Design of structural parameters and study on the energy dissipation characteristics of vertical jet-type energy dissipators.

Abstract

In order to isolate energy dissipators from hydraulic engineering projects and address the issues of vibration damage caused by the discharge structures. This study develops a novel vertical jet-type energy dissipator by placing fragmentation needles at the vertical jet pipe nozzle, which mainly uses the fragmentation needles to fragment the high-energy jet into multiple smaller jets. Along with the mixing of air into the water flow, the mechanical energy of the flow is converted into internal energy and dissipated in the air. The structural parameters of the vertical jet-type energy dissipator include the size, shape, and number of fragmentation needles. The study employs numerical simulations primarily, with physical model experiments for validation, to investigate the nappe characteristics, energy dissipation rate, and energy dissipation mechanisms of the vertical jet energy dissipator under various structural parameters. The results show that within the scope of this study, the energy dissipation rate of the vertical jet increases with the Reynolds number, the number of fragmentation needles, and the size of the fragmentation needles. Compared to the case without fragmentation needles, the energy dissipation rate increases by 1.04-4.89 times. Under the same Reynolds number, the total height of the jet and the height of the potential core decrease as the number and size of the fragmentation needles increase. The height and diameter of the nappe crown increase, and the diameter and thickness of the vortex ring decrease as the number and size of the fragmentation needles increase. The jet under the influence of rectangular fragmentation needles is more dispersed compared to the jet under the influence of cylindrical fragmentation needles. The total height and potential core height of the jet are smaller with rectangular fragmentation needles, while the height and diameter of the nappe crown are larger. The air concentration in the nappe under rectangular fragmentation needles is higher than that under cylindrical fragmentation needles, and the energy dissipation rate of the vertical jet is also higher under rectangular fragmentation needles than under cylindrical fragmentation needles. The vertical jet-type energy dissipator proposed in this study addresses key engineering challenges, such as terrain constraints and the need for flexible design solutions. Its ability to efficiently dissipate energy while maintaining adaptability makes it a valuable tool for hydraulic engineers designing energy dissipation systems. The conclusions of this study provide a reference for the application of vertical jet-type energy dissipators.