introduction to aerod ynamics for flight - brown...
TRANSCRIPT
![Page 1: Introduction to Aerod ynamics for Flight - Brown Universitycs.brown.edu/.../slides_10_14/jchen_aerodynamics.pdf · Introduction to Aerod ynamics for Flight Oct 14 2008 Bro wn Uni](https://reader031.vdocuments.us/reader031/viewer/2022030701/5aec60a87f8b9a45568e3d27/html5/thumbnails/1.jpg)
Introduction to Aerodynamics for Flight
Oct 14 2008Brown University
![Page 2: Introduction to Aerod ynamics for Flight - Brown Universitycs.brown.edu/.../slides_10_14/jchen_aerodynamics.pdf · Introduction to Aerod ynamics for Flight Oct 14 2008 Bro wn Uni](https://reader031.vdocuments.us/reader031/viewer/2022030701/5aec60a87f8b9a45568e3d27/html5/thumbnails/2.jpg)
• What do we want from aerodynamics?
• Basic ideas from 2D
• Differences between 2D and 3D
• The importance of unsteadiness
Outline
![Page 3: Introduction to Aerod ynamics for Flight - Brown Universitycs.brown.edu/.../slides_10_14/jchen_aerodynamics.pdf · Introduction to Aerod ynamics for Flight Oct 14 2008 Bro wn Uni](https://reader031.vdocuments.us/reader031/viewer/2022030701/5aec60a87f8b9a45568e3d27/html5/thumbnails/3.jpg)
• Aero
• Air
• Dynamics
What is aerodynamics?
![Page 4: Introduction to Aerod ynamics for Flight - Brown Universitycs.brown.edu/.../slides_10_14/jchen_aerodynamics.pdf · Introduction to Aerod ynamics for Flight Oct 14 2008 Bro wn Uni](https://reader031.vdocuments.us/reader031/viewer/2022030701/5aec60a87f8b9a45568e3d27/html5/thumbnails/4.jpg)
What do we want from aerodynamics?
•Predict forces and moments on a body due to motions relative to fluid
![Page 5: Introduction to Aerod ynamics for Flight - Brown Universitycs.brown.edu/.../slides_10_14/jchen_aerodynamics.pdf · Introduction to Aerod ynamics for Flight Oct 14 2008 Bro wn Uni](https://reader031.vdocuments.us/reader031/viewer/2022030701/5aec60a87f8b9a45568e3d27/html5/thumbnails/5.jpg)
What are the forces on an airplane?
![Page 6: Introduction to Aerod ynamics for Flight - Brown Universitycs.brown.edu/.../slides_10_14/jchen_aerodynamics.pdf · Introduction to Aerod ynamics for Flight Oct 14 2008 Bro wn Uni](https://reader031.vdocuments.us/reader031/viewer/2022030701/5aec60a87f8b9a45568e3d27/html5/thumbnails/6.jpg)
Four forces on an airplane
NASA Glenn Research center
What is the most important part that identifies the type, performance, and purpose of an airplane?
![Page 7: Introduction to Aerod ynamics for Flight - Brown Universitycs.brown.edu/.../slides_10_14/jchen_aerodynamics.pdf · Introduction to Aerod ynamics for Flight Oct 14 2008 Bro wn Uni](https://reader031.vdocuments.us/reader031/viewer/2022030701/5aec60a87f8b9a45568e3d27/html5/thumbnails/7.jpg)
2D Airfoil
![Page 8: Introduction to Aerod ynamics for Flight - Brown Universitycs.brown.edu/.../slides_10_14/jchen_aerodynamics.pdf · Introduction to Aerod ynamics for Flight Oct 14 2008 Bro wn Uni](https://reader031.vdocuments.us/reader031/viewer/2022030701/5aec60a87f8b9a45568e3d27/html5/thumbnails/8.jpg)
Vectors• Direction
• Magnitude
![Page 9: Introduction to Aerod ynamics for Flight - Brown Universitycs.brown.edu/.../slides_10_14/jchen_aerodynamics.pdf · Introduction to Aerod ynamics for Flight Oct 14 2008 Bro wn Uni](https://reader031.vdocuments.us/reader031/viewer/2022030701/5aec60a87f8b9a45568e3d27/html5/thumbnails/9.jpg)
Governing principles
• Conservation of mass
• Conservation of momentum
• Conservation of energy
Physics laws nothing in nature that violates.
