Eighteenth Symposium on Naval Hydrodynamics (1991) / Chapter Skim
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The Flow Past a Wing-Body Junction - An Experimental Evaluation of Turbulence
The Flow Past a Wing-Body Junction - An Experimental Evaluation of Turbulence
Pages 815-828
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From page 815... ...
In particular, new models based on measurements are needed for the pressurestrain term. The ability of six turbulence models to predict the magnitude of the shear-stress vector from the mean-velocity and/or turbulence kinetic energy is examined.
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From page 816... ...
In discussing turbulence models and parameters other coordinate systems will be used distinguished by subscripts. Subscripts 'f', 's' and 'g' refer to coordinates fixed in the local free-stream direction, the local mean-flow direction and the local direction of the meanvelocity gradient vector, respectively.
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From page 817... ...
Although the intensity of turbulent fluctuations in the vicinity of the vortex falls in the favorable pressure gradient the peak values of turbulence kinetic energy remain many times those in the surrounding boundary layer because of the bimodal unsteadiness. Bimodal histograms are seen in the vicinity of the vortex in planes 3, 4 and 5 (figures 4(b)
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Contours of turbulence kinetic energy k/Uref in the vicinity of the vortex. Dotted lines enclose the regions in which bimodal histograms are observed 818
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Contours of turbulence kinetic energy k/Uref2 in the vicinity of the vortex. Dotted lines enclose the regions in which bimodal histograms are observed
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From page 820... ...
The quantity of experimental data and the variety of turbulence structure in this flow make it, in our opinion, ideal for testing the generality and therefore usefulness of turbulence models. EVALUATION OF TURBULENCE MODELS General Remarks Before evaluating the validity of turbulence models it is appropriate to discuss the relationship between the turbulent shear stress and velocity gradient directions since many models use or imply such a relationship.
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From page 821... ...
measured by difference are therefore needed. Turbulence models In this section the assumptions of several prescribed eddy viscosity models, the k-e model an algebraic-stress model and Bradshaw's (1971)
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The Johnson-King model was originally designed for two-dimensional adverse pressure gradient and separated boundary layers in which the maximum shear stress appears to be an appropriate scaling parameter. In the turbulence model Am is determined from a differential transport equation.
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Unlike the above models the k-e, algebraic stress and Bradshaw's (1971) model were given the measured distribution of turbulence kinetic energy from which to calculate the shear-stress magnitude.
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3 Figure 9. Histograms of the ratio of computed to measured turbulence shear stress magnitude compiled from co baritone at points inside the boundary layer (Vu /U > 5%)
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k-e model Figure 9. Histograms of the ratio of computed to measured turbulence shear stress magnitude compiled from comparisons at points inside the boundary layer (VuZ/U > 5%)
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Histograms of the ratio of computed to measured turbulence shear stress magnitude compiled from co ~arisons at points inside the boundary layer (Vu /U > 5%) but outside the nearwall region (Y/T > .02)
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From page 827... ...
Bradshaw PP, 1971, "Calculation of threedimensional turbulent boundary layers", Journal of Fluid Mechanics, vol.46, p.417-445. Chen H C and Patel V C, 1988, "Near-wall turbulence models for complex flows including separation", AIAA Journal, vol.
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From page 828... ...
As I'm sure you are aware, this model is the workhorse of the aerospace industry and also used extensively by the Navy laboratories and others. Also, was it possible through the comparisons to reach any conclusion with regard to the quasi-steady assumption, which is made in most current turbulence models?
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