"Advances in Dynamic Wetting in Coating Flows. Dip coating, Slot over roll coating and Tension Web Slot coating experiments with smooth & rough substrates with air and other gases under reduced pressures"

Abstract

Dynamic wetting, its failure and ensuing air entrainment in relation to coating flows has attracted a lot of research attention in the past fifty years but its study has largely been based on the simple dip coating flow in atmospheric air and with smooth substrates.

In this presentation, we describe and discuss experimental work carried out with rough and smooth substrates in air and other gases (CO2 and Helium) under greatly reduced pressures (1bar-10mbar) to pin point exactly the onset of dynamic failure and explain the complex mechanism of air entrainment. The analysis which we shall present identify to a hitherto ignored physical property, the thin film gas viscosity which together with substrate roughness, contact angle and the physical properties of the coating fluid dictate the onset of air entrainment.

Bio

Professor of Coating & Polymer Processing, Hadj Benkreira (CEng, FIChemE) received his B.Eng and M.Sc degrees (Chemical Engineering) from the University of Bradford (UK) in 1976 and 1977 respectively. After a short spell in the Petrochemical Industry in Algeria, he returned to Bradford for PhD studies in the Fluid Mechanics of Coating Flows in 1980 under the eminent Professor W. L. Wilkinson (CBE, FREng, FRS). In addition to being a senior Professor of Chemical Engineering at the University of Bradford, he works across the university two Research & Knowledge Transfer Centres in Advanced Materials Engineering and Sustainable Environments. Hadj has been the principal investigator of over 20 EPSRC research awards since 1980 and has published over 100 papers in learned journals and conferences in the area of coating flows, rheology of waxy crude oils and other complex fluids, viscous mixing and polymer processing and nanocomposites. He leads with Professor Coates the University of Bradford Advanced Materials Engineering Research & Knowledge transfer Group integrated within the IRC in Polymer Science and Technology. Professor Benkreira's interest in Sustainability stems from his research to develop new acoustic and thermal insulation products using polymeric wastes residues that are normally dumped in landfills as the starting material. Honours/Editorship: Member of EPSRC Peer Review College (Materials); VP of the International Society of Coating Science and Technology (ISCST), Founder member of the European Coating Society, Editor of Proceedings of the ISCST series of conference in Journal Coating Technology and Research, Member of the Editorial Board of Coatings and the Journal of Coating Technology and Research.

(Prof. Kumar will deliver a joint lecture along with Prof. Francis, see above)

Bio

Satish Kumar is a Distinguished McKnight University Professor at the University of Minnesota where he is on the faculty of the Department of Chemical Engineering and Materials Science. Prof. Kumar received his undergraduate degree from Minnesota (1993), and his master's (1994) and doctoral degrees (1998) from Stanford University, all in chemical engineering. Following postdoctoral work at École Normale Supérieure (Paris) and the University of Michigan, he joined the faculty at Minnesota in 2001. Prof. Kumar currently serves as Faculty Director of the Industrial Partnership for Research in Interfacial and Materials Engineering (IPRIME), a university-industry consortium that has 15 member companies. He is both a Fellow and an Outstanding Referee of the American Physical Society, is Co-Editor-in-Chief of the Journal of Engineering Mathematics, serves on the editorial board of the Journal of Non-Newtonian Fluid Mechanics, is a member of the Executive Committee of the American Physical Society Division of Fluid Dynamics, and is a former president of the International Society of Coating Science and Technology. Prof. Kumar's research involves integration of transport phenomena, colloid and interface science, rheology, applied and computational mathematics, and experiments to address fundamental issues motivated by problems in materials processing. These fundamental investigations, which are described in over 130 journal articles and 21 PhD theses, are frequently inspired by industrial applications such as coating and printing processes, polymer processing, nanofluidics/microfluidics, and energy.

"Active nematics"

Abstract

Active materials such as bacteria, molecular motors and eukaryotic cells continuously transform chemical energy taken from their surroundings to mechanical work. Dense active matter shows mesoscale turbulence, the emergence of chaotic flow structures characterised by high vorticity and self-propelled topological defects. I shall describe the physics of active defects, discussing active microfluidics, active disclinations and examples of topological defects in biological systems.

