Bulletin of the American Physical Society
74th Annual Meeting of the APS Division of Fluid Dynamics
Volume 66, Number 17
Sunday–Tuesday, November 21–23, 2021; Phoenix Convention Center, Phoenix, Arizona
Session Q28: Particle-laden Flows: Non-Spherical Particles II |
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Chair: Gregory Voth, Wesleyan University Room: North 228 AB |
Tuesday, November 23, 2021 8:00AM - 8:13AM |
Q28.00001: Sedimentation of flexible fiber suspensions and large cluster formation at finite Reynolds number Vahid Tavanashad, Kourosh Shoele In this work, we numerically study suspensions of flexible fibers sedimenting in an otherwise quiescent fluid. The Navier-Stoke equations are solved as the governing equations for the fluid phase. The fibers are modeled using an incompressible hyperelastic Mooney–Rivlin material description. The governing equations of both phases are coupled together using the immersed boundary method. The fibers are initially distributed homogenously in the domain under the action of gravity. The hydrodynamic interaction of fibers and surrounding fluid modifies the initial structure of fibers, and regions of low and high concentration of fibers are generated within the domain. In this work, we focus on the effect of Galileo number and the initial concentration and flexibility of fibers on the system's behavior. We present results regarding the sedimentation velocity of the suspension, the changes in local concentration, and the orientation of fibers. Finally, the statistics of clusters in the system are discussed. |
Tuesday, November 23, 2021 8:13AM - 8:26AM |
Q28.00002: The dynamics of thin disks falling in quiescent air Amy Tinklenberg, Michele Guala, Filippo Coletti Laboratory experiments are performed with 1, 2, and 3mm diameter thin disks falling in a large quiescent air chamber, with results relevant to plate ice crystals in the atmosphere. Virtually all previous studies concerned with disk falling dynamics used larger analogue particles in liquid fluids, thus focusing on the behavior of singular particles at relatively small density ratios. In our experiment, we aimed to match the conditions typical of atmospheric precipitation more closely by releasing a controlled volume fraction of realistically sized disks with a high density ratio in air. Through high-speed 2D Particle Tracking Velocimetry (PTV), we obtain the planar disk trajectories as well as the necessary information to reconstruct their full 3D angular motion. This presentation will focus on results related to the individual disk dynamics – including their rotation rates, falling styles, and distinct behaviors based on the disk diameters and the fall style of each trajectory. Torque scaling and particle response times, both translational and rotational, will also be considered. |
Tuesday, November 23, 2021 8:26AM - 8:39AM |
Q28.00003: Interface-resolved simulations of non-spherical particles with collisions Yuanqing Liu, Lian Shen Particle collisions are likely to happen when particles are close to each other. These collisions change the trajectories of the particles and modify the flow field around them. While the collisions of spherical particles have been studied extensively, the scenario of non-spherical particles is less understood. In this work, we present numerical simulations of spheroid particles considering collisions among them. We use the immersed boundary method to resolve the interactions between the flow and particles. Collisions between particles are modelled by a linear spring-dashpot system. The Adaptive Collision Time Model is employed to calculate the contact force. These numerical tools enable us to study realistic flows where point particle model is not applicable, providing further insights into the effects of collisions on spheroids and fluid flows. |
Tuesday, November 23, 2021 8:39AM - 8:52AM |
Q28.00004: Dynamics of Finite-length Rods Near Solid Boundaries Jian Teng, Bhargav Rallabandi, Howard A Stone, Jesse T Ault The motion of finite-length cylindrical rods moving near a planar rigid surface is a scenario common across many engineering and natural settings. The rods are allowed to rotate or translate in directions perpendicular or parallel to the plane. We develop a three-dimensional lubrication theory to characterize the pressure and hydrodynamic resistances of the cylinders through a special consideration of the cylinder's end-effects. In addition, three-dimensional numerical simulations were used to solve these Stokes flows for cylinders of varying lengths and with varying gap sizes between the plane, and the numerical results support the developed analytical descriptions. Visualizations of the flow will be presented to provide qualitative insights and rationalize the effect of the ends on the dynamics of the cylinders. We demonstrate our newly developed theory can successfully account for the finite length effects of cylinders moving near planar boundaries. |
Tuesday, November 23, 2021 8:52AM - 9:05AM |
Q28.00005: Interplay between membrane and nanoparticle mechanical properties during cellular targeting and uptake of flexible nanoparticles Samaneh Farokhirad, Sreeja Kutti Kandy, Andrew Tsourkas, Portonovo S Ayyaswamy, David M Eckmann, Ravi Radhakrishnan It is becoming evident that engineered physicochemical characteristics of nanoparticles (NPs) are essential to improve their biological function for their cellular delivery and uptake. How NP mechanical properties impact multivalent ligand-receptor mediated binding to cell surfaces, avidity of NP adhesion to cells, and cooperative effects due to crowding remain largely unknown or unquantified, and how tuning NPs’ stiffness impacts their propensity for internalization is not clear. Here we focus on exploring the binding mechanisms of three distinct NPs that differ in type and rigidity (core-corona flexible NP, rigid NP, and rigid-tethered NP) but are otherwise similar in size; moreover, for the case of flexible NP, we tune NP stiffness by varying the internal crosslinking density. We employed our recent spatial biophysical modeling of NP binding to membranes together with thermodynamic analysis powered by free energy calculations and show that efficient cellular targeting and uptake of functionalized NP can be shaped by factors including NP flexibility and crowding, receptor-ligand binding avidity, state of the membrane cytoskeleton, and curvature inducing proteins. Our findings provide strong evidence that NP flexibility is an important design parameter for rationally engineering NP targeting and uptake in a crowded cellular adhesion microenvironment. |
