Triangular wings with subsonic leading edges

Fig. 6.7. A triangular wing with subsonic edges   Fig. 6.8. Pressure distribution in wing cross-section

Let's consider a triangular wing with subsonic leading edges. With the help of fig. 6.7. we get an internal sweep angle and .

Thus triangular wing with subsonic edges has reduced aspect ratio less than (). In this case there is an overflow from the lower surface to the upper surface The sucking force is realized on the leading edge what reduces induced drag. There is also non-linear additive to a lift coefficient . Pressure distribution along wing surface (fig. 6.8) submits to the law within the linear theory ()

,.9)

where and (refer to fig. 6.7); it is possible approximately define - the elliptical integral of II type dependent on parameter , by the formula .

It follows from the formula (6.9) for that on each ray value of , that is the feature of conical flows. At i.e. at approach to the leading edge (the similar situation takes place in a subsonic flow). For a sharp edge the site in nose section is equal to zero. Multiplying onto the nose section area and expanding the uncertainty , we receive final force value which projection onto incoming flow direction creates force reducing induced drag. This is the sucking force. The aerodynamic characteristics of a triangular wing with subsonic edges are determined by the following formulae:

, ; (6.10)

; (6.11)

; (6.12)

; (6.13)

; , (6.14)

where - a factor of realization of sucking force (), it is possible to adopt for sharp leading edges, that ; for rounded edges - at , further .

For a triangular wing . The last result follows from consideration of conical flow with constant pressure on rays outgoing from the wing top.

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