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Unformatted text preview: Fluids – Lecture 19 Notes 1. Airfoils – Overview Reading: Anderson 4.1–4.3 Airfoils – Overview 3-D wing context The cross-sectional shape of a wing or other streamlined surface is called an airfoil . The importance of this shape arises when we attempt to model or approximate the ﬂow about the 3-D surface as a collection of 2-D ﬂows in the cross-sectional planes. z y V 3−D Wing 2−D Airfoil section flows L L’ Γ x In each such 2-D plane, the airfoil is the aerodynamic body shape of interest. 2-D section properties become functions of the spanwise coordinate y . Examples are L ′ ( y ), Γ( y ), etc. Quantities of interest for the whole wing cn then be obtained by integrating over all the sectional ﬂows. For example, b/ 2 ′ L = L ( y ) dy − b/ 2 where b is the wing span. The airfoil shape is therefore an important item of interest, since it is key in defining the individual section ﬂows. It must be stressed that the 2-D section ﬂows are not completely independent, but rather they inﬂuence each other’s effective angle of attack, or the apparent vector V ∞ direction in each 2-D plane. Fortunately this complication does not prevent us from treating each 2-D plane as though it was truly independent, since the angle of attack corrections can be added separately later....
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- Fall '05
- Aerodynamics, Lift, Airfoil, α − αL=0, airfoil shape