could not be tolerated. The differencing scheme was arranged to be second order in both spatial directions on an arbitrarily stretched mesh. A variety of boundary condition options were implemented including specification of an external pressure gradient, specification of a wall temperature distribution, and specification of an external temperature distribution. Overall the results of the initial phase of this work indicate that the McDonald-Fish model does a poor job at predicting the details of the turbulent flow structure during the transition region.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Hampton Inst., NASA/American Society for Engineering Educ; Hampton Inst., NASA(
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    Energy transfer in isotropic turbulence at low Reynolds numbers (1988)
    In:  CASI
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    Publikationsdatum: 2013-08-31
    Beschreibung: Detailed measurements were made of energy transfer among the scales of motion in incompressible turbulent fields at low Reynolds numbers generated by direct numerical simulation. It was observed that although the transfer resulted from triad interactions that were non-local in k space, the energy always transferred locally. The results are consistent with the notion of non-uniform advection of small weak eddies by larger and stronger ones, similar to transfer processes in the far dissipation range at high Reynolds numbers.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Stanford Univ., Studying Turbulence Using Numerical Simulation Databases, 2. Proceedings of the 1988 Summer Program; p 169-177
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    Multifractal spectra in homogeneous shear flow (1988)
    In:  CASI
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    Publikationsdatum: 2013-08-31
    Beschreibung: Employing numerical simulations of 3-D homogeneous shear flow, the associated multifractal spectra of the energy dissipation, scalar dissipation and vorticity fields were calculated. The results for (128) cubed simulations of this flow, and those obtained in recent experiments that analyzed 1- and 2-D intersections of atmospheric and laboratory flows, are in some agreement. A two-scale Cantor set model of the energy cascade process which describes the experimental results from 1-D intersections quite well, describes the 3-D results only marginally.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Studying Turbulence Using Numerical Simulation Databases, 2. Proceedings of the 1988 Summer Program; p 157-167
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    Pressure-strain-rate events in homogeneous turbulent shear flow (1988)
    In:  CASI
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    Publikationsdatum: 2013-08-31
    Beschreibung: A detailed study of the intercomponent energy transfer processes by the pressure-strain-rate in homogeneous turbulent shear flow is presented. Probability density functions (pdf's) and contour plots of the rapid and slow pressure-strain-rate show that the energy transfer processes are extremely peaky, with high-magnitude events dominating low-magnitude fluctuations, as reflected by very high flatness factors of the pressure-strain-rate. A concept of the energy transfer class was applied to investigate details of the direction as well as magnitude of the energy transfer processes. In incompressible flow, six disjoint energy transfer classes exist. Examination of contours in instantaneous fields, pdf's and weighted pdf's of the pressure-strain-rate indicates that in the low magnitude regions all six classes play an important role, but in the high magnitude regions four classes of transfer processes, dominate. The contribution to the average slow pressure-strain-rate from the high magnitude fluctuations is only 50 percent or less. The relative significance of high and low magnitude transfer events is discussed.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Studying Turbulence Using Numerical Simulation Databases, 2. Proceedings of the 1988 Summer Program; p 143-156
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    Scalar entrainment in the mixing layer (1988)
    In:  CASI
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    Publikationsdatum: 2013-08-31
    Beschreibung: New definitions of entrainment and mixing based on the passive scalar field in the plane mixing layer are proposed. The definitions distinguish clearly between three fluid states: (1) unmixed fluid, (2) fluid engulfed in the mixing layer, trapped between two scalar contours, and (3) mixed fluid. The difference betwen (2) and (3) is the amount of fluid which has been engulfed during the pairing process, but has not yet mixed. Trends are identified from direct numerical simulations and extensions to high Reynolds number mixing layers are made in terms of the Broadwell-Breidenthal mixing model. In the limit of high Peclet number (Pe = ReSc) it is speculated that engulfed fluid rises in steps associated with pairings, introducing unmixed fluid into the large scale structures, where it is eventually mixed at the Kolmogorov scale. From this viewpoint, pairing is a prerequisite for mixing in the turbulent plane mixing layer.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Studying Turbulence Using Numerical Simulation Databases, 2. Proceedings of the 1988 Summer Program; p 69-76
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    Phase decorrelation, streamwise vortices and acoustic radiation in mixing layers (1988)
    In:  CASI
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    Publikationsdatum: 2013-08-31
    Beschreibung: Several direct numerical simulations were performed and analyzed to study various aspects of the early development of mixing layers. Included are the phase jitter of the large-scale eddies, which was studied using a 2-D spatially-evolving mixing layer simulation; the response of a time developing mixing layer to various spanwise disturbances; and the sound radiation from a 2-D compressible time developing mixing layer.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Studying Turbulence Using Numerical Simulation Databases, 2. Proceedings of the 1988 Summer Program; p 29-39
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    A numerical study of bifurcations in a barotropic shear flow (1988)
    In:  CASI
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    Publikationsdatum: 2013-08-31
