EFFECT OF VERTICAL TRAPEZOIDAL ROUGH BED ON HYDRAULIC JUMP CHARACTERISTICS AND ENERGY LOSS

Stilling basins with different layout of rough and appurtenances are commonly used to reduce the excessive energy of exiting flow downstream of hydraulic structures through the phenomenon of hydraulic jump. This paper deals with an experimental investigation on the effect of vertical trapezoidal cross bars on the characteristics of hydraulic jump. total of 126 runs are conducted where the Froude number of incoming flow to the basin ranged from 3.9 to 13.7.Three different heights (t) were selected for the rough elements with four different longitudinal spacing (s).The results showed that the non dimensional profile of the jump could be defined with a unique equation. It was also revealed that the sequent depth, length of hydraulic jump and roller length are reduced while the energy loss is increased, comparing with classic jump. These effects are intensified as the Froude number of incoming flow, the height and spacing of the rough bars increased. It is found the bed shear stress is 3.2-9.6 times bigger than that on smooth bed. The investigation resulted in some empirical relations to define the sequent depth, energy loss and bed shear stress for different flow conditions on used rough beds.