Thank you, David!
Here is a post I asked about mesh tube.
https://discourse.mcneel.com/t/how-can-i-get-the-contour-of-a-mesh-pipe-following-its-curvature-to-create-the-center-line/84934?u=w.wu
I think if the tube mesh can be found U and V, the process will be so easy.
Would you please have a look?