Velocity distribution in a gradually accelerating free surface flow |
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Authors: | Shu-Qing Yang Wei-Lin Xu Guo-Liang Yu |
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Affiliation: | aState Key Laboratory of Hydraulics and Mountain River Engineering, Sichuan University, Chengdu, Sichuan 610065, PR China;bSchool of Naval Architecture, Ocean and Civil Engineering, Shanghai Jiao Tong University, 200030, PR China |
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Abstract: | This study investigates the interaction of the vertical velocity v and the streamwise velocity u in a gradually accelerating flow. The analytical result shows that the momentum of uv driven by the mean velocities in a non-uniform flow is not negligible. This additional momentum directly results in the concave profiles of Reynolds shear stress in gradually accelerating flows, a departure from the expected linear profile. Consequently, this momentum causes the maximum velocity to be located below the free surface, i.e., the dip-phenomenon. This paper investigated the interactions of the Reynolds shear stress, non-zero vertical velocity and dip-phenomenon, it is found that the non-zero vertical velocity causes the dip-phenomenon. The approach is tested using the experimental data of Song and others, and good agreements between the predicted and measured velocity profiles have been achieved. |
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Keywords: | Velocity distribution Gradually accelerating flow Bed shear stress Reynolds shear stress Vertical velocity |
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