fluid and its properties
TRANSCRIPT
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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