Core impact force of vertical water jets on smooth and rough surfaces

A normal way to dissipate energy of the dam-released high-velocity jets is to allow them to free-fall into a plunge pool or impact a plane surface in case of dam site limitations. The water jets have an undisturbed core from nozzle outlet to a certain falling height, which has more impact force and less turbulence intensity than the developed part of the free jet. Experiments have been conducted to determine core impact pressure coeffcient of a vertical jet on smooth and rough plane surfaces. The experiment results for different jet diameters and falling heights have shown considerable increase in the mean dynamic pressure coeffcient with increase in the jet Froude number for both smooth surface and rough surface. In this study, a simple Froude based mathematical model had correlation in the estimation of jet core impact force on the smooth and rough plane surfaces. A considerable increase in the jet core length was observed with increase in the jet Froude number. Results also showed a strong correlation between turbulence intensity coeffcient and the jet core length.