Force bug in 1.5-dev???

hansel · September 7, 2009, 01:43

I've constructed a 2d 10mx10m wind tunnel with a 1m diameter cylinder right in the middle. I've blown air in the +x direction at several different speeds and used the libforces.so library to get the force on the cylinder.

In every case the largest force ends up in the -Y direction due to pressure. I would expect it to be in the +X direction. The small force in the pressure X component actually points upwind.

In paraFoam the pressure appears to be equal on the +Y and -Y side of the cylinder. The only asymmetry is in the X direction.

Were there any known bugs in 1.5 that swapped the force components?

Steve

hansel · September 7, 2009, 17:31

Update to this problem. I made my mesh 3x finer at the surface and now the forces are at least going in the right direction. Maybe this was all a mesh problem.

September 7, 2009, 01:43	Force bug in 1.5-dev???	#1
hansel Senior Member Steve Hansel Join Date: Jun 2009 Location: Colorado, USA Posts: 112 Rep Power: 5	I've constructed a 2d 10mx10m wind tunnel with a 1m diameter cylinder right in the middle. I've blown air in the +x direction at several different speeds and used the libforces.so library to get the force on the cylinder. In every case the largest force ends up in the -Y direction due to pressure. I would expect it to be in the +X direction. The small force in the pressure X component actually points upwind. In paraFoam the pressure appears to be equal on the +Y and -Y side of the cylinder. The only asymmetry is in the X direction. Were there any known bugs in 1.5 that swapped the force components? Steve

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September 7, 2009, 17:31		#2
hansel Senior Member Steve Hansel Join Date: Jun 2009 Location: Colorado, USA Posts: 112 Rep Power: 5	Update to this problem. I made my mesh 3x finer at the surface and now the forces are at least going in the right direction. Maybe this was all a mesh problem.