Aeorodynamics

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ME 425: AERODYNAMICS- Dr. A.B.M. Toufique Hasan

Associate Professor Department of Mechanical Engineering, BUET

Lecture # 1 (Introduction)March 2, 2015

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Aerodynamics is the study of dynamics of gaseous fluids(air/gas), especially the atmospheric interaction with movingbodies.

This field of engineering deals with the aerodynamics forcesnamely lift and drag and moments and the heat transfer ratesacting on a vehicle in flight.

These mechanical parameters greatly depends on the pattern offlow around the vehicle.

And the resultant flow pattern depends on the geometry of thevehicle (shape of the airfoil: NACA, SC, RAE, ONERA, BGK,NLR, DRA, OAT ), its orientation with respect toundisturbed free stream (Angle of Attack-AOA), and the speed(Mach No.) and altitude at which the vehicle is moving.

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Fig. Viscous Flow around a circular cylinder

Fig. Viscous Flow around a square cylinder

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Fig. Flow past an airfoil

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The complete flight of a vehicle/object is mostly comprises ofthe following matters:

Aerodynamics Propulsion and Power Structural mechanics/dynamics Stability and control

Aerodynamics is the fundamental of Aerospace engineering. Agreat scope is available for propulsion technology (Jetpropulsion and rocketry) and structural dynamics.

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The physics of aerodynamics can be learnt from

Theoretical aerodynamics (governing equations, simplification, theoretical modeling etc.)

Experimental aerodynamics (wind tunnel, flow visualization-PIV, instrumentation, measurements etc.)

Computational aerodynamics (governing equations, numerical techniques, computational resources, CFD)

Several promising commercial software for CFD are- ANSYS FLUENT ANSYS CFX FASTRAN STAR CCM+ ADINA

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Aerodynamics can be broadly classified to two groups-1. External aerodynamics 2. Internal aerodynamics

External aerodynamics Internal aerodynamics1. Helicopter2. Civil aircraft/passenger aircraft3. Cargo aircraft4. Military aircraft (most advanced)5. Rockets6. UAV7. Spaceships8. Wind turbine9. Racing car aerodynamics10.High speed train aerodynamics

1. Rocket nozzle (C-D nozzle)2. Compressor/turbine blade3. Fan blade4. Butterfly valve5. Cascade

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Air Berlin B737-700

B767 climbing in moist air

Lufthansa B737-300

Airbus A380

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First Flight: December 15, 2009The Boeing 787-8 Dreamliner is asuper-efficient airplane. It will bringthe economics of large jet transportsto the middle of the market, using 20percent less fuel than any otherairplane of its size.Cockpit crew: 2Seating: 210 -250 passengersRange 14200 15200 KmEngine (s) - Two GE GENX /TwoRolls Royces Trent 1000.Cruise speed: 902 Kph. (Mach 0.85)

Dreamliner: world's first major airliner touse composite materials for most of itsconstruction

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Lockheed Martin F-22A Raptor

A-10 Thunderbolt II

Avro Vulcan Bombar

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Space Shuttle

Space Shuttle Main Engine

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Ariane 5 just after lift-off

Shock diamonds

Flow structure inside nozzle

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Unmanned air vehicle (UAV)

Flying of bird

UAV is used for Remotely piloted Surveillance Detection of biological,chemical or nuclear materials

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Vehicles with wing spans less than approximately 6m andmasses less than 25 kg are usually considered as UAV.

UAV are either remotely piloted or autonomous with artificialintelligence.

Requirements for a typical low-altitude small UAV include Long flight duration at speeds between 20 and 100

km/h Cruise altitude 3 to 300 m Light weight All-weather capabilities

Because of recent availability of very small sensors, videocamera, and control hardware, systems as small as 15 cmwith mass of 80 g, referred to as micro-air vehicle (MAV),are now possible for limited missions.

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The most important parameter in fluid dynamics/aerodynamics isthe Reynolds number, Re which is the ratio of inertia force toviscous force.

Fig. Reynolds number range for flight vehicles*

* http://www.annualreviews.org/doi/pdf/10.1146/annurev.fluid.35.101101.161102

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Fig. Variation of Reynolds numbers with speed acrossinsects, micro-air vehicles, birds, Model airplanes,Human powered vehicles, aircraft, hang-gliders andlighter than air airships. Adapted from (Lissaman 1983)

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NACA 0012

NACA 0015

NACA 0024

NACA 2414

BOEING 737 Root

Boeing 737 Midspan

Boeing 737 Outboard

RAE 2822 (SC)

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Course content1. Aerodynamic forces-drag and lift2. Inviscid incompressible flow to include potential function,

stream function, circulation3. Basic potential flows4. Kutta Joukowski theorem5. Airfoil theory6. Wing theory7. Aircraft propulsion8. Aircraft performance; static and special performance9. Introduction to stability and control

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Reference texts:1. Fundamentals of Aerodynamics- J Anderson2. Aerodynamics for Engineers- John J Bertin3. Aerodynamics for Engineering Students - E. Lo Houghton

and PW Carpenter4. Introduction to Flight - J Anderson5. Aircraft performance and Design - J Anderson