Aerodynamics Concepts Quiz
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Questions and Answers

What does the term $q_{ ext{∞}}$ represent in aerodynamics?

  • Total energy
  • Lift force
  • Static pressure
  • Dynamic pressure (correct)

When calculating true air speed, which factor is NOT included?

  • Indicated air speed
  • Altitude of the aircraft
  • Weight of the aircraft (correct)
  • Density of air

Which ice protection system is mentioned as advanced?

  • Basic Anti-ice System
  • Standard Frost Control System
  • Enhanced Snow Protection System
  • 787 Advanced Ice Protection System (correct)

In aerodynamics, what is the difference between indicated air speed and true air speed primarily based on?

<p>Environmental air density (D)</p> Signup and view all the answers

What effect does icing have on the performance of an aircraft?

<p>May lead to reduced aerodynamic efficiency (B)</p> Signup and view all the answers

What is the lift per unit span for a wing at a 4° angle of attack, given the parameters?

<p>1.7894 × 10−5 N (A)</p> Signup and view all the answers

What is the chord length of the wing used in the given calculations?

<p>1.3 m (B)</p> Signup and view all the answers

At zero angle of attack, what was the drag on the wing model mentioned?

<p>34.7 N (D)</p> Signup and view all the answers

What is the velocity of the flow in the test section as described in the data?

<p>97 m/s (D)</p> Signup and view all the answers

What happens to the angle of attack of the wing to achieve zero lift?

<p>It must be decreased. (C)</p> Signup and view all the answers

What is the unit area considered for the calculations per unit span?

<p>1 m² (B)</p> Signup and view all the answers

From the performance of NACA 2412 airfoil, what can be inferred about its lift performance at specified conditions?

<p>It provides reliable lift per unit span. (A)</p> Signup and view all the answers

What defines a drag coefficient in the context of the example provided?

<p>The drag force divided by dynamic pressure and wing area. (C)</p> Signup and view all the answers

What does the inviscid flow airfoil theory primarily predict?

<p>Lift slope (B)</p> Signup and view all the answers

Which aspect does the inviscid flow airfoil theory NOT account for?

<p>Airfoil drag (A)</p> Signup and view all the answers

What is the relationship of the lift slope with Reynolds number (Re) in inviscid flow theory?

<p>Insensitivity to Re (C)</p> Signup and view all the answers

Which of the following components represents the force parallel to the freestream in the aerodynamic force?

<p>Drag (C)</p> Signup and view all the answers

What does the axial force represent in aerodynamics?

<p>Component of resultant aerodynamic force parallel to the chord line (D)</p> Signup and view all the answers

How is the resultant aerodynamic force calculated for an airfoil?

<p>By integrating pressure and shear stress distributions (B)</p> Signup and view all the answers

Given a normal force of 100 N and an axial force of 50 N, what is the lift when the angle of attack is 10 degrees?

<p>Unknown without additional information (B)</p> Signup and view all the answers

What does the angle of attack (α) measure with respect to the airfoil?

<p>Angle between chord line and freestream velocity (A)</p> Signup and view all the answers

What is the formula for calculating the Reynolds number (Re)?

<p>$Re = \frac{\rho_{\infty} V_{\infty} c}{\mu_{\infty}}$ (D)</p> Signup and view all the answers

What parameters are essential for determining the actual magnitude of Lift (L), Drag (D), and Moment (M)?

<p>All of the above (D)</p> Signup and view all the answers

In dimensional analysis, what is the dimension of Force?

<p>M(L/T²) (D)</p> Signup and view all the answers

What unit is used for measuring viscosity in the SI system?

<p>Kg/m·s (B)</p> Signup and view all the answers

Given a chord length of 1.3 m and a flow velocity of 50 m/s, which factor does NOT impact the Reynolds number for this scenario?

<p>Angle of attack (A)</p> Signup and view all the answers

What is the relationship of dimensional analysis in aerodynamic studies?

