Investigating Asymmetry and Beating Phenomena in Vortex-Induced Vibrations of Triangular Prisms

In this work, we embark on a thorough numerical exploration of vortex-induced vibrations in freely oscillating equilateral triangular prisms subject to a uniform flow. Utilizing the computational fluid dynamics toolbox, OpenFOAM, our simulations are conducted at a Reynolds number of 100, bringing to light the complex and fascinating dynamics of a triangular prism of mass ratio 10. A key finding is the emergence of a 'beating' phenomenon within the reduced velocity range of 4 to 5. Originating near the lock-in onset, this beating behavior intriguingly evolves such that the interval between consecutive beat cycles lengthens with increased reduced velocity, leading to a decrease in the beating frequency. Throughout these cycles, vortex shedding mainly follows a 2S mode and remains symmetric, yet the vortices are noticeably distorted compared to those shed in regular flows. At higher reduced velocities (beyond 6), we observe asymmetry in the flow, even though even numbers (two pairs) of vortices are consistently shed. This investigation illuminates the intricate fluid dynamics around freely oscillating equilateral triangular prisms, contributing significantly to the understanding and designing related engineering systems.