# kOmegaSST wall functions and mass inlet boundary

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 February 4, 2015, 05:58 kOmegaSST wall functions and mass inlet boundary #1 New Member   Frans Visscher Join Date: Dec 2014 Posts: 2 Rep Power: 0 Dear CFD'ers, For my master Thesis I have to model an semi-confined jet, starting from the flat plate to and later on extend the model to an bend and multiphase. However I am currently struggling with the kOmega (SST in particular) I have noticed the following things: The automatic wall functions for the kOmegaSST is calculating the dissipation omega as w = sqrt((w_vis)^2+(w_log)^2) which are given in Menter's publications. I found this verification in the wall function source code (the only one available in OF 2.3.x for omega for incompressible flow). So assume the wall function must be specified separately. The source code for the turbulence model however also indicates that it uses the modification by Hellsten to account for rough walls using the extra blending factor F3. Now here comes my first problem: why is the omega wall function than not equipped with the rough wall condition given i believe at first in Wilcox's paper as: w=(u_tau^2/nu)*S_R where u_tau is the friction velocity, nu is kinematic viscosity and S_R is a factor dependent on the non dimensional equivalent grain size? Secondly, how can I specify the mass injection boundary condition for omega at my inlet as suggested also by Wilcox: w=(u_tau^2/nu)*S_B where S_B is a factor depending on the normal velocity at this surface in a non dimensional form defined as v_n+=v_n/u_tau Note: w stands here for omega Now of course I can start coding myself but that would take me more time than I probably have for this 'introduction problem' and it will astonish me when these functions are never been missed before in OF by others (if they really are not part of it). So does anyone have an answer? Thanks in advance! Last edited by FransVisscher; February 4, 2015 at 07:01.

 Tags boundary, komegasst, menter, omega, wilcos

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