Bio

Julia Yeomans is a theoretical physicist researching the behaviour of soft condensed matter, such as polymers, gels and liquid crystals, at the tiny scale where viscous forces are high compared to inertial forces. Her work has advanced our understanding of droplets in microchannels, of super-water-repellent surfaces and of how certain bacteria ‘swim’. Julia’s research is important to areas as diverse as inkjet printing and the development of artificial ‘microswimmers’ for medical use.

As well as analytical techniques, Julia applies sophisticated computational methods to model behaviour at close to the molecular level. This brings together hydrodynamics — how fluids behave in motion — and statistical physics, which is the use of probabilistic methods to predict the collective behaviour of many individual systems.

Julia’s work was recognised with the EPJE Pierre Gilles De Gennes Lecture Prize in 2013. Julia was elected Fellow of the Royal Society in 2013. She also has a keen interest in outreach work, including service on the advisory panel of the Institute of Physics Women in Physics Group. She has 4 daughters and enjoys hiking and orienteering.

"Active Surface Agents: Active colloids at fluid-fluid interfaces"

Abstract

The concept of Active Surface Agents is a play on the classical term Surface Active Agents well known in surface chemistry. A Surface Active Agent is an amphiphilic molecule that adsorbs at fluid interfaces. Formulators of multiphase systems are adept at the selection of amphiphiles to generate desired properties. We advance the concept of an Active Surface Agent, an active colloid trapped at fluid interfaces, whose motion and trapping state can be designed to promote mixing and colloidal structure formation at fluid interfaces. This concept represents an important and as yet largely untapped degree of freedom to interfacial engineering. Bacteria and reactive Janus beads are examples of structures that propel themselves and interact with these complex boundaries, and can be developed as Active Surface Agents.

To develop this concept, we use theory and experiment. Fluid interfaces are highly non-ideal, complex domains because of the propensity of surfactants and colloids to adsorb and alter interfacial mechanics. All active colloids obey similar hydrodynamic descriptions, which we show differ significantly from their bulk phase counterparts. Because of their directed motion, active colloids accumulate near interfaces. They can swim adjacent to the interface, or they can adsorb directly and swim in an adhered state with complex trajectories that differ from those in bulk in both form and spatio-temporal implications. We study the consequences of active colloids on or near fluid interfaces on interfacial transport and colloid interaction. By understanding these consequences, we aim to establish design rules for Active Surface Agents in multiphase systems.

Bio

Kathleen J. Stebe was educated at the City College of New York, where she received a B.A. in Economics and a Ph.D. in Chemical Engineering at the Levich Institute advised by Charles Maldarelli. After a post-doctoral year in Compiegne, France with Dominique Barthes-Biesel, she joined the Department of Chemical Engineering at Johns Hopkins University, where she became Professor and served as the department chair. Thereafter, she joined the University of Pennsylvania, where she has served as department chair and as Deputy Dean. She has performed extensive service the AIChE, and is the former chair of the ACS Colloids and Surfaces Division and is Vice Chair elect of the Division of Soft Matter of the APS. She has been recognized as a member of the National Academy of Engineering, a Fellow of the American Academy of Arts and Sciences, of the American Physical Society, of the Radcliffe Institute and the Johns Hopkins Society of Scholars. Her research focuses on directed assembly in soft matter and at fluid interfaces, with an emphasis on confinement, geometry, and emergent structures for novel functional materials.

"Short Stories in Fluid Mechanics: Intersections of thin films, self-similarity, elasticity, and viscoelasticity"

In this talk, I provide a glimpse into fluid mechanics and soft-condensed matter flow problems that we have studied in recent years. In particular, I will describe (i) an experimentally motivated similarity solution involving three independent variables, which is rationalized with a nonlinear theory; (ii) problems of fluid-structure interactions at low Reynolds numbers, where the flow of a liquid and the deformation of a solid are coupled, and a solution is provided via an integral equation representation; and (iii) pressure-driven viscoelastic fluid flows, which generally require numerical solutions of nonlinear constitutive equations, even for steady flows in narrow, channel-like configurations, though here we show how analytical progress is possible in some new cases, including comparison with experimental measurements.

The research described was performed by many people in my research group, as well as some external collaborations.

