[yaseen wsu]

hellow everyone
as shown in the attached figure there is difference between outlet mass flow rate in CFX post and in solver after finishing, which one is correct?
https://www.cfd-online.com/Forums/at...1&d=1504038740

https://www.cfd-online.com/Forums/at...1&d=1504038763

[ghorrocks]

The solver calculates using the integration points. By default the results file has the results simplified back to just the nodes, so the post processor calculates using the nodal values. This will lead to a small difference between values calculated in the solver and the post processor. The difference should get smaller with a finer mesh. The "correct" value is the one calculated by the solver.

[Opaque]

I do not think you are comparing the same mass flows.

In the solver output, you are comparing the mass flow of water (Mass-Water) while in CFD-Post you are computing the total mass flow.

A more appropriate comparison would be to add the following to the CFX-Solver monitor output:

Water.massFlow()@outlet
massFlow()@outlet
<whichever other phase there is>.massFlow()@outlet

In CFD-Post, you should be able to compute the water mass flow by selecting the appropriate "Fluid" in the widget below. Also, you can select "Show equivalent expression" to see what expression is being computed.

[yaseen wsu]

Originally Posted by Opaque

I do not think you are comparing the same mass flows.

In the solver output, you are comparing the mass flow of water (Mass-Water) while in CFD-Post you are computing the total mass flow.

A more appropriate comparison would be to add the following to the CFX-Solver monitor output:

Water.massFlow()@outlet
massFlow()@outlet
<whichever other phase there is>.massFlow()@outlet

In CFD-Post, you should be able to compute the water mass flow by selecting the appropriate "Fluid" in the widget below. Also, you can select "Show equivalent expression" to see what expression is being computed.

Thanks for your explanation in detail, but I think the mass flow rate presented by solver after finishing is equal to that computed using monitor, is that right?

[Opaque]

One of them will, the other two will not.

Which one are you interested in verifying?

[yaseen wsu]

Originally Posted by Opaque

One of them will, the other two will not.

Which one are you interested in verifying?

I compared the outlet discharge which obtained from CFX-post with the experimental data, but without monitor as you said from previous post