阶梯形鱼道中的滚动流研究

最近，小型倾斜河流中的阶梯形鱼道建筑以它的简易与实用而变得日益重要。在这种鱼道中出现的滚动流将产生波涌，并继续向下传播，而且它的周期性滚动可能会严重危害鱼道，因此，我们着手研究了它的严重性以便设计者在设计鱼道时能考虑这些因素。由实验证实滚动流源于阶梯形鱼道的上游。滚动流在稳定流与半平滑流间转变，它在一定时间间隔内不断地从稳定流变成半平滑流，又从半平滑流变成稳定流。它的流量值随着阶梯形水道的几何形状变形而呈现上下限。流量值和时间间隔均随着水池长度的增加而增加。

TUMBLING FLOW IN STEPPED-WEIR CHANNEL-CUM-FISHWA

Construction of stepped-weir channel-cum-fishway in small scalemoderately gradient river has got greater importance from very near past because of its simplicity and greater purpose. Tumbling flow is appeared in this fishway which produces wave surge and continues to flow downward and may causes serious damage due to its behaviour of periodic tumbling action. Thus a study is undertaken to explore the extent of severity of this flow so that designer can keep in mind in designing these fishways. It is confirmed from the laboratory experiments that tumbling flow is originated at the upper most pool of the stepped-weir channel-cum-fishway. The tumbling flow is the transition between tranquil and quasi-smooth flow which continuously changing from tranquil to quasi-smooth and again quasi-smooth to tranquil in certain period of interval. The occurrence of this flow has the lower and upper limit of discharge which varies with stepped-weir channel geometry. Both occurrence discharge and occurrence time interval are increased with the increase of pool length.