List of EUROMECH Colloquia in 2014
 Dynamics of capsules, vesicles and cells in flow
Date: 15 July 2014 – 18 July 2014 Location: Université de Technologie de Compiègne, France Website: http://www.utc.fr/dynacaps2014/ Contact:
Dr. Anne-Virginie Salsac
Biomechanics and Bioengineering
Université de Technologie de
60205 Compiègne cedex
Dr. Mark Blythe
University of East Anglia
Encapsulated soft particles are commonly encountered in nature (seeds, cells, phospholipid vesicles) and in different industrial applications (biotechnology, pharmacology, cosmetics, food industry). The role of encapsulation is to protect a substance with a solid envelope. It avoids its dispersion in the ambient environment or its degradation in contact with it. The membrane may be a lipid bilayer (vesicles), a reticulated membrane with elastic properties (artificial capsules) or a lipid bilayer connected to a cytoskeleton (cells).
There are many open issues regarding the mechanics of capsules/vesicles/cells:
The characterization of their mechanical properties is difficult owing to their small size and fragility.
The role of the fabrication process on the physical and mechanical properties of artificial capsules or vesicles (shape, size, degree of reticulation, membrane mechanical properties) remains to be better understood. Controlling the membrane properties is essential to optimize the design and production of specific particles for each application.
When suspended in an external flowing fluid, capsules/vesicles/cells deform in a complex fashion and may eventually burst (the breakup is to be induced or prevented depending on the application). Relatively few experimental studies of these phenomena exist, but recent progress in microtechnology has opened new perspectives. Correlatively, the theoretical study of the motion and deformation of these particles is a complex fluid-structure interaction problem. The present numerical models all include simplifying assumptions, the relevance of which has yet to be established.
The occasion of the present Symposium will allow a unique analysis of the similarities and differences of the mechanics, physics and biology of capsules, vesicles and cells. It will provide the opportunity to confront the various approaches used to study these deforming particles and establish some guidelines for future research.
 Dimensionality in Turbulence
Date: 19 May 2014 – 21 May 2014 Location: Coventry University Technology Park, UK Website: euromech.complexity-coventry.org/overview.xhtml Contact:
Prof. Alban Pothérat
Professor of fluid mechanics
Applied Mathematics Research Centre
Priory Street, Coventry CV1 5FB, UK
Ph: +44(0) 2477 65 88 65
Prof. GertJan van Heijst
Professor of fluid mechanics
Department of Applied Physics
Eindhoven University of Technology
P.O. Box 513, 5600 MB Eindhoven, The Netherlands
Ph: +31 40-247 2722
Dr. Nicolas Plihon
ENS Lyon . Physics Laboratory
46 Allée d'Italie - 69007 Lyon
Ph: +33(0)4 72 72 84 72
One of the most remarkable features of turbulence is that it operates in a radically different way in two-dimensional (2D) flows than it does in three-dimensional (3D) flows. Whilst the former is characterised by an inverse energy cascade that sees larger, less dissipative structures emerge, the latter tends to very efficiently dissipate energy by transferring it to small scales where it is dissipated by viscous friction.
The question of whether turbulence obeys two or three-dimensional dynamics therefore has drastic consequences for the natural and industrial processes where it is involved. This concerns numerous classes of realistic systems under the influence of rotation, stratification or magnetic fields as well as in purely 2D geometrical configurations. The tendency to two-dimensionality in stratified flows and rotating flows is a prominent feature of planetary flows such as atmospheres and oceans. This feature has also been observed in electrically conducting flows under a strong magnetic field (MagnetoHydroDynamic flows), extending the relevance of the question of flow dimensionality to astrophysical and laboratory plasma flows (for instance, the understanding of particles and heat flux dynamics in the magnetic-field transverse directions has tremendous importance in the achievement of thermo-nuclear fusion), but also to liquid-metals engineering problems in the nuclear and metallurgical industries. The common tendency to two-dimensionality, however, hides a variety of physical mechanisms: the propagation of inertial waves along the rotation axis promotes two-dimensionality in rotating flows, while eddy currents induced play this role in MHD flows, by generating Alfven waves if magnetic advection is important (in plasmas for instance), or by diffusing momentum along the field if it isn't (as often in liquid metals). In magnetized plasmas, drift waves play a leading role in momentum transport perpendicular in the directions perpendicular to the magnetic field. Their dynamics share many characteristics with inertial (Rossby) waves, both modelled by the Charney-Hasegawa-Mima equation. The geometry of the fluid domain too can favour either 2D or 3D dynamics, in particular if it is very thin along one direction, as in Hele-Shaw cells, or soap films. Nevertheless, the question of dimensionality of turbulence is conditioned by a number of features that are common to these systems: the boundaries are part of the very definition of the concept of two-dimensionality. Consequently, experimentalists willing to investigate flows with 2D dynamics are confronted to their influence. The way in which the flow is driven leaves a non-universal signature in the flow dynamics too.
