Wake-Induced Oscillations of Two Cylinders in Tandem at Low Mass Ratio

Abstract

The flow around two cylinders in tandem and the response of the downstream cylinder is numerically investigated. The upstream cylinder is fixed whereas the downstream cylinder is free to vibrate in the transverse direction only. The numerical simulations are carried for different values of reduced speeds, ranging from 1 to 8 while the Reynolds number remains fixed at Re=100. The blockage in the computational domain is taken as 2% and the mass ratio is unity. The non-dimensional gap-size between the centers of the two cylinders is taken to be 5 so that the downstream cylinder lies in the wake-interference zone. For the solutions, the governing equations are discretized with the aid of Finite Element Method (FEM) and the computation process is carried out using the Generalized Minimal RESidual (GMRES) iterative solver. The vortex shed from the upstream cylinder combines with the respective vortex of the downstream cylinder thereby adding to its strength. The flow remains periodic for the values of reduced velocity in the range of 1 to 8, and exhibits quasi-periodic characteristics as the reduced velocity is further increased to 8.