Zero equation turbulence model velocity scale
Hello,
I am simulating a ventilated room with inlet, outlet, and heat flux. I have tried the zero equation turbulence model for the simplicity, and the question is how to compute the velocity scale. Here's the zero equation: mu_t = rho * f_mu * U_t * l_t where U_t, the velocity scale, is the defined as the maximum velocity in the domain. Does this mean that CFX takes the maximum inlet/outlet velocity? What if it's a closed room with inlet and outlet replaced with wall BCs. Then is U_t zero? What if pressure boundary conditions are placed at the inlet and outlet? Is there a way to output this variable? I would greatly appreciate your help! Sincerely, Kim 
Re: Zero equation turbulence model velocity scale
Hi,
If you have problems defining a length/velocity scale then why not use SST or ke and you don't need to define it? SST and ke are going to give much better accuracy than a zero eqn model for room ventilation and should not add too much computational overheads. Glenn Horrocks 
Re: Zero equation turbulence model velocity scale
Thank you for your response, Glenn. I am aware that the zero equation model is not the best option, but I tried it for the simplicity. My project involves performing Galerkin projection of the NavierStokes and the energy equations onto the basis (from SVD anaysis) I create from the CFD data. As a preliminary step towards doing the same to the ke equation, I ran the model with the zero equation model since I don't have to worry about time varying viscosity just yet.

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