Acoustic Reflection and Transmission of Gaussian Beams from Fluid Coupled Laminates and Circular Cylindrical Shells
This thesis presents an analysis of acoustic wave propagation across layered cylindrical structures that are immersed in fluids and obliquely insonified by acoustic Gaussian beams from the concave side. The acoustic nonspecular reflection is due to the interference of geometric reflection and leaky guided waves. Contrast to the ealier studies assuming that incident rays are all parallel to the central beam axis. The acoustic Gaussian beam is modeled by the complex source point (CSP) method and angular spectrum. In the present method the beam is not limited with well collimation. Spectral integral representation of the reflected and transmitted acoustic fields are replaced by a Fourier series due to circumferential period in polar coordinates. The exact forms of reflection and transmission coefficients of a layered cylindrical structure are derived using Thomson-Haskell method. The cylindrical structure made of chopped-fiber glass/epoxy is assumed to be isotropic. Two acoustic impedance matching layers added on both sides of the structure to construct a laminated acoustic window is also studied. Influences of various design parameters on nonspecular reflected and transmitted acoustic fields are well-disscussed.
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