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July 19, 2006, 09:54 |
mesh guidelines for reattachment
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#1 |
Guest
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Hi!
what are the guidelines, meshing the zone at the wall, where e.g. reattachment takes place?? I am using k-e and k-w turb. modells with different wall functions. Results are ok, except close to the reattachment point (cylindrer in axial flow). Is ther a y+ value, that has to be considered?? y+ values for the wall are well known... but they are valid only for equilibrium BL. Also, y+ is allways zero at the reattachment point! Any suggestions?? Ralf |
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July 20, 2006, 06:48 |
Re: mesh guidelines for reattachment
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#2 |
Guest
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Hi Ralf, I analysed the same problem. In the reattachment point, it's difficult to achieve solutions similar to sperimental measures, also if you refine the mesh a lot. I suggest you to begin from a coarse mesh with a few points and gradually refine it until you achieve a small numerical difference between the fine mesh and its previous.
Since the problem in reattachment point is not mesh dependent, to study turbulente flow and its laminar sublayer, the y+ should be on the order of unity (y+<5). y+ dependes on the wall friction stress. The wall friction coefficient is always zero at separation and reattachment point, then y+ must be zero in the same points. |
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