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Unformatted text preview: MAE 150B  Chap 4 part B Incompressible Flow Over Airfoils Airfoil Characteristics (4.3) Velocity difference leads to pressure difference and that results with a net lift The lift coefficient varies linearly within a range of Separation (stall) leads to a drop of lift Stall is a viscous effect, its occurrence is a function of Re Flying upside down Flying upside down is achieved by having negative for a negative lift. It is harder because stall occurs more easily. Airfoil Characteristics (4.3) Moment at aerodynamic center is independent of within a range of at aerodynamic center Examples 4.1 4.2 and 4.3 (pp. 305307) 4.1: NACA 2412 c=0.64m, standard sea level, V =70m/s L=1254 N/m, find and the drag per unit span 4.2: Calculate moment per unit span 4.3: L/D ratio for =0, 4, 8,12 Kutta Condition For fluid flow around a body with a sharp corner the Kutta condition refers fluid approaches the corner from both directions, meets at the corner, and then flows away from the body. The sharp TE will be either a stagnation point or having same velocity from both surfaces for a cusp TE. At TE, Kutta condition means (TE)=0 Kelvins Circulation Theorem and the Starting Vortex (4.6) Kelvins circulation theorem: In an flow that is inviscid, barotropic [ = ( p 29 ], conservative body forces the circulation around a closed curve moving with the fluid remains constant with time = Dt D Kelvins Circulation Theorem and the Starting Vortex (4.6) Having a loop enclosed the airfoil that is stationary in a still fluid =0 (why?) The starting motion of the airfoil will generate two circulations 3 and 4 . 3 stays with the airfoil and 4 is a trialing vortex Kevins circulation theorem implies 3 + 4 =0 (why?) The starting vortex has a circulation 4 =  3 Theoretical solution for lowspeed flow over airfoil: Outlines Theory Basis Vortex sheet representation (4.4) Kutta condition (4.5) Kevins theorem *4.6) Vortex sheet representation of a thin airfoil (4.7a) Symmetric airfoil results (4.7b) Cambered airfoils (4.8) Aerodynamic center (4.9) Vortex panel method for arbitrary body(4.10) Vortex Sheet of Thin Airfoil (4.7a)...
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This note was uploaded on 10/09/2009 for the course MAE 150B taught by Professor D during the Spring '09 term at UCLA.
 Spring '09
 d

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