Local scour due to free fall jets in non-uniform sediment

The results of experiments on the local scour due to free fall jets are presented in this paper. Experiments were conducted for various values of the densimetric Froude number, the relative tailwater depth, the relative drop height and the relative sediment size. It has been found that by increasing the sediment non-uniformity parameter the scour hole parameters decrease. Moreover, in non-uniform sediment, d 90 can be used instead of d 50 in the densimetric Froude number of the jet. By using the present and previous experimental data, new equations for the scour parameters were developed. The validity of the developed equations was checked by available prototype data on the scour depth.