{"id":368255,"date":"2024-05-23T08:22:24","date_gmt":"2024-05-23T08:22:24","guid":{"rendered":"\/forum\/forums\/topic\/low-drag-coefficient-for-sphere\/"},"modified":"2024-05-23T08:22:24","modified_gmt":"2024-05-23T08:22:24","slug":"low-drag-coefficient-for-sphere","status":"closed","type":"topic","link":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/low-drag-coefficient-for-sphere\/","title":{"rendered":"Low drag coefficient for sphere"},"content":{"rendered":"

I am conducting a simulation of a smooth sphere traveling through a flow to compare with experimental results. However, the drag coefficient obtained from the simulation is significantly lower (Cd = 0.11426044) compared to the experimental Cd of 0.45. The reference value settings are correctly adjusted, making it less likely the cause of the issue. I tried refining the mesh by decreasing the face and body sizing of the sphere and domain, but the Cd value still does not match the experimental results. I also adjusted the wall y+ value using the inflation of 10 layers with the first layer cell height obtained from the wall y+ calculator, which gave me a first layer height of 0.000738208399739557 m corresponding to wall y+ = 50. I need a wall y+ value between 30 and 200 as I am using the realizable k-epsilon model. However, when I calculate the wall y+ of the sphere in Fluent, it only shows 19. Can anyone tell me what I am doing wrong? link to Y+ calculator: https:\/\/volupe.se\/wall-y-calculator-when-meshing-a-geometry-for-cfd-analysis-this-handy-volupe-calculator-computes-the-height-of-the-first-mesh-cell-off-the-wall-required-to-achieve-a-desired-y-using-flat-plate-boun\/<\/a><\/p>\n

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