Stagnation and transonic effects in thermal blooming.

The effects of slewed high-energy beams on an absorbing medium are considered near regions where the relative air velocity is (a) zero and (b) transonic. Limiting effects on the density changes are buoyancy and sound speed changes, respectively. In both cases, the immediate environs of the singular point are greater contributors to phase changes in the beam than are the singularities themselves. Detailed hydrodynamic calculations are carried out for the stagnation region and the steady near-sonic region and compared (in the case of the stagnation region) with a perturbation calculation. Moment methods are used to estimate stagnation-region effects on the subsequent development of the beam.