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  • 1
    Publication Date: 2019-06-27
    Description: The question is considered of how complex a model should be used for the calculation of turbulent shear flows. At the present time there are models varying in complexity from very simple eddy-transport models to models in which all the equations for the nonzero second-order correlations are solved simultaneously with the equations for the mean variables. A discussion is presented of the relationship between these two models of turbulent shear flow. Two types of motion are discussed: first, turbulent shear flow in a stratified medium and, second, the motion in a turbulent line vortex. These two cases are instructive because in the first example eddy-transport methods have proven reasonably effective, whereas in the second, they have led to erroneous conclusions. It is not generally appreciated that the simplest form of eddy-transport theory can be derived from second-order closure models of turbulent flow by a suitably limiting process. This limiting process and the suitability of eddy-transport modeling for stratified media and line vortices are discussed.
    Keywords: FLUID MECHANICS
    Type: NASA. Langley Res. Center Free Turbulent Shear Flows, Vol. 1; p 233-258
    Format: application/pdf
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  • 2
    Publication Date: 2019-06-27
    Description: Model equations for studying compressible turbulen boundary layers
    Keywords: FLUID MECHANICS
    Type: NASA-CR-116781 , ARAP-71-4
    Format: application/pdf
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  • 3
    Publication Date: 2019-07-13
    Description: A second-order closure model for two-dimensional, compressible shear flows is investigated using the invariant modeling technique developed by Donaldson. The invariant model parameters were originally selected by comparison of model predictions with critical experimental data on basic incompressible flows. Additional modeling for compressible flows has been introduced. A number of different shear flows such as the free shear layer, flat plate boundary layer and a simulation of the mixing region of a chemical laser are computed. The model is consistent with first-order closure turbulence models for equilibrium flows and is further capable of predicting nonequilibrium flows that cannot be correctly solved by eddy viscosity models. The results are in generally good agreement with experimental measurements but suggest the need for inclusion of a Mach number dependent model of the pressure diffusion terms in order to adequately represent high speed compressible flows.
    Keywords: FLUID MECHANICS
    Type: AIAA PAPER 74-592 , Fluid and Plasma Dynamics Conference; Jun 17, 1974 - Jun 19, 1974; Palo Alto, CA
    Format: text
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  • 4
    Publication Date: 2019-07-13
    Description: Turbulent shear flows transport properties, computing atmospheric and vortex motions by invariant modeling of Reynolds stress term in boundary layer momentum equation
    Keywords: FLUID MECHANICS
    Type: AIAA PAPER 71-217 , AEROSPACE SCIENCES MEETING; Jan 25, 1971 - Jan 27, 1971; NEW YORK, NY
    Format: text
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