Bulletin of the American Physical Society
71st Annual Meeting of the APS Division of Fluid Dynamics
Volume 63, Number 13
Sunday–Tuesday, November 18–20, 2018; Atlanta, Georgia
Session M37: Suspensions: Rheology |
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Chair: Harishankar Manikantan, UCSB Room: Georgia World Congress Center B409 |
Tuesday, November 20, 2018 8:00AM - 8:13AM |
M37.00001: Flow Resistance and Structures in Viscoelastic Channel Flows at Low Re Boyang Qin, Paul Salipante, Steven Hudson, Paulo E. Arratia The flow of viscoelastic fluids in channels and pipes remain poorly understood, particularly at low Reynolds numbers. Here, we investigate the flow of polymeric solutions in straight channels using pressure measurements and particle tracking. The law of flow resistance is established by measuring the flow friction factor $f_{\eta}$ versus flow rate. Two regimes are found: a transitional regime marked by rapid increase in drag, and a turbulent-like regime characterized by a sudden decrease in drag and a weak dependence on flow rate. Lagrangian trajectories show finite transverse modulations not seen in Newtonian fluids. These curvature perturbations far downstream can generate sufficient hoop stresses to sustain the flow instabilities in the parallel shear flow. |
Tuesday, November 20, 2018 8:13AM - 8:26AM |
M37.00002: Rheology of sheared bidisperse and polydisperse suspension of hard spheres Rishabh V More, Arezoo M Ardekani In the past numerous studies have been conducted on the rheology of suspensions. It has been shown that including the interparticle friction and roughness on the particle surface is crucial to numerically reproduce many of the experimentally observed effects (e.g. shear thickening) in concentrated suspensions. Considering these observations, the aim of this study is to systematically study the effects of roughness and friction on the rheology of concentrated bi and polydisperse suspensions. We utilize resistance formulation to model the hydrodynamic interactions. Contact forces arising due to roughness and friction are modelled as in Discrete Element Method (DEM), a popular method in granular physics. In this talk, we will be presenting the results of these simulations. |
Tuesday, November 20, 2018 8:26AM - 8:39AM |
M37.00003: Isentropic viscosity of sheared suspensions in crystalline states Behrouz Abedian A geometric description of particle stresses in a mixture determines isentropic viscosity of solid spherical suspensions at arbitrary concentrations based on the suspensions’ microstructural crystallinity. For an equal-sized spherical suspension system, the resulting geometric expression predicts well the classical experimental and numerical viscosity data at different particle concentrations, when the crystalline states are considered as simple cubic, random distribution, face-centered cubic or body-centered cubic. It is concluded that some observed non-Newtonian behaviors of a suspension system can be construed as micro-structural transitions. This geometric model agrees remarkably well with light-scattering experimental observations on structural transitioning in colloidal and non-colloidal mixtures. Effects of particle inertia and particle Brownian fluctuations on the viscosity are taken to be dependent on solutions’ crystalline states. |
Tuesday, November 20, 2018 8:39AM - 8:52AM |
M37.00004: Interface-resolved simulations of particle suspensions in Newtonian, shear thinning and shear thickening carrier fluids Dhiya Alghalibi, Iman Lashgari, Luca Brandt, Sarah Hormozi We have performed simulations via employing an Immersed Boundary Method (IBM) to study flows of noncolloidal spherical and rigid particles suspended in Newtonian, shear thinning and shear thickening fluids. We consider a linear Couette configuration to explore a wide range of solid volume fractions and particle Reynolds numbers. We show that the existence of a wide spectrum of the local shear rate and its dependency on the solid volume fraction and particle Reynolds number points to the deficiencies of the mean field argument in estimating the rheology of noncolloidal complex suspensions. We indicate the role of inertia at the microstructural level and include it in the closure for the suspension shear stress for both Newtonian and power-law suspending fluids. |
Tuesday, November 20, 2018 8:52AM - 9:05AM |
M37.00005: Universal scaling law in frictional non-Brownian suspensions Frédéric Blanc, Enzo D'Ambrosio, Laurent Lobry, François Peters, Elisabeth Lemaire We compare the rheology of two kinds of non-Brownian suspensions. One is made of spherical monodisperse polystyrene particles (diameter 80 μm) and the other is made of faceted sugar particles (100μm), both suspended in a Newtonian silicon oil. We perform shear reversal experiments on both suspensions for several particle volume fractions, Φ, and several shear stresses, τ. The two suspensions behave in a quite different fashion. For the faceted particle suspensions (FPS), a large shear-thinning is observed while it is much more moderate for the spherical polystyrene particle suspensions (SPS). Another striking difference lies in the value of the jamming packing fraction, Φm that is much lower for FPS than for SPS. Despite these differences, we will show that shear reversal experiments make it possible to obtain a universal scaling that holds for both FPS and SPS. In this scaling, the difference between the steady viscosity and the viscosity at the minimum that follows the shear reversal, normalized by the steady viscosity is shown to depend only on the ratio Φ/Φm(τ). The collapse of all the data suggests that concentrated non-Brownian suspensions behave in a universal way regardless of the mechanisms responsible for flow-hindering (rotation frustration or sliding friction). |
Tuesday, November 20, 2018 9:05AM - 9:18AM |
