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-   -   Request (http://www.cfd-online.com/Forums/fluent/28118-request.html)

kalyan December 22, 2000 02:09

Request
 
Friends i am using fluent for solving flow in a driven cavity(Incompressible stedy flow)for this i took water is a fluid in side the square cavity.I took top wall of the square cavity(1mX1m) is mooving(mooving wall)with uniform velocity 1 m/s.How can i found out reynolds number??what is the formula?? I used re=(velocity(1m)Xlength of cavity(1m))*rho/mue but it will give very high reynolds number.And I am not getting reverse stream function in the corners of the stream function profile.pls help me how can i find out reynolds number?&How can i get the relevant stream function profile at high reynolds number.

John C. Chien December 22, 2000 03:30

Re: Request
 
(1). Based on your configuration,the Reynolds number of the cavity flow is slightly over 1,000,000. (2). Assuming that you are solving the laminar flow problem and assuming that the steady-state solution exist, then the boundary layer on the walls will be relatively thin. (3). In this case, you will need very fine mesh near the walls to resolve the thin boundary layer. (4). If you use coarse mesh in your formualtion, then the solution is not going to be correct. (5). My suggestion is: refine the mesh near the wall, and plot the computed velocity gradient at the middle of the moving wall, in terms of the total number of mesh points or cells as you refine the mesh. You have to obtain the mesh independent first in order to address the accuracy of the result. (6). If you are relatively new to CFD, then, my suggestion is: run the cavity at lower Reynolds numbers, say RE=10, 100, 400, 1000, etc. In this way, you can get a better feeling about the CFD solutions.


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