A Lawrence Livermore National Laboratory (LLNL) team has taken a closer look at how nuclear weapon blasts close to the Earth’s surface create complications in their effects and apparent yields. Attempts to correlate data from events with low heights of burst revealed a need to improve the theoretical treatment of strong blast waves rebounding from hard surfaces.
This led to an extension of the fundamental theory of strong shocks in the atmosphere, which was first developed by G.I. Taylor in the 1940s. The work represents an improvement to the Lab team’s basic understanding of nuclear weapon effects for near-surface detonations. The results indicate that the shock wave produced by a nuclear detonation continues to follow a fundamental scaling law when reflected from a surface, which enables the team to more accurately predict the damage a detonation will produce in a variety of situations, including urban environments.
The findings, featured in Proceedings A of the Royal Society Publishing, are authored by Andy Cook, Joe Bauer and Greg Spriggs. The work, “The Reflection of a Blast Wave by a Very Intense Explosion,” also is highlighted on the cover of the publication.
The paper demonstrates that the geometric similarity of Taylor’s blast wave persists beyond reflection from an ideal surface. Upon impacting the surface, the spherical symmetry of the blast wave is lost but its cylindrical symmetry endures. The preservation of axisymmetry, geometric similarity and planar symmetry in the presence of a mirror-like surface causes all flow solutions to collapse when scaled by the height of burst (HOB) and the shock arrival time at the surface. The scaled blast volume for any yield, HOB and ambient air density follows a single universal trajectory for all scaled time, both before and after reflection.
The team used the Miranda code and the Ruby supercomputer to compare theory against numerical simulations, and verified that Miranda reproduces Taylor’s similarity solution for a strong blast wave in an ideal atmosphere.