Vortex induced vibration of three rigidly coupled cylinders in equilateral triangle arrangement at small spacing ratio

Vortex-Induced Vibration (VIV) of three rigidly coupled cylinders arranged in an equilateral-triangular pattern is numerically investigated. The spacing ratio is set as L/D=1.5. Simulations are carried out for flow incidence angles with alpha=0 degrees, alpha=30 degrees, alpha=60 degrees and the reduced velocity is set from 3 to 16 with a step increment of 1. The corresponding Reynolds number is about 3000-16000. Two-dimensional Reynolds-Averaged Navier-Stokes equations in conjunction with the SST k-omega turbulence model are used to simulate the turbulent flow. The vibration equations are solved by Newmark-beta algorithm by C Programming language. Numerical results show that the flow incidence angles and the reduced velocity strongly influence the response of the three cylinders including vibration amplitudes, lock-in range, frequency response and vortex shedding mode.