Liquid-level detection based on the energy attenuation characteristics of hybrid model Lamb waves

A method for liquid level detection using hybrid model Lamb waves is proposed. The dispersion equation of the Lamb waves with liquid loading on a single side of the wall is derived, and the phase velocity dispersion curve is obtained. The relationship between the out-of-plane displacement of Lamb waves and the energy attenuation of the received signal is analyzed. The Lamb wave mode which is sensitive to the liquid surface is selected to detect the liquid level. The received hybrid time-domain signals and their energy corresponding to incident waves at different angles are simulated. The results of the tests in practice show that the detection discrimination of the hybrid wave containing B4 mode is much higher than the other hybrid waves and the longitudinal wave. The experimental test results are consistent with the theoretical calculations.