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Bottom ridges formed by sub-critical free-surface flow

Author(s): O. N. Melnikhova; V. P. Petrov

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Abstract: Using the results of experiments it is shown that ridges on the bed of free-surface flow are produced only when there is a stream wise variation in the mean velocity, i.e. ∂U/∂X ≠ 0 where U is the mean velocity, X is the flow direction. Current understanding of the ridge formation mechanism suggests that ridges are formed by stationary (lee) waves. In the steady flow the effect of the lee waves is to accelerate and decelarate the boundary layer flow. When the deceleration reaches a critical value, a turbulent boundary layer is separated and an eddy is formed downstream of the wave trough. The eddy moves upward in the shear flow with captured bottom particles. As ridges grow, the amplitude and the length of the wave increase. When the steepness of the lee waves increases, three-dimensional instability of the lee waves is observed.

DOI: https://doi.org/10.1080/00221689209498906

Year: 1992

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