权益分类	功能权益	普通用户	{{item.name}}会员
{{category.name}}	{{benefitItem.name}}

Basic Consideration on the mixed flow with Water and Air

水与空气混合流的基本考虑

基本信息

批准号：
06452275
负责人：
OGIHARA Kunihiro
金额：
$ 2.56万
依托单位：
Toyo University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
1994
资助国家：
日本
起止时间：
1994 至 1996
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-06452275/
关键词：
Two phase flow Similitude of Flow Buoyed ratio Flow in conduit Flow in vertical shaft 下水管縦シャフトの流れボイド率ダム越流部の流れダム放流管の中の流れ下水の縦シャフト内の流れ

项目摘要

The transportation of air by water flows in pipe line from the dam can be classified in two types by the process of motions as follows, the first in the motion of hydraulic jump and the second is the friction between water surface. There are many types of flow in long pipe line from the dam such as stratified flow, wavy flow and mixed flow are under the high water velocity and as plug flow and slug flow under the lower water velocity. So the first group is observed in upstream reach from the gate and the second group is in the downstream side where the water velocity becomes slower. There are three high air entrained conditions when the gate is opening from zero to 100% opening. The opening ratios of this condition are 0.25,0.6 and 0.8 in almost pipe diameter greater than 60mm diameter but it depends on the pipe lengh. The air entrained in the cases 0.25 and 0.8 opening is made by the motion of hydraulic jump and the case of 0.6 is by the friction of water surface. When the pipe diameter becomes smaller than 60mm, the case of 0.6 gate opening can not be observed, because the friction forces on the pipe wall becomes larger. This fact shows the air entrained flow is controlled by both the gravity force and friction force and the results by model test can not be applied to prototype directly except the consideration on the relations of these forces.The air distribution in the channel of dam can be measured by the sensor used of the infrared rays. The structures in mixed conditions between air and water can be determined in large scale model but in the smaller scale model it is difficult to catch those structures. This fact shows the results from small scale model can not applied to prototype.The theoretical model for the water and air mixed flow in vertical drop shaft can be made and the flow becomes different in the water velocity is greater than 6m/sec.

从运动过程上看，管道水流对空气的输送可分为两类，一类是水跃运动，另一类是水面摩擦运动。出坝长管段内的水流有多种形式，高流速时为分层流、波浪流和混合流，低流速时为塞流和弹状流。因此，第一组在闸门的上游河段观察到，第二组在水流速度变慢的下游侧观察到。当闸门从零打开到100%打开时，存在三种高空气夹带条件。在直径大于60 mm的管道中，这种情况下的开孔率几乎为0.25、0.6和0.8，但开孔率与管道长度有关。0.25和0.8开度时的空气夹带是由水跃运动引起的，0.6开度时的空气夹带是由水面摩擦引起的。当管径小于60 mm时，由于管壁摩擦力增大，不能观察到0.6开度的情况。这说明引气流动受重力和摩擦力的共同控制，模型试验的结果不能直接应用于原型，必须考虑重力和摩擦力之间的关系。在大尺度模式中可以确定气水混合条件下的结构，但在小尺度模式中很难捕捉到这些结构。这说明小比例模型的计算结果不能应用于原型，可以建立竖井水气混合流的理论模型，当水流速度大于6 m/s时，水流变得不同。