Bio

Professor Howard A. Stone received the Bachelor of Science degree in Chemical Engineering from the University of California at Davis in 1982 and the PhD in Chemical Engineering from Caltech in 1988. Following a postdoctoral year in the Department of Applied Mathematics and Theoretical Physics at the University of Cambridge, in 1989 he joined the faculty of the (now) School of Engineering and Applied Sciences at Harvard University. In 2000 he was named a Harvard College Professor for his contributions to undergraduate education. In July 2009 he moved to Princeton University where he is Donald R. Dixon ’69 and Elizabeth W. Dixon Professor in Mechanical and Aerospace Engineering.

Professor Stone is a Fellow of the American Physical Society (APS), is past Chair of the Division of Fluid Dynamics of the APS, and is currently on the editorial or advisory boards of Physical Review Fluids, Langmuir, Philosophical Transactions of the Royal Society, and Soft Matter, and is co-editor of the Soft Matter Book Series. Professor Stone is the first recipient of the G.K. Batchelor Prize in Fluid Dynamics, which was awarded in August 2008, and the 2016 recipient of the Fluid Dynamics Prize of the APS. He was elected to the National Academy of Engineering in 2009, the American Academy of Arts and Sciences in 2011 and the National Academy of Sciences in 2014.

"Properties of surfactant monolayers and their relation to microemulsions, emulsions and foams properties"

Abstract

Surfactants form monolayers at the air-water and oil-water interface, which can be characterized by a number of properties: surface tension, static and dynamic, surface curvature elasticity, surface compression and surface shear elasticities and viscosities. We will show how the knowledge of these properties allows predicting the behavior of oil/water or air/water dispersions. For instance, for microemulsions that are thermodynamically stable dispersions, one can predict dispersion type and size, as well as interfacial tensions between microemulsions, oil and water. For emulsions and foams that are thermodynamically unstable dispersions, the prediction of dispersion type and size is more difficult and will be discussed. Surfactant layer properties also control the destabilization processes: gravity effects (creaming, sedimentation, drainage), Ostwald ripening and coalescence of drops or bubbles (although in this case experimental evidence is still scarce).

Bio

Dominique LANGEVIN studied at Ecole Normale Supérieure Paris and became afterwards CNRS research scientist, being presently directeur de recherche emeritus. She began her research at the Physics laboratory of Ecole Normale Supérieure where she obtained a Docteur ès Sciences degree. She was post-doc at P.G.de Gennes’ laboratory, Collège de France. She directed later the Centre de Recherche Paul Pascal, Bordeaux. She works presently at the Physique des Solides laboratory, University Paris-Saclay. She is member of Academia Europea and received various awards among which a Grand Prix de l’Académie des Sciences, the CNRS silver medal, the L’Oreal-Unesco Women in Science award, the Overbeek Gold Medal. Her research topics are centered on studies of the dynamic behavior of interfaces between complex fluids (surfactants, polymers, liquid crystals, nanoparticles) with various techniques, mainly optical, such as light scattering. She is specialist of interfacial rheology and its relation with foam, emulsion and microemulsion properties. She authored more than 400 articles in peer-reviewed scientific journals, edited two books and wrote one on emulsions, microemulsions and foams in 2020.

"Thermalization in classical and quantum hydrodynamics"

Abstract

First, I will show the effects of spectral Fourier truncation on different conservative systems such as the 1D inviscid Burgers equation, the 2 and 3D Euler equation and the 2 and 3D Gross-Pitaevskii equation (GPE). Second, I will exhibit how finite temperature effects in superfluids can be described by the truncated GPE and estimate the corresponding effective viscosity. Finally, I will show some recent results indicating that the truncated Euler dynamics can correctly reproduce the transitional dynamics in confined 2D turbulence and the energy spectrum in forced 3D turbulence, at scales larger than the forcing scale.

Bio

Marc-Etienne Brachet is Directeur de Recherche CNRS (Émérite) at the LPENS, Paris, France, [PhD 1983]. He has carried out his research at MIT, at the Nice Observatory, and, since 1989, at the Laboratorire de Physique of the Ecole Normale Supérieure.

He received the Bronze Medal from the CNRS in 1983, the Special Prize of the Seymour Cray Competition in 1989, the Eugénie de Rosmond Prize from the Chancellery of the Universities of Paris in 1996 and the Emilia Valori prize of the French Academy of Sciences in 2016. Since 2012, he is a Foreign corresponding member of the Chilean Academy of Sciences.

