Roughness Effects on Flow and Shear Stress Near Outside Bank of Curved Channel

Velocity and turbulence distributions are measured in a 270° curved open channel of half trapezoidal section with extra roughness applied to the outside bank slope. The purpose of this investigation is to provide some understanding of flow mechanics that may be useful in the design of riprap protection. Profileaveraged velocity and bed shear velocity distributions are calculated. A significant variation of bed shear up the slope and a much higher stress near the toe of the slope are found for the roughened outside bank slope. It is found that a reasonable correlation of the velocity and bed shear stress on the bank is given by a form of the Colebrook equation. Lateral momentum transfer by secondary flow and turbulent stress are also evaluated and found to be significant in the bank vicinity.