Aerodynamics - Part 1

Aerodynamics - Part 1

• This presentation covers the fundamental concepts of aerodynamics, focusing on airflow around bodies, airfoil characteristics, and the relationship between forces in flight.

Introduction

• The learning objectives for this section in relation to airflow surrounding a body involves understanding: boundary layer, free-stream flow, laminar and turbulent flow, relative airflow, upwash and downwash, vortices and stagnation.

• Other learning objectives include different forces acting on a body, the interaction of forces with related terms like camber, chord, mean aerodynamic chord (MAC), profile, induced drag, form drag, centre of pressure, angle of incidence, wash in/wash out, and fineness ratio, wing shape and aspect ratio.

• Learning also includes the relationship between weight, thrust, and aerodynamic resultant, lift and drag generation, associated terms (angle of attack, lift coefficient, drag coefficient, polar curve, and stall curve).

• Aerofoil contamination (ice, snow, and frost) and the relationships between ground speed (GS), true air speed (TAS), and indicated air speed (IAS) are also covered.

Sketch of wing and airfoil

• Key elements of a wing's cross-sectional shape (airfoil) are illustrated, including leading edge, trailing edge, and the wing itself.
• A diagram of the wing structure, highlighting the rib, is also provided.

Sketch of wing and airfoil

• Spars, ribs, upper surface, leading edge, chord line, camber, and lower surface are explained.
• A specific wing design, known as the Flyer-I (Wright brothers), is featured.

Generation of Force

• Resultant lift is the net force, perpendicular to the relative airflow.
• Resultant drag is the net force, parallel to the relative airflow.

How do Wings generate LIFT?

• The presentation introduces the topic on how wings generate lift.

Free Stream Flow

• Free stream flow is the clean, undisturbed airflow around an object.
• Streamlines show the direction of the undisturbed airflow.
• Resistance is directly related to the amount of free stream air.
• The wake arises when the airflow separates from the object.

Friction

• Friction arises between airflow and a body, creating a boundary layer.
• The boundary layer is a layer of retarded air immediately adjacent to the surfaces of the body, characterized by differing airflow velocities.
• Drag depends on the nature and thickness of the flow in this layer.

Boundary Layer

• The boundary layer is a layer of air close to the body, slowed by friction due to the air's viscosity.
• Air velocity varies from zero at the surface to the free stream velocity at the boundary layer's edge.
• The boundary layer thickness is relative to velocity.

Laminar Flow

• Laminar flow is an orderly motion of air particles sliding past each other.
• Laminar flow usually occurs over a body's leading edge.
• Transition from laminar to turbulent flow occurs at the transition point (over the wing).

Turbulent Flow

• Turbulent flow is characterized by rotating air particles, exhibiting a greater drag.
• Separation happens as the speed increases.

Laminar and Turbulent Flow

• Presentation provides an image showcasing the difference between Laminar and Turbulent airflow.

Transition Point

• The transition point is where laminar flow changes to turbulent flow on a wing as speed increases.
• Airflow, pressure, and related forces change as the point transitions.

Stagnation Point

• The stagnation point is where the airflow is brought to rest by the leading edge.
• Flow over and under the wing starts here.

Separation Point

• The separation point is where the boundary layer breaks away from the wing surface, leading to additional drag.

Wake

• The wake is unsteady rotational flow caused by the separation of boundary layers from a wing, creating drag.

Boundary layer separation and stall

• An image showcases boundary layer separation.

Relative Airflow

• Relative airflow is the airflow with respect to the wing (or rotor, etc).
• Relative airflow moves opposite to the flight path.

Coanda Effect

• Viscosity is a resistant quality of fluids from moving.
• The Coanda effect refers to the tendency of a fluid to follow a curved surface.

Upwash

• Upwash occurs as the airflow curves upwards towards the top surface of a wing.
• Associated with lift.

Downwash

• Downwash, a downward deflection of airflow, has an opposite pushing-upward effect on the aircraft.
• Upwash and downwash are inherent to lifting surfaces.

Ground Effect

• Presentation introduces ground effect.

Vortices

• Vortices form when airflow above and below the wing meet at the trailing edge creating rotations (clockwise/counter-clockwise).
• Wingtip vortices form at each wing tip.
• Wing tip vortices are the major component of wake turbulence.

Understanding Vortices

• Introduction on the impact of vortices.

A380 Vortices and Condensation Effect

• Image displaying an aircraft and its vortices.
• Link to video showing the effect.

Jet Engine Vortices

• Image of aircraft engines and vortices.

Vortices - Winglets

• Image of aircraft with winglets.

Airfoil Nomenclature

• Defining elements of chord line, camber, maximum thickness location and other features of airfoil design.

Airfoil Nomenclature

• Details of maximum thickness, mean camber line, and maximum camber.

Chord Line

• The chord line is an imaginary straight line between the wing's leading edge center and trailing edge center.

