Where is the turbulence contribution
Dear All
I have been using turbulence models in CFD programs for quit some time now. So I thought I better start to get a better insight in how it affects the Navier Stokes Equation. What I have thought until now is that a turbulence model gives an additional contridution to the viscosity used in the Navier Stukoes equation!! Then I started reading and discovered that what the turbulence models actually contribute with is the Reynolds stress tensor. Is that it?? Does a turbulence model like the ke only calculate a Reynolds stress tensor that is used in the Navier Stokes equation?? And how is this then included in the linerised equation?? Is it just a part of the convective coefficient?? Regards Bo 
Re: Where is the turbulence contribution
A statistical turbulence model provides a closure for the unknown correlations that represent the turbulent fluxes of momentum (Reynolds stress tensor). The Reynolds stresses may be determined directly by solving a set of modelled transport equations for the Reynolds stresses themselves. The length scale must almost be determined, usually by solving for the dissipation rate e. However, conventional 2equation models, like the ke model, make use of the Boussinesq stressstrain relationship that relates the Reynolds stresses to the mean rate of strain through a scalar eddy viscosity. You can see how this enters the momentum equations if you substitute the Boussinesq stressstrain relationship for the Reynolds stresses in the statisticallyaveraged momentum equations.

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