Hydraulics of Open Channel Flow

Hubert Chanson

• Publisher: Butterworth-Heinemann
• Year: 2004
• ISBN:
  9780080472973
• Edition: 2
• Topic: Technology & Engineering
• Subtopic: Engineering General
• Index: Technology & Engineering

Since the publication of its first edition in 1999, 'The Hydraulics of Open Channel Flow' has been praised by professionals, academics, students and researchers alike as the most practical modern textbook on open channel flow available. This new edition includes substantial new material on hydraulic modelling, in particular addressing unsteady open channel flows. There are also many new exercises and projects, including a major new revision assignment.

This innovative textbook contains numerous examples and practical applications, and is fully illustrated with photographs. Dr Chanson introduces the basic principles of open channel flow and takes readers through the key topics of sediment transport, hydraulic modelling and the design of hydraulic structures.

• Comprehensive coverage of the basic principles of key application areas of the hydraulics of open channel flow
• New exercises and examples added to aid understanding
• Ideal for use by students and lecturers in civil and environmental engineering

Part 1

Basic Principles of Open Channel Flows

1

Introduction

Summary

The introduction chapter reviews briefly the basic fluid properties and some important results for fluids at rest. Then the concept of open channel flow is defined and some applications are described.

1.1 PRESENTATION

The term ‘hydraulics’ is related to the application of the Fluid Mechanics principles to water engineering structures, civil and environmental engineering facilities, especially hydraulic structures (e.g. canal, river, dam, reservoir and water treatment plant).

In the book, we consider open channels in which liquid (i.e. water) flows with a free surface. Examples of open channels are natural streams and rivers. Man-made channels include irrigation and navigation canals, drainage ditches, sewer and culvert pipes running partially full, and spillways.

The primary factor in open channel flow analysis is the location of the free surface, which is unknown beforehand (i.e. a priori). The free surface rises and falls in response to perturbations to the flow (e.g. changes in channel slope or width). The main parameters of a hydraulic study are the geometry of the channel (e.g. width, slope and roughness), the properties of the flowing fluid (e.g. density and viscosity) and the flow parameters (e.g. velocity and flow depth).

1.2 FLUID PROPERTIES

The density ρ of a fluid is defined as its mass per unit volume. All real fluids resist any force tending to cause one layer to move over another, but this resistance is offered only while the movement is taking place. The resistance to the movement of one layer of fluid over an adjoining one is referred to as the viscosity of the fluid. Newton’s law of viscosity postulates that, for the straight parallel motion of a given fluid, the tangential stress between two adjacent layers is proportional to the velocity gradient in a direction perpendicular to the layers:

(1.1)

where τ is the shear stress between adjacent fluid layers, μ is the dynamic viscosity of the fluid, V is the velocity and y is the direction perpendicular to the fluid motion. Fluids that obey Newton’s law of viscosity are called Newtonian fluids.

At the interface between a liquid and a gas, a liquid and a solid, or two immiscible liquids, a tensile force is exerted at the surface of the liquid and tends to reduce the area of this surface to the greatest possible extent. The surface tension is the stretc...