    Beschreibung: In the last few years, more and more evidence has emerged suggesting that transition to turbulence may be viewed as a succession of bifurcations to deterministic chaos. Most experimental and numerical observations have been restricted to Rayleigh-Benard convection and Taylor-Couette flow between concentric cylinders. An attempt is made to accurately describe the bifurcation sequence leading to chaos in a 2-D temporal free shear layer on the beta-plane. The beta-plane is a locally Cartesian reduction of the equations describing the dynamicss of a shallow layer of fluid on a rotating spherical planet. It is a valid model for large scale flows of interest in meteorology and oceanography.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Studying Turbulence Using Numerical Simulation Databases, 2. Proceedings of the 1988 Summer Program; p 41-47
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    Analysis of homogeneous turbulent reacting flows (1988)
    In:  CASI
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    Publikationsdatum: 2013-08-31
    Beschreibung: Full turbulence simulations at low Reynolds numbers were made for the single-step, irreversible, bimolecular reaction between non-premixed reactants in isochoric, decaying homogeneous turbulence. Various initial conditions for the scalar field were used in the simulations to control the initial scalar dissipation length scale, and simulations were also made for temperature-dependent reaction rates and for non-stoichiometric and unequal diffusivity conditions. Joint probability density functions (pdf's), conditional pdf's, and various statistical quantities appearing in the moment equations were computed. Preliminary analysis of the results indicates that compressive strain-rate correlates better than other dynamical quantities with local reaction rate, and the locations of peak reaction rates seem to be insensitive to the scalar field initial conditions.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Studying Turbulence Using Numerical Simulation Databases, 2. Proceedings of the 1988 Summer Program; p 243-255
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    Eddies, streams, and convergence zones in turbulent flows (1988)
    In:  CASI
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    Publikationsdatum: 2013-08-31
    Beschreibung: Recent studies of turbulent shear flows have shown that many of their important kinematical and dynamical properties can be more clearly understood by describing the flows in terms of individual events or streamline patterns. These events or flow regions are studied because they are associated with relatively large contributions to certain average properties of the flow, for example kinetic energy, Reynolds stress, or to particular processes in the flow, such as mixing and chemical reactions, which may be concentrated at locations where streamlines converge for fast chemical reactions (referred to as convergence or C regions), or in recirculating eddying regions for slow chemical reactions. The aim of this project was to use the numerical simulations to develop suitable criteria for defining these eddying or vortical zones. The C and streaming (S) zones were defined in order to define the whole flow field. It is concluded that homogeneous and sheared turbulent flow fields are made up of characteristic flow zones: eddy, C, and S zones. A set of objective criteria were found which describe regions in which the streamlines circulate, converge or diverge, and form high streams of high velocity flow.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Studying Turbulence Using Numerical Simulation Databases, 2. Proceedings of the 1988 Summer Program; p 193-208
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    Subharmonic resonance in a mixing layer (1988)
    In:  CASI
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    Publikationsdatum: 2013-08-31
    Beschreibung: The subharmonic resonance phenomenon in a spatially evolving mixing layer is studied using direct simulations of the 2-D Navier-Stokes equations. The computational domain extends to + or - infinity in the cross-stream direction with U(1) = 1.25 and U(2) = 0.25 imposed at + infinity and - infinity respectively. The domain is finite in the streamwise direction with inflow and outflow boundary conditions imposed at x/delta sub omega = 0 and 100, respectively. A hyperbolic-tangent mean velocity profile is assumed at the inlet and the Reynolds number based on the inlet vorticity thickness and velocity difference is Re = 600. It is observed that the phase angle between the fundamental and its subharmonic plays a key role in the spatial development of these modes. Contour plots of vorticity show that varying the phase will have a dramatic effect on the dynamics of the vortices. Pairing or shredding is observed depending on the phase. Fourier decomposition of the time traces show that the fundamental grows, saturates and decays with the downstream distance. The subharmonic has a similar behavior. However, the level at which the modes will saturate is affected by the phase. At 0 deg phase, it was found that as the fundamental saturates, the growth rate of the subharmonic is enhanced. At 90 deg phase, it was found that as the fundamental saturates, the growth rate of the subharmonic is inhibited. In the later case, the growth rate of the subharmonic recovers after saturation of the fundamental. These results are in qualitative agreement with experimental data.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Stanford Univ., Studying Turbulence Using Numerical Simulation Databases, 2. Proceedings of the 1988 Summer Program; p 57-68
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    Inflow/outflow boundary conditions and global dynamics of spatial mixing layers (1988)
    In:  CASI
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    Publikationsdatum: 2013-08-31