![Page 10: Introduction to Aerod ynamics for Flight - Brown Universitycs.brown.edu/.../slides_10_14/jchen_aerodynamics.pdf · Introduction to Aerod ynamics for Flight Oct 14 2008 Bro wn Uni](https://reader031.vdocuments.us/reader031/viewer/2022030701/5aec60a87f8b9a45568e3d27/html5/thumbnails/10.jpg)
Thrust
![Page 11: Introduction to Aerod ynamics for Flight - Brown Universitycs.brown.edu/.../slides_10_14/jchen_aerodynamics.pdf · Introduction to Aerod ynamics for Flight Oct 14 2008 Bro wn Uni](https://reader031.vdocuments.us/reader031/viewer/2022030701/5aec60a87f8b9a45568e3d27/html5/thumbnails/11.jpg)
Newton’s 1st lawapplied to airplanes
• “Every object persists in its state of rest or uniform motion in a straight line unless it is compelled to change that state by forces impressed on it.”
If Thrust == Drag, airplane holds constant airspeedIf Thrust , airspeed , then drag When Drag == thrust, airplane holds a new, higher constant airspeed
Isaac Newton(1643-1727)
![Page 12: Introduction to Aerod ynamics for Flight - Brown Universitycs.brown.edu/.../slides_10_14/jchen_aerodynamics.pdf · Introduction to Aerod ynamics for Flight Oct 14 2008 Bro wn Uni](https://reader031.vdocuments.us/reader031/viewer/2022030701/5aec60a87f8b9a45568e3d27/html5/thumbnails/12.jpg)
Newton’s 2nd lawapplied to airplanes
• Force = mass * acceleration
Excess Thrust = Thrust - DragForces on the fluid causes acceleration
Isaac Newton(1643-1727)
![Page 13: Introduction to Aerod ynamics for Flight - Brown Universitycs.brown.edu/.../slides_10_14/jchen_aerodynamics.pdf · Introduction to Aerod ynamics for Flight Oct 14 2008 Bro wn Uni](https://reader031.vdocuments.us/reader031/viewer/2022030701/5aec60a87f8b9a45568e3d27/html5/thumbnails/13.jpg)
Lift
• What cause it?
• How to explain it?
Air and motion
Newton’s lawsBernoulli’s principle
![Page 14: Introduction to Aerod ynamics for Flight - Brown Universitycs.brown.edu/.../slides_10_14/jchen_aerodynamics.pdf · Introduction to Aerod ynamics for Flight Oct 14 2008 Bro wn Uni](https://reader031.vdocuments.us/reader031/viewer/2022030701/5aec60a87f8b9a45568e3d27/html5/thumbnails/14.jpg)
Motion effects on lift (1)• Change in momentum
FF
F1
F2
Lift (wing goes up) Sir Isaac Newton
Force causes a change in velocity which in turn generates another force.
For every action , there is an equal reaction.
Conservation of momentum (m * v)
![Page 15: Introduction to Aerod ynamics for Flight - Brown Universitycs.brown.edu/.../slides_10_14/jchen_aerodynamics.pdf · Introduction to Aerod ynamics for Flight Oct 14 2008 Bro wn Uni](https://reader031.vdocuments.us/reader031/viewer/2022030701/5aec60a87f8b9a45568e3d27/html5/thumbnails/15.jpg)
Motion effects on lift (2)• Pressure difference
FF
Lift (wing goes up) Issac Newton
Faster flow = lower relative pressure
Streamlines
![Page 16: Introduction to Aerod ynamics for Flight - Brown Universitycs.brown.edu/.../slides_10_14/jchen_aerodynamics.pdf · Introduction to Aerod ynamics for Flight Oct 14 2008 Bro wn Uni](https://reader031.vdocuments.us/reader031/viewer/2022030701/5aec60a87f8b9a45568e3d27/html5/thumbnails/16.jpg)
• The speed of a fluid is directly related to pressure
Conservation of energy (Energy: the capacity for doing work)
![Page 17: Introduction to Aerod ynamics for Flight - Brown Universitycs.brown.edu/.../slides_10_14/jchen_aerodynamics.pdf · Introduction to Aerod ynamics for Flight Oct 14 2008 Bro wn Uni](https://reader031.vdocuments.us/reader031/viewer/2022030701/5aec60a87f8b9a45568e3d27/html5/thumbnails/17.jpg)
Motion effects on circulation (3)
• Circulation
Conservation of angular momentum
Kutta-Joukowski lift theoremhttp://hyperphysics.phy-astr.gsu.edu/
![Page 18: Introduction to Aerod ynamics for Flight - Brown Universitycs.brown.edu/.../slides_10_14/jchen_aerodynamics.pdf · Introduction to Aerod ynamics for Flight Oct 14 2008 Bro wn Uni](https://reader031.vdocuments.us/reader031/viewer/2022030701/5aec60a87f8b9a45568e3d27/html5/thumbnails/18.jpg)
Shape causes lift (1)
• Angle of attack
Higher angle of attack = larger lift But ...
