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A critical evaluation of two-equation models for near wall turbulenceA variety of two-equation turbulence models,including several versions of the K-epsilon model as well as the K-omega model, are analyzed critically for near wall turbulent flows from a theoretical and computational standpoint. It is shown that the K-epsilon model has two major problems associated with it: the lack of natural boundary conditions for the dissipation rate and the appearance of higher-order correlations in the balance of terms for the dissipation rate at the wall. In so far as the former problem is concerned, either physically inconsistent boundary conditions have been used or the boundary conditions for the dissipation rate have been tied to higher-order derivatives of the turbulent kinetic energy which leads to numerical stiffness. The K-omega model can alleviate these problems since the asymptotic behavior of omega is known in more detail and since its near wall balance involves only exact viscous terms. However, the modeled form of the omega equation that is used in the literature is incomplete-an exact viscous term is missing which causes the model to behave in an asymptotically inconsistent manner. By including this viscous term and by introducing new wall damping functions with improved asymptotic behavior, a new K-tau model (where tau is identical with 1/omega is turbulent time scale) is developed. It is demonstrated that this new model is computationally robust and yields improved predictions for turbulent boundary layers.
Document ID
19900016954
Acquisition Source
Legacy CDMS
Document Type
Contractor Report (CR)
Authors
Speziale, Charles G.
(Institute for Computer Applications in Science and Engineering Hampton, VA., United States)
Abid, Ridha
(Vigyan Research Associates, Inc., Hampton VA., United States)
Anderson, E. Clay
(NASA Langley Research Center Hampton, VA., United States)
Date Acquired
September 6, 2013
Publication Date
June 1, 1990
Subject Category
Fluid Mechanics And Heat Transfer
Report/Patent Number
ICASE-90-46
NAS 1.26:182068
AD-A227110
NASA-CR-182068
Accession Number
90N26270
Funding Number(s)
CONTRACT_GRANT: NAS1-18605
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.
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