Research On Vortex-induced Vibrations Of Two 2-D Circular Cylinders In Tandem And Side-by-side Arrangement

Vortex-induced vibrations of two 2-D circular cylinders in a cross-flow at low Reynoles number are studied by solving primitive variable Navier-Stokes equations using Arbitrary Lagrangian-Eulerian(ALE) method incorporating with Domain Decomposition Method(DDM). The two cylinders are elastically mounted with mass-spring-damping system. Fluid-structure interactions including the dynamic responses of the two cylinders and their effects on the fluid are considered in detail. The convection term and dissipation term in momentum equations are discretized using the third-order upwind compact scheme and the fourth-order central compact scheme, respectively and the Poisson equation for pressure is solved by normal second-order central scheme. The equation of the cylinders'motion can be solved easily using the Runge-Kutta method. Four central parts are presented in this paper.In the first part, vortex-induced vibrations of the downstream elastic cylinder with two-degree-of-freedom motion in the wake of an upstream stationary one are examined. The calculated results are comparied with that for an isolated cylinder set normal to freestream flow. Thus the compliment and development of this problem is achieved. The vortices shed from the upstream cylinder and the reduced mean velocity of the wake flow impinging on the downstream one, are parts of the rationale leading to the complicated dynamic reponses of the downstream cylinder.In the second part, vortex-induced vibrations of the downstream elastic cylinder with transverse motion in the wake of an upstream stationary one are also considered. The emphase is on the transition between wake states, which is characterized essentially in terms of the forces on the cylinder and the instantaneous patterns of the vortex structures in the near-wake.In the third part, effects of the upstream cylinder vibration on the flow-induced vibrations problem are further studied under the action of the two cylinders with two-degree-of-freedom motion together. The presence of the upstream cylinder vibration plays a repressive effect on the flow-induced vibration of the downstream one especially at low frequency band, which is associated with the changing flow...