His main recent scientific contributions focus on turbulence, fluid dynamics and superfluidity. He also contributed in nonlinear physics, statistical physics and numerical methods. His current research interests include finite-temperature effects in superfluids, singularities in ideal fluids and dynamics of Galerkin-truncated systems.

"Recent developments on the evaporation of sessile droplets: Competitive evaporation of multiple droplets and the evaporation of droplets on non-planar substrates"

Abstract

The evaporation of sessile droplets has been the subject of extensive experimental, numerical and analytical investigation in recent years, partly motivated by the wide range of everyday and industrial situations, such as protein crystallography, surface patterning, ink-jet printing (including that of OLED displays) and agrochemical spraying of plants, in which it occurs. In this talk I shall review some of the recent developments in the study of evaporating droplets, focusing on situations in which mathematical modelling can give new insights into this fascinating multidisciplinary problem, including the competitive evaporation of multiple droplets and the evaporation of droplets on non-planar substrates. The results presented in this talk are the outcome of joint work with a large number of collaborators, including Drs Brian Duffy, David Pritchard and Alexander Wray (University of Strathclyde), Professor Khellil Sefiane (University of Edinburgh) and Professor Colin Bain (University of Durham), and past and present research students, including Gavin Dunn, Jutta Stauber, Feargus Schofield, Hannah-May D’Ambrosio and Laura Mills, all of whose invaluable contributions are gratefully acknowledged.

Bio

Professor Stephen Wilson holds the 1984 Chair in Mathematics and is the leader of the Continuum Mechanics and Industrial Mathematics (CMIM) research group at the University of Strathclyde in Glasgow, United Kingdom, and has research interests in the application of mathematics to a wide range of real-world problems in fluid mechanics, including thin-film flows, rivulets and dry-patches, evaporating droplets, dielectrophoresis, microfluidics, liquid crystals, non-Newtonian fluids (including viscoplastic fluids, thixotropic fluids and nanofluids), anti-surfactants and self-rewetting fluids, fluid-structure interaction problems, biological flows, nucleate boiling, confined bubbles, thermocapillary (Marangoni) and thermoviscosity effects, spin coating, magnetohydrodynamics, and fluid impact problems. The common theme running through all of his work is the insightful and innovative use of a range of mathematical methods, notably asymptotic methods, to bring fundamental new insight into a wide range of fluid dynamics problems. In particular, he has used asymptotic methods to make fundamental contributions towards the understanding of droplet evaporation (selected references to which are listed below), rivulet flow, nucleate boiling, and fluid-impact problems. Professor Wilson and his collaborators were jointly awarded the Institute of Physics (IoP) Printing and Graphics Science Group Prize in 2009 for their “fundamental study of droplet evaporation”. Professor Wilson served two five-year terms (2010-2020) as the Joint Editor-in-Chief of the Journal of Engineering Mathematics published by Springer Nature, and is a Fellow of the Institute for Mathematics and its Applications (IMA) in the United Kingdom.

"Coastal ocean modeling for forecasting"

Abstract

Humans depend on the coastal ocean for our economy, our lifestyle, and even our food. Fish represents approximately 15.7% of the animal protein consumed worldwide. The economic activity associated with the oceans is crucial. World trade is highly dependent on maritime transport; approximately 50 thousand ships trade internationally, transporting 90% of world trade. The coasts, which concentrate 40% of the world's population, are of utmost importance for recreational activities, generation of green energy, etc.

Given these facts and figures, it is not surprising that the oceanic forecast is considered a vital activity. Since the first attempts at ocean forecasting during the world war II, the technique has evolved into what it is today, a complex body of codes, data and technologies capable of dealing with the chaotic and non-linear nature of ocean processes, thanks to the constant increase in computing capacity. Despite advances in global ocean modeling over the past two decades, coastal-scale forecasting still poses a particular challenge. Today, the scientific modeling community seeks to improve the reliability of these forecasts by advancing primarily in three cutting-edge areas: data assimilation, coupled forecasting, and ensemble modeling. During the talk, the state of oceanic forecasting models for coastal regions and the efforts being made in Argentina in relation to the subject will be discussed.

