Aerodynamic Analysis of Projectiles in Ground Effect at Near-Sonic Mach Numbers

Abstract

The behavior of projectiles at Mach 0.9, 1.1, and 1.2 when in close proximity to a surface were investigated using a synergy of live-range test firings, wind-tunnel experiments, and computational fluid dynamics simulations; the latter provided the majority of the insight into the problem. Building on work that previously indicated significant ground influence for a projectile at Mach 2.4 due to shock reflections, a similar projectile was investigated for ground clearances of height-to-diameter ratios from 0.25 to 8. It was found that at Mach 0.9 the projectile's drag, normal force, and pitching moment coefficients changed predictably, and with significant increasing magnitude below h∕d = 2. Drag increased, a strong normal (suction) force acting toward the ground developed with increasing strength of the shock developing on the lower side of the projectile, and a nose-up pitching tendency was established. At the supersonic Mach numbers, the ground influence was present at higher ground clearances, and influential shock reflections occurred; at high clearances, the reflected shock increased the pressure on the lower side, and at low clearances (h∕d < 1), the reflecting expansion waves lowered the pressure to produce a pronounced negative normal force. At the lowest investigated clearances, drag was approximately 30% higher, and the Mach 1.2 cases experienced more substantial fluctuations in the trends. The normal force and pitching moment behaviors would be unlikely to influence the projectile's path over any realistic distance, but the ground proximity drag increase would significantly alter the projectile's deceleration and therefore trajectory response.

Aerodynamics Analysis and Range Enhancement Study of 81mm Mortar Shell (French Design)

“…Doig et al, analyzed projectile behavior by using CFD simulation, wind tunnel and synergy live range fire testing at Mach 0.9, Mach 1.1 and Mach 1.2 [11]. It was observed that normal force, drag force and pitching moment change predictably at Mach 0.9.…”

Study on the performance of spatial discretization schemes for hypersonic flow

“…Although many near space hypersonic vehicles, such as X-37 (Gülhan et al, 2014), X-51 (Schimisseur, 2015) and Falcon HTVs (Walker et al, 2008), have been succeeded in their missions, the exploration of aerothermodynamic problems is the principle obstacle because the velocities and altitudes at which these vehicles would operate are different, and sometimes more severe (Huang and Huang, 2015;Hu et al, 2016aHu et al, , 2016bLi et al, 2016), than those went through in the past. As future hypersonic vehicle quests to fly higher and faster, the environment surrounding the vehicle could be more dramatically changed (Hu et al, 2016a(Hu et al, , 2016bCai 2016;Yuan et al, 2017) and more difficult to simulate in ground-based test facilities (Doig et al, 2016), which makes the numerical simulations become increasingly important issues (Park et al, 2016;Boyd et al, 2010). Whether the existing numerical methods can apply to higher velocity is an urgent problem to be solved.…”