NONLINEAR DYNAMIC ANALYSES OF THE FLUID-STRUCTURE INTERACTION PROBLEMS IN COCHLEAR MECHANICS

Two peculiar phenomena of the response in the cochlea (inner ear) have attracted considerable attention in applied mechanics. One is the phenomenon of the localization of the response with respect to frequency variations and the other is the nonlinearity of the response of the basilar membrane. The localization phenomenon is analyzed by implementing an orthotropic helicoidal shell model. This model takes into account the shell nature of the actual geometry of the basilar membrane. This nature has not been incorporated into previous analyses which are based on either beam or plate theory. The possibility of geometric nonlinearity being the major source is also investigated by an orthotropic circular plate model. Perilymph and endolymph are modeled as inviscid fluids interacting with the basilar membrane.;The results of the helicoidal shell analysis indicate that the coiled geometry of the cochlea has little effect on localization. However, the model does not take into account the taper of the basilar membrane along its length. The results of the circular annular plate analysis indicate that the geometric nonlinearity is unlikely to be the major source of the nonlinearity in the cochlea.