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SUMMARY:MEchanics GAthering -MEGA- Seminar: The Latest from LFMI - Fluid M
 echanics and Instabilities
DTSTART:20181004T161500
DTEND:20181004T173000
DTSTAMP:20260528T233832Z
UID:fe1fa0493b2b31bfca88e6638b6f24919e1b7fc5fbe2b19100a6d952
CATEGORIES:Conferences - Seminars
DESCRIPTION:Mathias Bechert\, EPFL STI IGM Laboratory of Fluid Mechanics a
 nd Instabilities (LFMI)\; Gaëtan Lerisson\, EPFL STI IGM Laboratory of 
 Fluid Mechanics and Instabilities (LFMI)\; \nTalk 1: Transport of fibers 
 in confined micro-channels by Mathias Bechert\nAbstract The behavior of 
 fibers transported by a flow in confined geometries is important for many 
 applications\, e.g.\, paper production\, hydraulic fracturing\, or biomedi
 cal technologies. The complex interactions between the fiber and the surro
 unding flow lead to various dynamical behavior\, e.g. oscillatory movement
  between the channel walls or rotation of the fiber. In this talk I will p
 resent a method using an approximative model of reduced dimensionality to 
 efficiently explore these dynamics with respect to practically relevant co
 ntrol parameters\, e.g.\, channel size or fiber properties. In particular\
 , we will have a look at the similarities and differences between symmetri
 c\, asymmetric and flexible fibers. Apart from helping to improve industri
 al and biomedical processes\, the new insights also open ways to develop f
 low sensors.\n\nTalk 2: Destabilization of a viscous liquid film below an 
 inclined flat substrate by Gaëtan Lerisson\nAbstract Falling liquid fi
 lm on a substrate have been extensively studied. While numerous studies ar
 e dedicated to the case where the gravity acts as a stabilizing force\, in
  particular for finite Reynolds number flows\, few focus on the case of a 
 liquid film below a substrate. Here we focus on non-inertial films with a 
 destabilizing gravity. This case is relevant for the very thin film dynami
 c (geophysics of cave\, morphogenesis\, engineering of cooling system) as 
 well as viscous films (glass flows\, etc.). This system relates to the Ray
 leigh-Taylor instability of a thin film where the substrate is now incline
 d. This inclination gives rise to a flow characterized by the flat film so
 lution (so-called Nusselt solution) that undergoes an absolute/convective 
 transition.\nWe built an experiment set-up that allows to produce a well-c
 ontrolled continuous flow below a flat substrate. We can accurately vary t
 he angle formed with gravity and the film thickness. We measure patterns i
 n the surface height. These patterns are forced by the natural boundaries 
 of the apparatus in convectively unstable situations. The experimental res
 ults are found to be in excellent agreement with 2D non linear numerical s
 imulations of the lubrication equation. Thanks to the local linear stabili
 ty analysis we show that the selected wavelength is not accurately predict
 ed by the linear stability theory but involves the group velocity of each 
 component of the wave packet that is forced by the sides and advected down
 stream. From simulations in a periodic domain\, we observe a non linear se
 lection mechanism of the patterns which is then confirmed by experiments.\
 n\n 
LOCATION:MED 2 2423 https://plan.epfl.ch/?room=MED22423
STATUS:CONFIRMED
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