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Pier Shape Effect on Backwater Rise and Drag Force in Open-Channel Flow

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An experimental study is presented on the quantification of the backwater effect and the drag force exerted on a single pier in an open channel under subcritical flow. Four typical cross-section shapes of piers were examined: cylindrical, rectangular, rectangle with semi-circular nose and tail, and rectangle with semi-circular nose and square tail. In all cases, the backwater rise upstream of the pier was measured, and the drag force exerted on the pier was calculated by applying momentum balance in a control volume that included the pier. The results indicate that the shape of the cross-section plays an important role on the backwater effect and the drag coefficient of the pier. The experimental results of backwater rise were fitted by a well-known empirical equation to compute the value of the corresponding shape coefficient of each pier.
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Backwater Effect; Bridge Pier; Drag Coefficient; Shape Coefficient; Subcritical Flow

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