Numerical investigation on two-degree-of-freedom vortex-induced vibration of a circular cylinder in power-law fluids

Abstract

Abstract In this paper, the two-degree-of-freedom (2DOF) vortex-induced vibration (VIV) of a circular cylinder in shear-thinning and shear-thickening non-Newtonian power-law fluids are numerically investigated. A virtual spring-damper-mass system is employed to predict the VIV of the cylinder. A comprehensive analysis is conducted to study the influence of dimensionless parameters, including reduced velocity ( 3 ≤ U r ≤ 12 ) and power-law index ( 0.4 ≤ n ≤ 1.8 ) at a low Reynolds number ( R e = 150 ) and low mass ratio ( m r = 2 ) on the vortex shedding pattern, displacement frequencies, local apparent viscosity, friction coefficient, trajectories of the displacements, drag and lift coefficients, and the cylinder displacements. The results indicate that the apparent viscosity and the natural frequency of the system have a substantial effect on the characteristics of the VIV of the cylinder. By changing the values of the reduced velocity, various vortex shedding patterns such as 2S, 2P, S + P, and complex modes are observed for the non- Newtonian fluids, and several motion trajectories other than the typical figure “8″ are analyzed. By increasing the power-law index, the range of the lock-in region and the corresponding reduced velocity of the maximum transverse vibration amplitude change.