trouble in applied BC

m.qafari · May 15, 2010, 03:01

I’m going to model viscous flow passes through porous duct in CFX or Fluent software. This process is time dependent and there are two immiscible fluids (Air and resin).
At first, there is air in duct. A vacuum pump in deferent produces vacuum at the duct’s outlet and exhausts air and air is replaced by resin.
What types of boundary condition are suitable for this simulation in CFX or Fluent software? Can I apply pressure inlet as intake boundary condition, while pressure outlet is applied as outlet vent?
I tried to model a viscous flow by “pressure inlet” and “pressure outlet” in CFX but there was a trouble and CFX announced “floating point exception” and solve was terminated with error so soon. CFX manual offers that applicants should use “velocity inlet”! But I don’t know anything about velocity of fluids in domain.
What can I do?
I would be very grateful for any advice.
Best regards.

ghorrocks · May 15, 2010, 07:05

You should be able to use a pressure inlet for this application.

The floating point exception just means the solver has diverged big-time. You just need to improve numerical stability - try smaller time steps, double precision solver, improving mesh quality etc. Also be careful with the porous region, that can cause convergence difficulties.

May 15, 2010, 03:01	trouble in applied BC	#1
m.qafari New Member mojtaba Join Date: May 2010 Posts: 1 Rep Power: 0	I’m going to model viscous flow passes through porous duct in CFX or Fluent software. This process is time dependent and there are two immiscible fluids (Air and resin). At first, there is air in duct. A vacuum pump in deferent produces vacuum at the duct’s outlet and exhausts air and air is replaced by resin. What types of boundary condition are suitable for this simulation in CFX or Fluent software? Can I apply pressure inlet as intake boundary condition, while pressure outlet is applied as outlet vent? I tried to model a viscous flow by “pressure inlet” and “pressure outlet” in CFX but there was a trouble and CFX announced “floating point exception” and solve was terminated with error so soon. CFX manual offers that applicants should use “velocity inlet”! But I don’t know anything about velocity of fluids in domain. What can I do? I would be very grateful for any advice. Best regards.

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May 15, 2010, 07:05		#2
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,700 Rep Power: 143	You should be able to use a pressure inlet for this application. The floating point exception just means the solver has diverged big-time. You just need to improve numerical stability - try smaller time steps, double precision solver, improving mesh quality etc. Also be careful with the porous region, that can cause convergence difficulties.