Logarithmic Friction Factor Equations of Open Channel Flow

Many researchers proposed the equations of friction factor or mean velocity for open channel flow. The existing equations were developed with the coefficient of equivalent roughness height or based on the assumption of rough turbulent flow. In open channel flow, however, from Varwick's laboratory data there are found several characteristic flows such as laminar flow, smooth turbulent flow, transitional turbulent flow and rough turbulent flow. In order to imply all the characteristics of such flow, the present workers developed the logarithmic equation of friction factor for smooth turbulent flow and rough turbulent flow in open channels and further developed explicit equations for smooth turbulent flow by adjusting several parameters.