Powerpoint presentation on Drag

7/30/2019 Powerpoint presentation on Drag

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Drag

Veronica, Patrick, Jimmy, Garrett



Simplistic View



Wingtip Vortices Revisited

http://www.capelaction.com/Source/38496_GOOBJ.jpg



•Lift generated from differences in pressure above the airfoil and below

•Air flow moves from high pressure to low pressure with freedom along tips

•Produces circular motion affects the air, clockwise of the left and counter-clockwise

on the right

http://www.centennialofflight.gov/essay/Theories_of_Flight/Vortex/TH15G1.jpg



Airflow varies

Less effect due to induced flow More effect due to induced flow



Induced Drag



Induced Drag

• Vortices reduce the

wings’ ability to

generate lift

• As a result of thesevortices, the local angle

of attack is increased.



Efficiency Factor

• Elliptical distribution

has the lowest induced

drag

• e=1• Other wing shapes: e<1

• Therefore, more

induced drag

http://3.bp.blogspot.com/_1fXv2yds-Xs/TMGvkAJMHtI/AAAAAAAABW8/8z5mzN2rgl0/s1600/spitfire.jpg



Minimizing Induced Drag

Twisted Wings:Less angle of attack at the

tips and higher angle of

attack on the inner wing

Curved Trailing Edges:

Wright Brothers used

curved trailing edges-

attempted to minimize

induced drag of

rectangular wings

http://i.telegraph.co.uk/multimedia/archive/01691/boeing767_1691451c.jpg



Winglets

• Minimizing the wingtip to a

fraction of total wing area• Weaken the vortices

20% less induced drag

http://www.flightglobal.com/blogs/flightblogger/assets_c/2008/12/48289-224-thumb-560x373.jpg



Minimizing Induced Drag

• Long and thin wingspan

leads to lowered

induced drag

• However, this designdoes not minimize

parasitic or form drag

well

http://1.bp.blogspot.com/_NSJHITf-yrc/SgrSXdyfljI/AAAAAAAAAuE/BUOB865IInc/s1600/glider.jpg



Viscosity

• Air has relatively low viscosity, however,

it still does have viscosity that creates

“internal friction”

• Air rubs against the surface of an

airplane, generating the force thatopposes movement



Boundary Layer

• A very thin

layer of air

flowing

around thesurface of an

object

• Friction dragoccurs here



Boundary Layer

- Ludwig Prandtl

introduced the conceptin the early 1900s

- Revolutionized fluid

dynamics



Reduce drag



Laminar Design

• Less friction drag

• More stability

•

Better fueleconomy

• Better looking

(personal

reference)



WAVE DRAG

Veronica Rico



What is Wave Drag?

• Force retarding an airplane,

especially in supersonic and

transonic flight, as a

consequence of theformation of shock waves

• a sudden and very powerful

form of drag that appears

on aircraft flying at high-subsonic speeds



So powerful that for some time, it was thought that engines

would not be able to provide enough power to easily

overcome the effect, which led to the concept of :



• New techniques

developed during

WWII that

reducedmagnitude of

problem



Reduction of Wave Drag

• Development of ‘perfect’ shapes to reduce

wave drag as much as possible: Sears-Haack

body

• Swept Wing

• Whitcomb Area Rule



Sears-Haack Body

•

Cross-sectional areadistribution along the body

determines wave drag

http://en.wikipedia.org/wiki/File:A380_singapore_airlines_takeoff_arp.jpg

http://localhost/var/www/apps/conversion/tmp/scratch_3//upload.wikimedia.org/wikipedia/commons/6/62/Area_rule_unifilar_drawing.png

http://en.wikipedia.org/wiki/File:Sears-Haack.png



Swept Wing

• Figure shows data confirming that a swept

wing reduces the wave drag Credits - NASA



Other High Speed Wing Designs

X-29: Forward Swept Wing NASA AD-1: Oblique Wing



Form Drag

• Drag due to flow separation

• As velocity increases, boundary layer

separation moves toward the leading edge of

the object

• This results in a larger pressure at the leading

edge than the trailing edge causing a large

drag force on the body



Examples of Form Drag



More Examples



Why Golf Balls have Dimples



Methods of Reducing Drag

• Important to reduce drag because it allows for

faster, more efficient travel

CAD Model of ORCA Flyer



Airfoil Selection



Fuselage Design

ORCA Flyer Fuselage Design



Winglets



Landing Gear Design

Powerpoint presentation on Drag

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