Phenomena And Prevention Of Water-wings Induced By Middle-piers Of Discharge Tunnels

Water-wings, usually taking place in hydropower engineering projects, are important problems. In the paper, the studies of water-wings were reviewed and the works were proformed of the water-wings induced by the middle-pier of a discharge tunnel according to the model tests and theoretic analysis. The works included:(1) Based on dimensional analysis, the influencing factors of the height and length of the water-wings were obtained.(2) Based on the theory of free projectile, the computation methods of the horizontal jet distance and vertical height for the water-wings were discussed.(3) The water-wings are related closely to the impact lengths of the two flows after the end of the middle-pier of the discharge tunnel. Therefore, a new kind of middle-piers, called as impact load uniformity type, was designed, and could modify water-wings efficiently.(4) Meanwhile, the water-wings are related closely to the depths of concave-surface in the end of the middle-pier. Another new kind of middle-piers, called as increasing surface type, was developed, and has better effects on the water-wings.