Exercise 3: Lift and Airfoils Purpose Using an on-line simplified simulated Wind tunnel, explore the relationships between Coefficient of Lift and Angle of Attack, Airfoil Camber, and Airfoil...

Exercise 3: Lift and Airfoils
Purpose

Using an on-line simplified simulated Wind tunnel, explore the relationships between Coefficient of Lift and Angle of Attack, Airfoil Camber, and Airfoil Thickness and the variables of the Lift Equation.

Scope

Connect on-line to NASA Glen Research Center education website. Feel free to explore the website to further explore aerodynamic concepts. We will use this web site as an on-line Lab. http://www.grc.nasa.gov/WWW/K-12/airplane/foil3u.html. You may have to load the Java plugin to enable the website to work.

Exercise A

Compare three airfoils that have different thickness and camber to see how thickness and camber affect Coefficient of Lift (C_L) vs. Angle of Attack (AOA).
Connect to FoilSim III.
SET UP
Initial Conditions:
Imperial Units
Input:
Change Flight
Speed 100 mph
Altitude 0 ft
Change to Size
Chord-5.0 ft
Span 40.1 ft
Area-200.5 Ft²

Change to Shape
Angle-0 deg
Camber-0 %
Thickness- 12%
Change to Analysis
Stall Model
Select Plot
Cl vs Angle
Data Window-Change Lift to C_L

Set up your own table in Microsoft Word or Excel (AOA vs. C_L) and use Shape to answer the following questions:
(AOA = -10, -5, 0, 5, 10, 14, 16, 18)
Airfoil 1-(0 % Camber/12 % Thickness)
Airfoil 2-(6% Camber/ 12 % Thickness)
Airfoil 3-(6% Camber/ 19.8 % Thickness)

Exercise A Questions

1. What is the relationship between Camber and CLmax?


2. What is relationship between Camber and zero lift (Cl = 0)?


3. What is the relationship between airfoil thickness and CLmax?

Exercise B Questions

Examine how True Airspeed and Altitude affect Lift.
Set up Angle-5 deg
Camber-6 %
Thickness-12%
Chord 5 ft
Span 40.1 ft
Data Window- Lift
Set up Table Flight
Airspeed (0 mph, 40 mph, 80 mph, 120 mph) vs. Lift
@ (0 ft Altitude, 10,000 ft Altitude, 40,000 ft Altitude)

Exercise B Questions

1. What is the relationship between True Airspeed and Lift?


2. What is the relationship between Altitude and Lift?


3. If your gross weight is 1050 lbs. Estimate the true airspeed in M PH to maintain level flight (Lift = Weight) at the given Angle of Attack conditions at sea level, 10,000 ft and 40,000 ft.

Exercise C

This exercise will evaluate an aircraft on a takeoff roll, takeoff and accelerate to flap speed and then accelerate to climb speed. With the given conditions find when wings can support aircraft weight and takeoff can occur on a takeoff roll in (mph) and compare AOA to Lift and Airspeed (0-120 mph) while maintaining level flight accelerating at sea level.

Exercise C Conditions

Aircraft weight: 1600 lbs Wing Area: 200.5 sf
Wing Span: 40.1 ft Chord: 5 ft
Thickness: 12% C
Camber 6% at speeds less than 65 mph(flaps in takeoff position).
Camber 0% at speeds greater than 65 mph (flaps up).
Let’s use AOA for takeoff is 10 deg. Once you get enough lift to equal weight.
Keep Lift = Weight and adjust AOA, Camber, and airspeed.

Exercise C Question

Make a table of Airspeed vs. Lift and AOA. Start at 10 deg AOA.
Then when Aircraft Weight = Lift that will be takeoff.
Then extend the table to greater airspeeds simulating the aircraft accelerating to 120 mph. Keep Lift at ~1600 lbs, but the AOA must change. Raise Flaps (Camber 0%) at 65 mph. Compare Airspeed to AOA in the accelerating aircraft keeping Lift @~1600 lbs.