CONTROLLING THE LOCATION OF HYDRAULIC JUMP IN RECTANGULAR CHANNEL

Abstract

As per the report of International Commission on Large Dams (ICOLD) demonstrate that over 20% of dam mishaps happened because of poor arrangement of energy dissipation. At present, energy dissipators are intended for ‘design discharge' of spillway. In this manner there is a need to build up a proper plan to perform expected function of energy dispersal even at lower discharge. Present work concentrated on hydraulic jump type energy dissipators. It is found that in majority of failure of dam, the jump position is not specified – i.e. jump is either swept up or drowned. So it is required to manage the position of hydraulic jump so that the front of jump is positioned near toe of spillway or sluice gate to get clear jump. A clear hydraulic jump occur inside stilling basic , once the ideal post jump depth as per Belanger momentum equation is available on apron. To restrain the formation of clear hydraulic jump within basin, a stepped weir at the end of apron is suggested. A mathematical method is developed to design the weir geometry which will form desired post jump depth corresponding to any discharge between design discharge and 20% of the design discharge and the given range of tail water submergence. Experiments in ansys fluent demonstrate that, for horizontal aprons, a designed weir section, designed for a specific range of tail water submergence, restricted the hydraulic jump to its desired location for different discharges. The correlation coefficients for ansys fluent studies with experimental value for horizontal apron ranged between 0.989 to 0.99. This technique is applicable for ‘inflow Froude number ≥ 4.5’. The methodology would provide promising results in real life projects.