Improving the measurement of air-water flow properties using remote distance sensing technology

TL;DR

This paper demonstrates that remote laser distance sensors can effectively measure air-water flow properties, including air concentration and flow parameters, advancing the potential for safe, accurate, and non-intrusive flow measurements in natural and engineered environments.

Contribution

The study introduces a novel application of laser distance sensors for measuring air-water flow properties, including air concentration and flow dynamics, using dual laser triangulation setups.

Findings

Laser sensors can measure entrapped air concentration in flows.

Dual laser triangulation enables extraction of flow parameters.

Sensor characteristics can influence measurement accuracy.

Abstract

In recent years, there has been an increasing research interest in the application of remote sensing technology to highly aerated flows, which is because this technology holds the ultimate promise to enable safe and accurate measurements of real-word air-water flows in natural and human made environments. Despite the increasing number of publications, some fundamental questions, such as ``what do we measure'' or ``what can we measure'', have not been answered conclusively. In this study, we hypothesize that laser distance sensors are able to measure the concentration of entrapped air, which we demonstrate using two seminal air-water flow types, namely a submerged hydraulic jump and flows down a stepped spillway. By converting our free-surface signals into time series of instantaneous air concentrations, we also show that a dual laser triangulation setup enables the extraction of basic air-water flow parameters of the upper flow region, comprising interface count rates, interfacial velocities, and turbulence levels, while we acknowledge that some sensor characteristics, such as beam diameters, can lead to measurement biases. Overall, this study represents a major advancement in the remote measurement of air-water flow properties. Future collective research effort is required to overcome remaining challenges.