Application of focused ultrasonic sensors for suspension measurement of solid-liquid two-phase flow

Suspended sediment is distributed in rivers of different depths, the content of which is a significant parameter for dynamics of river sediment movement, water conservancy projects, channel regulation, and even for oceanic ecosystems, oil production. A pair of new focused ultrasonic sensors using PZT as the arrays are proposed in this paper, with advantages of small scattering loss and high energy, and measurement system based on the focused ultrasonic sensors and ultrasonic attenuation theory is built to predict the suspended sediment concentration. Three groups of sand samples with different particle sizes are obtained by screening method, followed by a series of experiments on water-sediment mixture of different concentrations. The echo signals from the experiments are processed by tools of wavelet-based de-noising and FFT method, resulting in clear and smooth frequency spectrums. The attenuation coefficient is obtained by analyzing the amplitude changes. Combined with the results of the weighing method, the relationship between concentration and attenuation coefficient under different particle sizes is achieved and the error analysis is carried out. The results show that the proposed sensors and model can provide effective method for the measurement of suspended sediment parameters.