![Page 19: Introduction to Aerod ynamics for Flight - Brown Universitycs.brown.edu/.../slides_10_14/jchen_aerodynamics.pdf · Introduction to Aerod ynamics for Flight Oct 14 2008 Bro wn Uni](https://reader031.vdocuments.us/reader031/viewer/2022030701/5aec60a87f8b9a45568e3d27/html5/thumbnails/19.jpg)
Stall and Separation!
![Page 20: Introduction to Aerod ynamics for Flight - Brown Universitycs.brown.edu/.../slides_10_14/jchen_aerodynamics.pdf · Introduction to Aerod ynamics for Flight Oct 14 2008 Bro wn Uni](https://reader031.vdocuments.us/reader031/viewer/2022030701/5aec60a87f8b9a45568e3d27/html5/thumbnails/20.jpg)
What causes Separation?
Higher PressureLower
Pressure
Higher PressureLower
Pressure
Reversed Flow Region
![Page 21: Introduction to Aerod ynamics for Flight - Brown Universitycs.brown.edu/.../slides_10_14/jchen_aerodynamics.pdf · Introduction to Aerod ynamics for Flight Oct 14 2008 Bro wn Uni](https://reader031.vdocuments.us/reader031/viewer/2022030701/5aec60a87f8b9a45568e3d27/html5/thumbnails/21.jpg)
![Page 22: Introduction to Aerod ynamics for Flight - Brown Universitycs.brown.edu/.../slides_10_14/jchen_aerodynamics.pdf · Introduction to Aerod ynamics for Flight Oct 14 2008 Bro wn Uni](https://reader031.vdocuments.us/reader031/viewer/2022030701/5aec60a87f8b9a45568e3d27/html5/thumbnails/22.jpg)
Lower Pressure
![Page 23: Introduction to Aerod ynamics for Flight - Brown Universitycs.brown.edu/.../slides_10_14/jchen_aerodynamics.pdf · Introduction to Aerod ynamics for Flight Oct 14 2008 Bro wn Uni](https://reader031.vdocuments.us/reader031/viewer/2022030701/5aec60a87f8b9a45568e3d27/html5/thumbnails/23.jpg)
Camber in Actual Airfoils
![Page 24: Introduction to Aerod ynamics for Flight - Brown Universitycs.brown.edu/.../slides_10_14/jchen_aerodynamics.pdf · Introduction to Aerod ynamics for Flight Oct 14 2008 Bro wn Uni](https://reader031.vdocuments.us/reader031/viewer/2022030701/5aec60a87f8b9a45568e3d27/html5/thumbnails/24.jpg)
Design of an airplane is an Art(alternative ways to increase lift)
• Camber augmentation (Splat, flap, spoiler)
![Page 25: Introduction to Aerod ynamics for Flight - Brown Universitycs.brown.edu/.../slides_10_14/jchen_aerodynamics.pdf · Introduction to Aerod ynamics for Flight Oct 14 2008 Bro wn Uni](https://reader031.vdocuments.us/reader031/viewer/2022030701/5aec60a87f8b9a45568e3d27/html5/thumbnails/25.jpg)
Factors that affect Lift• Air
• Mass, viscosity, compressibility
• Motion
• velocity and inclination to flow
• Object
• Shape and size
Governed by Newton’s laws and Bernouli’s equation
![Page 26: Introduction to Aerod ynamics for Flight - Brown Universitycs.brown.edu/.../slides_10_14/jchen_aerodynamics.pdf · Introduction to Aerod ynamics for Flight Oct 14 2008 Bro wn Uni](https://reader031.vdocuments.us/reader031/viewer/2022030701/5aec60a87f8b9a45568e3d27/html5/thumbnails/26.jpg)
Drag
• A force of resistance when an aircraft moves through the air.
