Flow-induced vibration on isolated and tandem elliptic cylinders with varying reduced velocities: A lattice Boltzmann flux solver study with immersed boundary method

Abstract

Numerical simulations of flow-induced vibration on isolated and tandem elliptic cylinders with varying reduced velocities are carried out. Immersed boundary multi-relaxation-time lattice Boltzmann flux solver is used as numerical solution method so that the solution procedure can be conducted in a Cartesian grid. The accuracy and rationality of this method are verified by comparison with previous numerical results. For vortex-induced vibration on isolated elliptical cylinder, numerical simulations are conducted for different aspect ratio (0.7 ≤AR≤ 1.5) and reduced velocities (4.0 ≤Ur≤ 10.0). Vibration response mainly contains desynchronization regime, initial branch and lower branch. When reduced velocity drives to lower branch, transverse amplitude reach to the peak value and double vortex street is formed in the wake. For flow-induced vibration on two elliptical cylinders in a tandem arrangement, numerical simulations are conducted for different aspect ratio (0.7 ≤AR≤ 1.5) and reduced velocities (3.0 ≤Ur≤ 10.0) at gap spacing L/D= 3 and 6. Vibration and flow characteristics are more complex compared with a single elliptical cylinder. The beginnings of entering into lock-in region are delayed for both bluff bodies and vibration response of downstream elliptical cylinder is enhanced by coupling interaction at higher reduced velocity. The flow and vibration characteristics of upstream elliptical cylinder are close to that of single elliptical cylinder at larger gap spacing. The tandem system is beneficial to gain more energy for higher reduced velocity. When downstream elliptical cylinder drives into lower branch, the transverse amplitude is the largest and double vortex street is formed in the wake region.