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.

为开展高瞬态实验室实验，研究人员对激光剖面测量（laser profilometry）技术进行了升级，采用激光器与单台相机的组合方案，实现水下床面高程演变的监测。所提出的测量流程虽简便易行，却能达到与更为复杂且成本高昂的同类方法相当的性能表现。该技术被应用于带90°弯道的渠道内动床床面的溃坝（dam-break）实验工况中，实验期间在五个不同点位同步连续记录了水位与床面高程数据。随后通过摄影测量（photogrammetry）技术重构实验结束后的床面地形，且仅需分析少量经合理选取的线性床面剖面，即可阐释该地形的主要特征。综上，这种低成本、简便灵活且精度优异的方法，可作为复杂昂贵方法的理想替代方案，适用于快速瞬态流场下的地貌动力学（morphodynamics）研究。