Massflow vs. Velocity

Science2108 · September 9, 2019, 09:50

Hello everybody,

i have a simple question: is there any difference in CFD using massflow inlet or velocity inlet? People told me that with a massflow inlet i get better results and its more stable than using velocity inlet. Is that truth? is there any reasonable explanation for it?

Thanks!

Science2108

Carlo_P · September 9, 2019, 10:11

I would suggest you to use velocity.
It is more accurate, since your solver don't have to calculate the area.
If your mesh is not good enought, you can have an huge error.
This is my opinion...
On the other hand, engineering factories normally speaks on massflowrate kg/h.

What other peolple think about?

FMDenaro · September 9, 2019, 11:31

As a general observation, prescribing only the mass flow rate does not say nothing about the shape of the velocity profile. It can adjust from the interior condition, a case that is suitable for the subsonic compressible flows.
For the incompressible flows, setting the velocity inlet profile works well.

September 9, 2019, 09:50	Massflow vs. Velocity	#1
Science2108 New Member Join Date: Jul 2019 Posts: 6 Rep Power: 6	Hello everybody, i have a simple question: is there any difference in CFD using massflow inlet or velocity inlet? People told me that with a massflow inlet i get better results and its more stable than using velocity inlet. Is that truth? is there any reasonable explanation for it? Thanks! Science2108

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September 9, 2019, 10:11		#2
Carlo_P Senior Member Carlo_P Join Date: May 2019 Location: Italy Posts: 176 Rep Power: 7	I would suggest you to use velocity. It is more accurate, since your solver don't have to calculate the area. If your mesh is not good enought, you can have an huge error. This is my opinion... On the other hand, engineering factories normally speaks on massflowrate kg/h. What other peolple think about?

September 9, 2019, 11:31		#3
FMDenaro Senior Member Filippo Maria Denaro Join Date: Jul 2010 Posts: 6,768 Rep Power: 71	As a general observation, prescribing only the mass flow rate does not say nothing about the shape of the velocity profile. It can adjust from the interior condition, a case that is suitable for the subsonic compressible flows. For the incompressible flows, setting the velocity inlet profile works well.