hi, i am using FLUENT 6.1 to solve 3D flow over a circular cylinder in unbounded domain.i could validate drag(CD) and St for unsteady flow past a circular cylinder in 2D. But in my 3D calculations, the drag values for Re =100,200,300 are coming to be higher if i use a boundary layer on cylinder and lower if i dont use a Blayer. What could be the fault in my computations using FLUENT ??? please suggest me the efficient way to use FLUENT for 3D computations.

What do you mean boundary layer on cylinder?

i attached boundary layer on the cylinder surface using the option available in Gambit

well i have also observed such behaviour that if i use prism meshes near the walls of cylinder i get higher CD and if i am using tet meshes (i am using LES as model) i get better CD values (by better i mean close to experimental values). i am not able to figure out why. but i have observed that if i use ke-realisable with prism meshes near walls the results are close to experiments but then with k-e-realisable and tet meshes near wall the CD values are low.