Characteristics of flow over a circular cylinder with two attached filaments

In this work, the characteristics of flow over a circular cylinder with two filaments are numerically investigated. The circular cylinder is fixed, and the filaments with the same properties are symmetrically attached to the rear surface of the cylinder. Moreover, the leading ends of the filaments are fixed, and their trailing ends are free to flap in the wake of the cylinder. To implement numerical simulations, an improved immersed boundary-lattice Boltzmann, which is efficient for moving boundary problems, is employed. By fixing the length of two filaments, their influences on the flow control of the cylinder are examined systematically through varying the filament mass (Mr), the filament flexibility (wr), and the attachment angle between two filaments (α). Moreover, the effect of flow viscosity is also examined. Based on the numerical results established, it is found that the fluctuation of lift force together with the mean drag force can be suppressed effectively. In the meanwhile, the flow control of two filaments is independent of Reynolds number. Particularly, the filaments with relatively low flexibility and large attachment angle can achieve high performance, which is caused by the vortex interaction between the cylinder and the filaments as well as the pressure redistribution along the surface of the cylinder.