Development of a non-invasive airborne acoustic technique to monitor the dynamics of water systems

本计画提出一种新的理论方法，利用空气声波，非侵入性地量测二维紊流明渠流动之动态粗糙自由表面的关键特性。该项目的研究将涵盖数值模拟和近似解的解析推导，基于将基尔霍夫近似技术扩展到包含多尺度的粗糙表面的情况。这将用于开发一种基于麦克风阵列记录的数据恢复水面轮廓的技术。该方法将提供亚毫米级的精度，以确定存在于浅水流表面的各种尺度的重力毛细波。这些信息可能与水下条件和流速剖面有关。该项目的成果将提供一个虚拟环境，以证明非侵入性测量的概念，以及解释收集的数据的工具。数值模拟将适用于开源软件（即GNU Octave和Scilab）。为了传播结果和进一步开发，该软件将作为开源软件提供给声学和水力学社区。该项目的主要新奇在于，所提出的方法将能够可靠地处理河流、河口和部分填充的管道（下水道）中常见的各种流量，这些管道是水基础设施的关键组成部分，在水循环过程中至关重要。这项工作将使非侵入性仪器的发展，可以确定流速和沉积物输运的天然和人工渠道。这将提高我们评估洪水风险和监测污染的能力。

This project proposes a new theoretical method to measure non-invasively the key characteristics of a two dimensional dynamically rough free surface of a turbulent open channel flow using airborne acoustic waves. The research of this project will cover both numerical simulation and analytical derivation of the approximated solutions based on extending the Kirchhoff approximation technique to the case of rough surface containing multiple scales. This will be used to develop a technique of recovering water surface profile based on the data recorded on array of microphones. The method will provide sub-millimetre accuracy required to identify various scales of gravity-capillary waves present on the surface of shallow water flow. This information can potentially be linked to underwater conditions and flow velocity profile. The project outcomes will provide a virtual environment to prove the concept of non-invasive measurements as well as a tool to interpret the collected data. The numerical simulations will be adapted to open source software (i.e. GNU Octave and Scilab). For dissemination of the results and further developments, the software will be realised to acoustic and hydraulic communities as open source. The key novelty of this project is that the proposed method will be able to work reliably with a broad range of flows typically found in rivers, estuaries and partially filled pipes (sewers), which are the key components of water infrastructure and are critical in the water circulation process. This work will enable the development of non-invasive instrumentation which can determine flow rates and sediment transport in natural and man-made channels. This will enhance our capability for flood risk assessment and pollution monitoring.