Numerical Simulation For Flow Control Of Bluff Body

In this work, the characteristics of flow over a circular cylinder with two filaments are numerically investigated by employing an improved immersed boundary-lattice Boltzmann (IB-LBM).Two cases are considered. One (considering the effects of the filament massr, the filament flexibility wr, the attachment angle between two filaments ? and Reynolds number) is a fixed circular cylinder with two filaments, and the another (considering the effects of the filament mass Mr?the filament flexibility wr and the attachment angle between two filaments a ) is an elastically mounted circular cylinder with two filaments. The filaments are symmetrically attached to the rear surface of the cylinder and parallel to each other. Moreover, the leading ends of the filaments are fixed,and their trailing ends are free to flap in the wake of the cylinder.Results are as follows:(1) For the fixed circular cylinder with two filaments, it is found that amplitude of lift coefficient ?Cl and mean drag coefficient (?)d increase with Mr slightly and smoothly when Mr?0.5. Then the effect of filament mass can be neglected. For the effect of w, and ?, compared to a single cylinder, the use of two filaments generally performs better. For all parameters considered in this study, two filaments at wr = 0.6 and ?= 90° can achieve the lowest fluctuations of lift and drag coefficients together with the smallest mean drag coefficient. Moreover, in the range of studied Re the flow control via two filaments is almost independent of the flow viscosity. By examining the flow field around the cylinder and filaments, it is known that the flow control by two filaments is attributed to the vortex interaction between the cylinder and the filaments as well as the pressure redistribution along the surface of the cylinder.(2) The vortex-induced vibration (VIV) of a single cylinder at Re=200 is considered by investigating the effect of reduced velocity Ur, which results are in good agreement with the ones of Borazjani and Sotiropoulos. For the elastically mounted circular cylinder with two filaments, if Mr >0.1, the VIV cannot be effectively suppressed due to the interaction between the movement inertia of cylinder and the filaments' mass. When Mr =0.1, ?= 60°, wr = 0.5 , it can achieve the lowest value of maximum displacement, amplitude of lift coefficient and mean drag coefficient.