【作者】 弋鹏飞； 张健； 苗帝；

【Author】 YI Peng-fei;ZHANG Jian;MIAO Di;College of Water Conservancy and Hydropower Engineering,Hohai University;Yili Normal University;

【机构】 河海大学水利水电学院； 新疆伊犁师范学院；

【摘要】 本文以灌溉工程中的承插式与圆弧式90°圆形弯管构造为研究对象,基于RNG七-ε模型可以较好地模拟弯管流场的情况下,采用此模型对两种弯管类型管径DN40、DN50、DN80、DN110的流场进行数值模拟,并进行局部阻力系数与雷诺数关系的分析。结果表明:水流从上游直管段到下游直管段出口,管道平均压力逐渐降低。弯管外边壁由于水体质点的速度方向改变和水流剪切力的作用,外边壁的压力要大于内边壁,在质点分离区出现压强最低值。承插式弯管在下游直管段外边壁出现高速流速区,而圆弧式弯管在弯曲段内边壁出现流速最大值。能量损失主要发生在下游段,流动方向的改变和漩涡现象是引起两种弯管局部水头损失的主要原因。在流态进入阻力平方区后,两种弯管局部阻力系数随着雷诺数和流速的增大基本保持稳定。在DN50、DN80、DN110管径下,承插式弯管的局部阻力系数是圆弧式弯管的5.24、6.03、6.5倍,说明流态进入阻力平方区后,在相同管径条件下,承插式弯管的局部阻力系数要远大于圆弧式弯管,在实际工程中建议采用圆弧式弯管来减少能量损失。更多还原

【Abstract】 In this paper,the socket and circular arc with 90 degrees types in irrigation project are taken as research object.The model based on RNG_k-ε model is used for flow field of two different pipe diameters of DN40,DN50、DN80 and DN110,which is proved to be a high precision model for the simulation of flow field in elbow pipe.The relationship between local resistance coefficient and reynolds number is analyzed.The results show that,average pressure of pipeline from upstream to outlet downstream in straight pipe decreases gradually.The pressure of outer side wall is bigger than that of inner side wall,because of the particle velocity direction change and flow shear stress in outer side wall of bend pipe.The minimum appeared in particle separation area.The high speed area of socket type bend pipe appears in the outer side wall of straight pipeline downstream.And in the case of circular arc bend pipe,the maximum flow velocity appears in the inner side wall.The energy loss mainly appears in the lower reach.The main causes of local head loss are the change in flow direction and vortex phenomenon.The local resistance coefficient of two kinds of bend pipes keeps steady as the increasing of reynolds number and flow velocity in condition of the flow pattern entering the drag square area.The local resistance coefficient of socket type bend pipe is respectively 5.24,6.03 and 6.5 times that of circular arc bend pipe with different diameters of DN50> DN80 and DN110.It shows that the local resistance coefficient of socket type bend pipe is much higher than that of circular arc bend pipe in the case of same pipe diameter in condition of the flow pattern entering the drag square area.The circular arc bend pipe is recommended to reduce energy loss in actual engineering.更多还原