管道汇流口局部阻力试验研究

通过试验研究并结合水动力学原理，在分析汇流口独特水力特性及能量损失机理的基础上，提出了适用于任意角度汇流管路分析计算的局部能量损失系数的普遍表达式。分析了交汇角、流量比(支管流量／合流量)及面积比(支管面积／主管面积)等因素的影响规律，并对各影响因素进行了分析比较。研究结果表明，管道汇流口水流的局部能量损失，必须考虑汇入断面上支流沿下游主流方向的动量分量和主支流间相互掺混引起的附加摩擦阻力的影响。局部能量损失系数随交汇角、流量比增加而增加。当流量比较小时支流的局部水头损失系数出现负值，而当流量比较大时主流的局部水头损失系数出现负值。分离区内外压强差随交汇角增大而增大，随流量比的增大先增大后减小。

Experimental study on local flow resistance at junctions of circular pipes

The flow characteristics and mechanism of energy loss at junction of circular pipes were investigated experimentally. A universal expression for calculating the energy loss coefficient for junctions with arbitrary confluence angle was suggested. The effect of confluence angle, discharge ratio (ratio of branch pipe disc harge to total discharge in main pipe) and area ratio (ratio of branch pipe area to main pipe area) were analyzed. It is found that the momentum contribution of the branch flow in downstream direction and the additional friction induced by the mixing of the flow at the junction are important factors affecting the flow characteristics and energy loss. The coefficient of local energy loss increases as the confluence angle and discharge ratio increases. The local energy loss coefficient of branch pipe may be negative if the discharge ratio is small. Whereas, the local energy loss coefficient of main pipe will be negative if the discharge is great. The difference of pressure inside and outside of the separation zone increases as the confluence angle increases. This pressure difference tends to increase following the increase of discharge ratio at first and decreases after a peak value occurred.