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实验，本研究对激光剖面测量技术（laser profilometry technique）进行了升级，采用单激光器与单相机组合方案，实现水下床面高程演化的检测。所提出的测量流程虽简便易行，却可达到复杂度与成本均更高的同类方法的性能水准。该技术被应用于含90°弯道的渠道内动床床面的溃坝试验工况，该试验在五个不同监测点位同步连续记录了水位与床面高程数据。随后采用摄影测量法（photogrammetry）重建了试验最终床面地形，仅通过分析少量经合理选取的直线型床面剖面，即可阐释该地形的主要特征。综上，这种低成本、简便、灵活且高精度的方法，可作为复杂方法的优质替代方案，适用于快速瞬态流动条件下的河床形态动力学（morphodynamics）研究。