This paper reports an experimental investigation of a vertical vortex advected over a rigid wall. The main goal is to study an unstationary, isolated structure, which reproduces a tornado-like flow in an hydraulic environment. The focus is set on the near-wall region, with two types of boundary condition: a smooth wall and a non-erodible sediment bed. Optical methods such as planar and stereoscopic particle image velocimetry are used to measure the near-wall velocity fields: it provides information about the forces involved in the flow, e.g. the shear stress or potential erosive features. A main columnar vortex is identified, with the occurrence of strong tridimensional effects. Some upward velocity fluctuations, resulting of a pressure gradient over the rigid wall, are observed: the vortex topology is found to behave as aeolian events, like tornadoes. Vortex characteristics such as the circulation Γ, radius r c and tangential velocity u <...

中文翻译：

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孤立的柱状涡流产生：动量脉冲特性和壁粗糙度的影响

本文报道了对垂直于刚性壁上的垂直涡旋进行的实验研究。主要目标是研究一种不稳定的，孤立的结构，该结构在液压环境中再现龙卷风般的流动。重点放在具有两种边界条件的近壁区域上：光滑的壁和不可蚀的沉积床。光学方法（例如平面和立体粒子图像测速法）用于测量近壁速度场：它提供有关流中所涉及力的信息，例如剪切应力或潜在的侵蚀特征。识别出主要的柱状涡旋，并产生强烈的三维效应。观察到由于刚性壁上的压力梯度而导致的一些向上的速度波动：发现涡旋拓扑表现为风沙事件，像龙卷风。涡旋特性，例如循环Γ，半径rc和切向速度u <...