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SUMMARY:Influence of process and material parameters on the draw resonance
  instability
DTSTART:20170206T131500
DTEND:20170206T141500
DTSTAMP:20260509T161110Z
UID:84a24430336a2048cc135ff8e59a0ff72b7abcc617ff864039bc2bf4
CATEGORIES:Conferences - Seminars
DESCRIPTION:Mathias Bechert\, Institute of Polymer Materials\, Friedrich-A
 lexander-Universität Erlangen-Nürnberg\, Germany\nIn film casting and fi
 ber spinning processes\, liquid material is extruded through a die with pr
 edefined speed and taken up by a rotating chill roll in order to fabricate
  thin films and slender fibers. The main control parameter is the so-calle
 d draw ratio\, defined as the ratio of the inlet to the take-up velocity. 
 Exceeding a critical draw ratio results in steady oscillations of both the
  velocity field and film or\, respectively\, fiber geometry\, which is com
 monly known as draw resonance and which leads to inhomogeneous product pro
 perties and possible breakdown of the process.\n \nIn this talk\, a linea
 r stability study of draw resonance is presented. The first part concentra
 tes on the influence of practical relevant control parameters on the onset
  of draw resonance. For this purpose\, a simple one-dimensional Newtonian 
 model is used to investigate the effects of inertia and gravity. The neck-
 in effect\, which describes the reduction of film width along the stretchi
 ng direction\, and the influence of surface tension in fiber spinning are 
 discussed as well. Stability maps give a comprehensive overview of the sta
 bility behavior of the system and enable the identification of various reg
 imes\, including regions of unconditional stability and unconditional inst
 ability.\n \nIn the second part of the talk\, the influence of viscoelast
 ic properties is discussed. This is accompanied by a small experimental st
 udy on the dependence of the critical draw ratio on the Deborah number. Ne
 cessary properties of an appropriate viscoelastic constitutive equation ar
 e evaluated and underlying stability mechanisms are revealed.\nFinally\, t
 he theoretical prediction is compared to the experimental findings.\n\nRef
 erences\n[1] M. Bechert\, D. W. Schubert and B. Scheid\, Practical mapping
  of the draw resonance instability in film casting of Newtonian fluids\, E
 uropean Journal of Mechanics B/Fluids 52\, 68-75 (2015).
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STATUS:CONFIRMED
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