PROGRAMME


Monday 20

Multiscale approaches in mechanics


8:30 Welcome coffee

8:50 Introduction to the winter school

Christian Geindreau, Univ. Grenoble Alpes, 3SR, Director of the Fed3G, Deputy Director of Tec21

9:00 A brief introduction to fluid turbulence

Mickaël Bourgoin,
CNRS, Laboratoire de physique, ENS (Lyon)

In spite of centuries of active research Turbulence remains one of the deepest mysteries of fluid mechanics. The complexity relies on the random and multi-scale nature of the phenomenon. This lecture will review the origin and the characteristics of fluid Turbulence, as well as the phenomenological framework and statistical tools commonly used to describe the phenomenon. These rely on the concept of energy cascade, introduced by L. Richardson in the 1920’s, later refined by A. Kolmogorov, who’s ideas still dominate the Turbulence research community.

10:30 Coffee break

10:50 Multiscale approaches for the modelling and simulations of gas-particle reactive flows under dense regime

Olivier Simonin

INPT, Institut de Mécanique des Fluides de Toulouse

12:30  Lunch break, Galilée Building

13:45 Rheology of suspensions - Structure and flow properties of colloidal suspensions

Frédéric Pignon,

CNRS, LRP (Grenoble)

Courses objectives are the characterization of the link between the flow mechanical properties (flow field, shear or extensional stresses, viscoelasticity moduli) and the structural organizations (aggregation, orientation, phase changes). The goal is to bring an understanding of the mechanisms controlling the flows properties of colloidal dispersions used in several processes (membrane separation, extrusion, film casting) involved in several industrial applications (chemical, bio- and agro-industries, pharmaceutical, water treatment...)

14:30 Hydrodynamics of suspensions: when particles come to life

Philippe Peyla,
Univ. Grenoble Alpes, LIPhy

Suspensions are encountered in nature as well as in various industrial processes. Suspensions refer to particles immersed in a liquid like mud, fresh concrete, blood, paints or ink to site but a few examples. A very recent interest with an exponential growing number of publications concerns active suspensions where particles can actively swim in the liquid phase like planktonic suspensions. Usually, the small size of the particles often means that the surrounding flow is dominated by viscous effects, and therefore that inertial forces can be neglected relative to viscous forces. This means that the Reynolds number associated with the particles is small and the flow can be considered as a Stokes flow. The present course aims at providing a physically based introduction to the dynamics of particulate suspensions and focuses on hydrodynamical aspects. We will also briefly summarize recent researches concerning active suspensions.

15:15 Coffee break

15:40 Homogenisation of coupled phenomena in heterogeneous materials

Christian Geindreau,
Univ. Grenoble Alpes, 3SR

The macroscopic mechanical behaviour of heterogeneous material strongly depends on the arrangement of the constituents according to various microstructures (granular or porous media, fibrous network) and the physical phenomena involved at the microscale (heterogeneity scale). A fine scale description of such material is often impossible due to the large number of heterogeneities.

In practice, a macroscopic equivalent modelling is more efficient. An overview of the different methods that can be used to derived such equivalent macroscopic behaviour will be given.

17:10 Cocktail and poster session

All participants are kindly asked to prepare a poster about their work that will be exposed over the whole school.

Please don't forget to bring your poster with you on Monday morning.

19:30 End of the day

Tuesday 21

Numerical and experimental tools and methods


8:30  Coffee

9:00 A brief review of turbulence metrology

Mickaël Bourgoin,
CNRS, Laboratoire de Physique, ENS (Lyon)

Because of its intrinsic multi-scale nature, the experimental characterization of turbulence requires dedicated metrological tools, capable to resolve (simultaneously if possible) the whole range of relevant involved scales (both in time and space). The present lecture will review the main contemporary instruments used by the scientific community for such high resolution and multi-scale disgnosis. These include Eulerian methods (such as hot-wire anemometry, laser-Doppler velocimetry and Particle Image Velocimetry) as well as new Lagrangian methods, based on acoustical and optical 3D particle tracking.

10:30 Coffee break

10:50 Numerical predictions of turbulent flows

 Guillaume Balarac,
Grenoble-INP, LEGI

Turbulent flows are characterized by a large range of motion scales. When turbulent flows are studied by numerical simulations, the explicit discretization of the overall range of scales is still an issue, even with the exponential rise in computational capability over the last few decades. In this presentation, some methods to overcome this limitation will be presented. The methods can consist to model a part of the turbulent fields (RANS and LES approaches), but the methods can also consist to develop numerical algorithm to allow direct numerical simulation with a lower computational cost (hybrid method for turbulent mixing).