• We want to minimize it.
![Page 27: Introduction to Aerod ynamics for Flight - Brown Universitycs.brown.edu/.../slides_10_14/jchen_aerodynamics.pdf · Introduction to Aerod ynamics for Flight Oct 14 2008 Bro wn Uni](https://reader031.vdocuments.us/reader031/viewer/2022030701/5aec60a87f8b9a45568e3d27/html5/thumbnails/27.jpg)
Separation!• Pressure
TextLow pressure
Low pressure
![Page 28: Introduction to Aerod ynamics for Flight - Brown Universitycs.brown.edu/.../slides_10_14/jchen_aerodynamics.pdf · Introduction to Aerod ynamics for Flight Oct 14 2008 Bro wn Uni](https://reader031.vdocuments.us/reader031/viewer/2022030701/5aec60a87f8b9a45568e3d27/html5/thumbnails/28.jpg)
![Page 29: Introduction to Aerod ynamics for Flight - Brown Universitycs.brown.edu/.../slides_10_14/jchen_aerodynamics.pdf · Introduction to Aerod ynamics for Flight Oct 14 2008 Bro wn Uni](https://reader031.vdocuments.us/reader031/viewer/2022030701/5aec60a87f8b9a45568e3d27/html5/thumbnails/29.jpg)
Aside: Boundary Layer
![Page 30: Introduction to Aerod ynamics for Flight - Brown Universitycs.brown.edu/.../slides_10_14/jchen_aerodynamics.pdf · Introduction to Aerod ynamics for Flight Oct 14 2008 Bro wn Uni](https://reader031.vdocuments.us/reader031/viewer/2022030701/5aec60a87f8b9a45568e3d27/html5/thumbnails/30.jpg)
Friction Drag• Turbulence vs. Laminar Boundary Layers
Recrit
Transition
t0 t1
Viscosity
![Page 31: Introduction to Aerod ynamics for Flight - Brown Universitycs.brown.edu/.../slides_10_14/jchen_aerodynamics.pdf · Introduction to Aerod ynamics for Flight Oct 14 2008 Bro wn Uni](https://reader031.vdocuments.us/reader031/viewer/2022030701/5aec60a87f8b9a45568e3d27/html5/thumbnails/31.jpg)
Drag
• Pressure / Form Drag
• Delayed separation in Turbulent flow (less drag)
• Early separation in laminar flow (more drag)
• Friction Drag
• Low for Laminar flows
• High for turbulent flows
![Page 32: Introduction to Aerod ynamics for Flight - Brown Universitycs.brown.edu/.../slides_10_14/jchen_aerodynamics.pdf · Introduction to Aerod ynamics for Flight Oct 14 2008 Bro wn Uni](https://reader031.vdocuments.us/reader031/viewer/2022030701/5aec60a87f8b9a45568e3d27/html5/thumbnails/32.jpg)
Reynolds Number
• Predication of laminar vs. turbulent flow
• Defines dynamic similarity
Inertia force
Viscous forceRe =
Viscosity
Fluid Velocity *Length=
Blood flow in brain: ~100Blood flow in aorta: ~1000
Typical pitch in Major League Baseball: 200,000Person swimming: 4000,000Blue Whale: 300,000,000A large ship: 5000,000,000
![Page 33: Introduction to Aerod ynamics for Flight - Brown Universitycs.brown.edu/.../slides_10_14/jchen_aerodynamics.pdf · Introduction to Aerod ynamics for Flight Oct 14 2008 Bro wn Uni](https://reader031.vdocuments.us/reader031/viewer/2022030701/5aec60a87f8b9a45568e3d27/html5/thumbnails/33.jpg)
From 2D to 3D
What is missing from our discussion? What assumption did we make about
the geometry of the wing?
