Numerical Simulation of Sonic Boom from Hypersonic Meteoroids

Abstract

Meteoroids entering the Earth atmosphere at high hypersonic velocities are sources of sonic booms that are recorded as infrasound signals at the ground level. The boom pressure field is simulated by solving Euler equations for a spherical meteoroid. The numerical challenge is to capture the acoustical regime of weak shock waves in the very far field at several hundreds or thousands times the meteoroid diameter. Computational fluid dynamics simulations are then matched to nonlinear geometrical acoustics for long-range atmospheric propagation down to the ground. The numerical process is validated through comparison with an analytical model, considering for perfect gases the meteoroid as a line source of strong shock in the near field, matched to a weak shock N-wave in the far field. Compared with a perfect gas, real gas effects at thermochemical equilibrium induce a reduced amplitude at the source, along with a shorter signal duration at the ground level. Simulations are illustrated for the well-documented Carancas meteorite that impacted on Peru in 2007. Nomenclaturesound velocity, m∕s D = meteoroid diameter, m E 0 = source energy per length unit, J∕m M = v∕c 0 meteoroid Mach number p = pressure, Pa p 0 = atmospheric pressure, Pa R = radial trajectory distance, m R 0 = E 0 ∕p 0 p blast radius, m t = time, s v = meteoroid velocity, m∕s x = axial trajectory distance, m α = meteoroid trajectory azimuth angle relative to north and clockwise, deg β = meteoroid trajectory deflection angle relative to the horizontal plan, deg (0 deg no entry, 90 deg vertical fall) γ= ratio of specific heats c p ∕c v Δp = p − p 0 , overpressure, Pa ρ 0 = atmospheric density, kg∕m 3

Ballistic Wave from Projectiles and Vehicles of Simple Geometry

“…In contrast, the operating flight conditions of the USAF's strategic reconnaissance plane SR-71 Blackbird (Mach 3,26,000 m height) are at the limit of the validity domain of the theory. For this reason, the sonic boom generated by objects flying at hypersonic velocity at high altitude was the subject of specific studies [40][41][42][43][44][45][46][47][48][49]. The recent orientations concern the minimization of the sonic boom perceived at ground level by suitable aircraft geometry and flight trajectory on the one hand [50][51][52][53][54], the generalization of the computational fluid dynamics (CFD) to replace the analytical models on the other hand [55][56][57][58][59][60].…”

Element centered smooth artificial viscosity in discontinuous Galerkin method for propagation of acoustic shock waves on unstructured meshes

“…The acoustic shock waves can also be produced directly by the source itself and persist along propagation. Atmospheric acoustic shock waves arise in many situations, like for instance the sonic boom from a supersonic aircraft [52], bolide hypersonic atmospheric entries [33], or the so-called "buzz saw noise" due to the supersonic rotation of the tip of fan blades [54,25]. Lithotripsy [2] uses ultrasonic shock waves propagating in biological tissues to fragment kidney stones, while new medical applications are based on HIFU (High Intensity Focused Ultrasound) [11].…”

Computational Modeling of Meteor-Generated Ground Pressure Signatures

“…This relaxes the requirement of explicitly specifying the transition altitude. Henneton et al 18 explore a numerical approach that is much more general. They use computational fluid dynamics to determine the near-body flow around the meteoroid, extract a nearfield pressure signature, and then propagate this signature to the ground by solving the augmented Burgers' equation to accurately model atmospheric absorption.…”

“…Their numerical experiments agree well with the ReVelle model 7 in the asymptotic limits of infinite meteoroid velocity and vanishing size. Both Haynes and Millet 16 and Henneton et al, 18 however, test their simulations by reproducing the signature from the Carancas fireball-crater event, where details of the trajectory, energy and dynamics are very uncertain. 19,20 This paper investigates a computational approach based on our work in simulation-based aircraft sonicboom prediction.…”

“…19,20 This paper investigates a computational approach based on our work in simulation-based aircraft sonicboom prediction. 21 The approach is similar to that of Henneton et al 18 We use the new, homogenous dataset of Silber et al 15 to test our simulations. This dataset provides significantly better validation benchmarks than the Carancas event used in previous studies.…”