Acoustic analysis of an actively controlled pipe subject to vortex induced vibration

Pipe-like structures are utilised in a wide variety of engineering applications, which must often consider the impact of noise and vibration. This paper presents a numerical study into the Vortex Induced Vibration (VIV) of a flexible pipe in laminar flow and the resulting acoustic radiation, and explores the potential of an active vibration control strategy. The VIV is solved using a commercial CFD code, coupled with a finite element model (FEM) to obtain the pipe displacement. The hydrodynamic noise is solved using the FW-H equation based on the acoustic analogy and the vibrational noise is calculated by an acoustic FEM in the time-domain. Without control, when the vortex shedding frequency is approximately equal to the first structural natural frequency of the pipe, large amplitude vibration is induced. The fluid-pipe interaction causes hydrodynamic noise and the vibration of the pipe generates significant vibroacoustic noise. The simulations show that when the first mode of the pipe is well excited, the vibroacoustic noise dominates the sound radiation. A velocity feedback controller is then utilised to control the VIV of the pipe, which reduces both the vibrational and hydrodynamic noise, with the latter reduced to about the same level as a rigid stationary pipe.