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Old   April 12, 2006, 15:42
Default turbulence modells
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I have some questions to turbulence modelling.

The one eq-modell from Spalart and Allmaras solves an additional equation for nu_t. (nu = nu + nu_t) 1. What would you say are the weaknesses compared to the k-epsilon-modell (2-eq-modell)? 2. f_1 is kind of a damper to assure that the turbulent viscosity dominates only in the mainstream. What is the difference between nu_t and nu_t^hat (I hope you understand what I mean - LATEX would be quite useful to make it clear...)

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Old   April 13, 2006, 06:24
Default it is more complex
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I have read further books/manuals and I understood that nu_t_hat is simply a modified turb. kinetic viscosity which is used to solve the partial differential equation.

The first term of the transport-eq. (on the right hand side) descripbes the production (G = C_b1*...*S*nu_t_hat) of turbulent viscosity. Near a solid wall the turb. viscosity is reduced to zero (production --> 0) - What happens with the destruction Y = f(nu_t_hat)?

(I understand production as a tranformation of the energy from the mean velocity into turbulent fluctuations.)
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