基于CFD的90°弯管水头损失计算的参数敏感性分析

Parameter Sensitivity Analysis of Water Head Loss Calculationof 90° Curved Pipe Based on CFD

计算流体动力学在水利行业中得到了广泛的应用。【目的】从众多不确定因素中找出对CFD建模有重要影响的敏感性因素,并分析其对计算结果的影响程度,优化90°弯管的CFD建模方案。【方法】采用单因素分析方法,分析了网格尺寸、湍流模型、水体密度、运动黏滞系数、当量粗糙高度等参数对计算结果的影响。【结果】RNG k-ε湍流模型计算结果与经验系数计算结果相对误差在±5%以内,能有效模拟弯管湍流流态;该湍流模型无需较小的网格尺寸,能够利用较小的计算资源得到精度较高的计算结果;当水体温度高于15℃时,三维流场计算软件能够对水体密度和运动黏滞系数进行修正,使计算结果精度更高;模拟水力光滑管道时,水体密度和运动黏滞系数对计算结果影响较小。【结论】工程算例模拟计算中,应当充分考虑模拟对象的体型和材料特点以及水体温度等因素,选取适当的参数值,能有效地降低计算成本,提高计算精度。

Computational Fluid Dynamics(CFD)has been widely used in the water conservancy industry.【Objective】In order to optimize CFD modeling scheme of 90°curved tube.The sensitive factors which have important influence on CFD modeling were found out from a number of uncertain factors,while their impacts on the simulation results were analyzed.【Method】The effects of grid size,turbulence model,water density,dynamic viscosity and roughness height on the results were analyzed by single factor analysis.【Result】The relative error between the CFD result and the empirical coefficient calculation result was within 5%,which showed that the turbulent flow state of the bending pipe could be effectively simulated by the RNG k-εturbulence model.The less computing resources were required in those cases which using this turbulence model.When the temperature of the water was higher than 15℃,the water density and dynamic viscosity could be corrected for precision.The water density and dynamic viscosity had less impact on the simulation results of hydraulic smooth pipe.【Conclusion】In the simulation calculation of project cases,a number of various factors,for example the shape of model,characteristics of pipeline materials,water temperature and so on,should be considered seriously.The accurate results can be obtained when the suitable parameters are set in the model.