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The 8th Pacific Rim Conference on Rheology was held in Vancouver, on the Point Grey campus of the University of British Columbia (UBC)*, May 15 – 19, 2023.
For more information about the event, please visit prcr2023.ca
Click here to download the program at a glance
CONFERENCE TRACKS:
General Symposia
G01. Polymer Solutions and Melts
G02. Industrial Rheology in Polymer Processing
G03. Blends, Composites and Nanocomposites
G04. Suspensions and Colloids
G05. Emulsions and Foams
G06. Self-assembly and Flow-induced Systems and Gels
G07. Biomaterials and Biological Systems
G10. Non-Newtonian Fluid Mechanics and Stability
G12. Rheology in the Oil and Gas Industry
G13. Rheology in the Mining Industry
Special Symposia
(By invitation only)
S02. Hiroshi Watanabe – Honorary Symposium
Poster Session
P01. Posters on any topic of rheological interest
*UBC Point Grey Campus is on the unceded Traditional Territory of the xʷməθkʷəy̓əm (Musqueam) People
Conference registration will open in the Gallery Lounge & Patio (6133 University Blvd. UBC Campus) on Monday May 15 at 6:00 pm, which is a short stroll away from your accommodation. There will be dinner and drinks offered in the lounge up until around 10pm, with a nice patio to sit out on and reconnect with friends.
Ian Frigaard and Savvas Hatzikiriakos
Abstract:
Yield stress fluids are often thought about in a piecewise manner as behaving like elastic solids below the yield stress and like generalized Newtonian liquids above it. Accurate determination of the yield stress is therefore crucial to understanding and predicting the behaviour of yield stress fluids such as inks for 3D printing, foods and cosmetics, muds and soils, and many industrially and biologically relevant materials. Despite the centrality of the yield stress concept, there exist multiple methods by which researchers determine ‘the’ yield stress, and they can provide values that are orders of magnitude apart. Such discrepancies have even led to some asking the question of whether the yield stress exists at all.
In this work we study a series of yield stress fluids using recovery rheology concepts, where strain is decomposed into recoverable and unrecoverable components, and present evidence that yielding takes place gradually over a wider range of stresses than previously thought. It is shown that the overshoot in the loss modulus that has often been used as a measure of yielding is due to the acquisition of unrecoverable strain. It’s shown how these measurements led to the development of a model that describes spatially heterogeneous yielding in a mean-field manner and how accurately this model predicts the rheology of simple yield stress fluids.
In more complex materials, responses are observed with two overshoots in the loss modulus, a phenomenon often referred to as “double yielding”. It is shown that these dual features are really a combination of two distinct processes, only one if which is yielding. New protocols inspired by recovery concepts are also used to show that small amounts of flow occur below the yield stress determined by a Herschel-Bulkley fit to steady-shear flow measurements in a predictable manner as a function of stress amplitude, angular frequency, and applied stress phase angle. Relations are presented that show how these measures can be used to determine the contribution to the loss modulus from unrecoverable plastic deformations, providing some of the same information as the full iteratively performed recovery tests, but in a fraction of the time.
Recovery rheology therefore adds nuance to our understanding of yield stress fluids by highlighting the continuous nature of yielding and providing a general set of methods by which reliable and consistent yielding information can be rapidly obtained.
Bio: Simon A. Rogers is an Associate Professor in the Department of Chemical and Biomolecular Engineering, University of Illinois at Urbana-Champaign, USA. Dr. Rogers uses experimental and computational tools to understand and model advanced colloidal, polymeric, and self-assembled materials. He received his BSc in 2001, BSc (Hons) in 2002; and his PhD from Victoria University of Wellington in New Zealand in 2011. He completed his postdoctoral research at the Foundation for Research and Technology in Crete, the Jülich Research Center in Germany, and the Center for Neutron Research at the University of Delaware.
Abstract:
Sludge rheology is important for the design and operation of sludge treatment processes in terms of process optimisation and maintenance cost reduction. Sludge rheology has a significant impact on the performance of pumps, anaerobic digesters, dewaterability equipment, mixers, and heat exchangers.
A large portion of the total energy consumption in any sludge treatment plants is used for pumping sludge within the treatment processes. The efficient operation of sludge pumps requires an accurate calculation of friction losses for which sludge rheological parameters is an important parameter. Rheological parameters change as composition changes due to season, origin and treatment process. Furthermore, the type of selected rheological model and data fitting process impact on the pressure drop calculation. A validated pressure drops calculation toolkit was developed with up to 10% errors against actual data collected both at industrial scale and a pilot plant of sludge pumping system in a range of solid concentrations of sludge.
