College of Engineering

A master thesis was discussed in Department of Dams and Water Resources Engineering / College of Engineering at University of Mosul entitled “Experimental Study of Scour Downstream Piano Key Weir Type C With Change Height of Weir Width of Keys and Apron Solid” on Monday, Dec. 13, 2021 submitted by postgraduate student (Arwa Abdul Razzaq Jamal Malla Obaida).The study was conducted to find out the mechanism of the occurrence of the scour downstream piano key weir type C, using nine models of this weir made of fiberglass, with a thickness of 2 mm and a sharp edge.The study showed that the dimensions of the scour hole (the depth and length of the scour hole) decrease by decreasing the discharge value, increasing the width of the keys, the length of the apron solid and reducing the height of weir, where the highest value for the depth and length of the scour hole reached (18.4) cm and (184.8) respectively when discharge (36 liters/ Tha) and the ratio of key width (1) and height (35 cm) to the length of the protective floor (90 cm). The lowest value for the depth and length of the scour hole was (3.42 cm) and (15 cm), respectively, when duscharge (15 liters / sec) and the ratio of the width of the keys (1.5) and height (25 cm) to the length of the apron solid (120 cm). The results also showed that the percentage of decrease in the depth of scour by reducing discharge from (36-15) in constant height and the percentage of width of keys ranged between (45.65-65.4)%, and the percentage decrease in the depth of scour ranged from increasing the percentage of width of keys from (1-1.5) with constant discharge and height of weir Between (42.08-47.38)% for all experiments, and the percentage of decrease in the depth of scour by reducing the height of weir from (35-25) cm ranged between (28.57-57.7)% for all experiments. The highest and lowest value of the percentage decrease in scour depth by increasing the length of the apron solid from 90 cm to 120 cm ranged between (2.17-24)% for all experiments. The statistical program (21 IBM.SPSS-Statistics) was used to arrive at two situational equations for the maximum depth and length of the erosion pit in terms of variables and with a coefficient of determination of R2 = 0.958 and R2 = 0.969, respectively.