Hydraulic Characteristics of Lateral Deflectors with Different Geometries in Gentle-Slope Free-Surface Tunnels

Abstract

The gentle-slope tunnel has been adopted in many high dams, and aerators are usually required for high operating heads. For such tunnels, the lateral deflector is superior to the traditional bottom aerator, which loses its efficiency due to cavity blockage and fails to aerate the sidewalls. However, unfavorable flow patterns such as water-wings and shock waves are induced by the lateral deflectors. To address this problem, two novel lateral deflectors are proposed, and their hydraulic characteristics are comparatively investigated together with the triangular deflector by means of model test and numerical simulation. The triangular deflector was revealed to form a wide cavity that allows for the free rise up of the water-wings inside the cavity, leading to the development of a buddle-type shock wave, whereas the two-arc deflector yields a jet with a fluctuating surface, which induces water-wings and further develops into diamond-type shock waves. In contrast, the cavity formed behind the two-arc deflector with a straight downstream guiding line is stabler and shorter, thereby restricting the development of the rising flow and preventing the formation of water-wings and shock waves. Moreover, the two-arc deflector with a straight guiding line exhibits higher energy dissipation capacities and thus is recommended in practical engineering design.

Flow Hydrodynamic in Open Channels: A Constantly Evolving Topic

“…This Special Issue consists of thirteen manuscripts relating to the topic of flow hydrodynamics in open channels. Various arguments are addressed herein, including flow interaction with hydraulic structures [37,[40][41][42]45,48], flow dynamic in estuaries [38,39], flow-vegetation interactions [42,49], bed sediment effects on flow structures [42,43,45,46], and the effect of channel curvature on flow behaviors and sediment transport [44,47]. This Special Issue represents a significant contribution to the state of the art of the open channel flow fields, extending our knowledge and providing useful references for hydraulic engineers, experts, and those interested in the environment.…”

“…In [37], the authors dealt with understanding the hydraulic characteristics of lateral deflectors with different geometries in gentle-slope free-surface tunnels. Indicating their great importance for many engineering applications, such as in gentle-slope tunnels of high dams, in this study, the authors analyzed the results of both experimental and numerical modeling of two new deflector geometries.…”

“…The SI, entitled "Flow Hydrodynamic in Open Channels: Interaction with Natural or Man-Made Structures", comprises eleven original articles [37][38][39][40][41][42][43][44][45][46][47] and two reviews [48,49] on flow hydrodynamic structures in open channel flows.…”