Anaerobic digesters are used to treat sludge and produce biogas. The rheology of the sludge can affect the digestion process, as it can impact the ability of microorganisms to break down the organic matter in the sludge. Sludge with high viscosity may have a lower biodegradability, resulting in a longer retention time within the digester, which can increase the size and cost of the digester. Additionally, the rheology of the sludge can impact the efficiency of the mixing within the digester, affecting the biogas production and overall treatment performance. The impact of the extent of digestion in terms of the volatile solids destruction on rheological properties in semi-continuous pilot digesters is also presented. Experimental results from this study indicate that higher volatile solids destruction leads to increased difficulty to flow and dewater. Since rheological behaviour is interlinked with chemical organic content (COD) of sludge, On-line rheometers can be used to monitor this process performance indicator (COD) rather than conducting offline time consuming chemical tests.
There is still much to be learned about the complex interactions between different components in sludge, and that new measurement techniques will be needed to improve our understanding of sludge rheology and its applications in sludge treatment processes.
Bio:
Nicky ESHTIAGHI is a Professor of Chemical Engineering at RMIT University, an Engineers Australia (EA) Fellow and Chartered Engineer, a Fellow of the Higher Education Academy (FHEA, UK), and an Editor in Chemical Engineering Research and Design Journal (Q1, Elsevier). She was the President of Australian Society of Rheology (2020-2022). She leads Sustainable Waste Processing Laboratories which investigates the flow behaviour of solid residue (sludge) from wastewater treatment plants with the aim of optimizing the energy efficiency of processes in sludge treatment lines. She has extensive research experience in process optimisation, biomass pretreatment, anaerobic digestion, biomass to hydrochar and biofuels conversion technology, and circular economy.
Poster presentations
Abstract:
Viscoelastic and dielectric properties of type-A chains differently average the same chain
dynamics, so that comparison of those properties resolves some details of this dynamics in a purely experimental way. Some examples of this comparison are presented in the talk.
Bio:
Hiroshi Watanabe started his academic career as Assistant Professor in 1983 in Osaka University, Japan. He moved to Institute for Chemical Research, Kyoto University, Japan, as Associate Professor in 1994, and was promoted to Professor in 2003. In 2022, he retired from Kyoto University but is still active as Emeritus Professor of Kyoto University and Visiting Professor of Changchun Institute of Applied Chemistry, Chinese Academy of Sciences. His research interest has been placed on dynamics and rheology of various softmatters that include polymers, suspensions, and emulsions. He combined several experimental methods, for example, rheological, dielectric, and small angle scattering methods, to reveal physical factors underlying the dynamic behavior of softmatters, for example, the entanglement loosening process of polymers wherein the length and time scales can be consistently coarse-grained. Professor Watanabe has received many awards for his outstanding contributions to the science of Rheology including the Bingham medal of the Society of Rheology in 2015.
Abstract:
For next-generation electronics systems and devices, such as flexible displays and energy harvesting (or storage) devices, high performance, versatility, and flexibility are frequently necessary. A film, which is often a polymer or soft substrate with numerous layers of electrically conductive, semiconducting, and insulating materials superimposed on it, is a key component of these devices. These layers can be created using a variety of coating techniques. The continuous liquid coating technique, a kind of roll-to-roll process, is one of them and is widely acknowledged as an appealing way to generate affordable, high-throughput, and large-area coated layers. The coating liquid may exhibit complex rheological characteristics if it contains a variety of particles, additives (such a binder), and solvents. The main challenges in this process are how to regulate flows inside large manufacturing equipment to regulate microscopic properties, such as thickness homogeneity, particle microstructures inside coated layers, etc. Such problems require an understanding of the physical or chemical phenomena underlying them from a fundamental engineering perspective. Such knowledge might be beneficial for the process' analysis and design. For instance, while analyzing complex film formation flow in various types of applicators, such as slot die, roll, and spray, the rheological characteristics of a coating liquid must be taken into consideration. To help with the design of the drying machine, a microstructures index or indication must also be created. In this talk, various research initiatives to address these coating difficulties, including flows inside pipe systems and coating machines, will be shown. Some elements of these coating issues will also be highlighted.
