Semi-regular polygon as the best hydraulic section in practice (generalized solutions)

Abstract

The best hydraulic section is usually used as a guide or starting point in open channel design. The semi-circle and semi-regular polygons such as semi-square, semi-hexagon and semi-octagon have the minimum wetted perimeter for a given area, and consequently are the best hydraulic sections from the hydraulic point of view.This study introduces two types (Type I and Type II) of semi-regular polygons as the best hydraulic sections. Both of the sections have the same wetted perimeter and area and thus are equally efficient. However, Type I semi-regular polygon with flat bottom is suitable when excavation depths are shallow, and Type II semi-regular polygon with angled bottom is used when deeper cuts are needed. In this research, general solutions of the normal depth are also presented for Type I and Type II semi-regular polygon sections.