Problem 2.92 - than along the bottom. In the absence of...

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Problem 2.92 [Difficulty: 4] Open-Ended Problem Statement: How does an airplane wing develop lift? Discussion: The sketch shows the cross-section of a typical airplane wing. The airfoil section is rounded at the front, curved across the top, reaches maximum thickness about a third of the way back, and then tapers slowly to a fine trailing edge. The bottom of the airfoil section is relatively flat. (The discussion below also applies to a symmetric airfoil at an angle of incidence that produces lift.) It is both a popular expectation and an experimental fact that air flows more rapidly over the curved top surface of the airfoil section than along the relatively flat bottom. In the NCFMF video Flow Visualization , timelines placed in front of the airfoil indicate that fluid flows more rapidly along the top of the section
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Unformatted text preview: than along the bottom. In the absence of viscous effects (this is a valid assumption outside the boundary layers on the airfoil) pressure falls when flow speed increases. Thus the pressures on the top surface of the airfoil where flow speed is higher are lower than the pressures on the bottom surface where flow speed does not increase. (Actual pressure profiles measured for a lifting section are shown in the NCFMF video Boundary Layer Control .) The unbalanced pressures on the top and bottom surfaces of the airfoil section create a net force that tends to develop lift on the profile. NACA 2412 Wing Section...
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This note was uploaded on 10/19/2011 for the course EGN 3353C taught by Professor Lear during the Fall '07 term at University of Florida.

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