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Lecture # 3

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Lecture # 3

Airfoil Aerodynamics

- Cl = (Lift force/unit span)/(q c)
- Cd = (Drag force/unit span)/(q c)
- Cm = (Pitching moment/unit span)/(q c2)
where

q is the dynamic pressure, q = 0.5 r V2, and c is the airfoil chord

- What is an airfoil?

- What is an airfoil?
- What aerodynamic characteristics are we interested in knowing?

- What is an airfoil?
- What aerodynamic characteristics are we interested in knowing?
- What are the geometric parameters that describe an airfoil?

- What is an airfoil?
- What aerodynamic characteristics are we interested in knowing?
- What are the geometric parameters that describe an airfoil?
- What are the factors that influence the aerodynamic characteristics?

From NASA Sp-367 by Taly

From NASA Sp-367 by Taly

From Introduction to Flight by Anderson

Drag Bucket

What are some of the geometric factors that influence the aerodynamic performance of an airfoil?

Thickness to chord ratio, t/c

Location of max t/c

Nose radius

Camber

Maximum camber

Location of max camber

- What is the influence of thickness?

- What is the influence of thickness?
- Influence of t/c on lift coefficient
- Clmax increases with increasing t/c up to t/c in the order of 13-15% at t/c > 15% begins to Clmax decrease.

- What is the influence of thickness?
- Influence of t/c on lift coefficient
- Clmax increases with increasing t/c up to t/c in the order of 13-15% at t/c > 15% begins to Clmax decrease.

- Influence of t/c on drag coefficient
- Cdmin increases with increasing t/c

- What is the major effect of the leading edge radius on airfoil performance?

- What is the major effect of the leading edge radius on airfoil performance?
- Effects airfoil stall characteristics
- Small leading edge radius has a sharp stall break
- Large leading edge radius has a gentle stall break

- Effects airfoil stall characteristics

- What is the influence of camber on the aerodynamic characteristics?

- What is the influence of camber on the aerodynamic characteristics?
- Increasing camber increases zero lift angle of attack.

- What is the influence of camber on the aerodynamic characteristics?
- Increasing camber increases zero lift angle of attack.
- Camber can be used to get a low drag coefficient at the designed lift coefficient.

- What is the influence of camber on the aerodynamic characteristics?
- Increasing camber increases zero lift angle of attack.
- Camber can be used to get a low drag coefficient at the designed lift coefficient.
- The maximum lift coefficient of moderately cambered airfoil sections increase with increasing camber.

- What is the influence of camber on the aerodynamic characteristics?
- Increasing camber increases zero lift angle of attack.
- Camber can be used to get a low drag coefficient at the designed lift coefficient.
- The maximum lift coefficient of moderately cambered airfoil sections increase with increasing camber.
- Camber can effect the stall behavior.
- For airfoil sections that have the maximum camber far forward the stall is very abrupt

- Aerodynamic coefficients are a function of
- Geometry
- Angle of attack
- Reynolds number
- Mach Number