中文摘要：

2个U型组合的90°4片弯管流场非常复杂，确定其水头损失和相互影响系数不容易，一般水力计算手册中对此也尚乏介绍．采用计算流体动力学理论和计算方法，在验证了数学模型和网格划分方法可行性和准确性的前提下，模拟了2个u型组合的90°4片弯管流场并计算了该管段的局部水头损失，分析了相互影响系数随Ls／D的变化规律．研究表明：增大转弯半径可以减小局部水头损失；减小2个90°4片弯管间的直管长度可以减小局部水头损失；相互影响系数随Ls／D增大而不断趋近1．0；若R／D≥1，则当Ls／D等于0时，该值取得最小，局部水头损失也最小．

英文摘要：

Flow field of U-shaped 90° ducts is extremely complicated, figuring out the head loss and interac- tive coefficient is a tough task and not enough data can be referred. This paper simulates the flow field ap- plying the method of computational fluid dynamics, calculates local head loss and analyzes the varying rule of interactive coefficient according to the value of Ls/D, where Ls is the length of straight duct; D is diam- eter of duct. The results indicate that both increasing the radius of duct and cutting the straight duct be- tween them can decrease local head loss effectively; and that interactive coefficient approaches 1.0 as Ls/D mounts; meanwhile, in circumstances that Ls/D equalizes zero with the premise that R/D≥ be satisfied, where R is the turning radius, the value of interactive coefficient reaches the minimum and as conse- quences, local head loss get the minimum value.