Laser profilometry to measure the bed evolution in a dam-break flow

A laser profilometry technique was upgraded to detect underwater bed level evolution with a laser and a single camera for highly transient laboratory experiments. The proposed procedure is simple, but achieves a similar performance as that met by more complex and expensive methods. This technique was applied to a dam-break test case over a mobile bed in a channel with a 90° bend, for which water and bed levels were both continuously recorded at five different places. Photogrammetry was then used to reconstruct the final topography, whose main features could be explained by analysing only a few appropriately chosen linear bed profiles. This cheap, simple, flexible and accurate method thus proves to be an interesting alternative to more complex methods for morphodynamics investigations in the case of fast transient flows.

为适配高瞬态实验室试验需求，我们对激光轮廓测量法（laser profilometry）进行升级，使其可依托单台相机与激光完成水下床面演变的监测工作。所提出的方案流程简洁，却可实现与复杂度更高、成本更昂贵的同类方法相当的性能表现。该技术被应用于某带90°弯道的水槽内的动床溃坝试验工况（dam-break test case），在该试验中于五个不同位置同步连续采集水位与床面高程数据。随后借助摄影测量法（Photogrammetry）重建试验最终地形，仅通过分析少量经合理遴选的线性床面剖面，即可阐释该地形的核心特征。由此可见，这种低成本、简洁易用、灵活可靠且精度优异的方法，可作为快速瞬态流场景下开展地貌动力学（morphodynamics）研究时，复杂类方法的优质替代方案。