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-   -   Display Reynold Stresses in K-E (http://www.cfd-online.com/Forums/fluent/33486-display-reynold-stresses-k-e.html)

Andrew April 15, 2004 13:34

Display Reynold Stresses in K-E
 
I have searched long and hard to find a way to display the Reynolds Stress in the k-epsilon model, however the only way I can think of is to approximate by writing a custom defined function using Boussinesq approximation.

I need to be able to display:

uu vv ww uv

The easiest way I have found is once the solution has converged, is to switch to the RSM turbulence model and without doing anymore iterations go straight to the XY Plot and I am allowed to now select the Reynolds Stresses. Can I do it this way or not?

A further problem that I have is that I wish to display the above in a third order so that:

uuu uvv uww uuv vvv

Can be displayed,

(Of course all the above velocities have hats on them, I just cannot do that in this message)

Thank you

Andrew

ap April 15, 2004 18:55

Re: Display Reynold Stresses in K-E
 
The k-eps models doesn't calculate Reynolds stresses but directly solves for k and eps, so switching to RSM after the end of the calculation does not allow you to plot them.

Hi :)

ap

Andrew April 15, 2004 20:10

Re: Display Reynold Stresses in K-E
 
I just tried it and it allowed me to plot the reynold stresses, although I think it uses the RSM way of doing things.

I am just going to stick to typing in the Boussinesq hypothesis to a custom field function. I just wanted to avoid using more custom field functions.

gg April 16, 2004 05:30

Re: Display Reynold Stresses in K-E
 
Hi,

k-E is eddy viscosity model which means that Reynolds stress is replaced by turbulent viscosity. Turbulent viscosity is just link (in Boussinesq hyp.) between Reynolds stress and velocity gradients. Model has two additional transport equatitions (k, E) which are necessary to calculate turbulent viscosity.

If you switch to RSM than six transport equations (components of symmetric Reynolds stress tensor) are calculated. This is different level for turbulence modeling in CFD.

gg

ap April 16, 2004 19:12

Re: Display Reynold Stresses in K-E
 
What do you mean? You did your calculation with k-eps, then switched to RSM and, without iterating, did you plot the Reynold stresses? It seems strange.

Hi :)

ap


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