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-   -   Velocity gradient (http://www.cfd-online.com/Forums/cfx/69403-velocity-gradient.html)

saewoong98 October 21, 2009 20:43

Velocity gradient
 
Hi everyone.
I am trying to compute the each componet of shear strain rate, mean value of each velocity gradient component, and standard deviation of each velocity gradient component. I am doing my calculations with D.N.S.
Is there anyone how to compute those variables?

stumpy October 27, 2009 16:54

It looks like only the scalar Shear Strain Rate is available, so I can't help you there. The other variables are easily obtained:
- Create Additional Variables in CFX-Pre for each of the required velocity gradients. Set the AV values to "Velocity u.Gradient X", "Velocity u.Gradient Y", etc. During the solution you can now access these gradients via the AV's
- Under "Output Control > Trn Stats", create the required statistics for the AV's (mean and standard deviation).

saewoong98 October 28, 2009 12:14

Thank you for your help.
I tried to create additional variables in CFX-pre.
I opened " Edit in command".
I typed in Option = Value, Additional Varialbe Value = Velocity u.Gradient X.
But, it didn't work.
One more question, those variables didn't show up on the Trn Stats variable list.
Can you give me any advice?

stumpy October 29, 2009 14:09

When you say it didn't work, what was the error. Try running in the solver, it may work and it's jsut Pre that giving an error. I'm not sure why you're typing in values through the commend editor - use the GUI!

saewoong98 October 29, 2009 19:09

I created 9 additional variables for each velocity gradient.
The options that I can handle are variable type, unit, tensor type.
That's why I typed in command window.
Am I doing wrong way?


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