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Fakulteta za strojništvo, Ljubljana (FSLJ)
  • Annular laser beam metal droplet generation [Elektronski vir] : droplet detachment regimes and dynamics
    Govekar, Edvard
    In the laser droplet generation process a laser beam pulse is used to melt the wire-end of the vertically fedmetal wire and to detach the formed pendant droplet from the solid part of the wire-end. ... By step wisefeeding of the wire-end into the laser beam focus, a single drop on demand can be generated and by continuous feeding of the wire-end a droplet sequence can be generated. In both cases, the critical process phase is detachment of the pendant droplet. To characterize the pendant droplet formation, its detachmentand the corresponding process dynamics, images of a high speed IR camera were used. It has been observed experimentally that in the case of drop on demand generation by means of an annular laserbeam, the detachment of the pendant droplet is influenced by the annular laser beam focus position above the pendant droplet neck. Besides, that pendant droplet can be successfully detached or not detached it can be splashed into several or even reattached. The successful detachment is achieved via molten wire column break-up, above the pendant droplet neck, caused by the Rayleigh-Plateau (R-P) instability [1]. Incontinuous generation of a droplet sequence, it has been observed that the pendant droplet detachment isgoverned by the interaction between the laser pulse frequency and the dynamics of pendent droplet [1].Depending on the laser pulse frequency, three different detachment regimes accompanied by differentdynamics have been identified: a) spontaneous dripping, caused by the force of gravity alone, b) resonantdetachment, caused by a combination of the gravity force and the laser induced eigen oscillation modes ofthe pendant droplet, and c) break-up caused by the R-P instability. The observed mass spring resonantdetachment has been described by a nonlinear model which results are very well in agreement with theexperiments [2]. In addition to this, the nonlinear time series based analysis of the laser droplet generation process has shown that the spontaneous dripping and R-P instability break-up regimes are chaotic and that the transition between them corresponds to intermittency chaos-to-chaos transition [3].
    Vir: Synergetic approaches to complexity [Elektronski vir] : a symposium in memory of Rudolf Friedrich : International Focus Workshop, September 29 - October 2, 2013 (2013, F. 2)
    Vrsta gradiva - prispevek na konferenci
    Leto - 2013
    Jezik - angleški
    COBISS.SI-ID - 13199387

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