12:30 Lunch break, Galilée Building

13:45 3D experimental micromechanics at the grain scale: what for?

Cino Viggiani,
Univ. Grenoble Alpes, 3SR

With x-ray micro tomography it is now possible to acquire 3D full-field measurements of granular materials at suitable resolutions. In the first applications of x-ray tomography to soil mechanics, the distribution of porosity was investigated with the aim of analyzing the development of localization phenomena in the soil specimen. More recently, Digital Image Correlation (DIC) has been used to determine the distribution of strain in a specimen – in a continuum framework – and/or individual grain kinematics, i.e., displacements and rotations of individual grains. These works have provided a deep insight into the micro-mechanics of the processes governing the overall behavior of granular materials.

This lecture will present recent advances in experimental micro (geo)mechanics achieved thanks to x-ray tomography and digital image analysis. In particular, we will focus on some recent experimental measurements of a 3D fabric tensor and its evolution during shearing of granular materials. Triaxial compression experiments on natural sands are chosen to investigate the evolution of fabric. Two different subsets of the specimen are chosen for the contact fabric analysis: one inside and another one outside a shear band. Individual contact orientations are measured using advanced image analysis approaches within these subsets. Fabric is then statistically captured using a second order tensor and the evolution of its anisotropy is related to the macroscopic behaviour. Finally, some very recent results obtained on fabric evolution from triaxial compression of lentils (i.e., very anisotropic grains!) are also presented.

More generally, the lecture will try to convey the following two messages: 1) to convince the audience that x-ray imaging is a measurement tool, not only a way to provide fancy images, and 2) to discuss what sort of modeling applications these rather exotic data can help to inform or inspire.

15:15  Coffee break

15:40 Numerical investigations of macroscopic behaviour of heterogeneous materials

Bruno Chareyre,

Grenoble-INP, 3SR

The macroscopic effective properties or behaviour of heterogeneous materials are commonly invstigated by solving specific boundary value problem on Representative Elementary Volume (i.e. at the microscale) arising from the homogenization process. Nowadays, these boundary value problems (BVP) are commonly solved on 3D images of the material obtained by microtomography or idealized microstructure. Different numerical methods (Finite volume differences, Finite Element method, Discret Element method…) can used to solved the BVP. An overview of these methods is presented and illustrated.

Wednesday 22

High-tech lab courses


8:30 Coffee

9:00 Practical Session I

The participants will attend 2 out of the 9 proposed lab-courses (1 on Wednesday, the other one on Thursday). Groups of 4-5 participants will be made and each group will be given its planning and location depending on the chosen topic. The lab-courses will be held in parallel sessions at different places on the campus. The detailed description of the lab-courses can be seen here.

12:30  Lunch break, Galilée Building

14:00 Practical Session I

Thursday 23

High-tech lab courses


8:30  Coffee

9:00 Practical Session II

12:30  Lunch break, Galilée Building

14:00 Practical Session II

19h30 Gala dinner intown

The Gala dinner will take place at the Restaurant "le 5" near the art museum of Grenoble.

The Restaurant is easily accessible by tram, line B, "Notre Dame Musée" stop (about 15 minutes from the university campus). View the map

Friday 24

Waves in fluids and solids


Invited lectures

The indicated schedule may change slightly.

8:30  Welcome coffee

09:00  Nonlinear elastic waves in flexible architected materials

Vincent Tournat,

CNRS, LAUM, Le Mans, France

10:00  New trends toward seismic metamaterials : from laboratory to field experiments

Philippe Roux,

CNRS, ISTERRE, Grenoble

10:30  Coffee break

11:00  Rogue waves

Miguel Onorato,

University of Torino, Italy

12:00  Wave turbulence in fluids and solids

Nicolas Mordant,

Univ. Grenoble Alpes, LEGI

12:30  Lunch break, Galilée building

13:45  Tidal bore dynamics / non-dispersive and dispersive processes

Philippe Bonneton,

CNRS, EPOC, Univ. Bordeaux, France

14:45  Jumps along free-surface granular flows down inclines

Thierry Faug,

INRAE Grenoble

15:20  Photoacoustic imaging: seeing by listening to light absorption

Emmanuel Bossy,

LIPhy, Grenoble

16:20  Conclusion