小孔流速实验中的排水时间和流量系数的研究

本文以水作为理想流体,考虑到水头损失和孔口缩流效应,对小孔流速实验涉及的容器排水问题进行了系统的理论和实验研究.从理论上推导得出了圆柱形容器排水时间的解析解,分析了排水时间和自由液面速度、流量系数之间的规律,提出了排水时间的等效性.实验上,加工了底部开有不同小孔的大型圆柱形容器,测量了容器排水时间随液面高度的变化关系,借助实验结果计算了流量系数值,验证了容器排水时间的等效性关系,实验结果与理论计算符合较好.

Study on the drainage time and the flow coefficient in the experiment of the flow velocity of small holes

The tank drainage problems in the experiment measuring the flow velocity of small holes are systematically,theoretically and experimentally studied by taking water as the ideal fluid and considering head loss and orifice contraction effect.The analytical solution of the cylindrical tank drainage time is theoretically obtained for the first time.Furthermore,the variation of drainage time with free surface velocity and flow coefficient is discussed.Based on this,the equivalent interval of drainage time is proposed.In the experiment,large cylindrical tanks with different sized exit orifice locating at the bottom are designed and fabricated.The tank drainage time varying with the height of liquid surface is measured.The flow coefficient is calculated from the experimental data and the proposal of equivalent time interval is further validated.The experimental results are in good agreement with theoretical calculations.