Bio

Claudia G. Simionato is the Director of the “Center for Atmospheric and Oceanic Research” (CIMA/CONICET-UBA) and the International Research Laboratory “French-Argentinean Institute for the Study of Climate and its Impacts” (IRL/IFAECI), joint institute between the University of Buenos Aires (UBA) and the National Council of Sciences (CONICET) of Argentina, and the Centre National de la Recherche Scientifique (CNRS) and the Institut de Recherche pour le Développement (IRD) of France. She is also Professor of the School of Exact and Natural Sciences of the University of Buenos Aires (UBA) and Senior Reseacher (CONICET).

She obtained her Ph.D. in Ocean Sciences at the University of Buenos Aires. Her current research interests focus on the study and modeling of processes in coastal regions, with emphasis on the Río de la Plata estuary.

She has authored or co-authored a number peer-reviewed scientific journal articles and book chapters, as well as other planning documents and workshop papers and supervised several PhD and Master’s theses. She has been part of many national and international projects. She has been part of the scientific and/or organizing committee of several meetings. She has developed diverse management activities at the School of Exact and Natural Sciences of the UBA.

She has advised public entities in the frame of her research. In this sense, it is remarkable her participation in the international FREPLATA and FREPLATA II projects, where she did not only was responsible for the research conducted at CIMA, but also advised the Foreign Ministry and the Secretary of Environment and Sustainable Development.

She was also the President of the National Committee of the International Association for the Physical Sciences of the Oceans (IAPSO) and is a member of advisory committees of CONICET and the Ministry of Science and Innovation of Argentina.

"Historical line about the assumptions on to the aerodynamic forces in the resuspension of aerosol particles from surfaces"

Abstract

A micrometer solid particle adhered to a surface and subjected to the action of aerodynamic forces can be re-entrained into air flow when certain dynamical conditions are fulfilled. This phenomenon is called resuspension and is essential in a wide range of applications as well as in environmental issues, sediment re-entrainment and airborne particles. It is also closely related to applications in human health, to micro and nanotechnology and food and pharmaceutical industries. Besides, it is an important phenomenon associated to serious problems as radioactive particles release during nuclear accidents and to the present COVID-19 pandemic scenario where infected aerosol particles may re-enter into indoor ambient with hazardous consequences.

Physical models for the mechanisms setting aerosol particles into incipient movement have necessary to deal with two main types of actions: adhesion forces and aerodynamic forces. Each one of these is a complex issue in itself due to the difficulties in the measurement of both particle-surface and particle-fluid interactions.

In the present talk, we will concentrate on the aerodynamic forces involved in the movement initiation of a particle adhered to a flat surface. The assumptions frequently made in the problem and the main ideas participating in the explanation of the resuspension phenomenon from the “burst” concept to the rolling and lift off mechanisms, will be reviewed.

The last progress in literature for the calculation of drag and lift forces on non-spherical particles will be presented along with the promise of numerical models adding these new features to improve resuspension predictions in more realistic scenarios.

Bio

La Dra. Ana María Vidales se doctoró en la Universidad Nacional de San Luis en 1996 en el grupo de Fisicoquímica de Superficies y Medios Porosos y bajo la dirección del Dr. Giorgio Zgrablich. Durante 15 años se dedicó a la invesigación teórica y numérica de fenómenos de percolación y transporte en medios porosos para luego pasar paulatinamente al estudio numérico de sistemas granulares, particularmente en problemas de segregación, compactación y flujo. Ha dedicado un capítulo especial al estudio experimental de la descarga de granos en silos tanto cuasi 2D como en 3D. A sus intereses en el modelado de sistemas complejos ha sumado en los últimos años el estudio del fenómeno de resuspensión por acción de fuerzas aerodinámicas de partículas micrométricas depositadas sobre superficies lisas y rugosas. Actualmente es Investigadora Principal del CONICET y Profesora Titular en la UNSL, dirigiendo el Laboratorio de Medios Granulares del INFAP en dicha Casa de Altos Estudios y siendo la asesora científica del proyecto de Unidad Ejecutora de dicho Instituto. Ha formado y sigue formando estudiantes de grado y posgrado en física e ingeniería. Maniene una fuerte colaboración con grupos del país y del extranjero, especialmente con el Grupo de Medios porosos de la FI-UBA en Argentina, el IPR de la Universidad de Rennes 1, el IRSN del CEA-Saclay y el IMT Atlantique, Nantes, todos ellos en Francia.

