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Buoundary Condition for PisoFoam

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Old   October 13, 2010, 15:46
Default Buoundary Condition for PisoFoam
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Vishal Jambhekar
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Hallow all.

i am using pisofoam for simulation of surfboard fin.

I am using PisoFoam for both steady state and transient state calculation.

B.C inlet and oulet as patchs,

for velocity :
velocity inlet - inlet.
inletoutlet - outlet.
others are zerograd and symmetry plane at bottom.

for pressure :
pressure - outlet.
inlet - zerograd.
others are zerograd and symmetry plane at bottom.

value for k and epsilon are calculated for 3m/sec using formula mentioned in userguide.

Still i am getting sudden overshoot in current number after few iterations.

please help me in this regard.

Thanks a ton......
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Old   October 14, 2010, 02:40
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Sabin Ceuca
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I would start by checking if the mesh is fine enough at „problem zones“and then, if you don’t have good initial values for all your variables, to increase your U,k ,epsilon values in a ramp to the desired what you actually want to simulate.
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Old   October 16, 2010, 18:17
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Vishal Jambhekar
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Yes exactly, I am trying to do the same.

Does changing inlet and Outlet to walls from patch and applying wallfunctions can give better results. as used in cavity case for pisofoam. please let me know.

Thanks
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Old   October 18, 2010, 05:32
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Sabin Ceuca
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Well i don't think it is a good idea to change the inlet & outlet to wall, only if you have something like a tank.
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Old   October 21, 2010, 09:17
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Vishal Jambhekar
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Hi,

even i thoughe so, But i am really confused.

i am having a case as a wooden block is kept in stream of water.

Outlet : set to zero pressure
inlet : 3 m/sec.
side plaes: are symmetry.
bottom i set to zerograd.
and top also zerograd. i was wondering if i should set different condition at top surf as i have atmosphere there.

what do you think.
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