# Introduction - Fluid Mechanics is basically  a study of the :

1. Physical behaviour of fluids and fluid systems, and of the laws governing this behaviour.

2. action of forces on fluids and of the resulting flow pattern.

Fluid mechanics may be divided into three divisions :

1. Hydro-statics that studies the mechanics of fluid at absolute and relative rest: the fluid elements are free from shearing stresses/

2. Kinematics that deals with translation, rotation and deformation of fluid elements without considering the force and energy causing such a motion.

3. Dynamics that prescribes the relations between velocities and acceleration and the forces which are exerted by or upon the moving fluids.

Analysis of fluid problems is generally made by considering certain fundamental principles, concepts and laws such as the principles of conservation of mass, momentum and energy, the first and second laws of thermodynamics, equation state relating to fluid properties; Newton's law of viscosity and the restrictions caused by the presence of boundaries.

SOLID, Liquids and Gases

Matter exists in two principle forms; solid and fluid. Fluid is further sub-divided into liquid and gas. Distinguishing features amongst these are :

1. Spacing and the latitude of the motion of molecules is large is in a gas small in a liquid and extremely small in solid. Accordingly the intermolecular bones are very weak in a gas. week in a liquid and very strong in a solid. It is due to these aspect that solid is very compact and rigid in form accomodates itself to the shape of its container, and gas fills up the whole of the vessel containing it.

2. For a given mass, the liquid have a definite volume irrespective of the size of the container. The variation of volume with temperature and pressure is insignificant. liquid occupies the vessel fully or partially depending on its mass, and that it forms a free surface with the atmosphere. The gas, however expands to fill any vessel in which it is contained and does not from any free surface. Accordingly, it may be stated ; "A solid has volume but no shape ; a gas has neither".

3. For all practical purposes, the liquid like solids can be regarded as incompressible. This means that pressure and temperature changes have practically no effect on their volume. The gases are, however, readily compressible fluids. They expend infinitely in the absence of pressure and contract easily under pressure. Never the less when density variation is small.

### SIGNIFICANCE OF FLUID MECHANICS ;

1. Design of wide range of hydraulic structures (dams, canals, weirs etc.) and machinery (Pumps, turbines and fluid couplings).

2. Design of a complex network of pumping and pipelines for transporting liquids, flow of water through pipes and its distribution to domestic service lines.

3. Fluidic control devices, both pneumatic and hydraulic.

4. Design and analysis of gas turbines, rocket engines, conventional and supersonic aircrafts.

5. Power generation from conventional methods such as hydroelectric, steam and gas turbines, to a newer ones involving magneto fluid dynamics.

6. Methods and devices or the measurement of various parameters the pressure and velocity of a fluid at rest or in motion.

7. Study of man's environment in the subjects like metrology, oceanography and geology.

8. Human circulatory system flow of blood in veins and the pumping action of heart.