    Beschreibung: The numerical simulation of incompressible spatially-developing shear flows poses a special challenge to computational fluid dynamicists. The Navier-Stokes equations are elliptic and boundary equations need to be specified at the inflow and outflow boundaries in order to compute the fluid properties within the region of interest. It is, however, difficult to choose inflow and outflow conditions corresponding to a given experimental situation. Furthermore the effects that changes in the boundary conditions or in the size of the computational domain may induce on the global dynamics of the flow are presently unknown. These issues are examined in light of recent developments in hydrodynamic stability theory. The particular flow considered is the spatial mixing layer but it was expected that similar phenomena were bound to occur in other cases such as channel flow, the boundary layer, etc. A short summary of local/global and absolute/convective instability concepts is given. The results of numerical simulations are presented which strongly suggest that global resonances may be triggered in domains of finite streamwise extent although the evolution of the perturbation vorticity field is everywhere locally convective. A relationship between finite domains and pressure sources which might help in devising a scheme to eliminate these difficulties is discussed.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Stanford Univ., Studying Turbulence Using Numerical Simulation Databases, 2. Proceedings of the 1988 Summer Program; p 19-27
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    Chaos in a spatially-developing plane mixing layer (1988)
    In:  CASI
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    Publikationsdatum: 2013-08-31
    Beschreibung: A spatially-developing plane mixing layer was analyzed for chaotic behavior. A direct numerical simulation of the Navier-Stokes equations in a 2-D domain infinite in y and having inflow-outflow boundary conditions in x was used for data. Spectra, correlation dimension and the largest Lyapunov exponent were computed as functions of downstream distance x. When forced at a single (fundamental) frequency with maximum amplitude, the flow is periodic at the inflow but becomes aperiodic with increasing x. The aperiodic behavior is caused by the presence of a noisy subharmonic caused by the feedback between the necessarily nonphysical inflow and outflow boundary conditions. In order to overshadow this noise the flow was also studied with the same fundamental forcing and added random forcing of amplitude upsilon prime sub R/delta U = 0.01 at the inlet. Results were qualitatively the same in both cases: for small x, spectral peaks were sharp and dimension was nearly 1, but as x increased a narrowband spectral peak grew, spectra decayed exponentially at high frequencies and dimension increased to greater than 3. Based on these results, the flow appears to exhibit deterministic chaos. However, at no location was the largest Lyapunov exponent found to be significantly greater than zero.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Stanford Univ., Studying Turbulence Using Numerical Simulation Databases, 2. Proceedings of the 1988 Summer Program; p 3-18
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    Theoretical model for VITA-educed coherent structures in the wall region of a turbulent boundary layer (1988)
    In:  CASI
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    Publikationsdatum: 2013-08-31
    Beschreibung: Experiments on wall-bounded shear flows (channel flows and boundary layers) have indicated that the turbulence in the region close to the wall exhibits a characteristic intermittently formed pattern of coherent structures. For a quantitative study of coherent structures it is necessary to make use of conditional sampling. One particularly successful sampling technique is the Variable Integration Time Averaging technique (VITA) first explored by Blackwelder and Kaplan (1976). In this, an event is assumed to occur when the short time variance exceeds a certain threshold multiple of the mean square signal. The analysis presented removes some assumptions in the earlier models in that the effects of pressure and viscosity are taken into account in an approximation based on the assumption that the near-wall structures are highly elongated in the streamwise direction. The appropriateness of this is suggested by the observations but is also self consistent with the results of the model which show that the streamwise dimension of the structure grows with time, so that the approximation should improve with the age of the structure.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Stanford Univ., Studying Turbulence Using Numerical Simulation Databases, 2. Proceedings of the 1988 Summer Program; p 209-220
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    Optical propagation through a homogeneous turbulent shear flow (1988)
    In:  CASI
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    Publikationsdatum: 2013-08-31
    Beschreibung: Effects of organized turbulent structures on the propagation of an optical beam in a homogeneous shear flow were studied. A passive-scalar field in a computed turbulent shear flow is used to represent index-of-refraction fluctuations, and phase errors induced in a coherent optical beam by turbulent fluctuations are computed. The organized vortical structures produce a scalar distribution with elongated regions of intense fluctuations which have an inclination with respect to the mean flow similar to that of the characteristic hairpin eddies. It is found that r.m.s. phase error is minimized by propagating approximately normal to the inclined vortical structures. Two-point correlations of vorticity and scalar fluctuation suggest that the regions of intense scalar fluctuation are produced primarily by the hairpin eddies.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Studying Turbulence Using Numerical Simulation Databases, 2. Proceedings of the 1988 Summer Program; p 311-320
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    The structure of sheared turbulence near a plane boundary (1988)
    In:  CASI
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    Publikationsdatum: 2013-08-31
    Beschreibung: An analysis is presented of how a plane boundary affects the structure of turbulence in a sheared free stream. A uniform-shear boundary layer (USBL) is formulated with slip velocity condition at the surface, and inhomogeneous rapid distortion theory is applied. The effects of blocking by the surface on the turbulence structure in USBL is compared with those in the shear-free boundary layer (SFBL). Shear produces highly anisotropic eddies elongated in the flow direction. The vertical velocity variance is reduced with shear at all heights, roughly in proportion to the reduction in the homogeneous value, but the shape of the profile remains unchanged only near the surface. The streamwise integral scales increase with shear, indicating elongation of the streamwise extent of eddies.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Studying Turbulence Using Numerical Simulation Databases, 2. Proceedings of the 1988 Summer Program; p 221-241
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    Turbulence characteristics inside a turbulent spot in plane Poiseuille flow (1988)
