Fluid and Its Properties

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MEC251

UNIFIED MECHANICAL ENGINEERING-II


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THE COURSE

FLUID MECHANICS

THERMODYNAMICS

HEAT TRANSFER


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CHAPTER-1

FLUIDS AND FLUID PROPERTIES


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FLUID MECHANICS

Fluid Mechanics is that branch of

engineering science which deals

with the behavior of fluids underconditions of rest and motion.


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DIVISION OF FLUID MECHANICS

STATICSi. HYDROSTATICS

ii. AEROSTATICS

KINEMATICS

DYNAMICS


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CLASSIFICATION OF MATTER

SOLID STATE

FLUID STATE

i. LIQUID STATE

ii. GASEOUS STATE


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FLUID?

A Fluid is a substance which is capable offlowing.

OR

A Fluid is a substance which deformscontinuously when subjected to externalshearing force.


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Fluids

V

The upper plate keeps on moving, and the fluidkeeps on deforming. No equilibrium state butan equilibrium velocity Vof the plate.

The equilibrium velocity Vincreases as theshear force Fincreases.This means that mere deformation of fluid doesnot build up resisting forces.Since there is an equilibrium velocity (more thevelocity larger the force), a resisting force isdeveloping for sure.

The resisting force is, thus, dependent not ondeformation, but on deformation rates.

F


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A fluid at rest cannot sustain anyshear force.

Fluids


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CHRACTERISTICS OF FLUIDS

Has no definite shape ofits own

Continuously deforms

under applied externalshear force as long asforce continues to beapplied


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TYPES OF FLUIDS

LIQUID

GAS

VAPOUR


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The atoms in a liquid are closely packed while thosein a gas are separated by much larger distances.


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TYPES OF FLUIDS

IDEAL FLUIDS

Examples: Water, Air .

REAL FLUIDS

Examples: Lubricating Oils, Kerosene, Slurries

.


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FLUID PROPERTIES

DENSITYi. Mass Densityii. Weight Densityiii. Specific Volume

SPECIFIC GRAVITY PRESSURE VAPOUR PRESSURE

VISCOSITY SURFACE TENSION COMPRESSIBILITY


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PRESSURE

The force exerted by a fluid per unit area ofvessel containing it is called Pressure.

P = F/A

The pressure of a fluid on a surface alwaysact normal to the surface.

In SI units , Pressure is expressed in N/m^2

or PASCAL(pa).


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A womans high heels sink into the soft ground,but the larger shoes of the much bigger man do not.

Pressure =

force/area


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PRESSURE IN A FLUID


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PASCALS LAW:

Pascals law states that the intensity of

pressure at any point in a liquid at rest , issame in all the directions.


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The pressure exerted on the piston extends uniformlythroughout the fluid, causing it to push outward with equalforce per unit area on the walls and bottom of the cylinder.


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A small force F1 applied to a piston with a smallarea produces a much larger force F2 on the larger

piston. This allows a hydraulic jack to lift heavy objects.


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GAUGE AND VACUUM PRESSURES

Absolute zero pressure

Actual Pressure at a point

Absolutepressure

Atmosphericpressure

GaugePressure

Actual Pressureat another point

Absolutepressure

-ve gauge, orVacuum pressure

Fluid and Its Properties

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