There are two secondary vortices in the helical pipe with circular cross-section when the flow is turbulent. The vortex on the upper half rotates clockwise and is restricted on a very limited region.
静止圆截面螺旋管道内湍流的管道截面上，存在两个旋转方向相反的二次涡，上方顺时针旋转的二次涡被压缩在一个很小的范围之内，比层流状态下的要小很多。
参考来源 - 旋转曲线管道内湍流流动结构和传热特性研究·2,447,543篇论文数据，部分数据来源于NoteExpress
This expression becomes an exact one for a circular cross-section.
对于圆形的横截面这表达式即变为精确表达式。
The MHD equilibrium solutions of a toroidal plasma with non-circular cross-section and linear current distribution are written in terms of a fast convergent series.
用一个收敛很快的级数构造了非圆截面、线性电流分布环形等离子体的磁流体平衡解。
Based on shearing stress Theorem, we know that the shearing stress direction of all the spots on the edge of circular cross-section should be tangent to the circle.
由切应力互等定理可知，在截面边缘上各点处切应力方向必与圆周相切。
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