engleski

Hierarchical instability of vortex rings array in laser-matter interactions

By a repeted irradiation of the XeCl excimer laser pulse on the same target of Co-coated steel endowed with scaratches, we have realized a catastrophic generation of a quasi-linear array of vortex rings, by a cut-and-connect process, from ann array of wiggly vortex filaments witha series of loops on them. Subjected to randomly distributed local multipolar strain, unstable waves develop on the vortex rings, and the deformed shapes stay frozen permanently by a ultrafast cooling process.. By amodal analysis, an attempt is made at relating them to parametric resonance instabilities caused ba a dipole anda quadrupole field. Multipulse laser-matter interactions are thus capable of nonselective excitation of vortex ring instabilities of various sizes and various modal structures.

Laser ablation; Fluid surfaces and fluid-fluid interfaces; Fluid dynamics

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