Author(s): Youichi Yasuda
Linked Author(s): Youichi Yasuda
Keywords: Hydraulic jump, energy dissipater, hydraulic structures, drop structure, velocity profile
Abstract:
The free hydraulic jump in a rectangular channel has been investigated experimentally. Most of jumps are formed by using either sluice gate or gate nozzle (e.g., jet box). If the jump is formed at the immediate downstream of drop structure, the effect of curvature of stream-line at the toe of jump on velocity field in the jump might not be neglected. In this case, a high velocity turbulent flow continues near the bottom far downstream. Also, the velocity at the center line of the channel might not be represented as characteristics of the jump below the drop. From practical view point of hydraulic design, the jump formation at the downstream of drop structure should be studied precisely. This paper presents velocity fields in jumps at downstream of drop structures on the basis of velocity profiles, time averaged on maximum velocity decays, and the development of main flow in hydraulic jumps. Six different kinds of drop structures are utilized. In the jump region, three dimensional velocity profiles have been distributed by the formation of shock wave downstream of impingement point and also velocity profile like a wall jet has been continued until about 90 % of jump length. When the approaching supercritical flow is disturbed by the curvature of streamline, time averaged maximum velocity of main flow at each vertical section decays in a short distance is later compared with the case of a classical hydraulic jump. And, the main flow in the jump region does not lift to water surface, even if the turbulent boundary layer at the toe of the jump is developed. If the relative drop height becomes lower, the main flow continues along the bottom far downstream. In this case, the velocity profile is distributed as a wall jet in the jump region. (2621, 72, 313)
Year: 2017