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SUMMARY:Keynote 1 -  X-ray imaging of flowing concentrated suspensions
DTSTART;VALUE=DATE-TIME:20181210T123000Z
DTEND;VALUE=DATE-TIME:20181210T131000Z
DTSTAMP;VALUE=DATE-TIME:20260523T113213Z
UID:indico-contribution-496@lindico453.srv.lu.se
DESCRIPTION:Speakers: Guillaume Overlez (CNRS\, University of Bordeaux\, F
 rance)\nA key element to understand the rheological behavior of suspension
 s is their microstructure: the spatial distribution of particles depends o
 n flow history\, which has an impact on the suspension macroscopic propert
 ies. This appeals for the development of experimental tools allowing for t
 he 3D imaging of particles in viscosimetric flows. \nAt a macroscopic scal
 e\, concentrated suspensions often display concentration inhomogeneities\,
  due to shear-induced migration. These inhomogeneities can lead to the for
 mation of jammed regions\, which have a strong impact on the measured beha
 vior. It is crucial to describe this phenomenon near the jamming transitio
 n and in shear-thickening fluids. It is thus necessary to develop new tool
 s to get time- and spatially-resolved concentration fields in flowing susp
 ensions.\nIn this talk\, we present recent developments to tackle these is
 sues with the help of X-ray Imaging.\nWe first present a technique to imag
 e the microstructure of suspensions of non-Brownian particles in 3D\, usin
 g X-ray computed tomography and sub-voxel identification of particle cente
 rs. We illustrate its interest on a few examples. We show that one can get
  an isotropic microstructure after mixing. Under shear\, the microstructur
 e becomes anisotropic in the shear plane\, whereas it is isotropic in the 
 2 other planes. While for Newtonian suspensions the anisotropy is independ
 ent on the shear rate\, we show that for a yield-stress suspension it depe
 nds on it\; this implies a shear-dependent behavior of the suspension. Fin
 ally\, we evidence particle alignment along both solid surfaces and free i
 nterfaces.\nWe then present a technique to get time-resolved 2D concentrat
 ion fields in a rheometric flow\, thanks to 2D X-ray radiography. We illus
 trate its interest for shear-thickening fluids. We show that most suspensi
 ons display strong concentration inhomogeneities at the onset of Discontin
 uous Shear thickening (DST)\, which poses the question of the intrinsic (l
 ocal) behavior of DST suspensions and might lead to revisit the interpreta
 tion of this behavior.\n\nhttps://lindico453.srv.lu.se/event/67/contributi
 ons/496/
LOCATION:Elite Hotel Ideon Tera
URL:https://lindico453.srv.lu.se/event/67/contributions/496/
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