Laboratory studies of the effect of space and width of baffles on the length of hydraulic jumping in the downstream of baffles apron drop

摘要

The hydraulic jumping is one of the wonderful hydraulic phenomenons which cause the dissipation of kinetic energy of water. Hydraulic structures like stilling basins generally make use of the important feature of hydraulic jumping in the downstream ofcrests, drops, and gates. The dimension of these structures is directly related to the features of the hydraulic jumping. Hence, to make these structures economical, a myriad of studies have been done on the features of the hydraulic jumping, the ways of controlling it and/or to minimize its dimensions. Baffled apron drops in channels or discharging creeks to eliminate the excess energy resulting from lowering the line of bed slope. One of the main advantages of this structure is to dissipate a portionof total energy on the slope and to shortening of length of the hydraulic jumping. The current study is conducted based on above mentioned hypothesis. After identifying the effective parameters, the physical model of baffles was made in 3 different widths and placed in 3 different spaces on its bed, and then different experiments were conducted on their influence in the downstream of this type of drop. Data analysis revealed that baffles cause the decrease of length of jumping in average of 50 percentand decrease of the second depth of jumping about 25 percent comparing to the classic mode. The reason of this decrease can be resulted from increase in the amount of fluctuations and speed of turbulence between the baffles which lead in the increase ofshear stress.