Abstract
This research is motivated by an ongoing project whose goals are to measure rain acoustically by evaluating acoustic signals from raindrops obtained by attaching hydrophones to a mooring. Since a flow past the mooring and hydrophone setup will cause vibrations, it is important to know the flow-induced vibration characteristics of such a system, in order to determine whether the fluid flow will cause an interference with the targeted acoustic measurements. This thesis idealizes the mooring and hydrophone system as a two-dimensional flow past a two-cylinder system and investigates this system numerically. We first examine the classic problem of the flow past a single cylinder (FPC) for a range of freestream velocities characterized by laminar and turbulent Reynolds numbers and compare our numerical results for the single cylinder with previous literature. For a two-cylinder system, the diameter ratio, separation length, the angle between the orientation of the cylinders, and the laminar and turbulent flow, characterized by the Reynolds number are important parameters. We find the largest dominant frequency for this system and compare it with the acoustic frequencies of interest for rainfall (i.e., 1 to 22 kHz). Our numerical results explore the vortex shedding frequencies for a range of each of the above parameters without considering the flow-structure interaction. Our results show that the vortex-induced vibrations have a much smaller frequency than the acoustic rainfall frequencies of interest and therefore will not impact the estimation of rainfall.