Computations of projectile Magnus effect at transonic velocities

Abstract : The Magnus effect has long been the nemesis of shell designers. Although very small in magnitude, on the order of 1/10th the normal force, this spin-induced side moment has a significant destabilizing effect on projectiles. A combined computational and experimental research program has been ongoing at BRL in recent years to develop a predictive capability for the Magnus effect in particular and for projectile aerodynamics in general. This effort has been very successful in the supersonic regime. The research to be reported in this paper is an extension of this effort into the transonic regime. Utilizing the time marching, thin-layer Navier-Stokes computational technique developed at NASA ames Research Center, solutions have been obtained for a spinning, 6-caliber long, ogive-cylinder-boattail shape at Mach = 0.91 and angle of attack = 2degrees. The computed results predict the correct development of the Magnus force along the body, and comparisons between the computation and experiment are very favorable. Details of the flow field solution such as turbulent boundary- layer velocity profiles and surface pressure distributions are presented. The components which contribute to the Magnus effect are determined and presented as a function of axial position. A complete set of aerodynamic coefficients have been determined from the flow field solutions. Those to be presented here and compared with experimental data include the normal force and Magnus force coefficients. The computations for this research effort were obtained both on a CDC 7600 computer and Cray 1S. (etc.)

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