Effect of Reynolds number on amplitude branches of vortex-induced vibration of a cylinder

Abstract

The effect of Reynolds number on curves of the transverse-only motion amplitude of a circular cylinder with the body mass m∗=0.935 and the damping ratio ζ=0.00502 in the turbulent flow range is investigated systematically using a two-dimensional in-house code developed based on lattice Boltzmann method. Large eddy simulation is chosen as the turbulence model to describe viscous, incompressible and Newtonian fluid and the immersed boundary method is used to impose the boundary condition on the moving cylinder surface. Multi-block model is adopted to improve the accuracy and the computational efficiency. It is well established that when the variation of Reynolds number changes with the reduced velocity, there are three branches in the motion amplitude curve of a low mass cylinder, including initial, upper and lower branches connected by two jumps. However, in the present work, Reynolds number and reduced velocity are considered as independent parameters. Detailed results are provided for the variations of motion amplitude, motion frequency and lift coefficient against the reduced velocity in the lock-in region at different fixed Reynolds numbers. The results show that at a fixed Reynolds number the motion amplitude curve has two branches. At lower range of Reynolds number calculated, there are only initial and upper branches, and at higher range, there are only upper and lower branches. Also, the motion amplitude against the Reynolds number near the jumps is studied when the reduced velocity is fixed. It shows that the values of amplitude near the jumps are very sensitive to Reynolds number.