Bio: Jaewook Nam is an Associate Professor in the Department of Chemical and Biological Engineering at the Institute of Chemical Processes, Seoul National University in Korea. Dr. Nam performs creative research to understand microscale flow phenomena through experiment, theory, and computation to design a high-performance film production. He received his BSc in 2000, MSc in 2004; and his PhD from the University of Minnesota in 2009. He completed his postdoctoral research in the Department of Chemical and Biomolecular Engineering at Rice University.
Abstract:
Radial displacement flows of viscoplastic fluid in a Hele-Shaw cell can give rise to a range of instabilities. Theoretically, the viscoplastic version of the Saffman-Taylor interfacial instability [1] is predicted to occur when the yield-stress fluid is displaced by a Newtonian one. The interface is expected to remain stable, however, if the yield-stress fluid displaces the Newtonian one [2,3].
Experiments using an aqueous suspension of Carbopol show that the Saffman-Taylor instability is observed when the Carbopol is displaced by either air or an immiscible oil, and no instabilities are observed when the displacement is the other way around. However, when water is used in the displacement experiments, other instabilities appear that take the form of localized fractures of the Carbopol over the sections of the interface that are under tension. The fractures arise in both the stable and unstable Saffman-Taylor configurations, leading to a rich range of patterns within the Hele-Shaw cell.
Supported by these experimental observations, we argue that this pattern formation results from the solid-mechanical-like failure of the Carbopol gel. In particular, the fractures result from a reduction of the effective fracture toughness of the suspension when placed in contact with water, also observed in the spreading of Carbopol gravity currents into a shallow layer of water [5].
REFERENCES
1. Saffman P.G., Taylor G.I. The penetration of a fluid into a porous medium or Hele-Shaw cell containing a more viscous liquid, Proc. Roy. Soc. A, 245, (1242) 312-329, 1958.
2. Ball T.V., Balmforth N.J., Dufresne A.P. Viscoplastic fingers and fractures in a Hele-Shaw cell, J. Non-Newton. Fluid Mech., 289, 104492, 2021.
3. Coussot P. Saffman-Taylor instability in yield-stress fluids, J. Fluid Mech., 380, 363-376, 1999.
4. Sayag R., Worster M.G. Instability of radially spreading extensional flows. Part 2: Theoretical analysis, J. Fluid Mech., 881, 739-771, 2019.
5. Ball T.V., Balmforth N.J., Dufresne A.P., Morris S.W. Fracture patterns in viscoplastic gravity currents, J. Fluid Mech., 934, A31, 2022.
About the JNNFM Walters Award Prize.
Bio:
Thomasina Ball is a Warwick Zeeman Lecturer and Leverhulme Early Career Fellow in the Mathematics Institute. Dr. Ball uses theoretical and experimental techniques to understand non-Newtonian fluid dynamics and fluid-structure interactions with applications to geophysical phenomena. She received her MMath in 2015, and PhD from the University of Cambridge, U.K., in 2019. She completed her postdoctoral studies in Department of Mathematics at the University of British Columbia under the supervision of Prof. Neil Balmforth who is jointly awarded the JNNFM Walters Award Prize.
Bus will depart from the Gage Towers, between the Gage and the Orca building.
Bus will depart from the Gage Towers, between the Gage and the Orca building.
Bus will depart from the Gage Towers, between the Gage and the Orca building.
Abstract:
In classical wetting, the spreading of an emulsion drop on a surface is preceded by the formation of a bridge connecting the drop and the surface across the sandwiched film of the suspending medium. However, this widely accepted mechanism ignores the finite solubility of the drop phase in the medium. We present experimental evidence of a new wetting mechanism, whereby the drop dissolves in the medium, and nucleates on the surface as islands that grow with time. Island growth is predicated upon a reduction in solubility near the contact line due to attractive interactions between the drop and the surface, overcoming Ostwald ripening. Ultimately, wetting is manifested as a coalescence event between the parent drop and one of the islands, which can result in significantly large critical film heights and short hydrodynamic drainage times prior to wetting. This discovery has broad relevance in areas such as froth flotation, liquid-infused surfaces, multiphase flows and microfluidics.
Bio:
Arun Ramchandran is an Associate Professor in the Department of Chemical Engineering and Applied Chemistry at the University of Toronto. Dr. Ramchandran focuses on generating fundamental understanding in the area of suspensions of rigid and deformable particles through experiment, theory, and computation. He received his BSc in 2001and his PhD from the University of Notre Dame in 2007. He completed his postdoctoral research in the Department of Chemical Engineering at the University of California, Santa Barbara.