根据涡管定义，穿过涡管管壁的涡量为零。
The flux through the wall of the vortex tube is zero by its definition.
以截面法向涡量为基础，可求解得到与涡量对应的二次流速度场。
Secondary flow velocity can be obtained with respect to cross suction normal vorticity.
以截面法向涡量为基础，可求解得到与涡量对应的二次流速度场。
Secondary flow velocity can be obtained with respect to cross suction normal vorticity.
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