    In:  CASI
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    Publikationsdatum: 2013-08-31
    Beschreibung: In wall-bounded shear flows the transition to turbulence through localized disturbances goes through a pattern starting with a development of shear layers. The localized normal velocity fluctuations induce normal vorticity through the lift-up effect. These shear layers become unstable to secondary disturbances, and if the amplitudes of the disturbances are large enough, a turbulent spot develops. Investigations of the spot in boundary layers has shown that the turbulent part of the spot is very similar to a fully developed boundary layer. Wygnanski et al. (1976) showed that the mean profile at the center-symmetry plane has a logarithmic region and Johansson et al. (1987) showed that both the higher-order statistics and flow structures in the spot were the same as in the corresponding fully developed flow. In what respects the turbulence inside the Poiseuille spot is similar to fully developed turbulent channel flow is studied. The numerically simulated spot is used, where the characteristics inside the spot are compared to those of the wave packet in the wingtip area. A recent experimental investigation of the velocity field associated with the Poiseuille spot by Klingmann et al. is used for comparison.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Stanford Univ., Studying Turbulence Using Numerical Simulation Databases, 2. Proceedings of the 1988 Summer Program; p 179-192
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    Turbulence production near walls: The role of flow structures with spanwise asymmetry (1988)
    In:  CASI
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    Publikationsdatum: 2013-08-31
    Beschreibung: Space-time evolution of near wall flow structures is described by conditional sampling methods, in which conditional averages are formed at various stages of development of shear layer structures. The development of spanwise asymmetry of the structures was found to be important in the creation of the structures and for the process of turbulence production.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Stanford Univ., Studying Turbulence Using Numerical Simulation Databases, 2. Proceedings of the 1988 Summer Program; p 131-141
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    Sensitivity of mixing layers to three-dimensional forcing (1988)
    In:  CASI
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    Publikationsdatum: 2013-08-31
    Beschreibung: It is well known that turbulent mixing layers are dominated by large scale, fairly coherent structures, and that these structures are related to the stability characteristics of the flow. These facts have led researchers to attempt controlling such flows by selectively forcing certain unstable modes, which can in addition have the effect of suppressing other modes. Much of the work on controlling the mixing layer has relied on forcing 2-D instabilities. The results of forcing 3-D instabilities are addressed. The objectives of the work are twofold: to understand how a mixing layer responds to 3-D perturbations, and to test the validity of an amplitude expansion in predicting the mixing layer development. The amplitude expansion could be very useful in understanding and predicting the 3-D response of the flow to a variety of initial conditions.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Stanford Univ., Studying Turbulence Using Numerical Simulation Databases, 2. Proceedings of the 1988 Summer Program; p 91-116
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    Use of passive scalar tagging for the study of coherent structures in the plane mixing layer (1988)
    In:  CASI
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    Publikationsdatum: 2013-08-31
    Beschreibung: Data obtained from the numerical simulation of a 2-D mixing layer were used to study the feasibility of using the instantaneous concentration of a passive scalar for detecting the typical coherent structures in the flow. The study showed that this technique works quite satisfactorily and yields results similar to those that can be obtained by using the instantaneous vorticity for structure detection. Using the coherent events educed by the scalar conditioning technique, the contribution of the coherent events to the total turbulent momentum and scalar transport was estimated. It is found that the contribution from the typical coherent events is of the same order as that of the time-mean value. However, the individual contributions become very large during the pairing of these structures. The increase is particularly spectacular in the case of the Reynolds shear stress.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Studying Turbulence Using Numerical Simulation Databases, 2. Proceedings of the 1988 Summer Program; p 77-89
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    Dynamics of coherent structures in a plane mixing layer (1988)
    In:  CASI
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    Publikationsdatum: 2013-08-31
    Beschreibung: An incompressible, time developing 3-D mixing layer with idealized initial conditions was simulated numerically. Consistent with the suggestions from experimental measurements, the braid region between the dominant spanwise vortices or rolls develops longitudinal vortices or ribs, which are aligned upstream and downstream of a roll and produce spanwise distortion of the rolls. The process by which this distortion occurs is explained by studying a variety of quantities of dynamic importance (e.g., production of enstrophy, vortex stretching). Other quantities of interest (dissipation, helicity density) are also computed and discussed. The currently available simulation only allows the study of the early evolution (before pairing) of the mixing layer. New simulations in progress will relieve this restriction.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Studying Turbulence Using Numerical Simulation Databases, 2. Proceedings of the 1988 Summer Program; p 49-55
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    Observations of breakup processes of liquid jets using real-time X-ray radiography (1988)
    In:  CASI
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    Publikationsdatum: 2013-08-31
