code_saturne User's Forum

Dear Users,

I am on a learning phase of using code saturne. I simulated the Lagrangian particle tutorial. I am getting the velocity profile in the given image attached. I am not able to understand as if to why the velocity at the boundary is not zero as per wall conditions. Kindly help in this regard.

Regards
Mayank

Hello.
Fluid velocity will only be zero at the wall surface. In CFD codes, what you see in results depend on where are they discretised. If velocities are in cell centers, you only will see zero velocity at the wall with inflated mesh (SST turbulence model). If velocities are in mesh nodes (not cells) you may see zero velocity at the wall even without mesh inflation. It's normal, but, if you interested in near-wall region, you need appropriate inflation layers in your mesh with y+ <= 1...5 and SST model (you may need to relax pressure and velocity with relaxv parameter of 0.1...0.3 to obtain convergence). If you are not interested in precise heat exchange at the wall, pressure drop across long line or flow separation and reattachment, you may use k-epsilon or RSM model without mesh inflation layers (it's recommended to have y+ < approx 300 in this case). Velocity at the wall in postprocessor will not be zero, sub-cell wall functions will account for real near-wall velocity profile.