Investigation of jet flow effect on the hydraulic jump

In this study, effect of water jet with different flow rates on the hydraulic jump in horizontal channel has been investigated. The experiments were carried out in the 75 mm width, 150 mm depth and 5 m length water channel. Experiments were carried out for six different upstream Froude numbers in the range of 3.43- 4.83 and five different water jet discharges. Water jets were applied with 30o, 45o and 60o angles to the toe of the jump. Free jump and jumps with jets were analyzed by image processing technique with a high speed SVHS camera. Flow structures, roller lengths, water surface profiles and energy losses during free hydraulic jump and hydraulic jump with water jet were studied and compared. According to graphics plotted to determine the water surface profile change with water jets, hydraulic jumps were observed moved to upstream of the flow with increasing water jet flowrate. The steepness of the surface profiles during hydraulic jumps with water jet increased when compared with free hydraulic jump, also downstream water depth, y2, increases with increasing water jet discharge. Roller length increased with increasing upstream Froude number. Roller length decreased with respect to that of the free hydraulic jump when the hydraulic jump with water jet. The normalized energy losses with respect to upstream water depth and the energy loss of the free hydraulic jump increased with increasing Froude number both in free hydraulic jump and the hydraulic jump with water jet. The energy losses in hydraulic jump with water jet were obtained higher than that of the free hydraulic jump. The increase in energy loss was also observed as the jet flow rate increases. Key Words: Hydraulic jump, energy losses, effect of water jet, roller length.