BEGIN:VCALENDAR VERSION:2.0 PRODID:-//CERN//INDICO//EN BEGIN:VEVENT SUMMARY:Keynote 3 - Vorticity banding in shear-thickening suspensions DTSTART;VALUE=DATE-TIME:20181210T150000Z DTEND;VALUE=DATE-TIME:20181210T154000Z DTSTAMP;VALUE=DATE-TIME:20260523T152842Z UID:indico-contribution-86-500@lindico453.srv.lu.se DESCRIPTION:Speakers: Romain Mari (CNRS\, University Grenoble-Alpes\, Fran ce)\nDiscontinuous shear thickening of dense suspensions is a phenomenon i n which\, at a specific shear rate\, the viscosity increases discontinuous ly often by orders of magnitude. Recent modeling of the phenomenon suggest s that the viscosity jump in rate-controlled rheometry corresponds to an u nderlying S-shaped flow curve in stress-controlled conditions. This nonmon otonic rheology was observed in simulations with modest particle numbers\, showing a range of shear stresses for which the shear rate is a decreasin g function of the shear stress. In general\, however\, one expects that fo r large enough systems a decreasing flow curve leads to a mechanical linea r instability of the uniform flow and the appearance of banding or rheo-ch aos in the nonlinear regime. The exact mode of instability is nonetheless quite difficult to predict in absence of a proper tensorial constitutive m odel. In this talk I will show particle-based numerical simulations of thi ckening suspensions exhibiting an instability along the vorticity directio n and subsequent "traveling" vorticity bands. Interestingly\, because the mechanical description of the vorticity direction can be decoupled from th e flow and gradient directions\, a one-dimensional (scalar) constitutive m odel is enough to capture most of the features observed in the simulations . This model also gives hints as to the origin of the unsteady rheological response observed in experiments performed in similar conditions.\n\nhttp s://lindico453.srv.lu.se/event/67/contributions/500/ LOCATION:Elite Hotel Ideon Tera URL:https://lindico453.srv.lu.se/event/67/contributions/500/ END:VEVENT BEGIN:VEVENT SUMMARY:Keynote 4 - Quantitative Light Microscopy of Dense Suspensions: Co lloid Science at the Next Decimal Place DTSTART;VALUE=DATE-TIME:20181210T162000Z DTEND;VALUE=DATE-TIME:20181210T170000Z DTSTAMP;VALUE=DATE-TIME:20260523T152842Z UID:indico-contribution-86-503@lindico453.srv.lu.se DESCRIPTION:Speakers: Itai Cohen (Physics\, Cornell University\, USA)\n“ Why should one wish to make measurements with ever increasing precision? B ecause the whole history of physics proves that a new discovery is likely to be found lurking in the next decimal place.” (Floyd K. Richtmyer\, 19 31)\n\nSince the days of Perrin\, microscopy methods have played an import ant role in the study of colloidal suspensions. Along with the continued d evelopment of new imaging techniques\, colloid scientists have also implem ented a sophisticated range of computational analyses. These analysis tech niques are often the unsung heroes that hold the promise of unlocking scie ntific mysteries at the next decimal place of colloid science. They now en able precision measurements of particle location and size with nm precisio n as well as measurements of local stresses and forces. Here\, I spotlight exciting recent advances we have made focusing on the analysis of simple confocal microscope images of dense colloidal suspensions. I will then des cribe our plans for using these tools to unravel scientific mysteries rang ing from yielding in glasses\, training of colloidal gels\, and the stress networks governing shear thickening flows.\n\nhttps://lindico453.srv.lu.s e/event/67/contributions/503/ LOCATION:Elite Hotel Ideon Tera URL:https://lindico453.srv.lu.se/event/67/contributions/503/ END:VEVENT BEGIN:VEVENT SUMMARY:Contr. Talk 5 - The effects of high-power ultrasound on colloidal gels DTSTART;VALUE=DATE-TIME:20181210T170000Z DTEND;VALUE=DATE-TIME:20181210T172000Z DTSTAMP;VALUE=DATE-TIME:20260523T152842Z UID:indico-contribution-86-505@lindico453.srv.lu.se DESCRIPTION:Speakers: Noémie Dagès ()\nLow-intensity ultrasound is widel y used to probe and image biological tissues.Yet\, yltrasound can also be used at high power to destroy nodules or burn tumors. We try to