PRESSURE FLUCTUATIONS ON THE FLOOR OF THE HYDRAULIC JUMP

Abstract

Pressure fluctuations in the hydraulic jump, as an inseparable aspect of the turbulent flow in the jump, cause very undesirable effects on the performance of the jump type stilling basins. The knowledge of the pressure fluctuations on the floor of the hydraulic jump is, therefore, of immense prac-tical value in the design of these stilling basins. The present study deals with the experimental deter-mination of one aspect of the floor pressure fluctuations in the hydraulic jump, viz., the variation, along the floor, of the intensity of pressure fluctuations as measured by the r.m.s. (root-mean-square) value. For this, a free and a forced hydrau-lic jumps, formed downstream of a sluice gate in a horizontal rectangular channel, have been considered. The free hydraulic jump investigation covers a range of the inflow Froude number from 6.2 to 11.47. The investigation, in the case of the forced hydraulic jump, formed with the help of a two-dimensional U.S.B.R. standard shaped sill of two di-fferent heights of 25.0 mm and 50.0 mm, covers a range of the inflow Froude number of 6.8 -10.0. On the basis of dimensional considerations, functional relationships for the r.m.s. value of floor pressure fluctua-tions have been developed for both the types of jump. -iv- Acquisition of experimental data has been carried out by, an inductive type pressure transducer along with a carrier-amplifier, a r.m.s. voltmeter, an AD-convertor and, a digital integrator, Experimental results have been analysed in a para-metric manner and the variations of the r.m.s. value of the floor pressure fluctuations with the relevant parameters, have been graphically demonstrated.