<p>It provides a method to analyze the effects of parameters on performance. (D)</p> Signup and view all the answers

In British units, how is density expressed?

<p>Slug/ft³ (D)</p> Signup and view all the answers

Which of the following is NOT a parameter for dimensional analysis in aerodynamics?

<p>Mass of the wing (A)</p> Signup and view all the answers

Flashcards

Inviscid Flow Airfoil Theory

The theory predicts the lift slope (a0) and zero-lift angle of attack (a0). This theory simplifies the flow by assuming the fluid is inviscid and incompressible.

Limitations of Inviscid Flow Theory

The maximum lift coefficient (CLmax) and airfoil drag cannot be predicted by this theory.

Lift Slope (a0)

The lift slope of an airfoil, denoted as a0, is a measure of how much lift is produced for a given change in angle of attack.

Zero-Lift Angle of Attack (a0)

The zero-lift angle of attack (a0) is the angle of attack at which the airfoil produces no lift.

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Resultant Aerodynamic Force

The resultant aerodynamic force (R) acting on an airfoil is a combination of the normal force (N) and axial force (A).

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Normal Force (N)

The normal force (N) is the component of the resultant aerodynamic force (R) that is perpendicular to the chord line.

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Axial Force (A)

The axial force (A) is the component of the resultant aerodynamic force (R) that is parallel to the chord line.

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Angle of Attack (a)

The angle of attack (a) is the angle between the chord line and the freestream velocity vector.

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Lift Force

The force acting perpendicular to the chord line of an airfoil, generated by the pressure difference between the upper and lower surfaces.

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Drag Force

The force acting parallel to the chord line of an airfoil, caused by friction and pressure drag.

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Lift Coefficient (CL)

A dimensionless coefficient representing the ratio of lift force to dynamic pressure and wing area.

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Drag Coefficient (CD)

A dimensionless coefficient representing the ratio of drag force to dynamic pressure and wing area.

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Lift-to-Drag Ratio (L/D)

The ratio of lift force to drag force.

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Wing Area (S)

The area of the wing surface that interacts with the airflow.

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Chord Length (c)

The distance between the leading edge and trailing edge of an airfoil.

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Reynolds Number (Re)

A dimensionless quantity that represents the ratio of inertial forces to viscous forces in a fluid flow. It is used to predict the flow patterns around an object, such as an airplane wing.

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Chord (c)

The length of the wing from the leading edge to the trailing edge. It is used in calculating aerodynamic forces.

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Diameter (d)

The distance across a circular object, such as a propeller or a sphere. It's also used in calculating aerodynamic forces.

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Length (l)

The length of an object, such as the fuselage of an airplane. It's also used in calculating aerodynamic forces.

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Dimensional Analysis

The process of using physical dimensions to analyze the relationships between different variables in a problem. It helps us understand how these variables affect each other.

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Lift (L)

The upward force acting on an airplane wing that allows it to fly. It's directly related to the wing's shape, size, and the air flow around it.

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Drag (D)

The force that acts in opposition to the motion of the airplane. It's caused by the friction between the air and the airplane's surfaces.

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Dynamic Pressure

The pressure acting on a surface due to air flow, calculated using density of air, velocity of air, and a constant.

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True Air Speed (TAS)

The speed of an aircraft relative to the surrounding air, unaffected by wind.

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Ground Speed

The speed of an aircraft relative to the ground, taking wind into account.

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Indicated Air Speed (IAS)

Speed measured by an aircraft's instruments, used for measuring flight conditions.

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Airspeed Correction

The difference between true airspeed and indicated airspeed, primarily due to air density.

