Bulletin of the American Physical Society
77th Annual Meeting of the Division of Fluid Dynamics
Sunday–Tuesday, November 24–26, 2024; Salt Lake City, Utah
Session C03: Interact: Non-Newtonian and Granular Flows |
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Chair: Randy Ewoldt, University of Illinois at Urbana-Champaign Room: 155 B |
Sunday, November 24, 2024 10:50AM - 11:20AM |
C03.00001: INTERACT FLASH TALKS: Non-Newtonian and Granular Flows Each Interact Flash Talk will last around 1 minute, followed by around 30 seconds of transition time. |
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C03.00002: Protorheology: avoiding misinterpretation Randy H Ewoldt, Tanver Hossain, Ramdas Tiwari Protorheology is the paradigm that any observed flow, even in our daily encounters, is an experiment to infer quantitative rheological properties, such as shear viscosity, extensional viscosity, shear normal stress differences, viscoelasticity, and thixotropy without using a rheometer [1,2]. Although this can enable rapid insight, data validation, high-throughput characterization, and an inclusive approach to rheometry without needing a rheometer [3-5], there is also significant risk of misunderstanding the Newtonian and non-Newtonian fluid physics involved, owing to the potentially complex and uncontrolled nature of the flow that may conflate multiple forcing (e.g. gravity, capillarity) and resistance (e.g. viscous, viscoelastic, inertial). Here we describe several examples of embarrassing data misinterpretations of experimental protorheology flows and identify systematic approaches to avoid misinterpretation. Case studies show how serious the problems can be, e.g. mistaking a liquid as a solid, incorrectly assigning a viscoelastic relaxation time to a viscous flow time, and more. Whether you are making inference from a tilted vial, time-lapse gravity-driven flow, a bounce test, die swell, or any other protorheology observation, the examples here serve as a guide for avoiding bad data in protorheology by carefully understanding the flow physics involved. |
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C03.00003: Puff rheometer for fast and contactless measurements of viscosity and surface tension Coen van der Gracht, Nick O Jaensson, Ruth Cardinaels To enable in-situ and in-line characterization of the viscoelastic and interfacial properties of soft materials, we are developing a fast and non-manipulative apparatus. An air puff with a known pressure profile is applied to the surface of the material and the resulting surface deformation depends on the rheological, interfacial and physical properties of the material. Our puff rheometer combines measurements of the air-deformed surface and a numerical model within an optimization procedure. The numerical model, based on the finite element method, is used to model the deformation of the fluid caused by the air puff. The experimental setup uses pressurized air and a solenoid valve to control the air puff, and measures the deformation of the fluid surface with a laser sensor. With an optimization procedure, the numerical model can be matched to the live measurements, giving access to the surface tension and rheological properties. We analyze the sensitivity of the measurement results to various input parameters and material characteristics to quantify the potential of this method. Moreover, a simple analytical model capturing the main physical mechanisms is shown to accurately describe the experimental and numerical data for Newtonian fluids, which facilitates data extraction. |
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C03.00004: ABSTRACT WITHDRAWN
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C03.00005: The role of flow inhomogeneity in elastic turbulence Giulio Foggi Rota, Christian Amor, Giovanni Soligo, Rahul K Singh, Dhrubaditya MITRA, Marco Edoardo Rosti The addition of polymers to a Newtonian solvent can induce chaotic motion even at negligible inertia, resulting in a turbulence-like state known as Elastic Turbulence (ET)1. Predominantly driven by experimental studies, ET research has recently seen advances through direct numerical simulations aimed at unveiling its intricate dynamics. |
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C03.00006: Transition from elastic instability to drag reduction observed in two-dimensional turbulent flow Ruri Hidema, Kengo Fukushima, Robert J Poole, Hiroshi Suzuki To detect the flow regimes of Newtonian turbulence (NT), elasto inertial filament (EIF), elasto inertial turbulence (EIT) and maximum drag reduction (MDR) of polymer solution and their transition have been a hot topic in the last decade. We attempted to detect NT, EIF, EIT, and MDR by visualizing vortex shedding downstream of an array of cylinders that was inserted perpendicular to polymer-doped two-dimensional flow (2D). Polymers are stretched at the cylinders, and therefore, vortex shedding is affected as the consequent of viscoelasticity. The flow regimes are characterized based on Weissenberg (Wi) and Reynolds numbers (Re) with the relaxation time of the polymeric solution. The flow regimes are observed for different molecular weights of polymers in solution and are categorized as either vortex type 1, type 2 and type 3 on a Re-Wi map based on flow visualization using particle image velocimetry (PIV). In addition, turbulent statistics of these flow regimes are calculated to more fully quantify these flow regimes. We found that vortex types from 1 to 3 have a similarity to NT, EIF, EIT and MDR. In addition, characteristic turbulent energy transfer without an increase in turbulent energy production was found in the flow regimes of vortex types 2 and 3 of each polymer solution. |
