Author(s): Haitham K. Ghamry Ph.D.; Peter M. Steffler

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Abstract: The classical depth averaged De St. Venant equations, which are used for most of the computational models in open channels, are based on the fundamental assumptions of uniform velocity and hydrostatic pressure distributions. They are thus limited in their applicability to cases where vertical details are not of importance. Alternative two-dimensional vertically averaged and moment equations are developed, by a moment weighted residual method from the fundamental 3D Reynolds equations, to account for problems where more vertical details are significant and essential. The proposed model is applied to rapidly varied flow problems involved in open channel flow. These problems include flow in channel transitions with rapid contraction and/or expansion and flow over a hemispherical hump. Linear distribution shapes are proposed for the horizontal velocity components, while quadratic distribution shapes are considered for vertical velocity and pressure. The implicit Petrov-Galerkin finite element scheme is used in these simulations. A good agreement is attained. In addition, the obtained results show that more details are gained and the flow is better represented by the proposed model compared to the classical De St. Venant model.

DOI: https://doi.org/10.1080/00221680209499902

Year: 2002