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Study Notes

Aerodynamics - Part 2

  • Aerodynamics deals primarily with airfoil theory for inviscid, incompressible flow.
  • Inviscid flow airfoil theory cannot predict maximum lift coefficient (Clmax) or airfoil drag.
  • Lift slope (α₀) and zero-lift angle of attack (CL=0) can be predicted.
  • Clmax depends on Reynolds number (Re).
  • Lift slope is not influenced by Re except at large α.
  • The Cm is insensitive to Re except at large α.
  • Cm is approximately at c/4 point.
  • Clmax is approximately 1.7.
  • Zero-lift angle is approximately -2.1°.
  • Stall angle is approximately 16°.
  • The resultant aerodynamic force (R) is the integration of pressure (p) and shear stress (τ) distribution over the airfoil.
  • Chord (c) is the linear distance from leading edge (LE) to trailing edge (TE) of the airfoil.
  • Freestream velocity (V∞) is the flow velocity far ahead of the airfoil.

Airfoil Characteristics

  • This chapter deals primarily with airfoil theory for an inviscid, incompressible flow.
  • This theory can predict the lift slope (a₀) and zero-lift angle of attack (CL=0).
  • This theory cannot predict maximum lift coefficient (Clmax) and airfoil drag.

NACA 2412 Airfoil

  • The lift slope is not influenced by Reynolds number (Re) except at high angles of attack.
  • The maximum lift coefficient (Clmax) is dependent on Re.
  • Experimental data for different Reynolds numbers (Re) are provided for Clmax.
  • The moment coefficient (Cm_c/4) is approximately at c/4 point.

Experimental Results

  • The maximum lift coefficient (Clmax) is governed by viscous effects.
  • Clmax depends on Re.

The Resultant Aerodynamic Force

  • The total force acting on an airfoil is the integration of pressure and shear stress distribution.
  • The linear distance from leading edge to trailing edge is the chord (c).
  • The flow velocity far ahead of the body is freestream velocity (V∞).

Normal Force & Axial Force

  • Normal force (N) is the component of the resultant force (R) perpendicular to the chord line.
  • Axial force (A) is the component of the resultant force (R) parallel to the chord line.

Angle of Attack

  • Angle of attack (α) is the angle between the chord line (c) and the freestream velocity (V∞).
  • Angle of attack is also the angle between lift (L) and the resultant force(R).
  • Angle of attack is also the angle between drag (D) and the resultant force (R).

Lift & Drag

  • Lift (L) is the component of the resultant force (R) perpendicular to the freestream (V∞).
  • Drag (D) is the component of the resultant force (R) parallel to the freestream (V∞).
  • Lift relationship: L = N cos α - A sin α
  • Drag relationship: D = N sin α + A cos α

Reynolds Number (Re)

  • Re represents the ratio of inertial forces to viscous forces.
  • Re = ρ∞V∞c/μ
  • Where:
    • ρ∞ is freestream air density.
    • V∞ is freestream velocity.
    • c is the chord.
    • μ is the dynamic viscosity.

Dimensional Analysis

  • The magnitude of lift (L), drag (D), and moment (M) depends on various parameters like velocity, density, angle of attack.

Definitions

  • A knot is a nautical mile per hour.

Aircraft Speeds

  • Indicated airspeed (IAS) is the airspeed measured by an airspeed indicator.
  • Ground speed (GS) is the speed of the aircraft over the ground.
  • True airspeed (TAS) is the speed of the aircraft relative to the air mass.
  • Dynamic pressure is 1/2 * ρ * V^2.
  • Airspeed indicators are calibrated for standard conditions (sea level density)

Icing Effects

  • Icing can increase drag and decrease lift.
  • It can cause destructive vibrations, hamper true instrument readings, unbalance, or freeze control surfaces, cause radio jamming and affect engine performance.
  • Icing increases stalling speed.

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Aerodynamics - Part 2 PDF

Description

Test your understanding of key aerodynamics concepts, including the meanings of various terms and the impact of icing on aircraft performance. This quiz covers topics such as true air speed, indicated air speed differences, and advanced ice protection systems. Challenge yourself and see how well you know the principles of aerodynamics!

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