"On the concept of energy cascades in turbulence: from Richardson/Kolmogorov picture to multifractal and beyond"

Abstract

Turbulent flows are characterized by a self-similar energy spectrum, signature of fluid movements at all scales. This organization has been described for more than 70 years by the phenomenology of "Kolmogorov/Richardson cascade": the energy injected on a large scale by the work of the force that moves the fluid (e. g. a turbine) is transferred to smaller and smaller scales with a constant dissipation rate, up to the Kolmogorov scale, where it is transformed into heat and dissipated by viscosity. Such cascade phenomenology is at the basis of most turbulent models.

I will discuss in this talk how progresses in numerical simulations and laboratory experiments gradually changed such simple vision (starting from Landau objection in the 50’s), leading to a new picture where quasi-singularities living beyond Kolmogorov scale play a central role. This has important impact on resolution requirement of numerical simulations and call for new models of turbulence.

Bio

Bérengère Dubrulle is senior scientist at the Centre National de la Recherche Scientifique and presently Director of the Les Houches Physics School. She received her PhD in astrophysics in 1990 under the supervision of J-P. Zahn. She is a specialist of turbulence, and its application to astro and geophysical flows using theoretical, numerical or experimental approaches. Her major achievements are about theory of the solar system formation, statistical modelling of large scales and their bifurcations, or mathematical aspects of the small scale structure, in connection with singularities and intermittency. She was involved in the VKS dynamo experiment and in the SHREK superfluid (quantum) turbulence experiment.

"A glimpse into sediment transport and morphodynamic processes in rivers and transitional waters"

Abstract

During this talk, I will provide an overview of physical processes resulting from the interactions between flow, sediment transport and morphological processes in rivers and transitional waters, spanning a range of spatial and temporal scales. By natural causes or human pressures, the equilibrium of these highly heterogeneous natural environments can be altered. In consequence, understanding and predicting hydro-morphological changes is important to evaluate, among others, the modification of sedimentary features or to assess the departure from naturalness of the body of water.

Most of this work was performed together with PhD and master students, colleagues and external collaborators.

Bio

Pablo Tassi is research engineer expert at EDF R&D and Saint-Venant Hydraulics Laboratory since 2010. He also teaches at the Ecole des Ponts ParisTech, Polytech Nice Sophia and ESITC University of Caen in France. Pablo received the MSc degree from the Universidad Nacional del Litoral (Argentine) and the PhD from the University of Twente (The Netherlands). Following a post-doctoral position at the Ecole des Ponts ParisTech and Université Paris-Sud, he joined EDF in 2010. His research interests focus on the numerical modelling of large-scale environmental problems commonly found nearby harbours, water intakes and nuclear power plants. Most applications are related with sediment transport processes and interactions with inorganic substances in rivers, coastal and transitional waters.

"Hydrodynamic quantum analogs"

Abstract

In 2005, Yves Couder and Emmanuel Fort discovered that droplets walking on a vibrating fluid bath exhibit several features previously thought to be exclusive to the microscopic, quantum realm. These walking droplets propel themselves by virtue of a resonant interaction with their own wave field, and so represent the first macroscopic realization of a pilot-wave system of the form proposed for microscopic quantum dynamics by Louis de Broglie in the 1920s. New experimental and theoretical results allow us to rationalize the emergence of quantum-like behavior in this hydrodynamic pilot-wave system in a number of settings, and explore its potential and limitations as a quantum analog. A generalized pilot-wave framework is developed with a view to capturing additional quantum-like features inaccessible to the hydrodynamic system. A fledgling, trajectory-based description of quantum dynamics, informed by the hydrodynamic system, is proposed and explored.

Bio

John Bush is a Professor of Applied Mathematics at MIT. Having completed his BSc in Physics at University of Toronto, he went on to Harvard for his PhD in Geophysics, then the University of Cambridge for postdoctoral research at DAMTP. He joined the faculty of MIT in 1998, was tenured in 2004 and is now the Director of the Applied Mathematics Laboratory. His research began in geophysics, but then shifted towards surface-tension-driven phenomena and their applications in biology. For the past decade, his research has been focused on hydrodynamic quantum analogs.

