Analysis On Back Scattering Wave Structure Of Elastic Cylindrical Shell

One of the most important underwater acoustics research areas is to detect the position of projects, and the back scattering wave characteristic is the basic research subject in the mind of underwater acoustics researchers. This thesis focuses on the description of the back scattering wave structure especially when the submerged cylindrical shell excited by a plane wave at oblique incidence. There are only a few papers centered attention on this point because of the more complex situation, both on theory and experiment. My thesis, with the limited methods, tries to find some helpful results on this particular subject.At the first, the paper studies the dispersion characteristics with several kinds of limitations, as in the vacuum and with the load of water, e.g. Then, I derive the normal mode expression of the scattering function of a submerged infinite cylindrical shell excited by a plane wave at oblique incidence. Performing the Sommerfeld-Watson transformation on this solution, we get the particular form of helical surface waves.Based on sound excitation and reradiating of the elastic helical surface wave, we analyzed the echo's pulse response, calculate the time sequence of echoes. The experimental results and the theoretical results are compared, and they are basically in agreement.One of the keys of this paper is to solve the dispersion equations in the complex plane. Here, using the Winding Number Integral Method, we find the complex resonance poles in the normalized complex frequency plane. This method is superior to some other process in its clear conception and concision procedure. The thesis gives a introduction to this method and some advice on its future practice.The experiment aims to ensure the correctness of the dispersion curves and the appropriator of the time sequence modal, and the result is pleasant.At the last, the thesis makes a conclusion, and gives some helpful advice.