![Page 34: Introduction to Aerod ynamics for Flight - Brown Universitycs.brown.edu/.../slides_10_14/jchen_aerodynamics.pdf · Introduction to Aerod ynamics for Flight Oct 14 2008 Bro wn Uni](https://reader031.vdocuments.us/reader031/viewer/2022030701/5aec60a87f8b9a45568e3d27/html5/thumbnails/34.jpg)
Trailing edge vertices
![Page 35: Introduction to Aerod ynamics for Flight - Brown Universitycs.brown.edu/.../slides_10_14/jchen_aerodynamics.pdf · Introduction to Aerod ynamics for Flight Oct 14 2008 Bro wn Uni](https://reader031.vdocuments.us/reader031/viewer/2022030701/5aec60a87f8b9a45568e3d27/html5/thumbnails/35.jpg)
Downwash Introduces Drag
Flow from the lower side (higher pressure) wants to ‘leak’ to the low pressure side of the wing.
Starts from wing tip
Vorticity from trailing edge
![Page 36: Introduction to Aerod ynamics for Flight - Brown Universitycs.brown.edu/.../slides_10_14/jchen_aerodynamics.pdf · Introduction to Aerod ynamics for Flight Oct 14 2008 Bro wn Uni](https://reader031.vdocuments.us/reader031/viewer/2022030701/5aec60a87f8b9a45568e3d27/html5/thumbnails/36.jpg)
Vorticity
![Page 37: Introduction to Aerod ynamics for Flight - Brown Universitycs.brown.edu/.../slides_10_14/jchen_aerodynamics.pdf · Introduction to Aerod ynamics for Flight Oct 14 2008 Bro wn Uni](https://reader031.vdocuments.us/reader031/viewer/2022030701/5aec60a87f8b9a45568e3d27/html5/thumbnails/37.jpg)
Lifting Body Problems
![Page 38: Introduction to Aerod ynamics for Flight - Brown Universitycs.brown.edu/.../slides_10_14/jchen_aerodynamics.pdf · Introduction to Aerod ynamics for Flight Oct 14 2008 Bro wn Uni](https://reader031.vdocuments.us/reader031/viewer/2022030701/5aec60a87f8b9a45568e3d27/html5/thumbnails/38.jpg)
Ramifications of Downwash
Introduce dragReduce lift
![Page 39: Introduction to Aerod ynamics for Flight - Brown Universitycs.brown.edu/.../slides_10_14/jchen_aerodynamics.pdf · Introduction to Aerod ynamics for Flight Oct 14 2008 Bro wn Uni](https://reader031.vdocuments.us/reader031/viewer/2022030701/5aec60a87f8b9a45568e3d27/html5/thumbnails/39.jpg)
Aspect Ratio
![Page 40: Introduction to Aerod ynamics for Flight - Brown Universitycs.brown.edu/.../slides_10_14/jchen_aerodynamics.pdf · Introduction to Aerod ynamics for Flight Oct 14 2008 Bro wn Uni](https://reader031.vdocuments.us/reader031/viewer/2022030701/5aec60a87f8b9a45568e3d27/html5/thumbnails/40.jpg)
Oswarld’s efficiency
![Page 41: Introduction to Aerod ynamics for Flight - Brown Universitycs.brown.edu/.../slides_10_14/jchen_aerodynamics.pdf · Introduction to Aerod ynamics for Flight Oct 14 2008 Bro wn Uni](https://reader031.vdocuments.us/reader031/viewer/2022030701/5aec60a87f8b9a45568e3d27/html5/thumbnails/41.jpg)
Lift Distribution• For level flight, minimum induced drag occur
when the lift distribution is elliptical
• Either the wing shape is elliptical, or
• The incidence angle produces an elliptical lift
![Page 42: Introduction to Aerod ynamics for Flight - Brown Universitycs.brown.edu/.../slides_10_14/jchen_aerodynamics.pdf · Introduction to Aerod ynamics for Flight Oct 14 2008 Bro wn Uni](https://reader031.vdocuments.us/reader031/viewer/2022030701/5aec60a87f8b9a45568e3d27/html5/thumbnails/42.jpg)
Other 3D Effects
![Page 43: Introduction to Aerod ynamics for Flight - Brown Universitycs.brown.edu/.../slides_10_14/jchen_aerodynamics.pdf · Introduction to Aerod ynamics for Flight Oct 14 2008 Bro wn Uni](https://reader031.vdocuments.us/reader031/viewer/2022030701/5aec60a87f8b9a45568e3d27/html5/thumbnails/43.jpg)
Summary
• Four forces
• Momentum
• Reynolds number (steady, un-steady flow)
• 2D vs. 3D
![Page 44: Introduction to Aerod ynamics for Flight - Brown Universitycs.brown.edu/.../slides_10_14/jchen_aerodynamics.pdf · Introduction to Aerod ynamics for Flight Oct 14 2008 Bro wn Uni](https://reader031.vdocuments.us/reader031/viewer/2022030701/5aec60a87f8b9a45568e3d27/html5/thumbnails/44.jpg)
• Dave Willis: “so what?! we got all this lift / drag etc. Garbage!”
