Numerical analysis of the flow-induced vibrations in the laminar wake behind a blunt body with rear flexible cavities

We present a numerical study on the fluid–structure interaction of an incompressible laminar flow around a slender blunt-based body implementing a rear cavity of flexible plates. The study focuses on the use of this type of device to control the wake dynamics and the aerodynamic forces acting on the body, as well as to harvest energy from the flow. To that aim, the effects on the plates flow-induced vibrations (FIV) and on the dynamics of the flow of three control parameters, namely the reduced velocity, 0≤U∗<12, the mass ratio, m∗=[500,1000] and the cavity height hc, are evaluated at Reynolds number Re=500. Four different branches are identified in terms of dynamic response, as U∗ increases, regardless of the values of hc and m∗. At low values of U∗, an initial branch with a local peak of moderate amplitude response is observed, where the plates oscillate in counter-phase, in a varicose mode, with a frequency fp that is synchronized with the second harmonic of the vortex shedding frequency, 2fvs, and similar to the natural frequency of the solid, fn≃f1,n. For intermediate values of U∗, a transition towards a sinuous mode of oscillation occurs, where the plate frequency is synchronized with the vortex shedding frequency, fp=fvs. Initially, after such transition, the oscillation frequency is lower than the natural frequency of the plates fp更多