射流角度变化对矩形消力井水力特性的影响

Effect of Jet Angle Variation on Hydraulic Properties of Rectangular Dissipative Wells

泄水建筑物出口狭窄地形条件难以适应传统底流消能工在长度方向的布置要求时,矩形消力井成为一个可行的选择。针对泄水建筑物通常沿地面坡度布置的实际情况,采用数值模拟的方法研究了特定流量下不同射流角度对矩形消力井水力特性的影响。结果表明,当泄槽底坡不大于1∶6.5(θ≤8.75°)时,射流在消力井内出现明显的向上偏折(弹射)现象,不能形成淹没射流,流速衰减仅为44.5%,涡量主要集中在水流表面,消力井内水流紊动变化不大;当泄槽底坡介于1∶6.5~1∶2.5(8.75°<θ≤21.8°)时,射流几乎不发生偏折,流程范围内流速衰减先上升再下降(68.9%→79.6%→69.6%),涡量能够扩散至整个消力井,射流所引起的紊动范围增大后减小;当泄槽底坡增大至1∶2.5以上(21.80°<θ≤45°)时,射流呈明显的向下偏折,流速衰减随流程缩短进一步减小(69.6%~49.7%),涡量分布在射流上下两侧,水流紊动主要集中在射流附近。即淹没射流条件下,针对不同的入射角度,可合理选择井深,从而使得入射水体动能在流程范围内实现最大程度衰减。

When the narrow topographic conditions at the outlet of the discharge building make it difficult to adapt to the lengthwise arrangement of conventional underflow energy dissipators,rectangular dissipation wells become a viable option.In response to the fact that release structures are usually arranged along the slope of the ground surface,numerical simulation is used to study the effect of different jet angles on the hydraulic characteristics of rectangular dissipation wells under a specific flow rate.The results show that when the bottom slope of the spillway is not larger than 1∶6.5(θ≤8.75°),the jet in the dissipation well appears obvious upward deflection(ejection)phenomenon,and it cannot form a submerged jet;The flow velocity attenuation of only 44.5%,the vorticity is mainly concentrated in the surface of the water flow,and the turbulence in the dissipation well is not strong;When the bottom slope of the spillway is between 1∶6.5 and 1∶2.5(8.75°<θ≤21.8°),the jet hardly deflects,the flow velocity decay in the process range rises and then decreases(68.9→79.6→69.6%),vorticity is able to diffuse throughout the dissipation well,and the range of turbulence induced by the jet increases and then decreases;When the bottom slope of the spillway increases above 1∶2.5(21.80°<θ≤45°),the jet is obvious downward deflection,flow velocity attenuation with the shortening of the process to further reduces(69.6%-49.7%),vorticity distribution in the upper and lower sides of the jet,and water turbulence is mainly concentrated in the vicinity of the jet.Under submerged jet conditions,the well depth can be reasonably selected for different incident angles so that the kinetic energy of the incident water body can be attenuated to the greatest extent within the process range.