螺旋管内局部二次流强度计算及演变规律

Intensity Calculation and Development Law of Local Secondary Flow in Helical Tubes

为了掌握螺旋管内二次流强度的变化规律,对螺旋管内局部二次流强度及演变规律进行了研究,提出了无量纲数H作为局部二次流强度指标。通过数值模拟得到H的体积平均值Hm,与描述整体二次流强度的迪恩数进行对比。结果显示,在不同的雷诺数、曲率、螺距下,H_(m)与迪恩数的相关系数约为1,且呈现较好的正比关系,说明H能够准确计量局部二次流强度。同时,探究了几何参数对螺旋管内的二次流演变规律的影响。依据二次流的强度,管内流动可分为发展段、过渡段和稳定段。二次流在发展段迅速增强;在过渡段出现最大值;在稳定段呈小幅度周期性波动。雷诺数增大会显著增大二次流强度,但是不影响二次流在3个阶段出现的位置。曲率的增大会略微增大二次流的强度,且延长了二次流达到稳定段的路程。螺距对二次流的强度和演变规律影响非常小。

In order to grasp the variation law of secondary flow in helical tube,the local intensity and development law of secondary flow in helical tube were studied,and the dimensionless helical intensity H was proposed as the local secondary flow intensity index.By means of numerical simulation,the average volume of H H_(m) was taken and compared with the Dean number describing the overall secondary flow intensity.The results showed that with different Reynolds number,curvature and pitch,the correlation coefficient between H_(m) and Dean number was about 1,and there was a good proportional relationship,indicating that H could accurately measure the intensity of local secondary flow.At the same time,the influence of geometric parameters on the development law of secondary flow in the helical tube was explored.According to the intensity of secondary flow,the flow in the helical tube could be divided into development stage,transition stage and stable stage.The secondary flow increased rapidly in the development stage,reached its maximum value in the transition stage,and fluctuated periodically in the stable stage.The increase of Reynolds number could significantly increase the intensity of secondary flow,but could not affect the location of secondary flow three stages.The increase of curvature could slightly increase the intensity of the secondary flow and extend the distance of the secondary flow to the stable stage.The pitch had little influence on the intensity and development of secondary flow.