Schlieren visualization of leaky guided waves in a liquid immersion plate

In the ultrasonic testing of submarine pipelines by using guided waves, wave energy leakage is a main reason of signal decay. For overcoming the decrease of energy attenuation, the propagation of guided waves of immersion plates is studied in this paper. The dispersion equations of guided waves is numerically solved. Then the appropriated modes of which phase velocity are small or large are selected for optical Schlieren visualization and propagation of leaky waves is discussed. It is shown that selecting some modes of which imaginary part are small can retard guided wave decay and extend length of testing.