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f08_sp - Fluids Lecture 8 Notes 1 Wing Geometry 2 Wing...

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Fluids – Lecture 8 Notes 1. Wing Geometry 2. Wing Design Problem Reading: Anderson 5.3.2, 5.3.3 Wing Geometry Chord and twist The chord distribution is given by the c ( y ) function. Each spanwise station also has a local geometric twist angle α geom ( y ), measured from some reference line which is common to the whole wing. The freestream angle α is also defined from this same common reference line. The choice of the reference line for all these angles is arbitrary, although a common choice is the wing-center chord line. chord line zero lift line geom α α L=0 −α aero α common reference line for whole wing α i V local relative velocity How the geometric twist varies across the span is loosely described by the terms washout and washin : washout washin Washout: α geom ( y ) decreases towards the tip. Washin : α geom ( y ) increases towards the tip. If the wing has a spanwise-varying camber, the local zero-lift angle α L =0 ( y ) will also vary. It is useful to define an overall aerodynamic twist angle as α aero ( y ) α geom ( y ) α L =0 ( y ) α L ( y ) α ( y ) δ . zero lift line geom α aero α L=0 −α zero lift line L=0 −α δ geom α aero α The local =0 and hence aero can be changed by a flap deflection Local loading/angle relations The local lift/span can be given either in terms of the local circulation Γ( y ), or the local chord- c product. L ( y ) = ρ V Γ( y ) 1 L ( y ) = ρ V 2 c ( y ) c ( y ) 2 1
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Equating these gives the circulation in terms of the chord and c .
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