Tuesday, November 23, 2021 9:05AM - 9:18AM |
Q28.00006: Dancing Droplets Jeremy Horwitz Droplet motion and collisional processes are important in many applications including cloud growth and fuel spray combustion. Unlike rigid particles, whose surfaces, by definition are invariant to fluid stresses and neighbor impacts, droplets can experience large surface deformations and break up when subjected to external loads. In particular, surface deformation can couple to droplet migration whereby changes in a droplet’s projected area and moment of inertia changes the forces and torques it experiences. To study some of these effects, we introduce a Lagrangian droplet deformation model inspired by Taylor’s experiments in 1934 whereby a four-roll apparatus deforms a spherical droplet into an ellipsoid. The proposed model takes into account the dynamic evolution of the droplet’s principal axes allowing changes in shape to feed into the equations of linear and angular momentum. The model is formally valid in the limit of low Capillary number to ensure the assumption of ellipsoid deformation remains valid. We apply the Lagrangian model to a cellular flow considered by Maxey in 1987 for rigid particles to understand how the basic clustering mechanisms of strain-rate versus vorticity effect droplet clustering whose surface evolution and hence clustering are dependent on local fluid properties. |
Tuesday, November 23, 2021 9:18AM - 9:31AM Not Participating |
Q28.00007: Effect of viscoelasticity on the orientational dynamics of a prolate spheroidal particle in simple shear flow: Slender body theory and fully resolved simulations Arjun Sharma, Donald L Koch Particle-laden viscoelastic/ polymeric flows undergo shearing motion in many processing applications such as injection molding, spin casting, or flow casting. The orientation of prolate spheroidal particles in Newtonian Stokes flow follows one of the degenerate orbits, dependent on the initial condition, known as Jeffery orbits. Using a regular perturbation in low polymer concentration, we develop a slender body theory to characterize the effect of viscoelasticity on the orientational motion of a large aspect ratio particle. Depending on the polymer relaxation time and particle aspect ratio, the theory predicts four qualitatively different behaviors to arrive at a fixed orientation. The particle orientation either spirals across Jeffery orbits or aligns near the flow-vorticity plane and eventually aligns at either the vorticity axis or near the flow axis. We test our theory and investigate higher polymer concentration effects using a novel finite-difference numerical solver written in prolate spheroidal coordinates, which exactly models the particle surface as one of the coordinate surfaces. This code allows us to simulate large aspect ratio particles with fewer mesh points and less computation time than a solver written in Cartesian coordinates. |
Tuesday, November 23, 2021 9:31AM - 9:44AM |
Q28.00008: Study of shear-induced deformation and fragmentation of laboratory-cultured marine aggregates Yixuan Song, Matthew J Rau, Adrian Burd Mass transport of marine aggregates is one of the remaining uncertainties for understanding the oceanic carbon cycle. Marine hydrodynamics alter the size of these aggregates, regulating the total mass flux. Different from droplets and colloidal aggregates, marine aggregates have unique bonding forces among biological primary particles, which causes distinct mechanical properties relevant to deformation and fragmentation. To understand that, we conducted breakup experiments with lab-made aggregates from cultured diatoms. In this study, a novel rotating/oscillating tank provided calibrated laminar shear, in which the shear rate was comparable to that in the surface ocean. We also developed a particle matching and breakup detection algorithm that allowed for individual aggregate tracking. With high-speed imaging techniques, we observed aggregates deforming and disrupting under varying shear. The aggregate morphological evolutions can be coupled to their local shear exposure. With our database, we summarize the necessary hydrodynamic conditions for breakup and discuss the unique morphological changes that precede breakup in terms of aggregate shape, orientation, and Taylor deformation parameter. |
Tuesday, November 23, 2021 9:44AM - 9:57AM |
Q28.00009: Rotations of Large Non-spherical Particles in Turbulence Greg A Voth Many different approaches are used to define scale-local structures which can be used to quantify the multi-scale dynamics of the turbulent cascade. One very concrete option is to use the rotational motion of rigid bodies. For example, the tumbling rate of slender fibers has been shown to display inertial range scaling with the mean square tumbling rate scaling as d-4/3 where d is the fiber length. A measured particle history provides a sampling of the dynamic evolution of the flow structure at the scale of the particle. Particle shape plays a central role due to preferential alignment of non-spherical particles by the strain produced by the flow structure. This talk will discuss what we have learned from measuring rotations of large particles in turbulence and the picture that is emerging from recent numerical and experimental work. |
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