Aerodynamics of Wings Quiz

Aerodynamics - Part 1

• This presentation is the first part of a broader aerodynamics topic.
• The presentation covers various aspects of airflow around bodies, related to aerodynamics of aircraft.
• The learners will be able to describe airflow around a body in relation to specific terms.
• These terms include boundary layer, free stream flow, laminar and turbulent flow, relative airflow, upwash and downwash, and vortices and stagnation.
• The learners will also be able describe aspects of various terms and list their interaction with related forces. These include camber, chord, mean aerodynamic chord (MAC), profile (parasite drag), induced drag, form drag, centre of pressure, angle of attack, angle of incidence, wash in/wash out, and fineness ratio.
• The learners will be able to describe the relationship between weight, thrust, and aerodynamic resultant.
• The learner will understand how lift and drag are generated and define associated terms. these include lift coefficient, drag coefficient, polar curve, and stall.
• The presentation also covers aerofoil contamination including ice, snow, and frost.
• Relationships between ground speed (GS), true air speed (TAS), and indicated air speed (IAS) are discussed.
• The shape of wing and its airfoil are examined and the diagrams show leading/trailing edge, and the plane perpendicular to wing.
• A diagram shows a wing with ribs.
• A diagram details a simplified representation of a wing with relevant components including spars, camber, chord line, upper/lower surface.
• The resultant lift produced by an aerofoil is the net force produced perpendicular to the relative airflow. The resultant drag incurred by an aerofoil is the net force produced parallel to the relative airflow.
• The properties of free stream flow, describing the clean flow, distant enough from any object not affected and unaffected by any direction changes. The direction is indicated by streamlines and the least resistance shape is streamline. Resistance is directly related to airflow.
• The presentation covers the topic of friction, in which contact between the airflow and the body give rise to a layer of retarded air in immediate contact with the surface. This is the boundary layer and its nature and thickness determine the amount of drag produced.
• The boundary layer is the layers of air close to the surface of the body.
• The air velocity in the boundary layer changes, ranging from velocity zero at the surface to the velocity of the free stream at the outer edge of the boundary layer.
• The factors that cause boundary layer are: air viscosity, air sticking to the wing surface and succeeding layers of air. The thickness varies and depends on the type of flow, typically between 1.5mm and 6.0mm.
• The concept of laminar flow in that the flow is steady and uniform, also the tendency for the boundary layer to start by being laminar. Turbulent flow is not steady or uniform. The transition point in laminar flow to turbulent flow is described.
• Aerodynamic characteristics of turbulent flow are described, noting that the layer becomes more turbulent as the speed increases, and rotating particles moving backward and directions (clock/anti-clockwise), like ball bearings.
• The transition point is the point at which the boundary layer changes from laminar to turbulent flow. The transition point moves forward as speed increases, meaning more surface becomes turbulent. This increases drag.
• The stagnation point is the point at which the airflow is brought to rest by the leading edge. It is where the boundary layer originates.
• Separation points are the points on the wing where the boundary layers break away from the surface.
• The wake is a region of unsteady rotational flow created by separated boundary layers. It is visible behind the trailing edge.
• The wake for a 7ft chord is roughly 4–5 inches deep.
• Boundary layer separation and stall: This refers to separation of airflow from surfaces of a wing.
• Relative airflow is the direction of the airflow with respect to the wing.
• The Coanda effect is a fluid dynamics phenomenon where a jet of fluid is deflected toward a nearby surface, staying attached to the surface. It follows curved surfaces.
• Upwash is an inherent part of any upward-lifting surface, as air flows towards low-pressure areas.
• Downwash deflects downward and has upward action on the aeroplane.
• Ground effect is not addressed in the slides.
• Vortices form when airflow from the top of a wing is met by airflow from the bottom surface, at the trailing edge. These are called wingtip vortices, which are caused by the high-pressure air moving under the wing and lower pressure air above the wing.
• Wingtip vortices are often the main constituent of wake turbulence, which can be predictable. Jet engine vortices are also examined.
• Airfoil nomenclature: Concepts on terms such as chord line, camber, mean camber line, maximum thickness and other pertinent details are presented.
• Types of airfoils discussed in relation to their thickness-chord ratio, including high lift, general purpose and high-speed airfoils.
• Aspect ratio - dividing the square of the wing span by its area or the ratio of the wingspan to the average chord length. A high aspect ratio causes reduced drag and low manoeuvrability.
• Aspect ratio and maximum lift coefficient graphs.
• Aspect ratio and induced drag: Relationship between the aspect ratio and induced drag, whereby higher aspect ratio reduces induced drag.
• Wing planforms: various types discussed, including elliptical, rectangular, moderate taper, high taper and sweptback wings, and their characteristics.
• Mean aerodynamic chord (MAC): a way to define the MAC is to add root chord to tip chord and divide by two.
• Angle of incidence - the angle between the wing chord and longitudinal aircraft axis. This is fixed during manufacture.
• Angle of attack (AoA): The angle of inclination between the aerofoil chord and the relative airflow, significantly affecting lift values. It shows a steady increase with AoA until the stall region, when lift severely decreases.
• Centre of pressure (CP) is affected by the angle of attack with forward movement towards 25% chord and high speed (near 50% chord).
• Pressure distribution as a result of airflow over a wing with increasing AoA, showing the effect of pressure changes around the wing, for a 4°,12°, and 15° angle of attack.
• Lift coefficient: The lift coefficient (CL) is a measure of the lifting effectiveness of a wing under given conditions. The value will vary with angle of attack but not with velocity - only velocity determines lift force.
• Resultant lift- the net force produced, perpendicular to the relative airflow. Resultant drag-the net force ,produced parallel to the relative airflow.
• Drag: resistance of a body moving through a fluid. Various types, including parasite drag, form drag, skin friction, and interference drag, are examined.
• Factors influencing drag, including wing camber, airspeed, and angle of attack.
• Induced drag is the drag resulting from the production of lift. It is directly related to the angle of attack and airspeed, origin being wingtip vortices.
• The polar curve is discussed, which is a graph showing lift/drag ratio against AoA. Showing maximum lift/drag ratio and stall angle.
• Straight and level flight describes how lift and thrust are related to weight and drag to maintain straight line flight.
• Drag curves: A graph plotted against speed, with parasite drag and induced drag. A minimum is present where Total Drag is minimized.
• Stall: A stall occurs when separated airflow from the wings upper surface. Stall creates a rapid decrease in lift. Stall occurs at the same AoA regardless of speed.
• Stall is also an aerodynamic condition in which the smooth flow of air from the upper surface separates, the flow becomes turbulent, and thus lift decreases while drag increases. The critical angle of attack is approximately 15°.
• A stall graph is presented.
• End of part 1; further content is to be presented.

Test your knowledge on the key concepts related to the aerodynamics of wings. This quiz covers topics like laminar and turbulent flow, boundary layer separation, and the effects ground effect has on lift. Perfect for students and enthusiasts of aerodynamics.