SUMMARY

The fish ear contains three dense, bony bodies (otoliths) surrounded by fluid (the endolymph) and tissue. Under acoustic stimulation, the otoliths oscillate relative to their surroundings, stimulating the endolymph as well as the array of hair cells that are adjacent to the otolith and embedded in tissue. It is believed that the hair cells move with the surrounding fluid. This doctoral thesis attempts to visualize the steady streaming (i.e., time-independent) component of the acoustically induced fluid motion inside of the fish ear and to determine how the hair cell displacements due to the steady streaming could provide acoustically relevant information to the fish. This research characterizes the fluid flow around oscillating model otoliths, namely spheroids, grooved spheroids, and a 350% scale model of a cod saccular otolith. Particle pathline visualizations and particle-image velocimetry (PIV) are used to characterize the flow fields at various oscillation orientations, frequencies and amplitudes. These data are used to determine the location of the stagnation points on the body surface and at the boundaries of the inner rotating region of the flow. Studies were also conducted on bodies sinusoidally oscillated at both a single frequency and two (simultaneous) frequencies. Both the steady streaming flow patterns and velocity fields are found to contain acoustically relevant information, but given their very small displacements, it is unclear if the steady streaming flows can be sensed by the fish ear.