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-   -   How aspect ratio affects k-e isotropy? (http://www.cfd-online.com/Forums/fluent/28567-how-aspect-ratio-affects-k-e-isotropy.html)

JJ May 30, 2001 22:37

How aspect ratio affects k-e isotropy?
 
Hi there,

I currently simulating the dilution pattern of wastewater discharged into the ocean with currents from a multiport diffuser (number of pipes). The situation is as follows:

[1] Carried simple run with coarse grids and found dilution overpredicted due to numerical diffusion by approx. 30%

[2] Increased grid density by 2 times, and found dilution results an exact match with experiment.

[3] Further increased grid density by another 100 thousand and once again dilution was overpredicted by approx. 10-50%.

Qn 1. results should improved with increasing grids points, so why is the above happening?

Qn 2. The max aspect ratio of my grids are 200 for [2] and 40 for [3]. Shouldn't an improved results be obtained for a standard cube as compared to a cuboid?

Qn 3. K-e isotropy and aspect ratio of grid has anything to do with the results i'm getting??

Anybody has any idea what is happening? I'm really stumped! Please help...Any suggestions are welcome.

Thank You.

Regards, JJ

John C. Chien May 31, 2001 16:10

Re: How aspect ratio affects k-e isotropy?
 
(1). You are not reading my messages posted in the last three years!!1 (2). First of all, your solutions are not "the mesh independent solution". So, your solutions are a function of meshes used. (3). You have to be able to obtain the mesh independent solution first, in order to address the accuracy of the solution in comparison with the test data. (4). I don't know whether the software you are using can produce such solution or not, because the vendor never give warranty on such thing. (5). At the same time, enjoy playing with your toy.


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