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Time intergrate of mass flow

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Old   January 6, 2004, 00:50
Default Time intergrate of mass flow
  #1
Jackie
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Hi all,

I simulated an unsteady problem and like to know the total mass flow out at the portion interested. How could i calculate that value. Does CFX have the funtion to caculate it?.

Sincerely,

Jack
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Old   January 6, 2004, 17:58
Default Re: Time intergrate of mass flow
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Glenn Horrocks
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Hi Jackie,

What code are you using?

I don't think there is a function to integrate mass flow rate over a transient simulation to give total mass loss/gain. You can get the mass flow rate at each time step in CFX-Post, so you could write a script to extract it for each time step.

Alternatively in CFX5 you can make the mass flow rate at the current timestep an expression monitor point, and then you can easily extract the mass flow rate at each time step from the solver manager.

Glenn
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Old   January 6, 2004, 23:13
Default Re: Time intergrate of mass flow
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Jeff
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Jackie,

Create your expression monitor point, as Glenn suggests. Right click on the monitor point graph in the solver manager and "export data to file". This is much easier than extracting the data from the results file.

Import this data file into Excel and you can do a running integration of the mass flow (mass flow * dt + previous value). If you want to get fancy, use a trapezoidal integration using the average of the current and previous values times dt. The data will have just the time step number, so you'll have to know what you set the time step (dt) to in seconds.

Jeff
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Old   January 9, 2004, 00:18
Default Re: Time intergrate of mass flow
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Jackie
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Thank you very much Glenn and Jeff.
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