Influence Of Fin Planform Shape On Lift And Center Of Pressure For Supersonic Missiles


The missile fin-body interference factor, KW (B)(ratio of the normal force on a fin in presence of the missile body to the normal force on the isolated fin) is an important factor in the equivalent angle-of-attack preliminary design method. A finite-volume Euler code, ZEUS is used to numerically determine the fin forces as a function of fin trailing edge sweep for 2-, 3-, 4-, 5-and 6-fin missile configurations at small angles of attack. The fin forces are used to evaluate KW (B)as a function of fin span to body radius ratio at Mach numbers from 2.5 to 5 at various fin aspect ratios. The movement of center of pressure with changes in trailing edge sweep and Mach number is also evaluated. KW (B)and center of pressure values for the 2-, 3-and 4-fin configurations agree with slender body theory analytical solutions; however, the KW (B)predictions for the 5 and 6-fin cases breakaway from slender body theory as the fin span increases. 1 he fin span at which breakaway occurs is shown to be related to the position at which shock and expansion waves originating from the adjacent fins strike the fin of interest; consequently, it is a function of number of fins and Mach number. In some cases the shock and expansion wave interaction cause KW (B)to be less than one, which indicates a reduction in fin lift due to interference. Tables for KW (B)AND the center of pressure are presented for use in preliminary design.


Mechanical and Aerospace Engineering

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Article - Conference proceedings

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Publication Date

01 Jan 1990