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 a fundamental physical system. The fundamental physical system is an elastic, fluid-filled spherical shell containing a concentrically-located elastic sphere. The major assumptions in the analysis 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 are obtained numerically for the near-audible frequency range. Natural frequencies and mode shapes are presented for twenty cases. The results show that the spectra of natural frequencies for the physical system are distorted by the combined effects of volume exclusion and the elasticity of the inner sphere. The elastic inner sphere also introduces a pattern of additional frequencies to the spectra of natural frequencies of the physical system.
- Pub Date:
- January 1990
- Engineering: Mechanical; Physics: Acoustics; Engineering: Biomedical