mach number by suman
TRANSCRIPT
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MACH NUMBER
Presented by
SUMAN
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Definition
Mach number (Ma orM) is the speed of an objectmoving through air, or any other fluid substance,divided by the speed of sound as it is in thatsubstance.
where
M is the Mach number V is the relative velocity of the source to the
medium and
a is the speed of sound in the medium
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HISTORY BEHIND THE TERM MACH
The term is named in honor of Ernst Mach, aAustrian scientist .
Mach was actually the first person in history to
develop a method for visualizing the flowpassing over an object at supersonic speeds.
He was also the first to understand the
fundamental principles that govern supersonic
flow and their impact on aerodynamics.
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Ernst Mach
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Mach published the very first photograph ofthe shock waves formed by a bullet traveling
faster than the speed of sound.
The photo shown , illustrates the strong shock
wave formed by the nose of the bullet, theweaker shock wave created at the at end ofthe bullet.
Also visible in the photo are two vertical linesmade by the trip wires that triggered thecamera as the projectile passed by.
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Ernst Mach's photo of a bullet in
supersonic flight
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How a shadowgraph works
Light is passed through an airflow and
reflected onto a screen or film plate.
Since shock waves create changes in the
temperature and density of the airflow, thelight waves are bent, or refracted, as they pass
through the shock waves.
These refracted light patterns createshadows that can be seen on the screen.
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How a shadowgraph works
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Basic Definitions
Speed of sound: It defines the velocity at
which sound waves travel through a
substance, such as air.
subsonic: A vehicle that is traveling slower
than the speed of sound (M1) is said to beflying at supersonic speeds.
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Speed ofSound
The speed of sound, also known as Mach 1,
changes throughout the atmosphere based on
the temperature at any given altitude.
1,116.4 ft/s
340.3 m/s
761.2 mph 1,225.1 km/h
661.5 knots
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Speed of sound varies?
the speed of sound through the standardatmosphere is 761.2 mph (1,223 km/h) at sea
level, Mach 2 then follows as 1,522 mph
(2,447 km/h).
At an altitude of 30,000 Ft (9,150 m) it is only
1,356 mph (2,180 km/h) ,because the speed
of sound generally decreases as altitude
increases.
a is the speed of sound
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Significance of MachNumber
Vehicle traveling at a given Mach number willexperience similar aerodynamic properties,
regardless of its altitude or dimensional
airspeed.
In addition, similarity parameters make it
possible to measure the aerodynamic
properties of a subscale model in a wind
tunnel rather than having to test a full scale
vehicle in free flight.
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Shock wave
When an aircraft exceeds Mach 1 a largepressure difference is created just in front of
the aircraft. This abrupt pressure difference,
called a shock wave, spreads backward and
outward from the aircraft in a cone shape (a
so-called Mach cone).
The higher the speed, the more narrow the
cone; at just overM=1 it is hardly a cone at all,but closer to a slightly concave plane.
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Calculating Mach number
An aircraft Machmeter or electronic flightinformation system (EFIS) can display Mach
number derived from stagnation pressure
(pitot tube) and static pressure.
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ANY QUERIES?