M37.00006: Inertial shear thickening in non-Brownian suspensions Yasaman Madraki, Aaron Oakley, Guillaume Ovarlez, Sarah Hormozi In shear thickening suspensions, viscosity appears to increase when the shear rate increases. In non-Brownian suspensions, different modes of shear thickening behavior have been identified. These modes are attributed to different physical mechanisms such as hydrodynamic interactions among particles, transition from frictionless to frictional rheology, transition from a viscous to an inertial regime, microstructural effects, etc. We have designed a model non-Brownian suspension to study experimentally the viscous to inertial mode of shear thickening behavior. We discuss the inertial shear thickening mode in detail and show that transition from the viscous to the inertial regime may occur at particle Reynolds number smaller than 1 in the limit of jamming volume fraction. In addition, we provide a closure for shear stresses in inertial suspensions. |
Tuesday, November 20, 2018 9:18AM - 9:31AM |
M37.00007: Experimental study of electrorheological fluids Suchandra Das, Naga A Musunuri, Islam Benouaguef, Edison C Amah, Shriram Pillapakkam, Pushpendra Singh, Ian S Fischer The viscosity of an electrorheological (ER) fluid formed by suspending dielectric particles in dielectric liquids increases within a few milliseconds after an electric field is applied, and when the electric field is removed the viscosity goes back to the original value. Thus, ER fluids are appropriate for applications in which adjustable viscosity with a small response time is desired. The viscosity increases because when an electric field is applied the particles become polarized and interact with each other to form particle chains and columns that are aligned in the direction of the field. The aim of this work is to study the dependence of the electrorheological response on the properties and size distribution of the particles. We are also using a direct numerical simulation approach to model their electrorheological response. |
Tuesday, November 20, 2018 9:31AM - 9:44AM |
M37.00008: Attractive and Repulsive Particles: Relations Between Microstructure Formation and Yield Behavior of 2D Jammed Clays Larry Galloway, Douglas Jerolmack, Paulo E. Arratia To advance predictive models of bulk behavior of naturally occurring materials, such as clay or mud, it is important to understand the dynamics and structural properties of the material constituents (i.e. particles). Here, we investigate the flow and microstructure of clay suspensions using a custom made interfacial stress rheometer. This device measures suspension rheology (e.g. G’, G”) while simultaneously characterizing the fluid microstructure. We find the development of system-spanning networks of attractive particles that cause jamming at lower concentrations as compared to repulsive systems. The role of reversibility in yielding of naturally occurring, complex materials is elucidated by studying a system of clay. Kaolinite, a non-swelling plate shaped clay is chosen because these particles have opposite charges on faces as edges, creating bulk attraction. We observe evolution of the microstructure in the form of system-spanning aggregates and persistent voids. Inter-particle attraction is believed to create these aggregates, which in turn impede shear. It is expected that elasticity grows steadily with shear frequency, but at a critical amplitude loss due to viscosity sets in. |
Tuesday, November 20, 2018 9:44AM - 9:57AM |
M37.00009: Manipulating the sedimentation of Kaolinite clay suspensions through charge interactions Sebastien Kosgodagan Acharige, Ali Seiphoori, Douglas J Jerolmack, Paulo E. Arratia Clay minerals are present in many natural (landslides, river channels) and industrial processes (ceramics, cosmetics, oil recovery). They are plate shaped charged colloids and exhibit different rheological properties than suspended hard-sphere colloids, e.g. thixotropy and shear-banding. Kaolinite clay platelets are easily found in nature and when suspended in liquids, they possess non-zero yield stress at low concentrations, indicating that the particles structure themselves through attractive interactions. Here, sedimentation of kaolinite suspensions in water are performed as a model system for geophysical flows. Using salts (NaCl and (NaPO_{3})_{6}) to manipulate particle interactions from attractive to repulsive, we manipulate the sedimentation behavior from hard-sphere to gel-like behavior. Rheological experiments show that the repulsive kaolinite suspensions are Newtonian, while introduction of attraction leads to non-Newtonian behavior and flow hysteresis. Knowing that phosphate and chloride salts are common in nature, these observations provide insights for geophysical flows, like particulate gravity currents or the erosion threshold for cohesive river banks. |
Tuesday, November 20, 2018 9:57AM - 10:10AM |
M37.00010: A computational model of particle hydrodynamics and charge transfer for the carbon slurry in electrochemical supercapacitors Mehdi Karzar-Jeddi, Haoxiang Luo Slurries of porous carbon particles are being used as flowable electrodes in electrochemical supercapacitors such as electrochemical flow capacitors (EFCs) and flow-electrode capacitive deionization (FCDI). In these devices, the activated carbon beads absorb ions from the aqueous electrolyte and meanwhile store electronic charges by forming a dynamic, topology-varying percolation network. Our objective is to study how the hydrodynamic interactions of the carbon particles affect transfer of electrons and the charging/discharging process. In our computational model, the hydrodynamics of particles is simulated using a Stokesian dynamics approach that incorporates the presence of a no-slip wall representing the stationary electrode. The flow is driven by a specified shear. A generalized electrical circuit is introduced to represent the percolation network whose topology is constantly disrupted by random particle-particle and particle-wall contact and separation. The model parameters are either based on previous experimental setups or estimated from relevant studies. We explored three cases where the hydrodynamic time scale is either much smaller than, or comparable to, or much larger than the characteristic charging time scale. |
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