BIOD43H3 Lecture Notes - Lecture 12: Wing Loading, Airfoil
BIOD43 Lecture 12 Notes: Movement in fluid (water) III
Recap-
Camber = Degree of curvature of the wing, which acts as an airfoil.
Flat or Low CAMBER Wings?
• To achieve lift we need a pressure gradient, where there is lower air pressure on one side
of the wing than compared to the other. To get pressure gradient the wing must have a
curve.
• Air takes longer to pass over the top ‘humped’ or cambered surface of the outstretched
wing, resulting in lower air pressure above the wing.
• The difference in pressure results in a force acting upwards, which is lift
• As air flows faster its weight must become less. This means that air rushing over the
camber or curvature of the top surface of the wing generates a low pressure area,
resulting in lift.
• Hovering fliers have wings with LITTLE Camber.
Drag and Lift
Drag is the force that acts in the opposite direction of motion.
Drag works parallel to incident air flow
Drag; D = Cd ρSv2/2
Lift is the force that acts at a right angle to the direction of motion through the air.
Lift is created by the differences in air pressure
Lift works perpendicular to air flow
Lift; L = ClρSv2/2
Wing Loading (= Weight / Wing Area)
• The ability to generate lift depends on the surface area of the wing
• For bird to remain in the air the vertical component of lift must overcome weight; weight
is the mass of the bird x gravity (9.81 m/s2)
• Larger birds must generate greater Lift to overcome their body mass and gravity
• Gliding birds have lower wing loading
• Faster fliers have higher wing loading
For gliding to occur lift, drag and weight forces must Cancel each other out, because with no
power input there is no net acceleration. When birds glide they move forward and downwards at
constant velocity.
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Document Summary
Biod43 lecture 12 notes: movement in fluid (water) iii. Camber = degree of curvature of the wing, which acts as an airfoil. Flat or low camber wings: to achieve lift we need a pressure gradient, where there is lower air pressure on one side of the wing than compared to the other. This means that air rushing over the camber or curvature of the top surface of the wing generates a low pressure area, resulting in lift: hovering fliers have wings with little camber. Drag is the force that acts in the opposite direction of motion. Lift is the force that acts at a right angle to the direction of motion through the air. Lift is created by the differences in air pressure. For gliding to occur lift, drag and weight forces must cancel each other out, because with no power input there is no net acceleration. When birds glide they move forward and downwards at constant velocity.
