Unformatted text preview: Drag By: Ryan Cannon, Clint Johnson, and Reuben Smith What is Drag? Drag- is the term used to denote resistance to airflow. It is an aerodynamic force on a body that acts parallel and opposite to the relative wind. Types of Drag Parasite Drag Is caused by any aircraft surface which deflects or interferes with the smooth airflow around the plane. Induced Drag Is generated by the airflow circulated around the wing as it creates lift. Types of Parasite Drag Pressure Drag Skin Friction Drag Interference Drag Cooling Drag Profile Drag Pressure Drag Results from difference in pressure between the fore and aft sides of a wing. Pressure against the upwind face is greater than the wake formed behind the downwind face creating drag. Skin Friction Drag Also known as viscous drag, results from the frictional effect as it flows over a surface Amount of drag depends on the viscosity or (Stickiness) of the fluid (Air) Airfoils exhibit both skin friction and pressure drag, and the drag resulting on such a body is given the term parasite drag. Boundary Layers The area between the surface and the point where the velocity reaches that of the free air stream. The boundary layer at the front of the object is usually laminar (smooth) and relatively thin, but becomes turbulent and thicker towards the rear. The boundary layer is the mechanism by which skin friction drag is created and the extent of skin friction drag depends on shape and thickness of the boundary layer. The area where the boundary layer changes from laminar to turbulent flow is called the transition layer. Interference Drag Arises due to the juncture of two different bodies Whenever two surfaces meet at a sharp angle on an airplane, the air flow has a tendency to form a vortex In order to decrease interference drag engineers create fillets in order to decrease the sharp angles Cooling Drag Is associated with engine cooling Practically all light airplanes are air cooled and require continuous flow of air over the cylinders and other engine parts to dissipate excess heat. This intern creates a considerable amount of drag from pressure and frictional effects. Profile Drag It is simply the wings parasite drag The parasite drag on a wing is dependent on its airfoil, or profile shape, and hence the term profile drag. Induced Drag Induce Drag results from wingtip vortices, and will be around as long as we have wingtips. Unlike parasitic drag, induced drag is inversely proportional to the square of the airspeed Several factors that tend to increase drag are 1.High weight 2.Less efficient wing design 3.high altitude 4.low velocity 5.low wing span Ground Effect
Ground effect results from the reduction of wingtip vortices as they come in contact with the ground. This reduction of induced drag ultimately allows the plane to fly at airspeeds lower than normal. The reduction of wingtip vortices can amount to as much as 50% decrease of induce drag Contrary to popular belief ground effect has nothing to do with (a cushion of air) References Smith, H.C., (1992) The Illustrated Guide to Aerodynamics (2nd Ed.). New York: TAB Boo Federal Aviation Administration, (2003). Pilot's Handbook of Aeronautical (FAAH808325). Oklahoma City: U.S. Department of Transportation www.wikipedia.org www.aopa.org Knowled ...
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- Spring '08
- Aerodynamics, skin friction drag, Airfoils, Reuben Smith, Drag Interference Drag