# closure coefficients in 2-eq. turb. models

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 December 4, 2003, 11:59 closure coefficients in 2-eq. turb. models #1 Michael Guest   Posts: n/a I am interested in varying the closure coefficients of a two-equation turbulence model for a given CFD simulation in order to see the effect (or lack of effect) from the corresponding coefficients. Is there a standard way to do this? Most coefficients are rather small ~0.01 to ~10, so randomly varying them, which would result in very large numbers as coefficient inputs, would necessitate the collection of a huge amount of data in order to see the effects on the flow field. Any help on this topic would be greatly appreciated. Thanks in advance.

 December 6, 2003, 12:41 Re: closure coefficients in 2-eq. turb. models #2 Jarmo Monttinen Guest   Posts: n/a I would suggest something along the lines that was done with the Spalart-Allmaras model (AIAA-92-0439). Apply this approach to whatever you wish to do with the model in the end and built from the simplest case up. -- Jarmo

 December 8, 2003, 13:15 Re: closure coefficients in 2-eq. turb. models #3 sylvain Guest   Posts: n/a First of all, you may try to solve your two equtaions models manually in very simple case : Decay of homogeneous turbulence (U=0; k(t=0)>0; Eps(t=0)>0) Growing of homogeneous turbulence under constant shear stress (dU/Dy >0; k(t=0)>0; Eps(t=0)>0) Asymptotic boundary layer between two flat plane in the log low region (Production(k)=Eps), Du/Dy is known, uv is known... Then you may see what is the effect of each constant and try to guess what should be their best variation domain. As an example, forn the k-eps model : Decay -> Ceps_2 (k propto t^(x), x depends on Ceps_2) Homogeneus shear stress -> Ceps2-Ceps1; C_nu (uv/k(t->infinity) is known ...) Boundary Layer : C_nu, Sigma_eps (see Patel for Sigma_eps)

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