Experimental and numerical evaluation of local scouring around different bridge piers at a 90° convergent meander

The presence of several convergent meanders is a basic characteristic of natural flowing rivers. It is important to construct bridge piers in different geometric shapes at convergent meanders. The formation of secondary flows at meanders and their enhancement by the convergence effect can bring complexities and irregularity in the erosion pattern around bridge piers. The present study experimentally and numerically investigates the effects of the geometric shapes of bridge piers on local scour around piers at a 90° convergent meander. Tests were carried out within a channel with a 90° convergent meander and a centerline radius of 170 cm. Cylindrical piers with the diameters of 40 and 60 mm and cubic piers with the sizes of 40*40 and 60*60 mm were placed at the center of the meander, investigating scour in clear-water conditions. Also, a three-dimensional SSIIM-2 model was employed to simulate the problem and compare the results to the experimental ones. The results indicated that the shapes and sizes of the piers affected the scour depth, and the maximum scour depth was estimated to be smaller around the cylindrical piers than around the cubic piers in all the tests. Moreover, convergence-induced contraction along with the placement of the piers at the meander enhanced scour around the piers. The numerical SSIIM-2 results were found to be in a good agreement with the experimental results.