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FLUID MECHANICS
a physical science dealing with the action of fluids at rest or in motion, and
with applications and devices in engineering using fluids.
Two Major Areas of Fluid Mechanics
Fluid Statics
Fluid Dynamics
Fluid Statics
which deals
with fluids at rest.
is the study of fluids in which there is no relative motion
between fluid particles.
Fluid Dynamics
which
concerned with fluids in
motion.
HYDRAULICS
deals with the application of fluid mechanics to engineering
devices involving liquids, usually water or oil.
deals with such problems as the flow of fluids through pipes or in
open channels, the design of storage dams, pumps, and water turbines,
and with other devices for the control or use of liquids, such as nozzles,
valves, jets, and flowmeters.
Hydraulics
Fluid
is a substance whose molecules move freely past each other.
a substance that will continuously deform – that is, flow under the
action of a shear stress.
Hydraulics
-is the study of the flow of water through pipes, rivers, and open-
channels.
-includes pumps and turbines and applications such as
hydropower.
-important for ecology, policymaking, energy
production, recreation, fish and game resources, and water supply.
Hydrology
-is the study of the movement, distribution, and quality of water
throughout the earth.
-involves the hydraulic cycle and water
resource issues.
-provides results that are useful for environmental
engineering and for policymaking.
-is important nowadays because
of global challenges in providing water for human societies.
Aerodynamics
-the study of air flow.
-Topics include lift and drag on objects
(e.g., airplanes, automobiles, birds), shock waves associated with flow around a
rocket, and the flow through a supersonic or deLaval nozzle.
Computational fluid dynamics
is the application of numerical methods
implemented on computers to model and solve problems that involve fluid
flows. Computers perform millions of calculations per second to simulate fluid
flow.
Petroleum engineering
-the application of engineering to the exploration and
production of petroleum.
-Movement of oil in the ground involves flow through a
porous medium. Petroleum extraction involves flow of oil through passages in
wells. Oil pipelines involve pumps and conduit flow.
Atmospheric science
is the study of the atmosphere, its processes, and the
interaction of the atmosphere with other systems. Fluid mechanics topics
include flow of the atmosphere and applications of CFD to atmospheric
modeling.
-important for predicting weather and is
relevant to current issues including acid rain, photochemical smog, and global
warming.
Bio-fluid mechanics
-is an emerging field that includes the study of the lungs and
circulatory system, blood flow, micro-circulation, and lymph flow.
-is important for advancing health
care.
Bio-fluids
also
includes development of artificial heart valves, stents, vein and dialysis shunts,
and artificial organs.
Acoustics
the study of sound. Topics include production, control, transmission,
reception of sound, and physiological effects of sound. Since sound waves are
pressure waves in fluids, acoustics is related to fluid mechanics. In addition,
water hammer in a piping system, which involves pressure waves in liquids,
involves some of the same knowledge that is used in acoustics.
Microchannel flow
an emerging area that involves the study of flow in tiny
passages. The typical size of a microchannel is a diameter in the range of 10 to
200 micrometers. Applications that involve microchannels include
microelectronics, fuel cell systems, and advanced heat sink designs.
Electrical engineering
problems can involve knowledge from fluid mechanics.
For example, fluid mechanics is involved in the flow of solder during a
manufacturing process, the cooling of a microprocessor by a fan, sizing of
motors to operate pumps, and the production of electrical power by wind
turbines.
Environmental engineering
involves the application of science to protect or
improve the environment (air, water, and/or land resources) or to remediate
polluted sites. Environmental engineers design water supply and wastewater
treatment systems for communities.
Environmental engineers
are concerned with local and worldwide
environmental issues such as acid rain, ozone depletion, water pollution, and air
pollution.
VAPOR PRESSURE
Liquid molecules which possess sufficient kinetic energy are projected out
of the main body of a liquid at its free surface and pass into the vapor. The
pressure exerted by this vapor is known as
IDEAL GAS
is relationship between the pressure, density, and temperature for an ideal
gas.
normal stress
only stress that exist in fluid statics
Absolute pressure
is referenced to regions such as outer
space, where the pressure is essentially zero because the
region is devoid of gas.
absolute zero,
The pressure in a perfect vacuum
absolute pressure.
pressure measured relative to this zero
pressure is termed
gage pressure.
When the pressure is measured relative to prevailing local
atmospheric pressure, the pressure value is
called
vacuum pressure.
When pressure is less than atmospheric, the pressure can
be described using
is
defined as the difference between atmospheric pressure
and actual pressure.
is a positive number
and equals the absolute value of gage pressure (which will
be negative ).
BAROMETER
An instrument that is used to measure atmospheric
pressure
mercury barometer
is made by inverting a
mercury-filled tube in a container of mercury. The
pressure at the top of the mercury barometer will
be the vapor pressure of mercury, which is very
small: Pv = 2.4x10−6 atm at 20 °C.
aneroid barometer
works mechanically. An
aneroid is an elastic bellows that has been tightly
sealed after some air was removed.
BOURDON-TUBE GAGE
measures pressure by sensing
the deflection of a coiled tube.
is common
because it is low cost, reliable, easy to install, and
available in many different pressure ranges. There are
disadvantages: dynamic pressures are difficult to
read accurately; accuracy of the gage can be
lower than other instruments; and the gage can be
damaged by excessive pressure pulsations.
PIEZOMETER
is a vertical tube, usually transparent, in
which a liquid rise in response to a positive gage pressure.
Pressure in the pipe pushes the water column to a height
h, and the gage pressure at the center of the pipe is P=γh.
Advantages
✓ Simplicity direct measurement (no need for calibration)
✓ Accuracy
Disadvantages
✓ Cannot easily be used for measuring pressure in a gas
✓ Limited to low pressure because the column height
becomes too large at high pressures
MANOMETER
often shaped like the letter “U”, is a
device for measuring pressure by raising or lowering a
column or liquid.
Ph = horizontal component;
total hydrostatic pressure on
plane area “A” which is the
projection of the curved one
on the vertical
Pv = vertical component;
weight of
liquid whose volume is traced by
moving the curve vertically
“upward” until the liquid surface or
its prolongation
Dams
are structures that block the flow of a river, stream, or other waterway. Some
dams divert the flow of river water into a pipeline, canal, or channel.
PURPOSES OF A DAM
Irrigation and drinking water
Power supply
Navigation
Flood control
TYPES OF DAM
Gravity Dam
Embankment Dam
Arch Dam
Buttress Dam
law of buoyancy,
buoyancy, known as Archimedes’
principle,
Archimedes.
The law of buoyancy, known as Archimedes’
principle, dates back some 2200 years to the
Greek philosopher
ARCHIMEDES’ PRINCIPLE:
“When a stationary body is completely
submerged in a fluid, or floating so that it is only
partially submerged, the resultant fluid force
acting on the body is called the buoyant force.This force is equal to the weight of the fluid
displaced”
TRANSLATION
X=sway
y=surge
z=heave
ROTATION
x=pitch
y=roll
z=yaw
METACENTER (M)
point of interstection between the bouyant force and the tiled axis of the body which DETERMINES its stability
METACENTRIC HEIGHT (MG)
distance between the metacenter and the center of gravity of the body which MEASURES its stability