FLUID MECHANICS-1

LECTURE NO. 1 BY ENGR. NOORIMA MASUD

CHAPTER NO. 1                                          INTRODUCTION

FLUID:

It is defined as; A substance that continuously deform when acted upon by shearing stress of any magnitude. Fluid are a subset of the phases of matter and include liquids, gases, plasma's and , to some extent, plastic solids. 

Or

Any substance which can flow under the normal condition of temperature and pressure is called fluid.

for example;

• water flow in pipes, rivers, streams etc.

FLUID MECHANICS: 

Is concerned with behavior of fluids ( liquids and Gases) at rest or in motion.

Or

The mechanics of fluids (including water)

For example;

• water in a container etc.

HYDRAULICS:

The word 'Hydraulics' has been derived from Greek word ' Hudour', which means water. Thus the subject of Hydraulics may be defined as that branch of Engineering- sciences, which deals with water ( at rest or in motion ).

BRANCHES:

1. Fluid Statics
2. Fluid Kinematics
3. Fluid Dynamics

1. FLUID STATICS:

It is the branch of fluid mechanics which deals the fluids at rest or moving with uniform velocity is known as fluid statics. it embraces the study of the conditions under which fluids are at rest in Stable equilibrium.

Shearing stresses are Zero at this case.

For example; 

• Water in a glass, Container etc.

2. FLUID KINEMATICS:

It is the branch of fluid mechanics which deals the fluids with motion , by without considering any type of external forces is known as fluid kinematics.

For example;

• Water falls ( under the action of gravity ).

 

3. FLUID DYNAMICS:

It is the branch of fluid mechanics which deals the fluids with motions, by considering the external forces are involved is known as fluid dynamics.

For example;

• Pump the water from down, 
• Water in a pipe,
• CNG in cylinder etc.

PROPERTIES OF FLUIDS:

Ordinary, there is no difficulty in distinguishing a liquid from a gas or a solid;

a solid has a definite shape, which it retains, until some external force is applied to alter it. On the contrary , a liquid takes the shape of a vessel, into which it is poured. On the other hand, a gas completely fills up the vessel which contains it.

Among the liquids water will be mostly dealt , which has the following properties:

1. Density
2. Specific Weight
3. Specific gravity
4. Compressibility
5. Surface tension
6. Capillarity
7. Viscosity.

1. DENSITY OR MASS DENSITY:

Density or mass density of a fluid is defined as; 

The ratio of mass of fluid to its volume. Thus mass per unit volume is called density or mass density. 

It is denoted by a symbol ρ (rho).

The SI unit of mass density is Kg/m³.

Mathematically 

• The density of water is 1 g/cm³ or 1,000 Kg/m³ or 1.94 Slug/ft^3.
• ^{The Density of Mercury is 13600}  Kg/m^3.

Note: The variation in the density of water , with the variation of pressure and temperature is so small, that for all practical purposes it is generally neglected.

2. SPECIFIC WEIGHT OR WEIGHT DENSITY:

Specific weight or weight density is the ratio between the weight of a fluid to its volume. Thus the weight per unit volume is called specific weight. The SI unit is Kpa or  KN/m^{3 .}

It is denoted by (Gamma)  ᵞ .

Mathematically;

Note: The variation of specific weight of water , with the variation of pressure and temperature is also so small, that for all practical purposes it is generally neglected.

For all calculation related to Fluid mechanics , Hydraulic Machines etc. the specific weight of water is 9.81 KN/m³ or 62.46 lb/ft^3.The Specific weight of mercury is 132.8 KN/m³ 

3. SPECIFIC GRAVITY:

Specific gravity is defined as ;

The ratio of  specific weight of a fluid to the specific weight of standard fluid. For liquid the standard Fluid is taken Water, and for gases the standard fluid is taken air. Specific gravity is also called relative density. It is dimensionless quantity and is briefly written as sp. gr.

Mathematically;

for liquid 

Note: If density of a liquid is in ton per m³ (t/m³), it is numerically equal to specific gravity of the liquid.

You can place your request for any kind of E-book, Lecture notes, Lab- Manuals, Presentations etc. Through below Comments Box System.

Posted in: Fluid Mechanics-1 theory