阻塞式旋流泄洪洞空腔环流的能量特性

Kinetic Energy Characteristics of Horizontal Rotary Cavity in Spillway Tunnel with Blocking

旋流泄洪洞内的空腔环流既不同于常规有压流,也不同于明流,因此采用理论分析和模型试验相结合的方法,建立了空腔环流断面的能量积分表达式,并对具有较好抗空化特性的阻塞式旋流泄洪洞内空腔旋流的能量特性进行了研究。结果表明:建立的空腔旋流能量方程利用相关水力特性进行计算的结果符合洞内的能量变化和转化规律,随着阻塞面积收缩比的增大,空腔环流的压强势能所占比例明显增加,动能所占比例减小,与阻塞收缩比增大时壁面压强增大、流速减小的规律一致;在水平洞起始段,切向动能大于轴向动能的部位延长,在阻塞面积收缩比m=0.49时,约增长至5倍洞径长处;增加阻塞,对竖井段的能量损失影响很小,但能较大提升水平旋流洞段的消能率。

The cavity circulation in a rotary-flow spillway tunnel is different from both the conventional pressurized flow and the open flow.Therefore,the energy integral expression of the cavity circulation section is established by combining theoretical analysis and model test,and the energy characteristics of cavity circulation in a spillway tunnel with blocking with good anti-cavitation characteristics are studied.The results show that,(a)the calculation results of the established cavity circulation energy equation based on relevant hydraulic characteristics are in accordance with the energy change and transformation law of the tunnel;(b)with the increase of block orifice area contraction ratio,the proportion of pressure potential energy of the cavity circulation increases obviously,while the proportion of kinetic energy decreases,which is consistent with the law of wall pressure increasing and velocity decreasing when the block orifice area contraction ratio increases;(c)in the initial section of the horizontal tunnel,the length of tunnel section where the tangential kinetic energy is greater than the axial kinetic energy is lengthened,and the block orifice area contraction ratio m is 0.49,the length increases to about 5 times the diameter of tunnel;and(d)increasing the blockage has little effect on the energy loss of the shaft section,but can greatly improve the energy dissipation rate of the horizontal tunnel section.