Water Level Sensing in a Steel Vessel Using A₀ and Quasi-Scholte Waves

Abstract

This paper presents a water level sensing method using guided waves of A 0 and quasi-Scholte modes. Theoretical, numerical, and experimental studies are performed to investigate the properties of both the A 0 and quasi-Scholte modes. The comparative study of dispersion curves reveals that the plate with one side in water supports a quasi-Scholte mode besides Lamb modes. In addition, group velocities of A 0 and quasi-Scholte modes are different. It is also found that the low-frequency A 0 mode propagating in a free plate can convert to the quasi-Scholte mode when the plate has one side in water. Based on the velocity difference and mode conversion, a water level sensing method is developed. For the proof of concept, a laboratory experiment using a pitchcatch configuration with two piezoelectric transducers is designed for sensing water level in a steel vessel. The experimental results show that the travelling time between the two transducers linearly increases with the increase of water level and agree well with the theoretical predictions.

Numerical and experimental investigations on mode conversion of guided waves in partially immersed plates

“…The mode conversion between QS and A0 waves in partially immersed plates was widely used for liquid-level assessing [22,24,47] and fluid-property sensing [18,48,49]. The behaviors of A0 wave depend on the geometry and material properties of the plate, while QS wave reflects the properties of both the plate and the surrounding fluid medium.…”

“…Guo et al [24] developed two-dimensional (2D) finite element (FE) models to simulate guided wave propagation along an empty steel vessel and the steel vessel filled with water, respectively. At the selected excitation frequency, A0 and QS waves were identified on the water-free vessel and the water-filled vessel, respectively.…”

“…Therefore, the traveling time of the guided waves between two transducers could be also utilized for measuring the liquid level in the steel vessel. This study only considered a single excitation frequency, at which the leaky A0 wave mentioned in [18] was not detected in the water-immersed plate-like structure by both the 2D FE simulations and the experimental measurements [24].…”

Scattering characteristics of quasi-Scholte waves at blind holes in metallic plates with one side exposed to water

“…discontinuous in the shear direction because water cannot sustain shear loads [23,24]. The governing equations of guided waves in the one-side water-immersed plate can be expressed as [25,26] (…”

Estimation of the Filling Distribution and Height Levels Inside an Insulated Pressure Vessel by Guided Elastic Wave Attenuation Tomography

“…Their propagation in plate-like structures ensues lower geometrical damping rates than conventional bulk waves, which generally results in longer propagation distances and better signal–noise ratios [ 18 ]. Several researchers already described the possibility of estimating the fluid filling level with GEW [ 19 , 20 , 21 , 22 ]. In this work the GEW amplitude decay, measured at an outer vessel shell and processed by attenuation tomography is used to determine the filling distribution.…”