Fluid Mechanics, Hydraulics, Hydrology and Water Resources for Civil Engineers

Amithirigala Widhanelage Jayawardena

• Éditeur: CRC Press
• Année: 2021
• ISBN:
  9780429751004
• Édition: 1
• Sujet: Technologie et ingénierie
• Sous-sujet: Génie mécanique

One of the core areas of study in civil engineering concerns water that encompasses fluid mechanics, hydraulics and hydrology. Fluid mechanics provide the mathematical and scientific basis for hydraulics and hydrology that also have added empirical and practical contents. The knowledge contained in these three subjects is necessary for the optimal and equitable management of this precious resource that is not always available when and where it is needed, sometimes with conflicting demands.

The objective of Fluid Mechanics, Hydraulics, Hydrology and Water Resources for Civil Engineers is to assimilate these core study areas into a single source of knowledge. The contents highlight the theory and applications supplemented with worked examples and also include comprehensive references for follow-up studies.

The primary readership is civil engineering students who would normally go through these core subject areas sequentially spread over the duration of their studies. It is also a reference for practicing civil engineers in the water sector to refresh and update their skills.

Chapter 1

Introduction

Water is a precious resource essential for all forms of life. It is abundant in nature but has significant temporal and spatial variability. As a result, water is not always available when and where it is needed. Oceans hold approximately 97.5% of planet earth’s water, leaving with only about 2.5% in land areas. Of this 2.5%, approximately 1.925% is locked in ice caps and glaciers and not easily accessible for human needs. Some countries are water-rich, whereas some others are water-poor. With the unabated increase in population, the per capita share of water availability is decreasing with time, resulting in water stresses, water shortages and water scarcity in some countries and regions and during certain times of the year. Lack of safe drinking water is a major problem for over a billion inhabitants of the earth. Too much water also brings about misery, agony and destruction to many people, places and infrastructure. The former may be attributed to the physical lack of water, pollution or unaffordability, and the latter is attributed mainly to urbanization and livelihood issues. A major challenge facing humankind and the environment is how to share this precious freshwater resource in an equitable and optimal manner. This requires contributions from many disciplines, and civil engineering is one of them.

Civil engineering is a broad discipline encompassing key areas such as structural engineering, geotechnical engineering, water resources engineering, transportation engineering, environmental engineering, etc. These are also core subject areas taught in any civil engineering curriculum in any university. The three components of water resources engineering are fluid mechanics, hydraulics and hydrology. The objective of this book is to combine all these three core areas into a single source of reference targeted towards civil engineering students and practicing civil engineers.

The contents of this book are organized into the four sub-themes: fluid mechanics, hydraulics, hydrology and water resources. This chapter begins with a brief introduction to fluid mechanics.

1.1 Fluid mechanics

1.1.1 Definition of a fluid

Most materials are designated as solids, liquids or gases. Some materials have a dual designation, e.g. jellies, paints and polymer solutions (solid and fluid). All materials are deformable. Deformations of solids are small even for large external shear forces and do not continue to deform, whereas in the case of fluids, they are large even for small external shear forces and have no fixed shape.

Also, in solids the strong molecular forces between molecules tend to restore the deformed body to its original state (shape) when the external force is removed. There are limits to this, i.e. within the elastic limit (Figure 1.1).

Figure 1.1 (a) Deformation of a solid and a fluid; (b) deformation of a fluid and velocity profile.

A fluid continuously deforms when subjected to a shear stress. It cannot sustain a shear stress when at rest, implying that shear stresses exist only when the fluid is in motion.

In a real fluid (or viscous fluid), the shear stresses exist when the fluid is in motion. On the other hand, an ideal fluid (or inviscid fluid) has no shear stress when in motion.

Gases and liquids are both fluids. The most significant properties that distinguish gases from liquids are the bulk modulus ...