2008 – Modelling procedures used for the spillway upgrade for Lake Manchester Dam

Eric Lesleighter, Bronson McPherson, Karen Riddette, Jon Williams

Abstract: The paper describes in part the hydraulics investigations required for the major upgrade works for Lake Manchester Dam; investigations which utilised two modelling procedures. Following a brief outline of the dam rehabilitation program and works, the inadequacy of the former spillway for the revised hydrology is described. The urgency of the construction program led to the use of CFD modelling following preliminary desk studies of the hydraulics, in order to delineate certain features of the new spillway and the plunge pool area and allow the construction program to be fast-tracked. As part of the overall program to refine the spillway design, and due to the evident complexity of the flows over the spillway, physical hydraulic model studies were also carried out.

The investigations provided a very good opportunity to compare the results from two modelling approaches carried out within the same design activity. Specific results of aspects such as flow patterns, velocities, pressures, and wave action will be compared. A prominent purpose of the paper will be to acknowledge the advantages and limitations of both approaches, and seek to provide the guidelines and advice that designers and dam owners should follow and adopt to ensure the hydraulics requirements of projects are soundly engineered.

Keywords: spillways, physical modelling, numerical modelling, CFD.

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