LES of uniform flow over tandem circular disks

A large eddy simulation(LES) was conducted to investigate the uniform flow over tandem disks at low Reynolds number,mainly focusing on the influence of separation distance on wake structure.The results show that the Hopf bifurcation of flow field is delayed compared with that of a single disk when the distance between the two disks is small enough.The research was performed at Re=200 with distances l/d=1,1.5,2,3 and 6, respectively. It is concluded that the wake is stable and plane-symmetrical at l/d=1 and unstable but plane-symmetrical at  l/d=1.5. At l/d=2, the plane-symmetrical structure is broken.The upstream wake resumes plane-symmetry at l/d=3 while the wake of both disks resume plane-symmetry at l/d=6.