Detached-Eddy Simulation of flow over a sphere

Detached-Eddy Simulation (DES) is applied to prediction and investigation of the flow around a sphere. DES is a hybrid approach which has RANS behavior near the wall and becomes a Large Eddy Simulation in the regions away from solid surfaces. Results are presented for a range of Reynolds numbers, from 10⁴ to 1.1 × 10⁶. Laminar or turbulent boundary layer separation is specified via the initial and boundary conditions of the simulations. The turbulent separation cases are effectively tripped in the sense that the turbulence model is active over the entire surface of the sphere. DES predictions are evaluated using experimental measurements and with respect to grid refinement in the azimuthal direction. Also investigated is the influence of modifications to the baseline turbulence model to account for streamline curvature and one case in which the model is activated at a position corresponding approximately to the location of boundary layer transition on the sphere at Re = 1.1 × 10⁶. For both the sub- and super-critical solutions the agreement is reasonable for the drag, pressure, and skin friction coefficients. Shedding frequencies for the sub-critical flows agree well with measurements. The wake structure in the super-critical solutions is substantially changed compared to the sub-critical flows with the wake in the super-critical regime dominated by a pair of streamwise vortices.