Simulating a Supersonic Diffuser

noorsalehi · December 24, 2014, 01:33

Hi All,
I have tried to simulate an inviscid supersonic diffuser in CFX. The inlet boundary conditions are: mach number=3 , Total Pressure is 70000 pa & Total Temperature=300 K. I expect to have a normal shock in the throat or in the beginning of the diverging zone of the diffuser. Therefore the outlet flow regime must be subsonic.
In order to simulate an inviscid flow regime, the viscosity of the Air Ideal Gas is put to 1E-15 pa.s , the flow regime is laminar and the wall condition is free slip.
I have tested various back pressures at the outlet, but the normal shock has brought back to the converging zone and its position is not stable, so the solution will not be converged.

Is CFX a reliable software to simulate such internal regimes? If so, would you please help me solving this problem?

ghorrocks · December 25, 2014, 03:43

Yes, CFX should be able to model this.

Have you checked your boundary conditions are correct? Have you done a mesh sensitivity check? Also convergence criteria, time step size (if relevant) and boundary proximity?

This FAQ has more comments: http://www.cfd-online.com/Wiki/Ansys..._inaccurate.3F

samane_81 · November 23, 2022, 13:32

Hi Noorsalehi,
could you solve your problem?
Why didn't you use a pressure inlet?

December 24, 2014, 01:33	Simulating a Supersonic Diffuser	#1
noorsalehi New Member Hossein Noorsalehi Join Date: Dec 2014 Posts: 2 Rep Power: 0	Hi All, I have tried to simulate an inviscid supersonic diffuser in CFX. The inlet boundary conditions are: mach number=3 , Total Pressure is 70000 pa & Total Temperature=300 K. I expect to have a normal shock in the throat or in the beginning of the diverging zone of the diffuser. Therefore the outlet flow regime must be subsonic. In order to simulate an inviscid flow regime, the viscosity of the Air Ideal Gas is put to 1E-15 pa.s , the flow regime is laminar and the wall condition is free slip. I have tested various back pressures at the outlet, but the normal shock has brought back to the converging zone and its position is not stable, so the solution will not be converged. Is CFX a reliable software to simulate such internal regimes? If so, would you please help me solving this problem?

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December 25, 2014, 03:43		#2
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,703 Rep Power: 143	Yes, CFX should be able to model this. Have you checked your boundary conditions are correct? Have you done a mesh sensitivity check? Also convergence criteria, time step size (if relevant) and boundary proximity? This FAQ has more comments: http://www.cfd-online.com/Wiki/Ansys..._inaccurate.3F

November 23, 2022, 13:32		#3
samane_81 New Member samane Join Date: Dec 2012 Posts: 8 Rep Power: 13	Hi Noorsalehi, could you solve your problem? Why didn't you use a pressure inlet?