Experimental Investigation of One-Cycle Triangular Labyrinth Weirs with an Upstream Pool

Abstract

The hydraulic performance of triangular labyrinth weirs with an upstream pool was experimentally studied in both free and submerged flow conditions. The discharge coefficients based on channel width B and the weir length L were calculated from experimental data. It was found that the additional length provided by the pool can significantly increase the capacity of the new weir design. The tested weir models were found efficient and required less concrete in comparison with classical labyrinth weirs for a relatively low head water to weir height ratio of ho/P=0.17. Empirical formulations were developed to predict the discharge coefficient and the critical depth of flow for labyrinth weirs with an upstream pool. The discharge reduction factor ψ of the new weir design was found to be slightly lower than the ψ value of sharp-crested weirs. Performance of the tested weir models in submerged flow condition was directly compared with the sharp-crested weirs. It was found that the submerged flow discharges of the tested weir models were significantly higher than the corresponding submerged flow discharge in sharp-crested weirs. A power law model was proposed to predict the submerged flow discharge from a given water head. The superior performance of labyrinth weirs with an upstream pool over classical labyrinth and sharp-crested weirs in both free and submerged flow conditions make them a suitable choice as a flow measuring device, depth regulator, and flood control structure.