泄水建筑物掺气坎底空腔回水探讨

Discussion of aerator bottom cavity backflow of discharge structures

该文主要采用数值模拟的方法,对明流泄洪洞掺气坎底空腔回水问题进行了探讨。通过对连续坎及三维异型掺气坎(U型、V型和凸型掺气坎)后落水区形态,水舌三维流态以及落水区流场结构等水力特性进行分析发现:当水流经过掺气坎后,中间水流较为集中时,主流方向的能量较大,不利于水流在底部落水区域的充分扩散;水流出坎后横向扩散的方向对抑止空腔内回水壅堵较为敏感,掺气坎后水舌向两侧扩散的水流与边壁的相互作用容易产生回水。结合掺气坎后水流的细部结构得出,影响掺气坎后空腔回水的主要因素为:出坎水舌落水区的纵向分布范围与横向分布范围的关系以及水舌入水角度。

Numerical simulation was used to discuss to the aerator bottom cavity backflow of free-flow spillway tunnels. Through analyzing nappe flowing shape of continuous type,U type, V type and protruding type, three-dimensional flow state and falling region characteristics behind the aerator were obtained respectively. When the water body is comparatively centralized, the energy of the major flow is relatively great, and the water body of falling areas is not fully spread. The succession distribution of entering angle of water tongue can restrain backflow in the bottom cavity effectively. In addition the mutual action of spreading water and lateral sides is apt to cause back-water. It is concluded from the detail flow structure of different type aerator characteristic that main factors of influencing backwater of bottom cavity are the ratio of vertical distribution range to the horizontal of falling water areas and entering angle of water tongue.