Mass flow for symmetric geometry

andrew-c · March 17, 2023, 08:52

I have a 3D geometry of a pipe, which is cut down the center (r = 0) to exploit symmetry. So, the inlet and outlet faces are half-circles.

If I compute the mass flowrate at the inlet/outlet, does it adjust for the symmetry? I.e., with a mass flowrate of 1 kg/s, is it 1 kg/s for a half circle area or the whole circle area?

Thanks!

LuckyTran · March 17, 2023, 10:21

If you are specifying mass flowrate in kg/s then flowrate is according to the area that is in the mesh. You should provide a half-circle worth of kg/s.

If you have other BCs and are post-processing and using a mass flow report, then Fluent is reporting you the half-circle worth of kg/s and you need to multiply it by 2 to get the flow that you would have obtained through a full circle.

andrew-c · March 17, 2023, 11:11

Great! Thanks for your quick reply.

March 17, 2023, 08:52	Mass flow for symmetric geometry	#1
andrew-c New Member Andrew Join Date: Dec 2022 Posts: 29 Rep Power: 3	I have a 3D geometry of a pipe, which is cut down the center (r = 0) to exploit symmetry. So, the inlet and outlet faces are half-circles. If I compute the mass flowrate at the inlet/outlet, does it adjust for the symmetry? I.e., with a mass flowrate of 1 kg/s, is it 1 kg/s for a half circle area or the whole circle area? Thanks!

March 17, 2023, 10:21		#2
LuckyTran Senior Member Lucky Join Date: Apr 2011 Location: Orlando, FL USA Posts: 5,761 Rep Power: 66	If you are specifying mass flowrate in kg/s then flowrate is according to the area that is in the mesh. You should provide a half-circle worth of kg/s. If you have other BCs and are post-processing and using a mass flow report, then Fluent is reporting you the half-circle worth of kg/s and you need to multiply it by 2 to get the flow that you would have obtained through a full circle. soheil_r7 and andrew-c like this.

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March 17, 2023, 11:11		#3
andrew-c New Member Andrew Join Date: Dec 2022 Posts: 29 Rep Power: 3	Great! Thanks for your quick reply.