Flow-Induced Transverse Vibration of Three Equal-Diameter Cylinders in an Equilateral Triangle Using the Immersed Boundary–Lattice Boltzmann Flux Solver

Abstract

To explore the relationship between dynamic characteristics and wake patterns, numerical simulations were conducted on three equal-diameter cylinders arranged in an equilateral triangle. The simulations varied reduced velocities and gap spacing to observe flow-induced vibrations (FIVs). The immersed boundary–lattice Boltzmann flux solver (IB – LBFS) was applied as a numerical solution method, allowing for straightforward application on a simple Cartesian mesh. The accuracy and rationality of this method have been verified through comparisons with previous numerical results, including studies on flow past three stationary circular cylinders arranged in a similar pattern and vortex-induced vibrations of a single cylinder across different reduced velocities. When examining the FIVs of three cylinders, numerical simulations were carried out across a range of reduced velocities (3.0 ⩽ U_r ⩽ 13.0) and gap spacing (L = 3D, 4D, and 5D). The observed vibration response included several regimes: the desynchronization regime, the initial branch, and the lower branch. Notably, the transverse amplitude peaked, and a double vortex street formed in the wake when the reduced velocity reached the lower branch. This arrangement of three cylinders proved advantageous for energy capture as the upstream cylinder’s vibration response mirrored that of an isolated cylinder, while the response of each downstream cylinder was significantly enhanced. Compared to a single cylinder, the vibration and flow characteristics of this system are markedly more complex. The maximum transverse amplitudes of the downstream cylinders are nearly identical and exceed those observed in a single-cylinder set-up. Depending on the gap spacing, the flow pattern varied: it was in-phase for L = 3D, antiphase for L = 4D, and exhibited vortex shedding for L = 5D. The wake configuration mainly featured double vortex streets for L = 3D and evolved into two pairs of double vortex streets for L = 5D. Consequently, it well illustrates the coupling mechanism that dynamics characteristics and wake vortex change with gap spacing and reduced velocities.

Keywords

Flow-induced vibration / Equal-diameter cylinders / Lattice boltzmann flux solver / Immersed boundary method

RIGHTS & PERMISSIONS

Harbin Engineering University and Springer-Verlag GmbH Germany, part of Springer Nature