Marcheggiani, Joseph P.

This research presents findings from an in-situ experiment utilizing a hydrophone line array to capture the sound production of the Goliath grouper. Analysis revealed that Goliath grouper calls exhibit multiple frequency components, including one high-amplitude component and 2 to 3 low-amplitude components. The primary high-amplitude component is concentrated in the 30 to 70 Hz band, peaking around 50 Hz, while low-amplitude components span 20 to 30 Hz, 70 to 115 Hz, and 130 to 200 Hz. Comparison between in-situ data and results from a normal modes transmission loss model identified regions where echo level increased with propagation distance. This suggests that the loudness of the call may not necessarily indicate proximity, indicating the Goliath grouper might rely on other cues for localization, such as changes in the frequency profile of its call. Two methods for estimating call distance are presented. The first method vi utilized a transmission loss model and measured transmission loss across a hydrophone line array. This method could also determine the source level of the calls, yielding source level estimates ranging from 124.01 to 144.83 dB re 1 μPa. The second method employed match field filtering, validating the accuracy of the transmission loss model. Both methods produced similar call distance estimations, ranging from 11.5 to 17.1 meters, placing the grouper inside or near its typical habitat.

A non-invasive transient state measurement method for wind tunnels would be very valuable as an experimental tool. Traditional measurement techniques for transient flows, e.g., hot wire anemometry, require sensors that are placed in the flow. Alternatively, particle image velocimetry (PIV) may be used to measure transient flows non intrusively, but applying PIV requires sensors that are expensive, and it may take months to process the data. The non-invasive measurement techniques considered in this thesis utilize sensors that are imbedded into the wall of a wind tunnel, or the response of a Kevlar walled wind tunnel to obtain the pressure time histories of a transient flow. These measurements are suitable and accurate for analyzing steady state flows but the feasibility of using them on time varying flows has yet to be explored. If this method proves possible, it would be very beneficial even if it is less accurate than current invasive methods because it would give results in real time. This thesis investigates a simple
transient flow of the startup vortex of an airfoil caused by a step change in angle of attack. Based on thin airfoil theory, two models of an airfoil were created. It was determined that the response of a Kevlar wall can measure the unsteady lift of an airfoil.