"Free surface dynamics of coalescence and pinch-off of complex fluids"

(Prof. Corvalán will deliver a joint lecture along with Prof. Lu, see below)

Abstract

The coalescence and pinch-off of bubbles, droplets, and liquid filaments are typical free surface flows characterized by large interfacial deformations and flow singularities. Dramatic changes in the flow dynamics may initiate from a singularity, as at the onset of coalescence, or by approaching a singularity, as in filament pinch off. These flows often lead to self-similar behavior and frequently exhibit cross-over dynamics, such as transitions from viscous to inertial flows. In this talk we will discuss examples of interfacial flows near a singularity or undergoing cross-over dynamics, with focus on how rheology and the presence of surfactants affect the dynamics. These examples include engineering applications ranging from rocket propulsion to self-propelled microswimmers, and have been developed by our workgroup on interfacial flows from Purdue University, University of Massachusetts, and the Universidad Nacional de Entre Ríos.

Bio

Dr. Carlos Corvalán is an Associate Professor at Purdue University, with appointments in the departments of Biological Engineering, Food Science, and the School of Mechanical Engineering. He received his PhD in Chemical Engineering from the Universidad Nacional del Litoral and after his PhD, he held an appointment as Assistant Professor at the University of Entre Ríos and a postdoc appointment at Purdue University. His research focuses on computational fluid dynamics in collaboration with the industry and with federal agencies including NASA, US Department of Agriculture, and the US Department of Defense.

(Prof. Lu will deliver a joint lecture along with Prof. Corvalán, see above)

Bio

Dr. Jiakai Lu is an Assistant Professor at University of Massachusetts Amherst. He received his B.S. in Mechanical Engineering from Shanghai Jiaotong University and PhD in Mechanical Engineering from the Purdue University. His research focuses on fundamental complex fluids dynamics for applications related to agricultural and food processing using experimental and computational approaches. Currently his research is supported by US Department of Agricultura and Good Food Institution.

"The role of small dunes in the boundary resistance in large alluvial rivers (the case of the Paraná River, Argentina)"

Abstract

The dynamics of sandy rivers is a complex phenomenon linking the interactions between dunes, flow and sediment transport. An important issue related to flow over dunes is the separation zone downstream of alluvial dunes, which has been early recognized as one of the main sources of resistance to flow in alluvial streams, the “form” resistance. Bedforms in large sand-bedded rivers are characterized with slip face slopes lower than the angle-of-repose, the so-called low-angle bedforms. Over such bedforms, no permanent flow separation is observed. This talk deals with this topic using detailed dune measurements from the Paraná River, Argentina. For the sake of comparison, we also use data from the Tercero River, a small river located in the Province of Córdoba, Argentina. Despite the fact both rivers have bedform shape similarity there is a significant difference in the representative roughness height scale, dune steepness, lee angles, velocity profiles and flow recirculation. Both rivers obey Keulegan’s resistance law within the bounds of the normal flow approximation, which assumes a perfect balance between friction and gravity. Nevertheless, it is found that whereas the hydraulic resistance for the Tercero River scales with the dune sizes, the Paraná River needs to develop an intermediate roughness scale to accommodate the required balance between gravity and friction. We will show that this in-between length scale fits the size of small dunes found superimposed on the large dunes of the Paraná River.

(this work has been done in cooperation with students and colleagues from CONICET, UNL, Univ. Nac. Cba. & Univ. of Illinois).

Bio

Carlos Vionnet is a Professor of Numerical Methods at the Engineering & Water Resources Department of the Universidad Nacional del Litoral (UNL). He is also a member of the National Council for Scientific and Technical Research of Argentina (CONICET). Having completed his degree in Water Resources Engineer at UNL, he went to the Applied Lab of Hydraulics at Ezeiza for four years before joining the Aerospace and Mechanical Eng Dept of the University of Arizona, USA, where he obtained his PhD in Mechanical Engineer. He held visiting positions at the University of Western Australia, the University of Newcastle upon Tyne and the Polytechnic University of Catalonia. His current research focuses on dunes dynamics and the development of low-cost devices for agro-hydrological applications.