The Basics of Aerodynamics

Aerodynamics is a field of physics that studies the motion of objects moving through air. Aerodynamics is crucial in understanding how birds fly, designing aircraft, and even optimizing car efficiency. This article aims to explore the fundamentals of the vast topic that is aerodynamics.

The Four Forces of Flight

One of the most basic concepts in aerodynamics is the four forces of flight: lift, drag, thrust, and weight.

1. Lift: Lift is the upward force that opposes the weight of an object in flight. It is crucial for keeping an aircraft airborne. Understanding lift is essential, because it allows engineers to design wings and airfoils that generate sufficient lift to support the weight of the aircraft. By adjusting the shape, size, and angle of attack of wings, engineers can optimize lift production, leading to efficient and stable flight.
   

2. Drag: Drag is the resistance that opposes the forward motion of an object through the air. It is an important force to consider because it affects an aircraft's speed, fuel consumption, and overall efficiency. By minimizing drag, engineers can design streamlined aircraft shapes, reduce fuel consumption, and increase range. Different drag reduction techniques can greatly enhance aircraft performance and fuel economy.
   

3. Thrust: Thrust is the force that propels an object forward, opposing drag. It is generated by engines, such as jet turbines or propellers, and is essential for achieving and maintaining controlled flight. Understanding thrust is crucial for engine design and performance evaluation. It allows engineers to determine the power and efficiency requirements of engines and ensure sufficient thrust is available for flight.
   

4. Weight: Weight is the force exerted by gravity on an object. It acts vertically downward and must be balanced by an equal and opposite force of lift during flight. An understanding of weight is crucial for determining the structural integrity and load-bearing capabilities of an aircraft. Engineers need to consider weight distribution, center of gravity, and overall weight management to ensure that an aircraft remains stable, controllable, and safe throughout its flights.

Types of Flow

The flow of a fluid (like air) can be classified into various types based on factors such as pressure, density, velocity, and temperature. 

Incompressible flow	Flow maintains a constant fluid density
Compressible flow	Flow experiences significant density change
Uniform flow	Flow maintains consistent flow parameters across the flow system
Non-uniform flow	Flow parameters vary across the flow system
Steady flow	Flow maintains a uniform velocity at any point in time
Unsteady flow	Flow velocity experiences variations with time
Viscous flow	Flow is influenced by fluid viscosity
Inviscid flow	Flow is not influenced by fluid viscosity
Laminar flow	Fluid flows in parallel layers (streamlines)
Turbulent flow	Fluid layers (streamlines) mix and velocity fluctuates

Flow can also be categorized based on its value compared to the velocity of sound, also known as Mach 1:

1. Subsonic: velocity of flow is less than the velocity of sound (velocity < Mach 1)

2. Supersonic: velocity of flow is greater than the velocity of sound (velocity > Mach 1)

3. Transonic: velocity of flow is between subsonic and supersonic velocities (Mach 0.8 < velocity < Mach 1.2)

Modern airliners often fly at transonic speeds around Mach 0.85, while rockets traveling to space need to reach supersonic speeds to escape Earth’s gravitational pull.

Bernoulli's Principle

Bernoulli's Principle is a fundamental concept in aerodynamics. It states that as the speed of a fluid increases, its pressure decreases. This principle explains how an airfoil generates lift. The curved shape of the wing causes the air to travel faster above it, resulting in lower pressure, while the air below the wing moves more slowly, creating higher pressure. The pressure difference generates lift, allowing an aircraft to stay airborne.

Bernoulli’s Equation is as follows:

Where:

P is pressure;

p is the fluid density;

v is the fluid flow velocity;

g is acceleration due to gravity;

h is the elevation.

The equation states that static pressure (P), dynamic pressure (12v2), and hydrostatic pressure (gh) of the fluid remains constant along a streamline, or layer of fluid. The equation is one of the fundamental concepts of aerodynamics and allows engineers to design and optimize airfoil designs in order to maximize efficiency.

Conclusion

In conclusion, understanding the basics of aerodynamics is essential for designing efficient aircraft and optimizing vehicle performance. The four forces of flight—lift, drag, thrust, and weight—govern aircraft motion, while Bernoulli's principle explains lift generation. Categorizing flow types based on factors like pressure, density, and velocity provides insights into aerodynamic behavior. Mastering these fundamentals enables engineers to create stable and efficient aircraft, ultimately advancing our understanding of flight dynamics.

Works Cited

Cadence CFD Solutions (2023). What Are the Fundamentals of Aerodynamics? [online] Cadence Design Systems. Available at: https://resources.system-analysis.cadence.com/blog/msa2022-what-are-the-fundamentals-of-aerodynamics.

Hall, N. (2022). Four Forces on an Airplane. [online] NASA Glenn Research Center. Available at: https://www1.grc.nasa.gov/beginners-guide-to-aeronautics/four-forces-on-an-airplane/.

NASA STEM Team (2017). What Is Aerodynamics? [online] NASA. Available at: https://www.nasa.gov/learning-resources/for-kids-and-students/what-is-aerodynamics-grades-5-8/.

Science Facts (2021). Bernoulli’s Principle & Equation. [online] Science Facts. Available at: https://www.sciencefacts.net/bernoullis-principle-and-equation.html.