MODAL-ANALYSIS OF A FLUID-FILLED ELASTIC SHELL CONTAINING AN ELASTIC SPHERE

Auscultatory percussion (AP) is an examination used to detect brain disease. The physical mechanisms involved in AP are investigated by determining the natural frequencies and mode shapes of an elastic, fluid-filled spherical shell containing a concentrically located elastic sphere. The major assumptions are that the fluid is inviscid, the spherical shell is thin, and the modes of the physical system are axisymmetric. An analytical modal analysis results in a characteristic equation for the natural frequencies of the physical system. Roots of the characteristic equation were found numerically. The results show that the spectra of natural frequencies for the physical system are distorted by the combined effects of the elasticity of the inner sphere and the reduction of fluid volume due to the inner sphere. The elastic inner sphere also introduces a pattern of additional frequencies to the spectra of natural frequencies of the physical system. © 1992.