深孔泄洪洞工作（闸）弧门下游水流空化特性分析

深孔泄洪洞工作弧门下游体型及弧门开启方式决定着水流流态的变化,选择不合理有可能引起底板的空蚀破坏。为了明确与此相关的空蚀发生机理及条件,通过水力学模型试验,并结合简单数值模拟计算,对不同体型、不同水头、不同开度条件下的水流空化与空蚀特性进行研究。研究结果表明:受弧门出口射流流场分布影响,弧门下游抛物线及下游陡坡初始段底板压强随着底板以上总水头的增加及弧门开度的减小会快速下降,最大负压接近或超过-14 k Pa,连接闸室与抛物线之间的水平段长度增加5 m,虽然可以使底板压强有一定幅度增加,但高水头、小开度工况下的水流最小空化数仍然比较小,最小值不足0.2;如果以0.2作为抛物线及其上下游段水流初生空化数,同时底板的施工不平整度有所控制,则总水头40 m时弧门最小开度可以达到1/4,若总水头增加至65 m时,弧门只能全开或3/4开度运行,低海拔地区或水平段加长5 m后最小开度可到1/2~3/4。

Flow cavitation characteristics in the downstream of a service radial gate of a deep spillway tunnel

The flow regime change of the deep spillway tunnel is determined by the downstream flow shape and opening mode of the service radial gate. Unreasonable arrangement may cause cavitation damage to the gate floor. In order to clarify the mechanism and conditions of cavitation damage based on the hydraulic model test and simple numerical simulation, the cavitation and its erosion characteristics of water flow under different shapes, water heads and opening angles were studied. The results show that due to the influence of the jet flow field distribution at the gate outlet, the gate floor pressure rapidly decreases with the increase of the total water head and the decrease of the gate opening in the downstream of the radial gate and the initial section of the downstream steep slope and the parabola, with the maximum negative pressure approaching or exceeding -14 kPa. With an extension of 5 m between the lock chamber and the parabola, the floor pressure can increase to a certain level, but the minimum cavitation number of the flow under the condition of high head and small opening is still relatively small, which is less than 0.2. If 0.2 is taken as the initial cavitation number of the parabola sections, meanwhile, the construction unevenness of the gate floor is controlled; the minimum opening of the radial gate can reach 1/4 when the total water head is 40 m. If the water head increases to 65 m, the radial gate can only operate with full opening or 3/4 opening, and the minimum opening can reach 1/2-3/4 in low altitude area or after the horizontal section is extended for 5 m.