A Novel Noncontact Method for Phase Interface Measurement in Liquid-Filled Pipe Using Leaky L(0,2) Wave

In this article, we propose a novel phase interface measurement method in the liquid-filled pipe using leaky L(0,2) wave implemented by an electromagnetic acoustic transducer (EMAT). Two EMATs with flexible coils are circumferentially wrapped on the liquid-filled pipe, acting as an exciting EMAT and a receiving EMAT, respectively. The coil used in the excitation EMAT is a ten-turn meander-line-coil exited with a five-cycle Hanning windowed tone burst signal to produce pure leaky L(0,2) waves. The feasibility of this method has been verified by finite element (FE) model and experimental analysis. During experiments, the liquid levels in the vertical pipe and horizontal pipe can be obtained by means of the amplitude of the received L(0,2) wave. Various diameters of the rod were used to model different phase interfaces, and the results indicate that the diameter is linear to the arrival time of the leaking L(0,2) wave. Meanwhile, the amplitude of the leaky L(0,2) signal in a certain range is used to express the reflectivity of the phase interface. Based on these results, the proposed method can be used for phase interface measurement and provides a potential of phase interface imaging.