    Beschreibung: To unravel the liquid-jet breakup process in the nondilute region, a newly developed system of real-time X-ray radiography, an advanced digital image processor, and a high-speed video camera were used. Based upon recorded X-ray images, the inner structure of a liquid jet during breakup was observed. The jet divergence angle, jet breakup length, and fraction distributions along the axial and transverse directions of the liquid jets were determined in the near-injector region. Both wall- and free-jet tests were conducted to study the effect of wall friction on the jet breakup process.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: NASA, Marshall Space Flight Center, Mixing and Demixing Processes in Multiphase Flows with Application to Propulsion Systems; p 125-133
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    The application of single particle hydrodynamics in continuum models of multiphase flow (1988)
    In:  CASI
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    Publikationsdatum: 2013-08-31
    Beschreibung: A review of the application of single particle hydrodynamics in models for the exchange of interphase momentum in continuum models of multiphase flow is presented. Considered are the equations of motion for a laminar, mechanical two phase flow. Inherent to this theory is a model for the interphase exchange of momentum due to drag between the dispersed particulate and continuous fluid phases. In addition, applications of two phase flow theory to de-mixing flows require the modeling of interphase momentum exchange due to lift forces. The applications of single particle analysis in deriving models for drag and lift are examined.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Mixing and Demixing Processes in Multiphase Flows With Application to Propulsion Systems; p 3-13
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    Migration arising from gradients in shear stress: Particle distributions in Poiseuille flow (1988)
    In:  CASI
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    Publikationsdatum: 2013-08-31
    Beschreibung: Experimental evidence for the existence of shear induced migration processes is reviewed and the mechanism by Leighton and Acrivos (1987b) is described in detail. The proposed mechanism is shown to lead to the existence of an additional shear induced migration in the presence of gradients in shear stress such as would be found in Poiseuille flow, and which may be used to predict the amplitude of the observed short-term viscosity increase. The concentration and velocity profiles which result from such a migration are discussed in detail and are compared to the experimental observations of Karnis, Goldsmith and Mason (1966).
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: NASA, Marshall Space Flight Center, Mixing and Demixing Processes in Multiphase Flows with Application to Propulsion Systems; p 109-124
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    Transient heat transfer from shrinking LOX-drop (1988)
    In:  CASI
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    Publikationsdatum: 2013-08-31
    Beschreibung: In order to achieve prescribed experimental conditions in wind tunnels, the nitrogen-oxygen mixture is enriched by injection of liquid oxygen (LOX) upstream of methane burners. The objective of the study is to determine the LOX drop evaporation rate, which is dominated by heat transfer from the air stream (mass transfer mechanism can be later coupled with the solution from the present work). Since the concentration of drops in the surrounding gas is quite high, the concept of infinite medium cannot be utilized. Drop evaporation, as part of system's mass balance, is an important source-term in the finite-difference 2/3-dimensional network terms of laboratory-system (Eulerian) coordinates, while individual drop behavior, including its thermal history, is analyzed in Lagrangian coordinates.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Hampton Inst., NASA/American Society for Engineering Educ; Hampton Inst., NASA(
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    An investigation of turbulence models (1988)
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    Publikationsdatum: 2013-08-31
    Beschreibung: The accuracy to which a turbulent boundary layer or wake can be predicted numerically depends on the validity of the turbulence closure model used. The modeling of turbulence physics is one of the most difficult problems in computational fluid dynamics (CFD). In fact, it is one of the pacing factors in the development of CFD. In general, there are three main approaches to the description of trubulence physics. First is turbulence modeling in which the Reynolds averaged Navier-Stokes equations are used and some closure approximation is made for the Reynolds stresses. A second approach to turbulence is large eddy simulation (LES) in which the computational mesh is taken to be fine enough that the large scale structure of the turbulence can be calculated directly. An empirical assumption must be made for the small scale sub-grid turbulence. The third approach is direct simulation. In this technique the Navier-Strokes equations are solved directly on a mesh which if fine enough to resolve the smallest length scale of the turbulence. The Reynolds averaged equations are not used and no closure assumption is required. These last two approaches require extensive computer resources and as such are not engineering tools. The purpose of the work was to investigate the various engineering turbulence models for accuracy and ease of programming. This involved comparison of the models with each other and with experimental data.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Hampton Inst., NASA/American Society for Engineering Educ; Hampton Inst., NASA(
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  • 82
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    Development of optimized, graded-permeability axial groove heat pipes (1988)
    In:  CASI
    Details
    Publikationsdatum: 2013-08-31
    Beschreibung: Heat pipe performance can usually be improved by uniformly varying or grading wick permeability from end to end. A unique and cost effective method for grading the permeability of an axial groove heat pipe is described - selective chemical etching of the pipe casing. This method was developed and demonstrated on a proof-of-concept test article. The process improved the test article's performance by 50 percent. Further improvement is possible through the use of optimally etched grooves.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: NASA, Goddard Space Flight Center, 15th Space Simulation Conference: Support the Highway to Space Through Testing; p 397-408
