Original Article Minimum drag and heating 0.3-caliber projectile nose geometry Semih M O ¨ lc ¸men , Gary C Cheng, Richard Branam and Stanley E Jones Abstract Understanding the performance of penetrators and aerodynamic bodies of revolution (missiles, rockets, aircraft noses, etc.) requires a close look at the drag and the heat transfer characteristics at a wide range of supersonic flight conditions. This research utilizes computational study and compares the aerothermal loads of supersonic flows around a new penetrator geometry, derived based on the optimization of the nose factor, to those of other common projectile shapes: conical, tangent-ogive, and power series nose geometries. The abundance of research on 0.3-caliber projectile made the choice for this research simple in order to maximize our ability to compare to the existing data. The com- parison of our 0.3 caliber cylindrical projectile with other geometries shows that within the range of 500–1500 m/s flight speed the new geometry has the lowest aerodynamic drag, lowest body temperature, and least amount of heating. Keywords Nose factor, penetration length, aerothermal loads, computational fluid dynamics, aerodynamic drag Date received: 14 February 2018; accepted: 2 May 2018 Introduction The purpose of the current investigation is to employ the computational fluid dynamics (CFD) technique to determine the drag and the heat transfer characteris- tics on a nose shape previously discussed by Schinetsky et al., 1 Olcmen et al., 2 Holland et al. 3 The research focuses on comparing the aerothermal performance of different geometries within the super- sonic velocity range. In the previous investigation, 1 a new shape was defined based on the optimization to achieve the least nose factor, N, using the penetration mechanics theory, where the viscous effects were omitted. The aerodynamic drag characteristics of this new geometry and four other common nose sha- pes—a g power series nose shape, a tangent ogive, a conical nose, and a geometry defined using calculus of variations—were measured in a supersonic tunnel and compared to each other. These nose shapes are the most commonly encountered nose shapes, both as penetrators and as aerodynamic bodies of revolu- tion. 4–6 Previous researchers 1 determined that the new nose shape had the least aerodynamic drag. That work was then expanded to find nose shapes that would result in maximum penetration including the viscosity effects. 2 Penetrator nose geometry has a prominent role in penetration mechanics as well as in the aerodynamic characteristics of the penetrators. Hill 7 presented an analytical estimate to assess the effect of ‘‘headshape’’ (nose shape) on the rigid penetrator performance in thick targets. He borrowed the term ‘‘cavitation’’ from hydrodynamics to describe the phenomenon he observed and discussed how it degraded performance of the penetrator. More recently, researchers have addressed the nose factor, N, and its effect on the rigid penetrator performance. 8–10 Jones et al. 4 evaluated penetrators at various nose factors for several axisymmetric geometries. Applying the calculus of variations, Jones et al. 4 were able to show how a simple approximate analytical geometry (approximate minimal nose geometry (AMNG)) mini- mized the nose factor, N, and improved the perform- ance. The AMNG has a blunt tip, similar to that discussed by Eggers et al. 5 Batra and Chen 11 introduced the effects of friction on the study of penetrators. They concluded that at high velocities, the depth of penetration is most sig- nificantly influenced by nose geometry. Aerospace Engineering and Mechanics Department, The University of Alabama, Tuscaloosa, AL, USA Corresponding author: Semih M O ¨ lc ¸men, Aerospace Engineering and Mechanics Department, The University of Alabama, 255 HM Comer Hall, Box 870280 245, 7th Ave., Tuscaloosa, AL 35487-028, USA. Email: solcmen@eng.ua.edu Proc IMechE Part C: J Mechanical Engineering Science 0(0) 1–11 ! IMechE 2018 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav DOI: 10.1177/0954406218779094 journals.sagepub.com/home/pic