水垫塘的水流特征及其综合评价指标

 高坝下游挑跌水流在水垫塘内的流态是相当复杂的。定性上可看作为淹没冲击射流和淹没水跃流的混合流态。一方面射流入水后沿程不断扩散，在冲击区对水垫塘底部产生巨大的冲击压力，具有淹没冲击射流的特征；另一方面在冲击区下游，高速主流贴近床底并沿程扩散和迅速跃起，同时在主流区的顶部形成较大的表面漩滚区，流态特征类似于淹没水跃流。针对这种混合流态，提出一个综合评价水垫塘消能效率的新指标，以便为水垫塘设计提供科学依据。

Characteristics of flow in Plunge pool and Its Comprehensive Evaluation Index

The characteristics of the submerged impinging jet in a plunge pool downstream a high dam are quite complex. The flow in a plunge pool is regarded qualitatively as the composite flow of a submerged impinging jet and a submerged hydraulic jump. On one hand, the submerged jet diffuses continuously in the plunge pool and produces high impinging pressure at bottom which shows the behaviors of submerged impinging jet. On the other hand, the high velocity main flow diffuses downstream at the impaction zone along the bottom and forms a large surface roller at its top, which is similar to the submerged hydraulic jump. According to this composite flow pattern, a multiple evaluation index of energy dissipation for water cushion is suggested to provide the scientific base data for the design of a plunge pool.