how to calculated the mass boundary flow

cfx_ws1992 · March 29, 2018, 21:07

I have a question about the calculation of mass flow in CFX Solver .
There's only a single fluid (water) at the entrance(Inlet) of my model, and the water temperature is 293.15K, the water density is 997 kg/m3(constant), the water velocity is 3.981e-5 m/s(constant), and the area of the Inlet interface is 4.1755e-4 m2.But the mass boundary flow on Inlet (water) is 5.66784e-6 kg/s in CFX Monitor.
I want to know how to calculated the mass boundary flow on Inlet (water) in CFX. I can't calculate the same results manually.

urosgrivc · March 30, 2018, 01:09

1) This wlues are quite small so be sure to use double precision.

2) mesh quality and size (actual surface CFD solver uses is determined by the mesh not geometry) so check if the area you use for hand calculation difers from mesh inlet area gretely or is it prety much the same.
You can check the exact area of your meshed inlet in cfd
post and compare it to true size, is it a bit different?

3) Convergence, check domain imbalances

if these are all ok than the result should be simmilar to manual calculation in this case

cfx_ws1992 · March 30, 2018, 02:01

Thank you for your advice.I'm going to check it out one by one.

March 29, 2018, 21:07	how to calculated the mass boundary flow	#1
cfx_ws1992 Member Shuai Wang Join Date: May 2017 Location: TaiYuan.China Posts: 30 Rep Power: 9	I have a question about the calculation of mass flow in CFX Solver . There's only a single fluid (water) at the entrance(Inlet) of my model, and the water temperature is 293.15K, the water density is 997 kg/m3(constant), the water velocity is 3.981e-5 m/s(constant), and the area of the Inlet interface is 4.1755e-4 m2.But the mass boundary flow on Inlet (water) is 5.66784e-6 kg/s in CFX Monitor. I want to know how to calculated the mass boundary flow on Inlet (water) in CFX. I can't calculate the same results manually.

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March 30, 2018, 01:09		#2
urosgrivc Senior Member urosgrivc Join Date: Dec 2015 Location: Slovenija Posts: 365 Rep Power: 11	1) This wlues are quite small so be sure to use double precision. 2) mesh quality and size (actual surface CFD solver uses is determined by the mesh not geometry) so check if the area you use for hand calculation difers from mesh inlet area gretely or is it prety much the same. You can check the exact area of your meshed inlet in cfd post and compare it to true size, is it a bit different? 3) Convergence, check domain imbalances if these are all ok than the result should be simmilar to manual calculation in this case

March 30, 2018, 02:01		#3
cfx_ws1992 Member Shuai Wang Join Date: May 2017 Location: TaiYuan.China Posts: 30 Rep Power: 9	Thank you for your advice.I'm going to check it out one by one.