A Method for Computing Water-Surface Profiles in Ladder Channels

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Filed under: Fishladders

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Proceedings of the International Symposium on Fishways '90 in Gifu, Japan

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For designing ladder type fishways,, it is needed to compute the water-surface profile and average velocities in ladder channels. However, due to the occurrence of critical water depth it is unusually difficult to carry out the computation of water-surface profiles in pool-and-weir type ladder channels. A numerical model for computing the water-surface profile in ladder channels having abrupt drops has been developed in related research works, i.e. the evaluation of hydraulic characteristics and disaster prevention function of channel works in motion and continuity. These equations are expressed in the conservation form and solved by shock-capturing finite difference schemes, namely the two-step Lax-Wendroff and MaCCormack methods. In previous research works, it was indicated that the solution for steady flow by the two-step Lax-Wendroff scheme was dependant on the combination of increment in time and space in the computation, while the solution obtained by the MacCormack scheme was not affected by the selection of increments. Therefore, the MacCormack scheme can be applied to the flow profile computation in ladder channels with abrupt drops. To verify the computed results, experimental data for steady flow in a model channel were used. Comparison of numerical and experimental results shows very good agreement.

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