13-06-2014, 11:53 AM
Fluid mechanics
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Study of fluids is applicable in various branches of science and engineering as following
Biomechanics
Blood flow through arteries
Flow of cerebral fluid
Meteorology and Ocean Engineering
Movements of air currents and water currents
Chemical Engineering
Design of chemical processing equipment
Phases of Fluid Mechanics
Study of fluids was started in old era and in the journey many people have contribute in development of theories. These are some of them which are frequently remembered for their contributions
Density
Any substance present in nature, is having mass and it will occupy the space, i.e. has volume.
The mass is distributed in space, so we need a physical quantity which will provide the idea of that distribution of mass.
Density is the mass of the substance per unit volume.
How to measure the density of substance
Solid substance: heavier than water
here the liquid of known density in cylinder up to the tout and then solid substance of known mass will be immerged in that liquid.
As it will occupy the space in liquid, some amount of liquid will be displaced, that can be collected in measuring cylinder.
By doing so we will be able to measure volume of the solid substance because it is same as the volume of displaced liquid.
pressure
so pressure is defined as “force exerted on unit area perpendicularly”
SI unit of pressure is N/m2 or Pascal (Pa)
Atmospheric pressure is also expressed in mm of Hg or cm of Hg.
Another unit is torr. [1 torr= 1mm of Hg]
For meteorological purposes, the unit used is bar.
Pressure can be measured with the help of manometer
Generally here the pressure is measure in reference with atmospheric pressure.
Fluid used to prepare the manometer should be incompressible in nature.
Wall of the manometer are also considered rigid.
Pascal’s principle
This suggest perfect manner of pressure transmission and force magnification.
The law is implemented in various mechanical system to carry out task requiring large force with small force.
For example: hydraulic jack, hydraulic break, hydraulic lift system, in suspensions etc.
Hydraulic jack
WORKING PRINCIPLEThe working principle of a hydraulic jack may be explained with the help of Figure. Consider a ram and plunger, operating in two cylinders of different diameters, which are interconnected at the bottom, through a chamber, which is filled with some liquid.
Archimedes’ principle
Archimedes' studied the upthrust acting on a body, when it is partially or completely immersed in a fluid by performing several experiments and then stated the following principle known as the Archimedes' Principle.
According to this principle, when a body is partially or wholly immersed in a fluid, it experiences an upthrust (buoyant force) equal to the weight of the liquid displaced.
By theory we can calculate volume and density of the substance.
Application of Archimedes' Principle
1. Submarine: A submarine has a large ballast tank, which is used to control its position and depth from the surface of the sea. A submarine submerges by letting water into the ballast tank so that its weight becomes greater than the buoyant force (and vice versa). It floats by reducing water in the ballast tank.-thus its weight is less than the buoyant force.2. Hot-air balloon: The atmosphere is filled with air that exerts buoyant force on any object.
A hot air balloon rises and floats due to the buoyant force (when the surrounding air is greater than its weight). It descends when the balloon weight is more than the buoyant force. It becomes stationary when the weight = buoyant force.The weight of the Hot-air balloon can be controlled by varying the quantity of hot air in the balloon.