Recent work tends to show that both the walls and the forcing play a crucial role in deciding whether the dynamics of the flow is closer to a 2D or a 3D one. At least two basic forms of three-dimensionality exist too: variation of physical quantities in the third direction and appearance of a third component in the velocity field. These can interact with each other and but it also recently emerged both from theoretical and experimental work that this latter form is strongly connected to the existence of an inverse energy cascade.
The purpose of this Colloquium is to gather researchers from different communities who are in fact working on this same problem. The many recent advances, a few of which are mentioned above, provide the ideal ground to seed a concerted approach on the question of the dimensionality of turbulence. In exposing to each other the mechanisms that govern the transition between 2D and 3D dynamics in the particular type of turbulence they are studying, it is hoped that the participants will discover more common ground. This will bring progress in the general understanding not only of how three-dimensionality appears or vanishes but also, and perhaps most importantly, in how it determines whether turbulence obeys 2D or 3D dynamics. In particular, bringing together expertise from several disciplines, and from both theoretical and experimental background, will help us distinguish mechanisms that are discipline-specific from those linked to boundaries and flow forcing and to find out if universal mechanisms exist.
 Generalized Continua and their application to the design of composites and metamaterials
Date: 17 March 2014 – 21 March 2014 Location: Cisterna di Latina (Rome), Italy Website: www.memocsevents.eu/euromech563/?page_id=20 Contact:
Prof. Francesco dell’Isola
Università di Roma La Sapienza
Dipartimento di Ingegneria Strutturale e Geotecnica
Via Eudossiana 18
00184 Rome, Italy
Ph: +39 06 90286784
Prof. Samuel Forest
Centre des Matériaux - MINES Paristech
CNRS UMR 7633
10 rue Henri Desbruères, BP 87
F-91003 Evry Cedex, France
Ph: +33 01 6076 3051
Fax: +33 01 6076 3150
Main Topics :
- General concepts for second and higher gradient media
- Phenomenology of existing and designed composites and metamaterials
- Homogenization techniques and related numerical and mathematical problems
- Beams and plates constituted by metamaterials
- Strain and stress localization phenomena
- Dynamic behavior of metamaterials and composites
- Acoustic properties of metamaterials and composites
- Generalized continua in Biomechanics and mechanics of growing tissues
- Damage and fracture in generalized continua
 Subcritical transition to turbulence
Date: 6 May 2014 – 9 May 2014 Location: Cargese, Corsica Website: http://perso.limsi.fr/duguet/Cargese/cargese.html Contact:
Dr. Yohann DUGUET
F-91403 Orsay, France
Ph: + 33 1 6985 8072
Fax: + 33 1 6985 8088
Dr. José Eduardo WESFREID
PMMH-CNRS, ESPCI, 10,
F-75231 Paris, France,
Transition to turbulence in fluids remains one of the unsolved problems of modern mechanics, despite its importance in various fields of engineering ranging from aerodynamics to oil transport. An especially challenging topic is the question of "subcritical" transition in wall-bounded flows, i.e. when the base flow is linearly stable and classical stability analysis fails at explaining the coherent structures commonly observed in experiments and in simulations. This concerns most flows in simple geometries such as pipes, ducts, channel and also boundary layer flows. This special problem lies at the crossroad between hydrodynamics, chaos theory and statistical physics. Specific cutting-edge experimental and/or numerical strategies have been been developed in the last decade. New questions arise as to how this problem extends to non-Newtonian rheologies, or how to control or delay this transition in realistic situations.
The colloquium will feature individual contributions, poster sessions and round tables for discussions.
Non-exhaustive list of topics :
- Spatiotemporal aspects of subcritical transition: large-scale pattern formation, intermittency, lifetimes measurements, experimental techniques
- Dynamical systems approach to transitional flows: exact coherent structures, unstable periodic orbits, edge states, chaotic saddles, related numerical methods
- Localised states in fluids
- Low-dimensional modelling strategies
- Non-Newtonian rheologies
- Nonlinear control strategies
- Cross-disciplinary analogies