2 Basic properties of channel flow

Abstract

The equations of flow in an open channel relate the geometric parameters of the cross section, such as wetted perimeter and hydraulic depth, with the flow parameters, such as velocity and momentum, through laws of physics and experimental evidence. After a brief introduction of the types of flow encountered in practice, this chapter contains the derivation of geometric parameters of elementary shapes commonly used in drainage channels. This has been found necessary, so that they could be referred to when advancing the discussion through later chapters. Also included in the chapter is the derivation of forces and energies that constitute the flow mechanism. A section on the Froude and Reynolds numbers is also included. Since the flow may, or may not, occupy the whole cross section of the channel, in this text the term ‘cross section’ means the cross section of the flow, and not necessarily that of the channel. 2.1 Types of flow in open channels 2.2 Hydraulic properties, channel gradient 2.3 Geometric parameters 2.4 Geometric parameters, elementary shapes 2.5 Best hydraulic section, the conveyance 2.6 Mean velocity of flow and rate of discharge 2.7 Mechanism of flow 2.8 The law of momentum, the inertial force 2.9 Other forces 2.10 Momentum equation, specific force 2.11 Specific energy 2.12 Froude and Reynolds numbers References