The aerodynamics of sharp- and filet-edged cylinders in high supersonic flow

Abstract

To develop a physical understanding and accurate trajectory models for atmospheric re-entry objects like space debris, the influence of the flight attitude on the aerodynamic coefficients of cylindrical bodies in high-speed flow is of interest. Experiments were conducted in a Mach-4 Ludwieg tube at The University of Maryland to study the aerodynamics of cylinders with varying aspect ratios and edge sharpness. A free-flight technique with a high-speed object tracking apparatus was used that allows unconstrained model motion, free of any sting interference, over a full range of angle of attack. A piece-wise analytic function for the model outline combined with a subpixel edge-detection routine allowed measurements of the aerodynamic coefficients based on the 4-degrees-of-freedom model motion. Experimental results were compared to modified Newtonian flow solutions, with generally good agreement. The influence of the angle of attack on the aerodynamic loading was determined to vary strongly according to the aspect ratio and edge radius. In the case of sharp-edged cylinders, increasing the aspect ratio led to an increase in both the flight region for positive lift and larger regions of static stability. By adding curvature to the cylinder base edges, the location of the statically stable trim points occurs at the fully base-exposed and fully body-exposed orientations. It was also found that the flight attitude region for which the cylinder was statically stable was expanded due to the addition of edge curvature. Further, as the aspect ratio was increased for these filet-edged cylinders, the magnitude of the moment coefficient increased noticeably.