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How to define strain rate and shear rate magnitude in CFD-Post?

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Old   January 12, 2017, 22:17
Default How to define strain rate and shear rate magnitude in CFD-Post?
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Khan
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Hi there,

I was just wondering how to define "strain rate magnitude" and "shear rate magnitude" in CFD-Post. Actually, I have found an useful post from this forum (strain rate magnitude), but I was confused "what actual expression I have to enter" in order to define them in CFD-Post.

Thank you very much for your help!
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Old   January 13, 2017, 09:09
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If you have all the velocity derivatives, use those to calculate the strain rate. Have a look in the link you shared or in the Fluent User's Guide to see how the strain rate is defined. Alternatively, in Fluent you can just choose File -> Data File Quantities... and pick Strain Rate there. Save data and open in CFD-Post. Now the strain rate is available. Bear in mind that this strain rate is computed using only the velocity derivatives so it cannot capture the strain rate at scales smaller than the grid. One way how to estimate the "turbulent strain rate" would be: gamma=sqrt(eps*rho/mu)
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Old   January 13, 2017, 14:13
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Dear Zbynek,

Thanks for your reply.

As for your second suggestion, the "Data File Quantities" is not available in my Fluent (https://drive.google.com/open?id=0B1...Gtidk96VFRBR0U) Do you know how to address it by any chance?

Thanks!
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Old   January 13, 2017, 14:38
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I've addressed it. In order to use the "Data File Quantities" I have to initialize the solution using the Solution Initialization task page first.

Thank you!
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