Dane Johannessen. Aerodynamics What are the forces? How do these forces affect flight? What...

AERODYNAMICSDane Johannessen

Overview

Aerodynamics

What are the forces?

How do these forces affect flight?

What factors affect these forces?

What is Aerodynamics?

The study of forces acting on an object in motion as it passes through air.

Laws of Motion

Objects in motion stay in motion

Force is the change in momentum with respect to time For constant mass

For every action there is an equal and opposite reaction

What are the forces?

Lift

Drag

Weight

Thrust

The vertical forces pushing up on a body during flight.

General Equation: L = Lift Force ρ = density v = velociy A = area Cl = Lift coefficient that is usually determined

experimentally

Lift

Lift in Air Foils

Based on pressure differences (Bernoulli’s Principle) Top

Higher velocity and decreased pressure Bottom

Lower velocity increased pressure http://www.youtube.com/watch?v=zV06PgxarW0

Factors Affecting Lift

Factors Shape of object

Higher curve = greater lift Size of the object

L = constant x A Velocity of the object

L = constant x v² Properties of the air

L = constant x ρ Angle of attack

Increased angle = increased lift

Demonstration

For more information on paper airplanes Go here http://www.paperairplaneshq.com/

Drag

Drag is the force that acts in the same direction as airflow

General Equation: Fd = Drag Force ρ = density v = velocity A = area Cd = Drag Coefficient that is usually

determined experimentally

How Shape Affects Drag

Different shapes of the same frontal area lead to different drag coefficients:

Lift to Drag Ratio

General Equation:

Weight

Weight is the force on an object due to gravity Based on mass and gravitational acceleration General Equation:

W = Weight Force m = mass g = gravity

Thrust

Thrust is the force that propels an object through air

General Equation: F = thrust force t = time m = mass v = velocity ṁ = mass flow rate

ṁ = ρvA

Thrust

Producers of thrust Propellers Fans in jet engines Hot gases from rocket engines

Main thing to take away Thrust must be greater than weight

Thrust to Weight Ratio

General Equation:

If F/W is high High acceleration High Climb rate

If F/W > 1.0 Acceleration can be vertical

Summary

Aerodynamics 4 Forces on a plane

Lift Dependent on shape, size, velocity, air, angle

Drag Dependent on shape

Weight Thrust

Lift > Drag Thrust > Weight

Sources

Helpful Websites

http://www.nasa.gov/audience/forstudents/k-4/stories/what-is-aerodynamics-k4.html

http://www.grc.nasa.gov/WWW/k-12/airplane/topics.htm

http://www.paperairplaneshq.com/

Questions?