A Simplified Method for Predicting Aerodynamics of Multi-Fin Weapons.

Abstract

Abstract : A new semiempirical method was developed to compute aerodynamics of multi-fin missile configurations using cruciform missile aerodynamics as a baseline. The method was developed using full Euler Computational Fluid Dynamics codes to compare computations with wind tunnel data bases for cruciform missiles as a function of Mach number, angle of attack, and aspect ratio. The Euler codes were then used for the same free stream conditions and missile configurations except the number of fins were increased from four to six and eight respectively. A table of coefficients was then formed for the aerodynamics of six- and eight-fin configurations compared to that of four-fin cases for use in the aeroprediction code or other semiempirical codes. It was concluded that this approach worked well except for subsonic Mach numbers at moderate to large angles of attack, where the Euler codes failed to predict the leeward plane flow field adequately. It is believed that full Navier-Stokes solutions could be used to improve upon this semiempirical model. Engineering judgement, in conjunction with low angle-of-attack Euler solutions were used in the regions where Euler solutions were suspect. In comparing the new semiempirical method to a limited amount of wind tunnel data on several configurations, it was concluded that the model worked well at all the conditions where data was available. However, additional wind tunnel data at higher angles of attack on six- and eight-fin configurations is needed before the method can be truly validated.