Effect of Nozzle Diameter and Falling Height on the Dynamic Pressure Coefficient of Vertical Free Water Jets

Stilling basins are constructed at the downstream of dam spillways to dissipate the excess energy of the spilled flows. The turbulent flow velocity converts to the dynamic pressure due to impact of flow pockets with the basin's walls and bed. Experiments were conducted using a pressure transmitter system to measure the resulted dynamic pressures from the impact of a series of rounded non-submerged jet on a flat plate. The analysis of data showed that a 18% moderate decrement in nozzle diameter caused a 14% moderate increment in the dynamic pressure coefficient and a 34% moderate decrement in jet drop length caused an approximately 13% increment in the dynamic pressure coefficient. Nevertheless, variations of the dynamic pressure coefficient with the increment of nozzle discharge had no regular trend and it began to decrease after reaching a maximum point.