Aerodynamic and acoustic analysis of a self-excited oscillation cylinder in a low Mach flow using a hybrid method

Abstract

A cylinder placed in low Reynolds number flows can cause instabilities, such as unstable fluid induced forces and non-periodic vibrations of structures, leading to increased fatigue loading. It can also generate significant flow-induced noise. Therefore, understanding the vibrational behavior and its acoustic propagation mechanism in this configuration is crucial. This study investigates the aerodynamics and acoustic characteristics of a transversely self-excited oscillating circular cylinder at Ma = 0.2, Re = 150 and m* = 5. To simplify the problem, we model the movement of the cylinder using a mass-spring-damper system and solve the motion trajectory using the Newmark-β method. The acoustic governing equations formulated within viscous/acoustic splitting method in terms of a moving mesh are derived and validated by comparison with the direct numerical simulation method results. Key parameters, including amplitude ratio, frequency ratio, lift and drag coefficients, and phase angle between lift and displacement were analyzed over a range from reduced velocity U_r = 2 to U_r = 9. Various vortex-induced vibration phenomena, such as "lock-in," "phase switching," and "beating," are observed. The predicted sound signal exhibits distinct variations across the initial, lower and desynchronization branches:minimal impact of vibration on the acoustic field in the initial branch, a "beating" phenomenon between the initial and lower branches, the acoustic field rotation due to a sudden increase in drag force in the lower branch, and reduced acoustic wave intensity in the desynchronization branch due to vortex shedding suppression.