Operating pressure location

nima_nz · July 26, 2021, 12:53

Hi everyone

I'm working on the simulation of a bluff body (cubic obstacle) in the airflow domain by Ansys fluent. The domain has inlet and outlet and symmetry boundary conditions. The velocity inlet would have only velocity component in the stream-wise direction.
Where is the proper location for reference pressure in the domain? By reference pressure I mean the one we set in the operating condition tab.

Many thanks

LuckyTran · July 26, 2021, 16:12

If you have a pressure outlet as a BC then it doesn't even matter.

In most cases you can leave the location alone, since it's not that critical. You would only really want to specify the reference pressure location if you knew the absolute static pressure at a specific location, then you would set it at the known location.

nima_nz · July 26, 2021, 16:59

Quote:

Originally Posted by LuckyTran

If you have a pressure outlet as a BC then it doesn't even matter.

In most cases you can leave the location alone, since it's not that critical. You would only really want to specify the reference pressure location if you knew the absolute static pressure at a specific location, then you would set it at the known location.

It’s not pressure outlet. It’s outflow B.C.
I know it doesn’t matter but in the model I get the negative static pressure where it should be maximum pressure

LuckyTran · July 26, 2021, 22:15

You should set the location at the cell where the absolute pressure is exactly equal to the operating pressure. Fluent is going to search for the cell nearest that location. Since that cell is guaranteed to be somewhere in the computational domain, that means the operating pressure will be specified somewhere on the domain. If you still encounter roundoff errors despite that, then you must be doing something special or your operating pressure is just tens of orders of magintude off. If the former, then you simply have no pressure changes in the domain that is greater than roundoff error and having a negative pressure is not even significant. If the latter happened, then the problem was not the reference location in the first place.

July 26, 2021, 12:53	Operating pressure location	#1
nima_nz Member Nima Join Date: May 2014 Location: Ireland Posts: 51 Rep Power: 11	Hi everyone I'm working on the simulation of a bluff body (cubic obstacle) in the airflow domain by Ansys fluent. The domain has inlet and outlet and symmetry boundary conditions. The velocity inlet would have only velocity component in the stream-wise direction. Where is the proper location for reference pressure in the domain? By reference pressure I mean the one we set in the operating condition tab. Many thanks

July 26, 2021, 22:15		#4
LuckyTran Senior Member Lucky Join Date: Apr 2011 Location: Orlando, FL USA Posts: 5,675 Rep Power: 66	You should set the location at the cell where the absolute pressure is exactly equal to the operating pressure. Fluent is going to search for the cell nearest that location. Since that cell is guaranteed to be somewhere in the computational domain, that means the operating pressure will be specified somewhere on the domain. If you still encounter roundoff errors despite that, then you must be doing something special or your operating pressure is just tens of orders of magintude off. If the former, then you simply have no pressure changes in the domain that is greater than roundoff error and having a negative pressure is not even significant. If the latter happened, then the problem was not the reference location in the first place. nima_nz and aero_head like this.

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July 26, 2021, 16:12		#2
LuckyTran Senior Member Lucky Join Date: Apr 2011 Location: Orlando, FL USA Posts: 5,675 Rep Power: 66	If you have a pressure outlet as a BC then it doesn't even matter. In most cases you can leave the location alone, since it's not that critical. You would only really want to specify the reference pressure location if you knew the absolute static pressure at a specific location, then you would set it at the known location.