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C03.00007: Elasto-inertial transitions in particle-laden viscoelastic Taylor-Couette flow Charles Carré, Masoud Moazzen, Tom Lacassagne, S. Amir Bahrani The Taylor-Couette flow of dilute to semi-dilute suspensions of neutrally buoyant spherical particles in viscoelastic base polymer solutions is investigated. Friction measurement are synchronized with flow visualisation to characterize the critical conditions for the onset of elasto-inertial regimes. Lower particle volume fractions do not affect the nature of the primary transition to elastoinertial turbulence (EIT), even reducing the critical Weissenberg number for the onset of EIT, despite a decrease in the apparent fluid elasticity. For semi-dilute particle volume fractions, an apparent relaminarization occurs with yet not further decrease in fluid elasticity. A new regime termed here Elasto-Inertial Dissipative replaces EIT. Increasing particle volume fraction in the semi-dilute regime delays the onset of EID similarly to what was observed previously for EIT in lower elasticity fluids. After the onset, a decrease in the pseudo-Nusselt number observed with increasing inertia and particle-to-polymer concentration ratio confirms a particle-induced alteration of energy transfers in the flow. |
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C03.00008: Elastic turbulence in channel flows Marco Edoardo Rosti, Giulio Foggi Rota, Christian Amor In micro-scale systems, the efficient mixing of different species proves challenging since inertial turbulence gives way to the dominance of viscous diffusion, due to the small geometries and flow rates. To recover a chaotic fluid motion at vanishing inertia, elastic properties can be conferred upon the fluid dissolving small amounts of polymers, resulting in what is known as elastic turbulence. In our study, we employ fully resolved 3D numerical simulations and the FENE-P polymer model to characterize this turbulent state in planar geometries, and compare it with what observed at large Reynolds number. In the talk, we will present how the shear momentum balance is altered by polymers at vanishing inertia, and investigate the resulting mean and fluctuating components of the velocity field. |
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C03.00009: A Period-Doubling Route to Chaos in Viscoelastic Kolmogorov Flow Becca Thomases, Robert D Guy, Jeffrey Nichols Polymer solutions can develop chaotic flows, even at low inertia. This purely elastic turbulence is well studied, but little is known about the transition to chaos. In 2D channel flow and parallel shear flow, traveling wave solutions involving coherent structures are present for sufficiently large fluid elasticity. We numerically study 2D periodic parallel shear flow in viscoelastic fluids and show that these traveling waves become oscillatory and undergo a series of period-doubling bifurcations en-route to chaos. |
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C03.00010: Direct measurement of individual polymer dynamics reveals the conformation tensor in viscoelastic cross-channel flows Jeffrey S Guasto, Louison Thorens, Gabriel Juarez, Paulo E. Arratia Much effort has been devoted to quantifying and understanding the continuum-level stresses responsible for the flow behavior of polymeric fluids. However, the underlying stretching dynamics and relaxation of individual polymers in complex, viscoelastic fluid flows remain relatively unexplored. In this study, single molecule tracking reveals the individual Lagrangian dynamics and spatially resolved conformations of dilute polymer suspensions in a microfluidic cross-slot flow. Fluorescently labeled DNA molecules are tracked for a range of Weissenberg numbers, including two different polymer contour lengths and concentrations. The Lagrangian polymer stretching is correlated with the fluid deformation history from measured flow fields that exhibit spatially non-uniform velocity gradients. A direct comparison of the measured polymer conformation tensor with a theoretical Oldroyd-B model demonstrates a strong dependence on the rheological model, while worm-like chain simulations more broadly capture features of the measured conformation. This work highlights the crucial role of complex individual molecular dynamics in refining models to predict polymeric flow behavior. |
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C03.00011: Flow and Final Shapes of Printed Yild Stress Filaments Maziyar Jalaal, Hugo França Various coating, inkjet printing, and 3D printing techniques utilize the deposition of droplets and filaments of yield stress fluids on a substrate. On small scales, surface tension is the primary driving mechanism, determining the dynamics and the final shape of the deposited material. We present experimental and theoretical results within the plastocapillarity limit, where the competition between surface tension and the complex elasto-viscoplastic rheology of the material determines the dynamics of spreading and the final shape of the deposition. To this end, we analyze single filaments and the coalescence of two filaments on the surface. |
