Effects of otolith geometry on steady streaming flows in the fish ear

Abstract

The dense, bony otolith contained in the fish ear oscillates relative to its fluidic surroundings in the presence of a sound wave. How the otolith actually transduces this acoustically induced fluid motion into the hair cell displacements that the fish hears is not fully understood, however. Nevertheless, it is likely that the complicated geometry of the otolith, including the groove (sulcus) where most of the hair cells are found, contributes in some fashion to shaping the flow patterns that excite the hair cells. The effect of these grooves on the induced steady streaming flows was studied experimentally using both oscillating grooved spheroids and scaled models of actual otolith sulci to simulate acoustically induced motions of the otolith for oscillation orientation angles ranging from 0 deg to 90 deg. Particle‐image velocimetry and flow visualization results obtained from images phase‐locked to the oscillations are presented for normalized oscillation amplitudes, ε≡s/L=0.05–0.2 and Reynolds number, Re≡ωL2/ν≊1–102, where s is the oscillation amplitude, ω is the oscillation frequency, L is a typical otolith length scale, and ν is the fluid kinematic viscosity. The effect of phase on these data was also studied. [Work supported by ONR.]