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-   -   Visualization of coherenet structure (http://www.cfd-online.com/Forums/main/4238-visualization-coherenet-structure.html)

Jongdae Kim December 27, 2001 18:47

Visualization of coherenet structure
 
I'm doing simulation of flow around square prism three dimensionally.

The Re. based on prism dimension is 245. There will be mode A and mode B wake.

I'd like to visualize these flow structures.

Please let me know which method or which tool is appropriate.

I tried the method proposed by Jeong & Hussain. But the problem is the shear rate near the wall is very high and these are not the coherent structures. In tecplot, I'm not sure how to remove these high shear, incohrent part. And I'd like to know how to visualize the flow (coherent) structures reasonalbly. The objectivity is to visualize the streamwise and spanwise coherent structures and to investigate the reason of flow instability.

Mayank Tyagi January 2, 2002 18:33

Re: Visualization of coherenet structure
 
Hi Jongdae,

Try using the positive iso-surfaces of laplacian of pressure field. I am assuming that you are doing incompressible flow simulation. For this case you can show that the pressure laplacian is difference of two terms (vorticity magnitude squared- strain rate squared)..I'm omitting the constants here... and can be related to the invariants of the velocity gradient tensor....therefore the positive levels of laplacian of pressure should take care of high shear rate region.

However, I'm surprised to know that Jeong & Hussain's criterion is not doing the same...mathematically it is richer than laplacian of pressure field criterion.

There is a new paper by Horiuti in Physics of Fluids (basically extension of Jeong and Hussian's work)...may be that gives a sharper estimate of Coherent structure

Good luck Mayank


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