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C03.00012: Dynamic mechanical analysis of alginate/gellan hydrogels under controlled conditions relevant to environmentally sensitive applications Juan Pablo Segovia, José Alberto Rodríguez Agudo, Jürgen Utz, Natalie Germann Hydrogels are suitable for a wide range of applications including wearable sensors, biomedicine and agriculture. However, due to their nature, their performance is sensitive to temperature, humidity, and mechanical strain. In this work, we investigate the mechanical response of filled and unfilled alginate/gellan hydrogels using combined axial-torsional rheometry. Cylindrical samples with large length/diameter ratios are used in a controlled environment. The approach allows dynamic mechanical analysis of the same sample in both torsion and extension under identical conditions in a single measurement run. This ensures consistent initial and boundary conditions, which are essential for reliable estimation of the dynamic moduli G* and E* and their dependence on frequency and environmental factors. Our results indicate that humidity variations critically affect the mechanical response due to the observed sample volume shrinkage, requiring corrections to the moduli. We also find that temperature plays a role only under significant changes in humidity. Unfilled specimens in breaking tests show only slippage due to twist-induced surface water excess, in contrast to the breakage of specimens filled with mesoporous silica particles, which is likely related to restricted water diffusion. |
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C03.00013: Rheology of hydrogels using ultrasound and rheometer Megan Anderson, Michael W Plesniak, Kartik Venkat Bulusu, Lijie Grace Zhang, Kausik Sarkar Tissue engineering applications necessitate biocompatible hydrogel scaffolds that helps in cell growth and differentiation. There is a growing interest in characterizing the mechanical properties of such hydrogel scaffolds geared toward a variety of tissue engineering applications such as native tissue enhancement, tissue replacement, and drug delivery. This study examines chemically cross-linked gelatin methacrylate (GelMA) and poly(ethylene glycol) diacrylate (PEGDA) hydrogels, two popular biomaterials used in tissue engineering. We characterized an array of scaffolds, fabricated by varying both GELMA and PEGDA concentrations and ultraviolet (UV) light exposure time. Pulse-echo ultrasound techniques were used to non-invasively determine the sound speed and attenuation of the scaffolds, revealing significant dependence on GelMA and PEGDA concentrations. Steady shear and frequency-controlled oscillatory shear tests were performed using a rotational rheometer (Model: DHR-2, TA Instruments) varying strain rates, oscillation frequencies, and amplitudes. By probing hydrogels using acoustic and rotational rheometer techniques, we establish a relationship between the two methods additionally offering an understanding of the effect of chemical crosslinking on the dynamic response of hydrogels. They can inform the selection of scaffold materials in tissue engineering applications. [Partially supported by the National Science Foundation]. |
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C03.00014: Unravelling Wrinkle Formation in a Lubricated Viscoplastic Beam Thomasina V Ball, Jerome A. Neufeld, Anthony F Bonfils Wrinkles or creases in the surface of a material are indicative of compression. On Earth, mountain ranges formed due to the plate tectonics exhibit regular spaced folds on the surface; and buckles on the surface of ice sheets are observed due to compression from sea ice. Both examples have a layered structure with contrasting rheological behaviours where compression leads to an instability causing the stiff surface to buckle. |
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C03.00015: Interplay between complex fluid rheology and wall compliance affects the hydrodynamic resistance of deformable channels Evgeniy Boyko Viscous flows through configurations manufactured from soft materials apply pressure and shear stress at the solid-liquid interface, leading to deformation. The resulting fluid-structure interaction affects the relationship between the pressure drop and the flow rate or the hydrodynamic resistance, which is the ratio between the two. While the hydrodynamic resistance in deformable configurations has been extensively studied for Newtonian fluids, it remains largely unexplored for non-Newtonian fluids even at low Reynolds numbers. In this work, we present a theoretical framework for calculating the hydrodynamic resistance of complex fluids in deformable axisymmetric channels. Our theory applies to a wide class of shear-thinning and viscoelastic constitutive models in the weakly non-Newtonian limit and provides the leading-order effect of the interplay between complex fluid rheology and wall compliance on the hydrodynamic resistance, bypassing the detailed calculations of the non-Newtonian fluid-structure-interaction problem. We illustrate our approach for a viscoelastic Oldroyd-B fluid and a shear-thinning Carreau fluid, highlighting the physical mechanisms underlying the response for each non-Newtonian fluid. |
