By the theory of ray optics, the bend losses of fiber as function of fiber parameters such as core index, cladding index, core radius and bend radius are set up.

Tube bending is a process by which a straight piece of tube is formed to a selected radius and angle of bend.

Secondly, different changes in river programs, it's outside of river bend shows erosion status in different flood frequencies. And the localscour depth is different with different bend radius.