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  • 83
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    Confined turbulent fluid-particle flow modeling using multiple-realization particle trajectory schemes (1988)
    In:  CASI
    Details
    Publikationsdatum: 2013-08-31
    Beschreibung: A multiple-realization particle trajectory scheme has been developed and applied to the numerical prediction of confined turbulent fluid-particle flows. The example flows investigated include the vertical pipe upflow experimental data of Tsuji et al. and the experimental data of Leavitt for a coaxial jet flow, comprising a particle-laden central jet and a clean annular jet, into a large recirculation chamber. The results obtained from the numerical scheme agree well with the experimental data, lending confidence to the modeling approach. The multiple-realization particle trajectory turbulent flow modeling scheme is believed to be a more elegant and accurate approach to the extension of single-particle hydrodynamics to dilute multi-particle systems than the more commonly employed two-fluid modeling approach. It is also better able to incorporate additional force items such as lift, virtual mass and Bassett history terms directly into the particle equation of motion as appropriate. This makes it a suitable candidate for particle migration studies and an extension to situations involving liquid particulate phases with possible propulsion applications, such as in spray combustion, follows naturally.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Mixing and Demixing Processes in Multiphase Flows With Application to Propulsion Systems; p 55-85
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  • 84
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    Heat exchanger expert system logic (1988)
    In:  CASI
    Details
    Publikationsdatum: 2013-08-31
    Beschreibung: The reduction is described of the operation and fault diagnostics of a Deep Space Network heat exchanger to a rule base by the application of propositional calculus to a set of logic statements. The value of this approach lies in the ease of converting the logic and subsequently implementing it on a computer as an expert system. The rule base was written in Process Intelligent Control software.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: The Telecommunications and Data Acquisition Report; p 232-244
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  • 85
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    Multivalued velocity field model of turbulence (1981)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: The considered study is based on new theoretical concepts regarding a post-instability model of a fluid discussed by Zak (1980). The model permits the completion of the governing equations of turbulence by introducing multivalued fields of velocities. Attention is given to the mechanism of energy dissipation, the characteristic wave propagation, a simplified model, the formation of turbulence around stagnation points, the formulation of boundary conditions, and the mechanism of turbulence formation. The mechanism of turbulence formation can be understood as propagation of initial discontinuities from the boundaries into a flow with the characteristic velocity which is defined by the normal (to the boundary) velocity components. These components emerge at the boundary as a result of jumps in the tangential components due to the continuity equation.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Mechanics Research Communications; 8; 2, 19; 1981
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  • 86
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    On the mixing of a rectangular jet (1981)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: Hot-wire measurements in an incompressible rectangular jet, issuing into a quiet environment at ambient conditions, are presented. A blow-down-type air supply system was used to provide the airflow to a cylindrical settling chamber 1.75 m in length and 0.6 m in diameter. The measurements were made with constant-temperature anemometers in conjunction with linearizers. The two signals from the linearizers were sent through a sum and difference unit which was calibrated from dc to 100 kHz. The distributions of mean velocity and the turbulence shear stresses were measured in the two central planes of the jet stations up to 115 widths downstream of the nozzle exit. Three distinct regions characterized the jet flow field: a potential core origin, a two-dimensional-type region, and an axisymmetric type region. The onset of the second region appeared to be at a location where the shear layers separated by the short dimension of the nozzle meet; and the third region occurred at a downstream location where the two shear layers from the short edges of the nozzle meet. In the central plane, similarity was found both in the mean velocity and shear stress profiles beyond 30 widths downstream of the nozzle exit; profiles of rms velocity showed similarity in the second, but not the third region.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Journal of Fluid Mechanics; 107; June 198
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  • 87
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    Knowledge-based zonal grid generation for computational fluid dynamics (1988)
    In:  CASI
    Details
    Publikationsdatum: 2013-08-31
    Beschreibung: Automation of flow field zoning in two dimensions is an important step towards reducing the difficulty of three-dimensional grid generation in computational fluid dynamics. Using a knowledge-based approach makes sense, but problems arise which are caused by aspects of zoning involving perception, lack of expert consensus, and design processes. These obstacles are overcome by means of a simple shape and configuration language, a tunable zoning archetype, and a method of assembling plans from selected, predefined subplans. A demonstration system for knowledge-based two-dimensional flow field zoning has been successfully implemented and tested on representative aerodynamic configurations. The results show that this approach can produce flow field zonings that are acceptable to experts with differing evaluation criteria.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: NASA. Lyndon B. Johnson Space Center, 2nd Annual Workshop on Space Operations Automation and Robotics (SOAR 1988); p 73-80
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  • 88