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C03.00016: Agglomeration and de-agglomeration of cohesive particles in a vertically vibrated bed Manaswita Bose, Alok Tiwari Cohesive forces play an important role for particles with sizes below 100 microns. The focus of the current work is investigation of deagglomeration under vibration using simulations based on discrete element method. Simulations are performed using the opensource software LAMMPS. Analyses are carried out at two different levels. First, a system of multiple agglomerates, where agglomeration and deagglomeration occur simultaneously, in a vibrated bed, were studied. Second, the deagglomeration of a single agglomerate under vibration is investigated to determine the rate of the attrition and/or breakage of the cohesive cluster. Particles with a wide range of sizes from 50 nm to 100 microns are used. Simulations are performed with different contact models. A set of simulations were carried out using a combination of a linear spring and van der Waals force model. Simulations were also performed in which Hertz-JKR model was used to determine the contact force between the particles. This is to ensure the size indepence of the results. In multiple agglomerate systems, three different regimes exist depending on the ratio of the maximum energy of the vibrating base to that of cohesive energy. Deagglomeration of a single cluster under vibration is observed to obey first-order kinetics. The deagglomeration rate constant shows an Arrhenius-type behaviour. Results obtained with linear-spring-van-der-Waals are consistent with those of the Hertz-JKR model. |
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C03.00017: The "sticky" sands of time : effects of cohesion on silo discharge Alban Sauret, Ram Sudhir Sharma, Alexandre Dillon Leonelli, Eckart Heinz Meiburg The flow rate of cohesionless granular materials exiting a silo is commonly described by the ``Beverloo's law" which captures the role of the aperture size and grain diameter. Yet, the role of interparticle cohesive force in the emptying of a silo remains unclear. Indeed, the presence of cohesion can lead to clogging of the aperture. Even when the cohesive grains freely flow through the aperture, the flow rate must account for the cohesion. Here, we experimentally rely on model cohesive grains to extend the Beverloo's law to cohesive particles. A flat-bottomed cylindrical silo with a circular aperture is filled with cohesion-controlled particles. First, more inter-particle cohesion requires larger openings for any flow. For large enough apertures, flow is indeed observed for cohesive particles as well, but the discharge is systematically less for greater cohesion. These observations are quantitatively connected to the magnitude of cohesion between the particles. |
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C03.00018: Discharge of non-spherical particles from a monolayer silo Devaraj R.M. Van Der Meer, Muhammad Ahmed Hanif, Diego Maza We performed well-controlled experiments comparing the outflow of monodisperse batches of spheres and of several non-spherical particles from a quasi-two-dimensional monolayer silo. We investigate the velocity and solid fraction profiles at the orifice and test whether the profiles for the non-spherical particles have similar self-similar properties as in the spherical case. We find that the magnitude and shape of the velocity profiles for all particle types are in the same range. In contrast, the solid fraction at the orifice has a dome-shaped profile for the non-spherical particles, whereas the profile for the spherical case is rather flat. The discharge rate determined from the velocity and solid fraction profiles describes the independently measured experimental discharge rate very well for all investigated particle types. |
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C03.00019: Structured Bubbling Flow in Granular Matter with Oscillated Gas Injection Which Alternates with Horizontal Position Javad Omidi, Christopher M Boyce Gas bubbling in fluidized granular beds has a strong influence on particle mixing and heat transport. Gas bubble dynamics are often mathematically chaotic and vary significantly with system size, complicating scale-up, control and optimization of fluidized bed reactors. Oscillating gas flow or vibrating fluidized beds can lead to the formation of structured bubbling patterns which do not change with increasing system width or height, potentially addressing issues with chaotic bubbling. However, studies have shown that the triangular lattice array of rising structured bubbles forces mixing to be compartmentalized. Here, we model structured bubbling in fluidized beds using two-fluid modeling with gas flow oscillated with different oscillation phases for different regions of the gas distributor. Varying the phase in different sections of the distributor achieves different lattice structures for arrays of structured bubbles, and these different patterns lead to different mixing rates for particles. The effects of gas phase offset and number of slices in the distributor are investigated. We discuss the mechanisms for pattern formation and the implications on having a wider range of bubble patterns achievable in structured bubbling fluidized beds. |
Sunday, November 24, 2024 11:20AM - 12:50PM |
C03.00020: INTERACT DISCUSSION SESSION WITH POSTERS: Non-Newtonian and Granular Flows After each Flash Talk has concluded, the Interact session will be followed by interactive poster or e-poster presentations, with plenty of time for one-on-one and small group discussions. |
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C03.00021: ABSTRACT WITHDRAWN
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