Post on 23-Feb-2016
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Fluid Mechanics in
Aeronautics and Astronautics
Marc WilliamsSchool of Aeronautics and
Astronautics
Aeronautics = Airplanes
Astronautics = Spacecraft
Parts of Aero & AstroAerodynamics
Design Dynamics & Control Structures
Propulsion
Three forces from fluids
• LIFT - Force perpendicular to flight directionThe Air pushes the airplane “up”
• DRAG - Force opposite the flight directionThe Air pushes the airplane “back”
• THRUST - Force in the flight directionInternal pressure inside the engine pushes the
aircraft/rocket forward
LIFT
Newton say :
The air pushes the airplane up
So
The airplane pushes the air down
Cessna Citation
Boeing 777
Boeing 757
DRAG
•The air sticks to the airplane, pushing it back (Viscosity== Friction drag)
•The airplane imparts kinetic energy to the air behind it…. This energy comes from the engines, And shows up as a drag(Induced Drag, or Drag due to Lift)
Flight Regimes – A Vocabulary
00 1.0 2.0 3.0 6.0
Mach Number – M
Altitude(1000 ft.)
100
80
60
40
20
Subsonic Supersonic Hypersonic
Structural Limit(Dynamic pressure and heating) Aerodynamic
Limit
Transonic
V = flight speed
a = speed of sound
M = V / a
Wing Loading (N/m2)
All the Worlds Flyers
• Flyers meeting MAV requirements abound in nature
• Flyers with most remarkable performance leverage unsteady aerodynamics
• Flapping provides access to game-changing aerodynamic mechanisms for meeting MAV requirements
Conventional Aircraft(Steady)
Large Birds(Quasi-steady)Small Birds
(Transition)
Insects/Hummingbirds(Unsteady)
Cruising Speed (m/s)
Wei
ght (
N)
Micro Air Vehicles (MAVs)
• Unmanned aerial systems becoming for missions too dull, dirty, dangerous, or difficult for pilots– Persistent ISR– Chemical/biological sensing– “Over the hill”/“Around the
corner” scouting• Operation space is changing
– Urban canyons– Building interiors– Subterranean caverns/bunkers
• MAVs are new class of vehicle to fill new operational roles
Images from wikipedia.org, defense-update.com, delta.tudelft.nl
DYNAMICS AND CONTROL
http://www.grc.nasa.gov/WWW/K-12/airplane/alr.html
Mach Number Effects
•Mach Number = Speed / Speed of Sound
Speed of Sound = 340 m/s = 770 mph
•Mach squared = Kinetic Energy / Thermal Energy
An F/A-18 Hornet at transonic speed
F4 phantom ii breaking the sound barrier
Mars Exploration Rover (MER) aeroshell, artistic rendition
Thrust
• Thrust is produced by throwing something opposite to the direction you want to go (Newton again)
You can throw airYou can throw hot exhaust gases
You can throw rocks… but fluids are easier to work with
Air Thrower
http://www.youtube.com/watch?v=nSQzvimD3cc
Turbofan Engine
This throws air and hot exhaust gases
Turbofan Flowpath
Tomahawk Cruise Missile
Mi-24 Hind Military Aviation Helicopter
Air Thrower
Joint Strike Fighter- Marine Version
Lift Fan
Another Air Thrower
OSPREY- Tilt Rotor
And another… but you get to change the throw direction
Rockets – Pure Hot Gas Throwers
How a Rocket Produces Thrust
ROCKETS
BIG (SSME)
A micro-thruster array measuring one-quarter the size of a penny, designed by a TRW-led team for use on micro-, nano- and pico-satellites, has successfully demonstrated its functionality in a live fire test aboard a Scorpius sub-orbital sounding rocket. Individual micro-electromechanical system (MEMS) thrusters, each a poppy seed-sized cell fueled with lead styphnate propellant, fired more than 20 times at 1-second Intervals during the test staged at the White Sands Missile Range. Each thruster delivered 10(-4) Newton seconds of impulse.
ROCKETS: SMALL
SidewinderAir to Air supersonic missile
THE END
Have a great summer
Boeing 757
Vortex break-up on a delta wing at high incidence