单根缠绕管绕流的二维数值模拟

2D Numerical Simulation of Fluid Flow around the Single Spiral Tube

在横向流的作用下, LNG 绕管式换热器的缠绕管会因漩涡脱落而振动, 从而影响换热器的安全运行.为此, 通过数值模拟方法对该换热器中单根缠绕管进行绕流分析, 借鉴圆柱体绕流方法研究LNG 缠绕管在雷诺数、管径和螺旋角的不同参数组合下, 压力系数、脉动升力系数、漩涡脱落频率和斯特劳哈尔数的变化规律.研究结果表明, 在θ = 75°左右表面压力系数最小, 在θ =120°～130°时发生边界层分离; 随着螺旋角和雷诺数的增大, 边界层分离点位置向后移动; 随着管径增大, 边界层分离点位置向前移动; 漩涡脱落频率随雷诺数的增大而升高, 随管径的增大而降低, 螺旋角对漩涡脱落频率的影响不大; 随着雷诺数的增大, 斯特劳哈尔数先增大后减小,且最大斯特劳哈尔数为0. 185.

The lateral flow would lead to vibration of the winding pipe of the LNG spiral pipe heat exchanger due to vortex shedding, thus impacting the safety of the heat exchanger operation?The flow around a single spiral pipe in the heat exchanger has been analyzed through numerical simulation?Taking the method of flow around a cir?cular cylinder as reference, variation rule of the pressure coefficient, fluctuating lift coefficient, vortex shedding frequency and the Strouhal number have been studied with the LNG spiral pipe under different parameter combina?tions of Reynolds number, pipe diameter and helix angle?The results show that the surface pressure coefficient rea?ches the minimum when θ= 75°.The boundary layer separation occurs whenθ= 120° ~ 130°.The boundary layer separation point moves backward with the increase of the helix angle and Reynolds number, but moves forward with the increase of pipe diameter.The vortex shedding frequency increases with the increase of Reynolds number, but decreases with increased pipe diameter, and has been little influenced by the helix angle?With the increase of the Reynolds number, the Strouhal number increases first and then decreases with peak value of 0.185.