Baroclinic mixing in HE fireballs

Conference · Sun Aug 01 04:00:00 EDT 1993

OSTI ID:10189744

Kuhl, A L ^[1]; Ferguson, R E; Priolo, F; Chien, K Y; Collins, J P ^[2]

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1. Lawrence Livermore National Lab., El Segundo, CA (United States)
2. Naval Surface Warfare Center, Silver Spring, MD (United States)

Numerical simulations of the turbulent mixing in the fireball of an HE blast wave were performed with a second-order Godunov code. Adaptive mesh refinement was used to capture the convective mixing processes on the computational grid. The calculations revealed that the interface between the shock-compressed air and the dense detonation products was unstable. Vorticity was generated in that region by baroclinic effects. This caused the interface to roll-up into a turbulent mixing layer. Four phases of mixing were identified: a strong blast wave phase, where the mixing region was swept outward by the shockinduced flow; an implosion phase, that stretched the inner boundary of the mixing region back toward the origin; a re-shocking phase, where the imploding shock expands back outward from the origin and re-energizes the mixing later by RichtmyerMeshkov effects; and an asymptotic mixing phase, where line-scale structures are continually recreated by folding effects but the overall vorticity decays through a cascade process. The flowfield was azimuthally averaged to evaluate the mean-flow profiles and r.m.s. fluctuation profiles across the mixing layer. The mean kinetic energy rapidly approached zero as the blast wave decayed, but the fluctuating kinetic energy asymptotically approached a small constant value. This represents the rotational kinetic energy driven by the vorticity field, that continued to mix the fluid at late times. It was shown that the vorticity field corresponds to a function that fluctuates between plus and minus values-with a volume-averaged mean of zero.

• Research Organization: Lawrence Livermore National Lab., El Segundo, CA (United States)
• Sponsoring Organization: USDOE, Washington, DC (United States); Department of Defense, Washington, DC (United States)
• DOE Contract Number: W-7405-ENG-48
• OSTI ID: 10189744
• Report Number(s): UCRL-JC--114892; CONF-9308185--1; ON: DE94001607; CNN: Contract DNA IACRO 92-824
• Country of Publication: United States
• Language: English

Related Subjects

45 MILITARY TECHNOLOGY, WEAPONRY, AND NATIONAL DEFENSE
450100
661300
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
99 GENERAL AND MISCELLANEOUS
990200
CHEMICAL EXPLOSIONS
CHEMICAL EXPLOSIONS AND EXPLOSIVES
COMPUTERIZED SIMULATION
FIREBALLS
FLUCTUATIONS
MATHEMATICS AND COMPUTERS
MIXING
OTHER ASPECTS OF PHYSICAL SCIENCE
SHOCK WAVES
TURBULENT FLOW
VORTICES