[Jason777]

Hey guys, really need ur help.

im studying on 350m tall 35 diameter cylindrical building, with Re at 10^7. Aim to capture vortex shedding using transient analysis and fluent meshing. 800K elements, average flow velocity at 50m/s.

I can capture vortex shedding under K-e (St = 0.14), but it gives me a very small Cd around 0.2, which i believe is wrong. then i switch to K-o, which gives me 0.55 Cd, but no vortex shedding can be capture (Cl is completely above 0).

i know it is y+ determines where flow separation is occurred. and everytime i tried to refine first layer thickness, i will receive exceeding turbulent viscosity ratio warning and floating point exception.

what can i do to decrease y+ ? thanks in advance