Profile selection specifics of a soft wing on a sling suspension

Aeronautical and Space-Rocket Engineering


Аuthors

Shved Y. V.

e-mail: yuriy-shved@mail.ru

Abstract

When a soft wing profile selecting, it should be borne in mind that the data adduced in the atlases of airfoils appears to be insufficient. This is associated with the fact that these documents reflect the data of blowing rigid models, which preserve their shape even when the area with the reverse, directed downward lifting force, is being formed at the nose of the profile. The profile of the soft wing is losing stability under these conditions. Thus, the additional parameters such as the form of the graph of the total pressure coefficient along the upper and lower surfaces distribution at its nose, the angle of attack of this value transition to the negative region and the length along the profile chord captured by this transition affect the soft wing profile selection. This length indicates how expansive the profile extra turn is when it goes beyond the critical angle, and hence the degree of danger. Besides the above said parameters, the range of the accessible angles of attack for the soft wing depends upon location and size of its air intakes and slots (if any), and obtained as the result coefficient of pressure on the surface and in the wing cavity as the profile housing stability criterion to the local crushing. This criterion should be less than one everywhere for the stable profile shape. When the soft wing yeilding of the negative angles of attack, for example due to entering the down-flow, its air intakes lose their ability to keep up the excessive pressure. The upper leading edge herewith crushes, and airfoil deforms in such a way that its centerline in the nose attains reduced or reversed curvature, and, consequently, its aerodynamic force, acting on the wing leading edge sharply changes direction turning the front segment of the carrying plane. The extra effect while the profile deformation introduces the center of pressure shift, which forces the wing forward and additionally, reduces its angle of attack (this movement is being compensated to a certain extent by the deformed profile resistance).

Keywords:

soft wing, double-shell wing, soft wing safety, soft wings airfoils

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