Indexed on: 12 Apr '06Published on: 12 Apr '06Published in: Physical review. E, Statistical, nonlinear, and soft matter physics
Motion of a fluid interface in Richtmyer-Meshkov instability is examined as a vortex sheet with the use of Birkhoff-Rott equation. This equation coupled with an evolution equation of the strength of the vortex sheet can describe all inviscid and incompressible fluid instabilities, i.e., Kelvin-Helmholtz, Rayleigh-Taylor, and Richtmyer-Meshkov instabilities, when Atwood numbers and initial distribution of vorticities are given. With these equations, detailed motion of a vortex core in the Richtmyer-Meshkov instability is investigated. For the Kelvin-Helmholtz and Rayleigh-Taylor instabilities, it is known that the curvature of a vortex sheet diverges at a finite time t=tc. This fact indicates that the solution loses its analyticity at tc. We show that the singularity formation also occurs in the Richtmyer-Meshkov instability and at the same time, accumulation of vorticity to some points where singularities are formed develops to the roll-up of a sheet when the sheet is regularized. We investigate motion of these accumulation points, i.e., vortex cores, and present that their trajectories and the strengths depend on the Atwood numbers.