Detached-eddy simulations past a circular cylinder

The flow is calculated with laminar separation (LS) at Reynolds numbers 50, 000 and 140,000, and with turbulent separation (TS) at 140,000 and 3 x 10(6 ). The TS cases are effectively tripped, but compared with untripped experi ments at very high Reynolds numbers. The finest grid has about 18,000 point s in each of 56 grid planes spanwise; the resolution is far removed from Di rect Numerical Simulations, and the turbulence model controls the separatio n if turbulent. The agreement is quite good for drag, shedding frequency, p ressure, and skin friction. However the comparison is obscured by large mod ulations of the vortex shedding and drag which are very similar to those se en in experiments but also, curiously, durably different between cases espe cially of the LS type. The longest simulations reach only about 50 shedding cycles. Disagreement with experimental Reynolds stresses reaches about 30% , and the length of the recirculation bubble is about double that measured. The discrepancies are discussed, as are the effects of grid refinement, Re ynolds number, and a turbulence-model curvature correction. The finest grid does not give the very best agreement with experiment. The results add to the validation base of the Detached-Eddy Simulation (DES) technique for smo oth-surface separation. Unsteady Reynolds-averaged simulations are much les s accurate than DES for LS cases, but very close for TS cases. Cases with a more intricate relationship between transition and separation are left for future study.