We have observed coherent patterns of the magnitude of the normalized vortex stretching vector \| during the "bursting" reconnection phase of the evolution of identical initially orthogonally offset vortex tubes. We propose that the intensification and reconnection of initially tubelike vortex regions be viewed as a scattering process and that the topology of vortex lines during this phase of the process contributes to limiting vortex stretching (intensification). Furthermore, we advocate the use of these patterns (some rendered in color) as signatures of turbulent intermittency in exploring massive data sets. 47.15.Ki Interacting tubelike vortex regions are an ever-present fluid-dynamical phenomenon. They are observed in the vapor-dyed wing-tip vortices of steady [1] and maneuvering [2] aircraft, in the wing-tip vortices of pitching and plunging airfoils [3], in boundary layers as "hairpin" and "ringlike" vortex structures [4], and in simulations of liquid-helium turbulence with local induction vortex filament models ).If two tubelike vortex regions are sufficiently close together or are convected towards each other, they form a "scattering" reconnection configuration. That is, we consider the ingoing state of the scattering process to originate from two straight, well-separated, nonintersecting vortex tubes of compact support with relative angle 0/, O°<0/< 180°.Many studies of vortex reconnection have been initialized with the perturbed antiparallel configuration (0/ = 180°), since they were motivated by the contrail problem and the intermediate time evolution of the Crow instability [8]. We prefer the orthogonally offset (0/ =90°) configuration, which yields a high effective resolution within a given domain. Our selection is motivated by the works of Melander and Zabusky [9,10], who observed intensification and reconnection with this configuration but did not explore the essential dynamics.In both perturbed antiparallel and orthogonally offset initial conditions, initially compact tubes of equal or nearly equal circulation evolve into an ingoing state where a highly intensified dipolar vortex "pancake" forms in a small domain (Pumir and Siggia [11], and Boratav, Pelz, and Zabusky [12,13]). For 0, =90°, there is also a well-defined outgoing state. Thus, we advocate a scattering paradigm to focus attention on the physical processes which occur in the "complex" core state. Within this temporal interval, coherent spatial patterns form which provide alternate signatures for reconnection and turbulent intermittency.A Biot-Savart model with a cutoff was used by Dhanak and de Bernadinis [14] to study the close approach of tubes during the evolution of a high-aspect-ratio elliptical ring. Siggia [15] also used the Biot-Savart model and referred to the ingoing phase as one of "collapse and amplification" but did not employ topological reconnection of filaments nor emphasize the scattering process. Such models fail when the cores overlap with each other as occurs just prior to the reconnection phase.We de...
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