Lattice Boltzmann Modeling of Cholesteric Liquid Crystal Droplets Under an Oscillatory Electric Field

查看全文 作　　者：[1,2,3]F.Fadda;[4]A.Lamura;[5]A.Tiribocchi 机构地区：[1]Institute of Physics,University of Amsterdam,1098 XH Amsterdam,The Netherlands;[2]Department of Chemical Engineering,Kyoto University,Kyoto 615-8510,Japan;[3]Dipartimento di Fisica and Sezione INFN,Universit`a di Bari,Via Amendola 173,70126 Bari,Italy;[4]Istituto Applicazioni Calcolo,CNR,Via Amendola 122/D,70126 Bari,Italy;[5]Istituto Applicazioni Calcolo CNR,via dei Taurini 19,00185 Rome,Italy 出　　处：《Communications in Computational Physics》索引2023年第33卷第1期,共26页 基　　金：funding from the Japan Society for the Promotion of Science(JSPS)KAKENHI grant 17H01083;funding from the National Science Foundation under Grant No.NSF PHY-1748958;D-ITP consortium,a program of the Netherlands Organization for Scientific Research(NWO)that is funded by the Dutch Ministry of Education,Culture and Science(OCW);funding from the European Research Council under the European Union’s Horizon 2020 Framework Programme(No.FP/2014-2020)ERC Grant Agreement No.739964(COPMAT);A.T.also warmly thanks Livio Carenza and Davide Marenduzzo for useful discussions.A.L.acknowledges funding from MIUR Project No.PRIN 2020/PFCXPE. 摘　　要：We numerically study the dynamics of quasi-two dimensional cholesteric liquid crystal droplets in the presence of a time-dependent electric field,rotating at constant angular velocity.A surfactant sitting at the droplet interface is also introduced to prevent droplet coalescence.The dynamics is modeled following a hybrid numerical approach,where a standard lattice Boltzmann technique solves the Navier-Stokes equation and a finite difference scheme integrates the evolution equations of liquid crystal and surfactant.Our results show that,once the field is turned on,the liquid crystal rotates coherently triggering a concurrent orbital motion of both droplets around each other,an effect due to the momentum transfer to the surrounding fluid.In addition the topological defects,resulting from the conflict orientation of the liquid crystal within the drops,exhibit a chaotic-like motion in cholesterics with a high pitch,in contrast with a regular one occurring along circular trajectories observed in nematics drops.Such behavior is found to depend on magnitude and frequency of the applied field as well as on the anchoring of the liquid crystal at the droplet interface.These findings are quantitatively evaluated by measuring the angular velocity of fluid and drops for various frequencies of the applied field. 关 键 词：Lattice Boltzmann simulations liquid crystals non-Newtonian fluids