# Wall pressure interpolation for buoyant flow

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 April 27, 2010, 23:22 Wall pressure interpolation for buoyant flow #1 New Member   KaySee Join Date: Apr 2010 Posts: 4 Rep Power: 7 Dear CFD experts: I am developing an unstructured code and encounter a problem whereby the flow vector is pointing in/out near the wall when buoyancy model is on. I read from FLUENT manual that we can't set the normal pressure gradient at the wall = 0 when buoyant flow is simulated. Can anyone please guide me on the proper method to interpolate the wall pressure? Any references to share? I need the wall pressure in order for me to evaluate the cell pressure gradient near the wall. Please help. Thanks a lot.

April 28, 2010, 11:34
wall pressure
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CFDtoy
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Mirroring is not a good method when you have grav forces. Interpolation is the best way to achieve the pressure at the boundaries. Given this, use a second order gradient interpolation to connect Pcell with Pb - gives you second order accuracy.

/CFDtoy

Quote:
 Originally Posted by khaiching Dear CFD experts: I am developing an unstructured code and encounter a problem whereby the flow vector is pointing in/out near the wall when buoyancy model is on. I read from FLUENT manual that we can't set the normal pressure gradient at the wall = 0 when buoyant flow is simulated. Can anyone please guide me on the proper method to interpolate the wall pressure? Any references to share? I need the wall pressure in order for me to evaluate the cell pressure gradient near the wall. Please help. Thanks a lot.
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CFDtoy

 April 28, 2010, 21:04 #3 New Member   KaySee Join Date: Apr 2010 Posts: 4 Rep Power: 7 Dear CFD Toy: Thanks for your prompt reply. I tried to use the gradient projection method to interpolate the wall pressure, i.e. p_wall = p_cell + grad(p_cell) * d; where d is vector pointing from the near-wall cell to the wall face. For the evaluation of grad(p_cell), I use Grauss divergence theorem. Is it the method that you have suggested in your previous reply? In fact, I still see some velocities pointing in/out near the wall.

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