Outflow boundary condition for compressible flow

liebowitz · February 16, 2018, 01:11

Hi

I am using Fluent to simulate the interaction of a shock with a turbulent boundary layer in a wind tunnel.

My inlet boundary condition is a velocity, while the outlet parameters are not known. This means that the ideal boundary condition to be applied at the exit is an "outlet", which extrapolates pressure from within the domain.

However, I see that Fluent does not allow you to specify this boundary condition for the density-based solver which I am using. I don't really see that any of the other options are possible, since I do not have data at the exit.

Is there any way I can get around this problem?

Thanks in advance

LuckyTran · February 16, 2018, 10:15

You mean your outlet is supersonic? Otherwise it needs a BC.

If your outlet is supersonic then just a pressure outlet, use any pressure.

liebowitz · February 16, 2018, 11:56

Yes, the outlet is expected to be supersonic.

Wouldn't the outlet pressure affect how much the flow is accelerated by? Or would you say that my problem is not fully-specified unless I have this data?

February 16, 2018, 01:11	Outflow boundary condition for compressible flow	#1
liebowitz New Member Mathew Liebowitz Join Date: Jun 2017 Posts: 7 Rep Power: 8	Hi I am using Fluent to simulate the interaction of a shock with a turbulent boundary layer in a wind tunnel. My inlet boundary condition is a velocity, while the outlet parameters are not known. This means that the ideal boundary condition to be applied at the exit is an "outlet", which extrapolates pressure from within the domain. However, I see that Fluent does not allow you to specify this boundary condition for the density-based solver which I am using. I don't really see that any of the other options are possible, since I do not have data at the exit. Is there any way I can get around this problem? Thanks in advance

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February 16, 2018, 10:15		#2
LuckyTran Senior Member Lucky Join Date: Apr 2011 Location: Orlando, FL USA Posts: 5,676 Rep Power: 66	You mean your outlet is supersonic? Otherwise it needs a BC. If your outlet is supersonic then just a pressure outlet, use any pressure.

February 16, 2018, 11:56		#3
liebowitz New Member Mathew Liebowitz Join Date: Jun 2017 Posts: 7 Rep Power: 8	Yes, the outlet is expected to be supersonic. Wouldn't the outlet pressure affect how much the flow is accelerated by? Or would you say that my problem is not fully-specified unless I have this data?