Internal Flow BC: Increasing Inlet mach No.

syavash · March 3, 2012, 17:53

Dear friends,

I am dealing with the internal flow problem in Fluent. I have set the pressure Inlet BC so that the inlet mach be equal to 0.77. unfortunately in the very initial iterations the inlet mach No. begins to increase until it reaches to 1.2. I have tried Far-field BC for Inlet Condition but the the result is still the same.
How can I stop increasing Mach No.?

Far · March 4, 2012, 01:49

What is boundary condition at outlet and its non dimensional distance in terms of characteristic length from region of influence? Can you post pic of domain, mentioning the in and out? Rule of thump: lower the outlet pressure, higher the velocity at inlet

syavash · March 4, 2012, 16:25

Dear Far,
The geometry belongs into a Transonic Intake and I cant show the case due to job restrictions. The outlet BC is p-outlet and total length is about 3 meters, the major problem is that I have shock formation at the inlet throat and can't make it clear whether it is because of geometry or not. Principally the geometry should act as a diffuser (because that's an Intake!!) so we shouldn't get any shocks and this is somehow troubling. I have a validation case using NASA S-Duct at Mach 0.74. Anythings seems to be right but about the intake I'm not sure.
tnx for ur consideration

Far · March 4, 2012, 21:17

increase the back pressure

March 3, 2012, 17:53	Internal Flow BC: Increasing Inlet mach No.	#1
syavash Senior Member Syavash Asgari Join Date: Apr 2010 Posts: 473 Rep Power: 18	Dear friends, I am dealing with the internal flow problem in Fluent. I have set the pressure Inlet BC so that the inlet mach be equal to 0.77. unfortunately in the very initial iterations the inlet mach No. begins to increase until it reaches to 1.2. I have tried Far-field BC for Inlet Condition but the the result is still the same. How can I stop increasing Mach No.?

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March 4, 2012, 01:49		#2
Far Super Moderator Sijal Join Date: Mar 2009 Location: Islamabad Posts: 4,553 Blog Entries: 6 Rep Power: 54	What is boundary condition at outlet and its non dimensional distance in terms of characteristic length from region of influence? Can you post pic of domain, mentioning the in and out? Rule of thump: lower the outlet pressure, higher the velocity at inlet

March 4, 2012, 16:25		#3
syavash Senior Member Syavash Asgari Join Date: Apr 2010 Posts: 473 Rep Power: 18	Dear Far, The geometry belongs into a Transonic Intake and I cant show the case due to job restrictions. The outlet BC is p-outlet and total length is about 3 meters, the major problem is that I have shock formation at the inlet throat and can't make it clear whether it is because of geometry or not. Principally the geometry should act as a diffuser (because that's an Intake!!) so we shouldn't get any shocks and this is somehow troubling. I have a validation case using NASA S-Duct at Mach 0.74. Anythings seems to be right but about the intake I'm not sure. tnx for ur consideration

March 4, 2012, 21:17		#4
Far Super Moderator Sijal Join Date: Mar 2009 Location: Islamabad Posts: 4,553 Blog Entries: 6 Rep Power: 54	increase the back pressure