wall boundary condition

safa_c · August 7, 2010, 04:37

My question is about the wall boundary condition in cell-centered finite volume solver.

I assume when fixed and uniform wall boundary condition is applied to a surface of a 3D geometry before my CFD simulation, it should remain uniform and unchanged during the simulation.

When I check the contours of temperature of wall boundary condition after the simulation is converged, I can see that the solver (FLUENT) gives me a non-uniform temperature over the surface. (I checked it with and without node value)

Can anybody give me a hint why it happens?

falopsy · August 9, 2010, 13:55

In cell-centred finite volume method, the boundary conditions are implemented directly in the equations and the no values is stored for the variables at the boundaries (wall, symmetry etc). During post-processing, the values at the boundaries are actually extrapolated from the values close to the boundaries, so you end up not getting exactly the values implemented in the equations as the values now depends on the type of interpolation. The values will be very close though.

I'll advice you check the values and see if the differences is not too great. Check the range of your temperature contour and see if the discrepancies is not too great. If you have too high discrepancies, then maybe your solution is not yet converged enough (grid independence and lower residuals) and check everything is implemented well.

I hope this helps.

August 7, 2010, 04:37	wall boundary condition	#1
safa_c New Member Safa van Jansen Join Date: Aug 2010 Posts: 2 Rep Power: 0	My question is about the wall boundary condition in cell-centered finite volume solver. I assume when fixed and uniform wall boundary condition is applied to a surface of a 3D geometry before my CFD simulation, it should remain uniform and unchanged during the simulation. When I check the contours of temperature of wall boundary condition after the simulation is converged, I can see that the solver (FLUENT) gives me a non-uniform temperature over the surface. (I checked it with and without node value) Can anybody give me a hint why it happens?

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August 9, 2010, 13:55		#2
falopsy New Member Akinola Join Date: Jul 2010 Posts: 25 Rep Power: 16	In cell-centred finite volume method, the boundary conditions are implemented directly in the equations and the no values is stored for the variables at the boundaries (wall, symmetry etc). During post-processing, the values at the boundaries are actually extrapolated from the values close to the boundaries, so you end up not getting exactly the values implemented in the equations as the values now depends on the type of interpolation. The values will be very close though. I'll advice you check the values and see if the differences is not too great. Check the range of your temperature contour and see if the discrepancies is not too great. If you have too high discrepancies, then maybe your solution is not yet converged enough (grid independence and lower residuals) and check everything is implemented well. I hope this helps.