This document provides an overview of chapter 1 in the subject "Introduction to Water Engineering A". The chapter covers the key properties of fluids including: - Defining fluids and their ability to flow and conform to containers. - Dividing fluids into liquids and gases and their compressibility. - Units used to measure mass, length, time, force, acceleration, and pressure. - Density, which can be expressed through mass density, specific weight, and specific gravity. - Viscosity, including dynamic and kinematic viscosity, and how it relates to resistance of motion for fluids. - Compressibility and the bulk modulus relationship between changes in pressure and volume.

1. FACULTY: Engineering and the Built Environment
DEPARTMENT: Civil Engineering
QUALIFICATION: Diploma in Engineering Technology, Civil Engineering
QUALIFICATION CODE: DICVE1
SUBJECT: Introduction to Water Engineering A
SUBJECT CODE: IWEA201
SAQA CREDITS: 12 Credits
Chapter 1: Properties of fluids

2. Objectives
• To be able to define a Fluid;
• To know the SI Units and fundamental
dimensions and derive others needed;
• To understand the various properties of a
fluid;
• Self evaluation exercises.

3. Properties of fluids
• A fluid can be defined as a substance
capable of flowing under it’s own weight
and which will conform to the shape of a
containing vessel;
• A fluid at rest or in equilibrium cannot
resist shear forces causing it to change
shape;
• Shear forces acting in a fluid cause it to
flow thus change shape;
• Fluids are divided into liquids and gases;

4. Properties of fluids
• (1) Liquids are normally said not to be
compressible whereas gasses can be;
• (2) fluids occupy a given volume and have a
free surface whereas a gas will expand to
fill a given container.

5. Units of measure
• Mass (kg);
• Length (l) m;
• Time (t) s;
• Force (F) N;
• Acceleration (a) m/s2;
• Pressure (P) N/m2.

6. Density
• The density of fluids can be represented in
three forms, namely:
1) Mass density (p – Rho) and is defined as the
mass per unit volume, and is expressed in
kg/m3.
p = M/ Vol. = kg/m3.
2) Specific Weight (w) and is defined as the
weight per unit volume, and is expressed in
N/m3.

7. Density
Weight = mass * gravitational acceleration
Hence w = pg
3) Specific Gravity (s) or relative density, is
defined as the ratio of the weight of any
given substance to an equal volume of water
at 4˚C.
s = mass substance / mass of equal vol. water
Or
Density of substance / density of water.

8. Viscosity
• Viscosity can be defined as that property of
a fluid that causes it to resist motion;
• When a fluid is at rest it cannot resist
shearing forces, but when in motion it
experiences shearing forces due to the
various layers within the fluid having
different velocities;
• Dynamic Viscosity (n – mu) is defined as the
shear force required to move one layer of
fluid past another and is expressed in kg/m-s
or otherwise known as the “poise” (1poise =
1g/cm-s)

9. Viscosity
• Kinematic Viscosity (v-nu) is the ratio of
absolute viscosity to mass density
V = absolute viscosity/ mass density
Or n/p
Note – if n is in kg/m-s then p must be in kg/m3.
• Viscosity of liquids decreases with an
increase in temperature but is not affected
by pressure.

10. Compressibility
• Is the relationship between the change of
pressure and change of volume, and is
known as the bulk modulus (K).
• K = change in pressure intensity/ volumetric
strain
• or = change in pressure intensity/ (change in
volume/ original volume)

11. End of Chapter 1