三角形螺旋流道充分发展层流流体的流动性能

基于角钢螺旋夹套，展开了对三角形螺旋流道层流流动性能的实验和数值研究。经对比，同一模型下的实验结果和模拟结果吻合良好。采用数值方法得到了充分发展状态下流体的主流速度、二次流速度、流函数及涡量的分布特点，分析了三角形边界上局部阻力系数的分布规律，并与半圆管螺旋流道进行了比较。结果表明：在所研究的Dean数及量纲1曲率（k）内，流道横截面上的二次流为稳定的两涡结构，内、外壁面局部阻力系数的分布明显不同，外壁面局部阻力系数的平均值约为内壁面阻力系数平均值的1.54～2.72倍；随着Dean数及k 的增大，二次流动增强，内、外壁面阻力系数均增大；对于量纲1挠率及Dean数均较小的三角形螺旋流道，挠率对流体流动的影响很小；通过对比，两种流道具有相同内壁面面积、曲率半径、螺距及Reynolds数时，三角形螺旋流道的流动阻力小于半圆管螺旋流道。

Characteristics of fully developed laminar flow in triangular helical duct

Based on jackets with triangular flow channels, laminar flow characteristics in triangular helical duct were investigated experimentally and numerically. The simulation results were in good agreement with experimental values. Then the main flow velocity, secondary flow, stream function and vorticity were obtained with numerical method. The distribution of local frictional factor on the boundary of the triangular helical duct was analyzed and compared with that of half-coil helical duct. The results show that the structure of secondary flow is steady two vortices in the range of Dean number and dimensionless curvature ratio. The distribution of local frictional factor along the outer walls differs obviously from that along the inner wall. The mean value of the local frictional factors at the outer walls is 1.54—2.72 times that at the inner wall. With the increase of Dean number and dimensionless curvature ratio, the secondary flow is enhanced and the frictional factors on the outer walls and inner wall increase. For triangular helical ducts with small dimensionless torsion and Dean number, the torsion has little effect on the flow resistance. Compared with the semicircle helical duct with the same area of inner wall, curvature radius, pitch and Reynolds number, the flow resistance in the triangular helical duct is smaller.