Numerical study of the near wake of a circular cylinder

A series of direct numerical simulations (DNS) of incompressible flow around a circular cylinder at Re=3300Re=3300 – based on the far field velocity and the diameter of the cylinder D   – were performed. After taking an offset in the streamwise direction into account, the results were found to be in good agreement with experimental data obtained at a slightly higher Reynolds number of Re=3900Re=3900. Increasing the spanwise size of the computational domain from lz=4D–8Dlz=4D–8D was found to only marginally affect the profiles of turbulence statistics in the wake of the cylinder, although even in the simulation with lz=8Dlz=8D the spanwise autocorrelation of u   did not completely converge to zero towards the sides of the computational domain. The phase-averaged statistics showed the existence of shear layers immediately downstream of the cylinder, which originated from the boundary layers along the top and bottom surface of the cylinder. As the shear layers rolled-up, significant production of turbulence kinetic energy was observed inside the rolls of recirculating flow. At x/D=6x/D=6 snapshots of the flow field were gathered. At this location, individual vortices – shed from the upper and lower shear layer, respectively, behind the cylinder – could still be identified. The gathered wake data will be used to study the influence of large meandering coherent structures on the promotion of laminar heat transfer along a body located downstream of the cylinder.