Degree Type

Dissertation

Date of Award

1992

Degree Name

Doctor of Philosophy

Department

Mechanical Engineering

First Advisor

Richard H. Pletcher

Abstract

Wall functions are often employed to model turbulent flow near solid walls. A method has not been available, however, for the application of wall functions to generalized curvilinear coordinate systems, particularly those with nonorthogonal grids. A general method for this application is developed herein;A k-[epsilon] turbulence model suitable for compressible flow, including the new wall function formulation, has been incorporated into an existing compressible Reynolds-averaged Navier-Stokes code, F3D. The low-Reynolds-number k-[epsilon] model of Chien (1982) was added for comparison with the present method. A number of features were also added to F3D, including improved far-field boundary conditions and viscous terms in the streamwise direction;A series of computations of increasing complexity was run to test the effectiveness of the new formulation. Flow over a flat plate was computed using both orthogonal and nonorthogonal grids, and the friction coefficients and velocity profiles compared with a semi-empirical equation. Flow over a body of revolution at zero angle of attack was then computed to test the method's ability to handle flow over a curved surface. Friction coefficients and velocity profiles were compared to test data. The same case was also computed using the Chien (1982) low-Reynolds-number k-[epsilon] model and the Baldwin-Lomax (1978) algebraic model for comparison. All three models gave good results on a relatively fine grid, but only the wall function formulation was effective with coarser grids. Finally, in order to demonstrate the method's ability to handle complex flowfields, separated flow over a prolate spheroid at angle of attack was computed, and results were compared to test data. The results were also compared to the computation of Kim and Patel (1991), in which a k-[epsilon] model with a one-equation model patched in at the wall was employed. Both models gave reasonable solutions, but they require improvement for accurate prediction of friction coefficients in the separated regions.

DOI

https://doi.org/10.31274/rtd-180813-11746

Publisher

Digital Repository @ Iowa State University, http://lib.dr.iastate.edu/

Copyright Owner

Douglas L. Sondak

Language

en

Proquest ID

AAI9223968

File Format

application/pdf

File Size

172 pages

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