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    The role of the turbulent Prandtl number in turbine blade heat transfer prediction (1988)
    In:  CASI
    Details
    Publikationsdatum: 2013-08-31
    Beschreibung: Improvement of the prediction of external (gas-to-blade) heat transfer coefficients in gas turbine engines was undertaken. The effects of improved eddy diffusivity of heat modeling in the turbulence model was specifically investigated. A two-dimensional boundary STAN5, was selected and modified by incorporating several different turbulent Prandtl number models. Results indicated that slight effects were attributable to the modified turbulence model. Boundary layer character appeared to be much more significant.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Alabama Univ., Research Reports: 1988 NASA(ASEE Summer Faculty Fellowship Program; 20 p
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  • 89
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    Vortex methods for separated flows (1988)
    In:  CASI
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    Publikationsdatum: 2013-08-31
    Beschreibung: The numerical solution of the Euler or Navier-Stokes equations by Lagrangian vortex methods is discussed. The mathematical background is presented and includes the relationship with traditional point-vortex studies, convergence to smooth solutions of the Euler equations, and the essential differences between two and three-dimensional cases. The difficulties in extending the method to viscous or compressible flows are explained. Two-dimensional flows around bluff bodies are emphasized. Robustness of the method and the assessment of accuracy, vortex-core profiles, time-marching schemes, numerical dissipation, and efficient programming are treated. Operation counts for unbounded and periodic flows are given, and two algorithms designed to speed up the calculations are described.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: VKI, Computational Fluid Dynamics, Volume 1; 64 p
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  • 90
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    Convergence speeding up in the calculation of the viscous flow about an airfoil (1988)
    In:  CASI
    Details
    Publikationsdatum: 2013-08-31
    Beschreibung: A finite volume method to solve the three dimensional Navier-Stokes equations was developed. It is based on a cell-vertex scheme with central differences and explicit Runge-Kutta time steps. A good convergence for a stationary solution was obtained by the use of local time steps, implicit smoothing of the residues, a multigrid algorithm, and a carefully controlled artificial dissipative term. The method is illustrated by results for transonic profiles and airfoils. The method allows a routine solution of the Navier-Stokes equations.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: DGLR, Flows with Separation; p 301-312
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  • 91
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    Ammonia transfer across rotating joints in space (1988)
    In:  CASI
    Details
    Publikationsdatum: 2013-08-31
    Beschreibung: Thermal control of future large space facilities, such as the space station, will require the transfer of anhydrous ammonia across rotating joints with near zero leakage. Anhydrous ammonia is the primary heat transfer fluid aboard the station, providing critical thermal management of habitat and payload systems. The solar radiator joints, as well as the various payload pointing systems, are obvious examples of the need for a reliable fluid transfer device. Low weight, tight temperature control, low parasitic drag torque, long life, and high reliability, in addition to near zero leakage, are important characteristics necessary for the successful operation of such a device. In late 1986, Lockheed initiated a project to develop a Rotary Transfer Coupling (RTC) directed toward space station requirements. Fabrication and assembly of this device is now complete and testing is scheduled. The design and development of the face seal-type rotary fluid coupling that utilizes a unique cover gas concept (an inert gas such as nitrogen) to provide full containment of the ammonia was addressed.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: NASA. Langley Research Center, The 22nd Aerospace Mechanisms Symposium; p 341-353
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  • 92
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    Analysis of capacitive heat exchangers, part 1 (1981)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: Governing equations are developed for a simple capacitive heat exchanger. This type of heat exchanger consists of hot spherical particles falling through an ascending cold gas stream. The assumptions made in deriving the continuity, momentum and energy equations are clearly stated. The analysis yields a system of first order, ordinary, nonlinear equations which form a complex boundary value problem. The method of solution is presented together with a comparison between the performance of capacitive heat exchangers and conventional counter flow ones.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: The Telecommun. and Data Acquisition Progr. Rept. 42-64; p 207-221
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  • 93
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    Role of coherent structures in turbulent shear flows (1981)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: A definition for the large-scale coherent structure is presented, and the nature and role of coherent structures in turbulent shear flows are examined. The equations governing the coherent motions and the experimental considerations as well as constraints in the investigations of coherent structures in wall-bounded and free turbulent shear flows are discussed. Results from a few of our recent and on-going studies of coherent structures in excited and unexcited free turbulent shear flows are reviewed. These results show that coherent structures are dominant in transport in the early stages of their formation, but not in the self-preserving regions of turbulent shear flows.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: vol. 4; Aug. 198
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  • 94