transpose and understand the latter effects in soft matter. We first show that high- power ultrasound softens colloidal gels. Upon applying ultrasound at 45kHz for a few tens of seconds on various gels in a rheometer\, we find that t he elastic modulus of the gel is weakened and that its fluidization is fas tened. As ultrasound is turned off\, the gel recovers its elasticity. To i nvestigate this process at the micron scale\, we then probe the gel under ultrasound with small-angle X-ray scattering (ESRF\, ID02). These experime nts show a strong effect of the ultrasound excitation on the SAXS spectra both on a colloidal gel at rest and under flow.\n\nhttps://lindico453.srv. lu.se/event/67/contributions/505/ LOCATION:Elite Hotel Ideon Tera URL:https://lindico453.srv.lu.se/event/67/contributions/505/ END:VEVENT BEGIN:VEVENT SUMMARY:Contr. Talk 4 - Linking transient shear profiles to the microscopi c structure and dynamics in concentrated colloidal suspensions DTSTART;VALUE=DATE-TIME:20181210T160000Z DTEND;VALUE=DATE-TIME:20181210T162000Z DTSTAMP;VALUE=DATE-TIME:20260523T152842Z UID:indico-contribution-86-502@lindico453.srv.lu.se DESCRIPTION:Speakers: Andreas Pamvouxoglou (Heinrich Heine University Duss eldorf)\nWe performed start-up experiments with concentrated hard-sphere s uspensions around the glass transition. Rheo-confocal experiments were car ried out to link the macroscopic rheological response to the single-partic le structure and dynamics. During the start-up of shear\, suspensions of l arge particles (diameter ≈1.6μm) showed a transient non-linear velocity \, resembling shear bands without a clear boundary. We performed a quantit ative analysis to elucidate the correlation between the shear profile and microscopic properties\, such as the local velocity\, shear rate and volum e fraction. They show a strong dependence on the position in the gap and h ence indicate a significant heterogeneity. Based on the microscopic proper ties we propose a mechanism that leads to the transient non-linear shear p rofiles.\n\nhttps://lindico453.srv.lu.se/event/67/contributions/502/ LOCATION:Elite Hotel Ideon Tera URL:https://lindico453.srv.lu.se/event/67/contributions/502/ END:VEVENT BEGIN:VEVENT SUMMARY:Contr. Talk 3 - Flow-assisted droplet assembly in a 3D microfluidi c channel DTSTART;VALUE=DATE-TIME:20181210T154000Z DTEND;VALUE=DATE-TIME:20181210T160000Z DTSTAMP;VALUE=DATE-TIME:20260523T152842Z UID:indico-contribution-86-501@lindico453.srv.lu.se DESCRIPTION:Speakers: Zhouyang Ge ()\nSelf-assembly of soft matter\, such as droplets or colloids\, has become a promising scheme to engineer novel materials\, model living matter\, and explore non-equilibrium statistical mechanics. In this talk\, we present detailed numerical simulations of few non-Brownian droplets in various flow conditions\, specifically\, focusin g on their self-assembly within a short distance in a three-dimensional (3 D) microfluidic channel\, cf. [Shen et al.\, Adv. Sci.\, 2016\, 3(6):16000 12]. Contrary to quasi two-dimensional (q2D) systems\, where dipolar inter action is the key mechanism for droplet rearrangement\, droplets in 3D con finement produce much less disturbance to the underlying flow\, thus exper iencing weaker dipolar interactions. Using confined simple shear and Poise uille flows as reference flows\, we show that the droplet dynamics is most ly affected by the shear-induced cross-stream migration\, which favors cha in structures if the droplets are under an attractive depletion force. For more compact clusters\, such as three droplets in a triangular shape\, ou r results suggest that a non-uniform cross-sectional inflow profile is fur ther required. Overall\, the accelerated self-assembly of a small-size dro plet cluster results from the combined effects of strong depletion forces\ , shear alignments\, and fine-tuned inflow conditions. The deterministic n ature of the flow-assisted self-assembly implies large throughputs\, thoug h calibration of all effects is likely difficult at the same time.\n\nhttp s://lindico453.srv.lu.se/event/67/contributions/501/ LOCATION:Elite Hotel Ideon Tera URL:https://lindico453.srv.lu.se/event/67/contributions/501/ END:VEVENT END:VCALENDAR