旋流式竖井底部消能区压力特性研究

Pressure Characteristics of Vortex Flow Intake Shaft at the Bottom of Energy Dissipation Zone

旋流式竖井主要利用水流的螺旋运动和底部消能区消能,是一种较为新型的泄洪消能工,但在高水头、大流量条件下,旋流式竖井泄洪洞内水流流态复杂,底部消能区承受较大压力,对结构安全形成严峻考验。通过1/30模型试验与理论分析的方法研究在不同深度下底部消能区侧壁及底部的压力特性,并针对环状水跃位置不易确定的问题提出一种新的思路确定底板的冲击压力,给出底板最大冲击压力的计算公式。结果表明:旋流式竖井底部消能区侧壁压力与井深关系不大,随流量同步增减,则控制侧壁结构的因素是大流量时的压力;各体形下侧壁压力最大值均出现在竖井侧壁最低点,随着竖井深度加深,最大时均压力呈增加趋势;通过拟合的底板最大冲击压力公式,建议竖井深度与直径比大于1.2。

The vortex flow intake shaft by combining water spiral motion and bottom dissipation area for energy dissipation is a relatively new type of energy dissipation works. However, flow pattern inside the cave of swirl shaft spillway performed complex phenomenon in the condi- tion of high head and huge discharge, bottom dissipation area withstand greater pressure, which means a severe test on the structural safety. Pressure characteristics for different depths at the side wall and the bottom of the pressure dissipation area were researched by model tests of 1/30 combining theoretical analysis, and a new idea to determine impact pressure of the bottom floor was proposed aiming at uncertainty of the location of the circular water jump. Furthermore, calculation formula of the maximum impact pressure for bottom floor was presented. Such conclusions can be got, there are little relationships between the pressure of sidewall of vortex flow intake shaft and the depth of vertical shaft and it has a synchronous variation with the flow, so the structure of sidewall is determined by the pressure in the condition of large flow. The maximum of the sidewall pressure always appearance at the lowest zone of vertical shaft, and the maximum increase with the addition of depth of vertical shaft. On the basis of the fit for calculation formula of the maximum impact pressure for bottom floor, it can be proposed that the ratio of the depth and diameter should more than 1 or 1.2.