Hello:
COMSOL solves 5 equations for 2D turbulent flow: continuity equation, 2 momentum equations (u,v), equation for k end equation for eps.
In my study I do a simulation of 2D turbulent flow with k-eps model of COMSOL, I used the boundary conditions : inlet, outlet, wall , and in the top condition I want to impose a zero gradient for all variables except the epsilon (eps) which must have the Derechlet ie : eps=0.09*k^(1/3).
I want a help to impose eps=0.09*k^(1/3) in the upper lilmite of my channel, and the zero gradient for the other variables.
I'm not familiarized to COMSOL, but I guess adding Lagrange multipliers would do the trick.
May I ask why you set your BC eps=0.09*k^(1/3)? Is it the center line of pipe?
hello, thanks for your answer.
I want to simulate a Free surface Flow . If I use a plane of symmetry for the uper condition it is as if I simulate a closed flow (ie zero gradient for all variables in this plane) , but in my case the gradient of eps is not zero but a Dirichlet condition ie eps=0.09*k^(1/3) in this plane.
Thanks
Not quite sure if you can model the free surface as a symmetry plane.
hello, thanks for your answer
if the free surface is not deformable we can use the free surface as plane of symmetry , but we impose the Dirichlet condition for the dissipation rate in this plan (see Celic and Rodi (1982)).
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