Analysis of acoustic echo-signal from gas pipeline with long crack

The scattering of plane non-stationary sound wave from a viscous gas-filled thin cylindrical shell weakened by long linear slit and submerged in ideal fluid is studied. The vibrations of elastic object are modeled on the base of Kirchhoff-Love thin shell-theory approximation. The solution of problem is obtained using the integral Fourier transform over time and in form of cylindrical harmonic series for spectral characteristics. The numerical analysis is carried out for the steel shell filled up methane and immersed in seawater. The scattering amplitudes, directivity patterns of the scattered field, and echo-signals from object are investigated with taking into consideration the orientation of slit on elastic shell surface. The obtained plots show the considerable influence of the slit and presence of gas in tube on diffraction process.