JET AND VORTEX FLOW-INDUCED BY ANISOTROPIC BLAST WAVE - EXPERIMENTAL AND COMPUTATIONAL STUDY

This paper discusses gas-dynamic aspects of intense explosions in unif orm environments. In experiments, the energy of a laser is almost inst antaneously released in a volume of air shaped as either a flattened o r stretched cylinder generating a blast wave. Its shape evolves in tim e and ultimately becomes spherical. But momentum transferred to the ai r when the blast wave is strongly nonspherical is anisotropic. As a re sult, a subsonic jet and a vortex are induced and propagate along the symmetry axis or along the perpendicular plane, depending on the initi al configuration of the blast wave. Simulations based on a free-Lagran gian method for a nonviscous gas are in good agreement with the experi ments. Velocities, circulation, and positions of fluid particles found in computations give an insight into the causes and details of the fl ow. Two simultaneous and contrary processes take place - vorticity pro duction by the anisotropic shock wave and baroclinical generation of v orticity at the boundary of the heated gas - which give rise to net ci rculation.