水平运动、部分淹没、穿透表面的垂直壁面上的紊流边界层
The Turbulent Boundary Layer on a Horizontally Moving, Partially Submerged, Surface-Piercing Vertical Wall
摘要：
本文考虑了垂直表面穿透板产生的边界层剪切流中湍流与自由表面之间的复杂相互作用，包括空气卷吸过程。建立了一个实验室规模的装置，该装置利用表面穿孔不锈钢带，该不锈钢带围绕两个垂直辊成环行进，辊之间的一段带充当水平移动的平壁。带既作为突然启动的板操作以再现边界层流，又在存在平行于带定位的静止平板的稳定状态下操作以产生具有自由表面的库埃特流。表面轮廓测量与电影激光诱导荧光系统在这两个实验和空气夹带事件和气泡运动观察立体水下白光电影中突然开始带实验。据发现，RMS表面高度波动，$η$，峰值附近的边界的流动和增加近似线性带速度。在库埃特流动实验中，在$\partialη/\partial t$的光谱中的主峰被发现在无量纲频率$fH/U\approx 0.7$处。在突然启动的带实验中，表面波动似乎强烈地影响到次表面湍流内的边界层，而波纹传播自由时，远离带。此外，观察到空气夹带的一些机制，并与Brocchini和Pregrine（J. Fluid Mech.，499，225-254，2001）。
英文摘要：
The complex interactions between turbulence and the free surface, including air entrainment processes, in boundary layer shear flows created by vertical surface-piercing plates are considered. A laboratory-scale device was built that utilizes a surface-piercing stainless steel belt that travels in a loop around two vertical rollers, with one length of the belt between the rollers acting as a horizontally-moving flat wall. The belt is operated both as a suddenly-started plate to reproduce boundary layer flow or at steady state in the presence of a stationary flat plate positioned parallel to the belt to create a Couette flow with a free surface. Surface profiles are measured with a cinematic laser-induced fluorescence system in both experiments and air entrainment events and bubble motions are observed with stereo underwater white-light movies in the suddenly started belt experiment. It is found that the RMS surface height fluctuations, $η$, peak near the boundaries of the flows and increase approximately linearly with belt speed. In the Couette flow experiments, a dominant peak in the spectrum of $\partialη/\partial t$ is found at the dimensionless frequency $fH/U\approx 0.7$. In the suddenly started belt experiment, surface fluctuations appear to be strongly influenced by sub-surface turbulence within the boundary layer, while ripples propagate freely when farther from the belt. Additionally, some mechanisms for air entrainment are observed and comparisons are made to predictions of incipient entrainment conditions in Brocchini and Pregrine (J. Fluid Mech., 499, 225-254, 2001).
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