Effects of the Shape of Broad-Crested Weir with Side Slopes and the Length of Horizontal Apron on Downstream Scour Hole Size

Prediction of local scouring at downstream of hydraulic structures is one of the subjects which has been paid attention by researchers in recent years. In this study, the effects of shape of broad- crested weir with side slopes at different Froude numbers on local scouring were investigated at different particle Froude numbers. Firstly, the main factors affecting the process of downstream scouring were detected and adjusted as dimensionless parameters using dimensional analysis. Then variation of the sizes of scour hole dimensions were investigated by changing the lengths of weir crest and the horizontal apron, downstream slope of the weir at different particle Froude numbers. The results showed that the effects of weir crest length and the angle of downstream slope on scour hole depended on particle Froude number, while the scouring was less affected by particle Froude number with changes of the length of horizontal apron. Meanwhile, it was confirmed that there was a similarity between the various profiles of the scour. The parameters of the scour hole were presented as the dimensionless graphs that could be used in structure design to protect the bed against scouring.