Beslemeli katı madde hareketi durumunda köprü ayakları etrafında oluşan yerel oyulmaların deneysel ve sayısal araştırılması

Although local scour around bridge piers were studied numerous times, researches mostly tended to investigate clear water scour. Live bed scour was investigated in few number of studies and unsteady flow conditions were not examined in detail. The aim of this study is to investigate live bed scour under flood hydrographs. During the experiments, 16 different triangular hydrographs were generated. Circular piers with three different diameters were tested under these hydrographs. Uniform bed material of 1.63 mm diameter was used during the experiments. Experimental observations about mechanism of scour were presented by means of images obtained from the experiments. The effects of the peak flow rates and duration of hydrographs on scouring were discussed. Numerical analysis was performed by using a computational fluid dynamics (CFD) software called Flow-3D. One of the hydrographs was selected to realize numerical study by using LES, RNG and two-equations k-ε turbulence models. Numerical results were compared with experimental findings. Simulation results of LES turbulence model was more compatible with experimental results. It was observed that the dominant element of the scour was flow rate during the rising limb and sediment transport rate during the falling limb. Three empirical equations were derived to predict time scale of maximum scour depth, temporal scour depth and maximum scour depth. Statistically significant determination coefficient values are obtained.