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Numerical Study of Vortex-Induced Vibrations of Three Circular Cylinders in Equilateral-Triangle Arrangement

Vortex-induced vibrations (VIV) of three circular cylinders in equilateral-triangle arrangement are numerically investigated. The Reynolds number based on the free stream velocity D is 150. The gap spacing between the cylinders is set as 4D and all cylinders are free to vibrate in both transverse and in-line directions. The incompressible Navier-Stokes equations in two dimensions are solved by a four-step fractional finite element method. Simulations are carried out for three typical flow incidence angles (i.e., α = 0°, 30°, and 60°) and a wide range of reduced velocities (3 ≤ Ur r ≤ 12). Numerical results show that the responses of these cylinders, including the vortex shedding frequencies, the vibration amplitudes, and the motion trajectories, are significantly affected by the flow incidence angle and the reduced velocity. Some typical vorticity fields are also shown to investigate the flow interference between the cylinders.