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    Laminar free convection boundary layer heat transfer over non-isothermal surface (1981)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: Accurate heat transfer results are provided for the case of nonisothermal objects. A steady, laminar, free convection boundary layer flow over two-dimensional or rotationally symmetrical bodies of nonuniform surface temperature situated in an ambient fluid of undisturbed temperature is considered analytically. The surface heat flux is given in terms of the Nusselt number and wall derivatives of universal functions for Prandtl numbers of 0.72 and 100 are provided. The method is shown to be valid up to a temperature/radius ratio of 130 deg.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
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  • 95
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    Vortex shedding experiment with flat and curved bluff plates in water (1988)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: Vortex shedding experiments were conducted in a water flow facility in order to simulate the strong discrete 4000-Hz vibration detected in the Space Shuttle Main Engine (SSME) which is thought to be associated with the SSME LOX inlet tee splitter vanes on the Main Injector. For the case of a flat vane with a blunt trailing edge excited by flow induced vortex shedding, lock-in with the first bending mode of the plate was observed. A curved vane displayed similar behavior, with the lock-in being a more discrete higher amplitude response. Aluminum vanes were employed to decouple the first vane bending mode from the vortex shedding mode. The application of an asymmetric 30-deg trailing edge bevel to both the flat and curved vanes was found to greatly reduce the strength of the shed vortices.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
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  • 96
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    Acoustics and dynamics of coaxial interacting vortex rings (1988)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: Using a contour dynamics method for inviscid axisymmetric flow we examine the effects of core deformation on the dynamics and acoustic signatures of coaxial interacting vortex rings. Both 'passage' and 'collision' (head-on) interactions are studied for initially identical vortices. Good correspondence with experiments is obtained. A simple model which retains only the elliptic degree of freedom in the core shape is used to explain some of the calculated features.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Fluid Dynamics Research (ISSN 0169-5983); 3; 1-4,
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  • 97
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    Nonlinear spatial evolution of an externally excited instability wave in a free shear layer (1988)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: This paper considers a disturbance evolving from a strictly linear finite-growth-rate instability wave, with nonlinear effects first becoming important in the critical layer. By incorporating viscous effects into the nonlinear critical-layer analysis of Goldstein and Leib (1988), it was possible to demonstrate how an initially linear instability wave evolves as it propagates downstream and how the viscous effects eventually become important, even when the viscosity is very small, due to continually decreasing scales generated by the nonlinear effects.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Journal of Fluid Mechanics (ISSN 0022-1120); 197; 295-330
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  • 98
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    The mean flow structure around and within a turbulent junction or horseshoe vortex. I - The upstream and surrounding three-dimensional boundary layer (1988)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: An experimental study of the mean flow structure upstream, around, and in a turbulent junction or horseshoe vortex is presented for the case of an incompressible subsonic flow. Mean velocity field and turbulent kinetic energy field measurements (obtained with hot film anemometry) and local wall shear stress measurements are used to monitor the upstream and surrounding three-dimensional turbulent boundary layer-like flow away from separation. Freestream or edge velocity and floor static pressure results are reported.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: ASME, Transactions, Journal of Fluids Engineering (ISSN 0098-2202); 110; 406-414
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  • 99
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    Observations of the frequencies in a sphere wake and of drag increase by acoustic excitation (1988)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: Vortex shedding and instability wave frequencies have been measured in the wakes of spheres in the Reynolds number range 500 less than Re less than 60,000. The effect of acoustic excitation was examined and an interaction between the two frequency modes was found at the lower Reynolds numbers; through this interaction, external forcing at the instability frequency could change the vortex shedding frequency. The development of the mean wake was manipulated by forcing near to the dominant shear layer instability frequency. With this forcing, the separated shear layer moved closer to the surface of the sphere and the reversed flow region of the wake was shortened. Concomitantly, the base pressure decreased and drag increased.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Physics of Fluids (ISSN 0031-9171); 31; 3260-326
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    Investigation of the flow between a pair of circular cylinders in the flopping regime (1988)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: The wakes of a pair of circular cylinders are grossly unsteady when the cylinders are separated in a direction normal to the approaching flow by less than one cylinder diameter. The wakes flop randomly between two asymmetric states. The time-scale for the flopping is several orders of magnitude longer than the timescale of vortex shedding, and also several orders of magnitude longer than the timescale for instability of the separating shear layers. When a splitter plate is positioned suitably on the centerline of the cylinders, the flopping can be stopped and the flow made to assume either of the asymmetric states, or a symmetric steady state. For a range of plate positions a new, periodic oscillation occurs. Acoustic excitation can also destroy the flopping mean flow, replacing it by a symmetric flow.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Journal of Fluid Mechanics (ISSN 0022-1120); 196; 431-448
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