Hydraulic Criteria of a Bubble-Pump System for Destratification

由于热分层条件下的垂向交换作用，人工水库深层常出现低浓度氧。低氧水团促使泥床微孔中磷的再分解，导致水库水体富营养化。探索了利用大尺度气泡进行水体分层的可行技术方法，大尺度气泡的形状为上表面球形，底部近平。上升速度解释的空气释放量和预测通过一个潜在的理论与实验结果一致。由类似于涡环的结构产生的循环区将周围的流体夹带到气泡的尾流区中，然后将其向上输送。单个气泡的输运体积约为单个气泡体积的25倍。第二阶段分析了圆柱形气泡泵系统。圆柱内的垂直速度随气泡的上升而上升。而气泡离开圆柱顶部后，垂直方向的速度减小，并转为向下运动。当下一个气泡刚好在速度方向发生变化之前释放时，获得最高效率。对圆柱内垂直速度随时间的变化进行了理论估算，与实验结果吻合较好。的水平尺度的传播解除较重的水被解释为一个函数的密度弗劳德数在一个圆柱体的出口和一个圆柱体的淹没。在圆柱体出口上方设置缓冲板，能有效地改变负浮力射流的上升方向，但对提高较深水体的抽水效率作用不大。

Low concentrain of oxygen frequently appears in a deep layer of a man-made reservoir due to search vertical exchange under thermal stratification. Low oxygen water mass accelerates phosphorus in micro pores of muddy bed to resolute again and then results in entrophication of reservoir water. Feasible technical methods are sought for destratification of water body on use of a large scale air-bubble.Shape of a large, single bubble is spherical in the upper surface and the bottom is nearly flat. The rising velocity is explained in terms of air volume released and the prediction through a potential theory agreed well with experimental results. A circulation zone generated by a structure similar to a vortex ring entrains surrounding fluid into the wake zone of a bubble and then transport it upward. Transported volume by a single bubble is observed to be about 25 times of the volume of a bubble.In a second phase a bubble-pump system used a cylinder is analyzed. The vertical velocity in a cylinder is upward in accordance with the rise of a bubble. But after a bubble leaves the top of a cylinder, the vertical velocity reduces and turns into downward. The highest efficiency is obtained when a next bubble is released just before this change in the direction of velocity takes place. Time variation of the vertical velocity in a cylinder is theoretically estimated with good accordance with experimental results. The horizontal scale of the spreading of lifted heavier water is explained as a function of the densimetric Froude number at the outlet of a cylinder and the submergence of a cylinder. A buffl plate set above an outlet of a cylinder is effective to change the direction of a rising negative buoyant jet but has scarse effect in gaining better efficiency of the pumping rate of a deeper water body.