Experimental Study of the Effect of Fluid Jet Swirl on Circular Hydraulic Jump

When an axially symmetrical fluid jet impacts on a horizontal target plate vertically, a hydraulic jump is formed. Flow rate, fluid jet diameter, nozzle opening distance to the target plate, surface tension of the fluid, etc. are different parameters important for investigating this phenomenon. The impact of the important and key parameter of fluid jet swirl on hydraulic jumps is not investigated. The main purpose of this study is to investigate the impact of fluid jet swirl on circular hydraulic jump. The results of this study, achieved by using experimental method, show that the higher the angular velocity, the higher the increase in the radius of circular jump. The increase in jump radius with angular velocity of nozzles 132.8, 266.4 and 400.8 rpm compared to nozzle without swirl is 3.29, 5.89 and 8.34 percent, respectively. Drawing the diagram of the dimensionless radius of jump based on the dimensionless number of swirl shows two categories of lines. The first category is the fixed angular velocity lines with a negative slope and the second category is the fixed flow rate lines with a positive slope. Experiments also show that the hydraulic jumps created by a swirling jet follow the trend results of modified Watson's theory with a non-significant difference.