Basic Canal Hydraulics

Abstract

Canals are designed for uniform flow considering economy and reliability. Uniform flow is described by a resistance equation. This chapter describes uniform flow equations for viscous flow, turbulent flow, and sediment-transporting channels. Open-channel sections are used for transferring viscous fluids in chemical plants. The Navier-Stokes equations are the governing equations for viscous flow. For steady viscous uniform flow, the Navier-Stokes equation is reduced to two-dimensional form of Poisson’s equation, and solution for a rectangular channel has been included in the chapter. For turbulent flow in channels, different uniform flow equations are described with pointing out that Manning’s equation is applicable only to the fully rough turbulent flow and in a limited bandwidth of relative roughness. For other flow conditions, a more general resistance equation based on the Colebrook equation is more appropriate. Direct analytic solution of the normal depth in natural/stable channel section is not possible, as the governing equation is implicit and it requires a tedious method of trial and error. Explicit expressions for normal depth associated with viscous flow in rectangular channel and turbulent flow in triangular, rectangular, trapezoidal, circular, and natural channel sections are presented in the chapter. Furthermore, Chap. 3 describes canal operations through normal sluice gate, side sluice gate, and side weir. Moreover, canal discharge measurements using sharp- and broad-crested weirs and linear weir are addressed in the chapter. Finally, the chapter includes explicit critical depth relations for power law and trapezoidal and circular canal sections.