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-   -   velocity gradient issue in cfx (http://www.cfd-online.com/Forums/cfx/69712-velocity-gradient-issue-cfx.html)

rystokes November 2, 2009 06:01

velocity gradient issue in cfx
 
HI,

I'm trying to study shear rate in a simulation by generating the velocity gradient value in cfx. This value should have a dimension of inverse second. However, when I plot the magnitude of velocity gradient , I didn't find any unit there. So what's the definition of the variable "velocity gradient " in cfx?

Another question is about a variable, taking "velocity u. gradient" as an example, is it defined this way please?

velocity u. gradient=sqrt[(partial u/partial x)^2+(partial u/partial y)^2+(partial u/partial z)^2]?


Thanks a lot for your help in advance~!

alinik November 28, 2010 01:02

Hi

Did you find out about the definition of Velocity u.Gradient x in cfx?
I almost have the same problem.
There is one more thing, how can I define (partial u)/(partial x) in CEL expressions? do you have any idea?

ghorrocks November 28, 2010 18:21

But the variable velocity u.gradient does have units of s^-1, as expected.

And yes, velocity u.gradient=sqrt(velocity u.gradient X^2+velocity u.gradient Y^2+velocity u.gradient Z^2).

Ali's question is quite different. Read the documentation about getting spatial derivatives of variables. There is built in functions to calculate this in CEL.

alinik November 29, 2010 01:43

I found it in documentations
Thank you ghorrock


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