LES and DES investigations of turbulent flow over a sphere

Abstract

Large Eddy Simulation (LES) and Detached Eddy Simulation (DES) are applied to prediction and investigation of the ow around a sphere. DES is a hybrid approach in which the closure is a simple modi cation to the Spalart-Allmaras model, reducing to Reynolds-Averaged Navier-Stokes (RANS) in attached regions, and LES away from the wall . Calculations are performed at a Reynolds number, Re = 10, in the sub-critical regime where there is a laminar boundary layer separation from the sphere. A fth-order upwind-biased treatment of convection is su cient for capturing the development of the separated shear layers and for the velocity spectra to display an inertial range without excessive decay at the smallest resolved scales. The closest agreement with LES predictions is obtained in DES with the model constant CDES = 0:65. Both techniques yield predictions of the drag, position of laminar separation, and the mean pressure and skin-friction distributions along the sphere are in good agreement with measurements .