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-   -   Reattachment Point in separated flow (http://www.cfd-online.com/Forums/fluent/45499-reattachment-point-separated-flow.html)

Eric July 24, 2007 18:07

Reattachment Point in separated flow
 
Hello all

I am working on backstep problem. I am facing some problems regarding the accuracy and postprocessing the results,

1. While ploting the Stanton number against non dimensional heat wall length, my results are underprdicted. For eg, in benchmark solutions the peak reach upto 3.1 but in my solutions (with all possible 2 equation turbulence models and wall functions) the peak value is 2.6 at the maximum. Also, it appeared to be depending a lot on wall function, I used.

2. An important criterio for postprocessing the results is to compare the reattachment length. Could someone suggest a method to calculate the reattachment length. Inputs from previous posts suggest to calculate it on basis of length of recirculation region. If this is the only method, please give some more input on how to analyse the length of recicrculation region. Calculating it from the contours display seems very vague option.

I am new with Fluent. Would be really thankful, if someone could please suggest some info regarding the same.

Thanks in advance

Regards Eric

Joe July 24, 2007 19:40

Re: Reattachment Point in separated flow
 
2)

Sign change in wall shear stress.

Mahesh July 25, 2007 03:38

Re: Reattachment Point in separated flow
 
Hi Joe,

Thanks for your input.

Certainly this seems a reasonable way to obtain the reattachment length but unfotunately, when I plot wall shear stress on heat wall, I could-not obtain any negative value of it. At point approximately 3.29H, there is a sharp local minima and the wall shear stress attain zero values.

Does this suggest some error in solutions process.

Regards Mahesh


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