Shock Mitigation by Dust Lofting: Theoretical Perspective

Abstract

Roughly 50–60 % of the total energy released by a nuclear explosion in lower atmosphere air is converted into blast wave [1] mechanical energy. When the burst point is moderately high above the ground such that a crater is not formed (roughly about 7 m scaled height), a significant mass of dust and sand is lofted and entrained into the blast wave flow fields. Detailed computation of the lofting effect is important since this dust may carry adsorbed fission products over large distances. In circumstances where dust is being lofted, the shock wave propagates in a diluted air-particles suspension rather than in a pure air environment. Constitutive characteristics of the suspension may affect the wave propagation dynamics [2]. Thus, in computational modeling of the blast wave several phases have to be accounted for (air, dust, sand etc.), including interphase coupling effects. The lofting phenomenon is a turbulent phenomenon. Due to computer limitation it is impractical to model the turbulent lofting process in a full nuclear blast wave simulation. The dust lofting process is thus modeled analytically and the result is embedded as a boundary condition based on an extended boundary layer theory for blowing boundary layers that takes into account lofting of sand particles into the air flow [3, 4].