Camber

• Camber describes the curvature of the airfoil.
• The amount of camber is defined by a ratio.
• Upper and lower camber can be identical.

Mean Camber

• Mean camber is equidistant from the upper and lower wing surface.

Fineness Ratio

• Fineness ratio is a measure of an airfoil's thickness.
• It describes thickness relative to the length/span.

Types of Airfoils

• Symmetrical and cambered airfoils are highlighted.
• The classifications are visually presented.

Types of Airfoils

• Presenting further classifications/examples of airfoils (symmetric, positive camber, negative camber).

Negative Cambered Airfoil

• Example of a negative cambered airfoil.

Aerofoil Shapes

• There are various classes of airfoils, distinguished by their lift, general purpose, and speed aspects.

High Lift Aerofoil

• Thickness/chord ratio and leading edge characteristics are key features of high-lift airfoils.
• Factors like camber and centre of pressure are highlighted.

Aerofoil Shapes

• General purpose airfoils are a type of airfoil that are less thick and less cambered.

High Speed Aerofoil Shape

• Low t/c ratio, no camber, and a sharp leading edge define high speed airfoils.

Aspect Ratio

• Aspect ratio describes the wing span relative to its average chord.
• High aspect ratios means less drag, but less maneuverability.

Aspect Ratio and Maximum Lift Coefficient

• Maximum lift coefficient and aspect ratio have a relationship.
• The maximum lift decreases as aspect ratios are reduced.

Aspect Ratio and Induced Drag

• High aspect ratios reduce induced drag
• Induced drag is high with low aspect ratios.

Wing planform

• Various wing shapes (elliptical, rectangular, moderate, high taper, and sweptback) are presented.
• Efficiency, building costs, and speed are linked to their respective wing shapes.

Mean Aerodynamic Chord (MAC)

• The MAC is a mean chord value calculated by combining root chord, tip chord, and dividing by 2.

Angle of Incidence

• Angle of incidence is the acute angle between the wing chord and the longitudinal axis of the aircraft.

Angle of Attack (AoA)

• The angle of attack is the angle between aerofoil chord and relative airflow, crucial for lift generation.
• Lift increases with increasing angle of attack, reaching a peak and then rapidly decreasing.

Center of Pressure

• Center of pressure (Cp) position changes with varying angles of attack.

Pressure Distribution

• Pressure distribution over an airfoil changes with angle of attack.

Lift Coefficient

• Lift coefficients reflect the wing's efficiency in generating lift under different conditions.
• Lift coefficient increases with increasing angle of attack.

Lift Coefficient

• Lift coefficient calculation formula and factors are presented.

Resultant Lift

• Lift is a resultant force, perpendicular to relative airflow.
• Drag is a resultant force, parallel to relative airflow.

Drag

• Drag is resistance of a body moving through a fluid.
• Drag classification (parasite, induced).

Drag

• Types of drag, such as parasite drag (skin friction, form, interference) and induced drag.

Understanding Drag

• Introduction to the concept of understanding drag.

Parasite Drag

• Parasite drag components (skin friction, form, and interference).
• How this drag varies with airspeed.

Form Drag

• Form drag is presented in terms of structures protruding into relative airflow and the size/shape's impact.

Skin Friction

• Skin friction drag, from surface roughness, and related airflow.

Interference Drag

• Interference drag due to interactions between air currents on aircraft.

Induced Drag

• Induced drag, related to lift and angle of attack.
• Relationship between induced drag and airspeed.

The Polar Curve

• Lift-to-drag ratio increases with angle of attack up to a certain point where it rapidly decreases.
• Stall angle.

Straight and level

• Maintaining straight and level flight depends on lift (equals weight) and thrust (equals drag).
• The concept of adjusting thrust for climb, descent

Aerodynamics Forces

• Aircraft flight depends on the relationship between lift, weight, thrust, and drag.

Aerodynamics Forces

• Definitions for lift, weight, thrust and drag in relation to flight.

Forces in Straight and Level flight

• Balancing forces for straight and level flight (lift equals weight, thrust equals drag). - How to manipulate forces to climb or descend.

Drag Curves

• Drag curves indicate drag's variation with speed.
• Induced drag is high at low speeds, then parasite drag dominates at higher speeds.

Stall

• Stalling occurs when airflow separates from the wing.
• Stalling leads to a rapid decrease in lift.
• Stall angle of attack.

Stall

• Stall is an aerodynamic condition in which airflow separates, decreasing lift.

Stall

• Stalling occurs at a critical angle of attack and can happen at any airspeed, flight attitude or weight factors.

To be continued in Part 2...

• This section signifies an ongoing topic for further study.

This quiz covers fundamental concepts of aerodynamics, including airflow around bodies, airfoil characteristics, and the forces related to flight. You'll explore critical terms such as boundary layer, laminar flow, and induced drag. Test your understanding of how these concepts interact in the context of flight dynamics.