A Study on Drainpipe with Vortex Chamber Controlling Suction Force with Fluid Action

本研究旨在研制一种新型的涡流室排水管，以避免游泳池排水口对人体的吞噬危险。该排水管利用涡流的作用，可以控制吸力的大小。值得注意的是，控制动作是在没有任何机械设备的情况下利用水流本身来执行的。首先通过实验验证了抽吸力的降低效果，获得了有关流动特性的基础数据。分析了涡流室厚度、排气管直径等形状参数对涡流室流动特性的影响。研究结果表明：（1）与常规排水管相比，新型排水管的吸力明显减小。另外，排水管的流阻也比普通排水管的流阻小。2.排水管的设计要点是减小粘滞状态下的吸力。并且，在正常流动状态下流动阻力应该小也是重要的。为此，排气管直径与涡流室直径之比的合适值为0.22左右。涡室壁厚与直径之比在0.3左右有较好的变化趋势。3.涡室内部流动的分析模型由外部区域的自由涡和中心区域的强制涡组成。通过对2002年发生的游泳池事故的调查，获得了有关排水口形状和循环泵规格的数据。

The purpose of this study is to develop a new drainpipe with vortex chamber in order to free from danger of engulfing the human body in the drain-port of swimming pool. The proposed drainpipe can control the suction force with the working of vortex flow. It is worthy of note that the control action is performed with water flow itself without any mechanical equipment. At first, the reduction effectiveness of the suction force was confirmed in experiment, and fundamental data concerning about flow property were obtained. Then, the author analyzed the effects of shape parameters of the vortex chamber, such as thickness of the chamber, diameter of discharge pipe, and so on, on the flow property. And, theoretical model of flow in the drainpipe was also investigated.Results obtained here are as follows :1.It was evident that the suction force of the proposed drainpipe can be reduced drastically compared with usual one. In addition to that, the flow resistance of the drainpipe was smaller than the value of usual drainpipe.2.The point of design for drainpipe is to reduce the suction force at stick state. And, it is also important that the flow resistance should be small in normal flow state. For those purpose, the appropriate value of the ratio of discharge pipe diameter to vortex chamber one was nearly 0.22. And the ratio of chamber thickness to chamber diameter showed good tendency at about 0.3.3.The analytical model of the flow in the vortex chamber consists the free vortex in the outer area and forced vortex in the central area. And the mode can analyze the effect of the vapor cavity generated at the center of vortex.4.The author investigated the swimming pool accident happened in 2002, and obtained data concerning with the shape of drain-port and the specification of circulation pump.