CHAPTER ONE

GENERAL INTRODUCTION

1.1      Introduction

As humans our entire living from the very beginning through to the end is surrounded and

facilitated by fluids; the very beginning being in the amniotic fluid (a mixture of liquids

and gases). Coupled with this is the fact that these fluids are responsive to variations in

temperature (heating and cooling) which in turn affects the normal functioning of our

intelligently designed body systems causing it to seek redress in various reactive ways to

maintain normalcy. In the same manner, the unintelligent inventions of science and

engineering such as machine parts, electricaland electronic components, nuclear reactors,

etc, that either generate heat or are subjected to heating must be harnessed to seek redress

if they must last long and serve their purpose efficiently without going berserk. This can

be effectively achieved if we understand the behaviour of fluids and fluid properties to

these variations. For this, natural convection has continued to be and is still of extreme

applicability as a means of cooling these systems. Again, fluids influence our movement

by all kinds of means whether on land, water or in the air as well as the movement of

mass and heat around (circulation), into (injection) and out (suction) of living things and

inventions. This has made the study of fluid dynamics a worthwhile endeavor that cannot

be over-emphasized.

The study of natural convection under different physical phenomena has received the

attention of many authors. Gebhart (1962) showed that the heating of fluids by viscous

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dissipation cannot be neglected for fluids with high Prandtl number when steady free

convective flow is considered because it can greatly affect the flow characteristics. When

fluids are sheared, viscous dissipation is induced by the friction between the different

layers of particles of the fluid as they move against each other, generating heat in the