基于CFD的弯管数值计算及水力特性分析

Numerical calculation and hydraulic characteristics analysis of elbow based on CFD

为探究弯管局部水头损失影响因素,揭示弯管内部流场、二次流分布情况,用六面体结构化网格对弯管进行O型剖分,采用RNG k-ε模型对不同雷诺数、不同相对弯曲半径、不同弯曲角度、不同管径的三维弯管进行数值模拟研究,计算结果与其他学者的实验结果相吻合。结果表明,局部阻力损失系数ζ随着雷诺数的增大而减小,当雷诺数较小时,随着雷诺数增大,局部阻力损失系数降幅较大,当雷诺数较大时,随着雷诺数的增大,开始进入阻力平方区,局部阻力损失系数趋于稳定;局部阻力系数ζ随着相对弯曲半径跟直径的增大呈多项式减小,随着弯曲角度呈线性增加;当相对弯曲半径增加到一定范围时,在弯曲角度大于π/4的情况下,角度的变化对二次流的影响不再明显;对模拟数据结果采用SPSS进行多元非线性回归分析,给出弯管局部阻力系数准则关系式;在管道设计或工程应用中,条件允许的情况下,尽量采用相对弯曲半径、直径较大,弯曲角度较小的管道,以降低能量损耗,同时,在弯头凹侧进行相关保护措施,防止压力过大造成管壁破坏,以期提高弯管的使用寿命。

In order to explore the influencing factors of the local head loss of the elbow,reveal the internal flow field and the distribution of the secondary flow in the elbow,the elbow is divided into O-shaped with a hexahedral structured grid,and the RNG k-εmodel is used for different Reynolds numbers and different relative values.Numerical simulation study of three-dimensional bends with different bending radii,different bending angles,and different pipe diameters is carried out,and the calculation results are consistent with the experimental results of other scholars.The results show that the local drag loss coefficientζdecreases with the increase of the Reynolds number.When the Reynolds number is small,the local drag loss coefficient decreases with the increase of the Reynolds number.As the number increases,it begins to enter the resistance square area,and the local resistance loss coefficient tends to stabilize;the local resistance coefficientζdecreases polynomially with the increase of the relative bending radius and diameter,and linearly increases with the bending angle;when the relative bending radius When increasing to a certain range,when the bending angle is greater thanπ/4,the change of the angle will no longer have an obvious effect on the secondary flow;SPSS is used to perform multiple nonlinear regression analysis on the simulation data results,and the local resistance of the elbow is given.Relational formula of coefficient criterion:In pipeline design or engineering application,when conditions permit,try to use pipelines with a relatively large bending radius,larger diameter,and smaller bending angle to reduce energy loss,and at the same time,perform correlation on the concave side of the elbow Protective measures to prevent damage to the pipe wall caused by excessive pressure,in order to increase the service life of the elbow.