Experimental study of the effect of obstacles on flow energy loss in piano key weir

Piano key weirs have a longer crown length than linear weirs. Increasing the length of the weir crest in a limited width increases the water flow coefficient. Considering the importance of these weirs and the solution to increase the energy loss and finally reduce scour in them; therefore, in this research, it used a C-type trapezoidal piano key weir. Four flow rates of 0.025, 0.03, 0.035 and 0.04 cubic meters per second were also used. Three barriers with heights of 0.01, 0.03 and 0.05 meters were also used at the end of the overflow output keys. The results show that with the increase in the height of the obstacles, the amount of energy loss also increases. Also, by increasing the flow rate, the amount of energy loss is reduced. In barriers of 0.01, 0.03 and 0.05 meters, the amount of energy loss increases by 1.20, 2.13 and 2.53%, respectively, compared to the weir without obstacles. The average energy loss in weirs with barriers of 0, 0.01, 0.03 and 0.05 meters at the end of the outlet switches is equal to 57.8, 58.5, 59.06 and 59.3, respectively. At the end, a relationship was obtained to calculate the amount of energy loss in the C-type trapezoidal piano key weir along with the barrier at the end of the output keys with a correlation coefficient of 98.9%.