![Page 45: Introduction to Aerod ynamics for Flight - Brown Universitycs.brown.edu/.../slides_10_14/jchen_aerodynamics.pdf · Introduction to Aerod ynamics for Flight Oct 14 2008 Bro wn Uni](https://reader031.vdocuments.us/reader031/viewer/2022030701/5aec60a87f8b9a45568e3d27/html5/thumbnails/45.jpg)
How to use the knowledge to:
- Design an airplane- Study bats flight kinematics and flow wakes- Conduct visual design
![Page 46: Introduction to Aerod ynamics for Flight - Brown Universitycs.brown.edu/.../slides_10_14/jchen_aerodynamics.pdf · Introduction to Aerod ynamics for Flight Oct 14 2008 Bro wn Uni](https://reader031.vdocuments.us/reader031/viewer/2022030701/5aec60a87f8b9a45568e3d27/html5/thumbnails/46.jpg)
![Page 47: Introduction to Aerod ynamics for Flight - Brown Universitycs.brown.edu/.../slides_10_14/jchen_aerodynamics.pdf · Introduction to Aerod ynamics for Flight Oct 14 2008 Bro wn Uni](https://reader031.vdocuments.us/reader031/viewer/2022030701/5aec60a87f8b9a45568e3d27/html5/thumbnails/47.jpg)
FastAero Bat flight simulation, Dave Willis et al.
![Page 48: Introduction to Aerod ynamics for Flight - Brown Universitycs.brown.edu/.../slides_10_14/jchen_aerodynamics.pdf · Introduction to Aerod ynamics for Flight Oct 14 2008 Bro wn Uni](https://reader031.vdocuments.us/reader031/viewer/2022030701/5aec60a87f8b9a45568e3d27/html5/thumbnails/48.jpg)
Tatjana Hubel et al.
![Page 49: Introduction to Aerod ynamics for Flight - Brown Universitycs.brown.edu/.../slides_10_14/jchen_aerodynamics.pdf · Introduction to Aerod ynamics for Flight Oct 14 2008 Bro wn Uni](https://reader031.vdocuments.us/reader031/viewer/2022030701/5aec60a87f8b9a45568e3d27/html5/thumbnails/49.jpg)
Conclusion
• Physical conservation principles to gain insights into fluid flow
• Trailing edge vortices play important role
• Reduces lift and increases drag
• Unsteady effects are complicated due to vorticity distributions and added mass acceleration effects.
![Page 50: Introduction to Aerod ynamics for Flight - Brown Universitycs.brown.edu/.../slides_10_14/jchen_aerodynamics.pdf · Introduction to Aerod ynamics for Flight Oct 14 2008 Bro wn Uni](https://reader031.vdocuments.us/reader031/viewer/2022030701/5aec60a87f8b9a45568e3d27/html5/thumbnails/50.jpg)
Acknowledgment
• David Willis (U Ma. Lowell)• for his slides from last year and many
pretty pictures
• Tatjana Hubel (Brown)• for her suggestions on this presentation
![Page 51: Introduction to Aerod ynamics for Flight - Brown Universitycs.brown.edu/.../slides_10_14/jchen_aerodynamics.pdf · Introduction to Aerod ynamics for Flight Oct 14 2008 Bro wn Uni](https://reader031.vdocuments.us/reader031/viewer/2022030701/5aec60a87f8b9a45568e3d27/html5/thumbnails/51.jpg)
Love in Looking and Comprehension is the Nature’s Most Beautiful Gift.
- Albert Einstein