Numerical simulation and experimental visualization of the influence of the deformation frequency of a radially deforming circular cylinder impulsively started on cylinder wake

摘要

A periodic superimposed motion may notably influence the flow structure and the development of the convective heat transfer relative to non-deformable case. In particular, a radial deformation of a circular cylinder, may cause a possible synchronization with the cylinder wake, which is itself periodic when vortex Street takes place. This synchronization phenomenon, often called 'lock-in', may cause undesirable effects, but may also constitute a way of controlling the wake development. Body deformability may be used as wake control device that would favourably affect the interplay of primary and secondary vorticities, thus reducing the drag coefficient. These numerical and experimental studies are done herein for a Reynolds number equal to 23500. The problem is resolved by using the Navier-Stokes equations in the vorticity-stream function form. The vorticity transport equation is solved by a second-order finite difference method in both directions of the domains. The Poisson equation for the stream-function is solved by a SOR method. The advance in time is achieved by a second-order Adams-Bashforth scheme. The effect of turbulence is represented by eddy viscosity V_t, which is determined by a sub-grid-scale model. In the present study, we use a Smagorinsky model.