# Mesh Size

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 November 15, 2005, 14:59 Mesh Size #1 Mohamed Yousuf Guest   Posts: n/a Hello Friends !! How i calculate Local mesh size for 2D and 3D?? My project is Compressible flow analysis on unstructured meshes. Now i am working in Quadratic reconstruction. At present i am developing code for quadratic reconstruction. for that i have to calculate the gradients with 2nd order accurate. It accomplished by both Green-Gauss and Least-square...I am confused in Constant coefficient matrix for Least square method. so plz give the clear view of quadratic reconstruction. One more help... I need this below mentioned paper for my further progress.. Baldwin and Lomax "Thin layer approximation and algebraic model for separated turbulent flows", AIAA Paper, No. 78-257, 1978.

 November 17, 2005, 08:41 Re: Mesh Size #3 Yousuf Guest   Posts: n/a Thanks for ur reply... But in Delaneye and Essers 1997 AIAA paper.. they considered 2nd order accurate gradient.. Then one more help.. In viscous computation, I am facing problem with calculation of gradient at faces(edges). I used GG theorem.. but i am not getting exact zero velocity at No-slip wall. Somewhere i am making mistakes but i cant realize.. Any other approach to calculate gradients for viscous? Advance thanks...

 November 17, 2005, 11:43 Re: Mesh Size #4 ganesh Guest   Posts: n/a Dear Yousuf, In Delanye and Essers 1997 AIAA paper, they have first used GG to obtain gradients to first order and then corrected it to second order. This is possible option you could try. The fact that GG cannot by itself give gradients to second order accuracy on arbitrary meshes is still valid. In calculating the gradients at the boundary, use the boundary condition (say no-slip)and consider a co-volume made up by the nodes of the face and the cell centroid of the cell containing the boundary face. The viscous gradient computations are calculated using GG/QR. The AIAA 97 paper you referred to is a very good reference. Hope this helps Regards, Ganesh

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