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Problem with convergence using 2nd order scheme for multiple elements car wing

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Old   December 31, 2016, 10:42
Default Problem with convergence using 2nd order scheme for multiple elements car wing
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Stan
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Hello,

firstly, Happy New Year for everyone I have a problem with convergence in calculations of multiple element front wing for car. I use k-omega SST turbulence model, velocity value 20m/s. First, I used first order for all equations exclude pressure (2nd order). After I got convergence (point 1 on picture) I changeg for 2nd order for everything. Unfortunately I canít get converge solution using 2nd order scheme. Residuals stuck and only oscillates about some average value, but the Cl and Cd takes aprox. state values. I tried decrease under-relaxation factors (point 2 on the picture one), but it doesnít help. I want to be implement the wall law so I must have y plus between values <30,300>, right? I calculated estimated y plus value and used an inflation option in meshing (the mesh is on the picture, Iím using ANSYS mesher). When I plot x-y plot of y plus value some values falls behind 30 (for plot I choose all surfaces of wing, is it right or maybe it should be done different?). I tried also double precision, but nothing changed, residuals got stuck. My question is, what can I do for getting convergence result, is this maybe problem of mesh (max. orthogonality about 0,78) or maybe even the residuals got stuck the solution is proper? Also how can I control the mesh for getting everywhere y plus value above 30? And the last question is that in the k-omega model wall law is implemented automatically? Please give me some advices.


Regards!
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File Type: png mesh.png (103.0 KB, 9 views)
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airfoil, convergence, wing

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