COMPUTATION OF CHEZY’S RESISTANCE COEFFICIENT IN A PARABOLIC SHAPED-CHANNEL FOR TURBULENT FLOW

Mohammed Lakhdar Nebbar

Abstract:

The Chézy formula describes the average flow velocity in open channel turbulent flow and is widely used in fields related to fluid mechanics and fluid dynamics. Open channels refer to any open conduit, such as rivers, ditches, canals, or partially full pipes. In this context, the calculation of Chezy’s resistance coefficient is typically not provided a priori in a design problem, and its value is often selected subjectively from the literature for most open channels and conduits under uniform flow conditions. However, in most practical cases, if these coefficients are not expressed by implicit models, they are generally taken as constant and arbitrary. To this end, and in a rational manner, the dimensioning and design of channels require the expression of the resistance coefficient in an easily and explicitly defined form by adopting numerous flow parameters, namely the roughness of the walls, the aspect ratio, the slope of the channels, and essentially the viscosity of the liquid. To achieve this aim, Chezy’s resistance coefficient is identified using the rough model method (RMM), which provides the discharge under uniform flow conditions appropriate to a parabolic-shaped channel.Some examples are presented showing how to calculate Chezy's resistance coefficient with a minimum practical data.

Keywords: Aspect Ratio; Chezy’s Resistance Coefficient; Kinematic Viscosity; Modified Reynolds Number; Parabolic-Shaped Channel; Roughness; Rough Model Method (RMM); Turbulent Flow