水平旋转空腔环流的壁面切应力的变化规律

The wall shearing stress of level rotary flow

本文推导了水平旋转内消能泄洪洞空腔环流壁面切应力的理论分析表达式。水平旋转空腔环流的壁面切应力不仅与泄流量、旋流夹角、切向流速的速度矩、空腔环流的内外界面的压强差及空腔半径有关,还与空腔环流的内外界面压强差及空腔半径沿程变化率有关。壁面切应力在水平洞的前半段急剧减小,随后沿程缓慢减小,按指数规律衰减变化;上游水位、下游水位越高,其值越大,沿程的衰减变化率也越大;通气孔的直径对壁面切应力的影响较小。壁面切应力的变化规律表明,能量的耗散和易于空化的部位主要在水平洞的前部。

Theoretical expression ot the wall shearing stress has been deduced for the level rotary flow in an internal energy dissipation tunnel. It has been shown that the wall shearing stress is not only influenced by the discharge of the tunnel Q, the rotary flow angle aw, the moment of tangent velocity C, the difference between the wall pressure and the gassy pressure in level hole rotary flow Pw-Po, and the hole radius of the level hole rotary flow ro, but also by the change rate of P^-Po and ro along the level tunnel. It has been found that the wall shearing stress sharply reduces in the initial part and gradually reduces in the middle part of the level tunnel with a exponential law, the higher is the up and down water level, the larger the wall shearing stress becomes in the initial part of the level tunnel and the bigger the change rate becomes along the level tunnel, and the diameter of the vent has a little influence on the wall shearing stress. The behavior of the wall shearing stress along the level tunnel reveals that the initial part of the level tunnel is the part of which there is larger energy dissipation and more possibility of cavitation damage.