Detailed Programme

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Monday 16: Multiscale approaches in mechanics

 

8:15 - 8:45 Coffee

 

 

 

8:45 - 9:00

Introduction to the summer school

 

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



9:00 - 10:30

A brief introduction to fluid turbulence

 

Speaker: Mickaël Bourgoin, CNRS, LMFA (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 - 10:50 Coffee break

 

 

 

10:50 - 12:20

Multiscale phenomena in multi scale flows

 

Speaker: Olivier Desjardins, Cornell Univ.


In engineering and environmental fluid flows, the presence of multiple interacting phases is ubiquitous. One phase can be dispersed into another (e.g., solid grains in gas), or both phases can be continuous, separated by a phase interface (e.q., liquid-gas flow). In both cases, the resulting flow is often turbulent, and spans many characteristics scales. Multiphase flows exhibit processes at the microscale such as inter-particle collisions and droplet coalescence, and flow dynamics on significantly larger scales such clusters in particle-laden flows and instabilities in liquid-gas flows.

 

12:30 - 14:00 Lunch break, Galilée Building

 

 

 

 

14:00 - 15:30

Rheology of suspensions: two examples

 

Speaker: Frédéric Pignon, CNRS, LRP (Grenoble)

 

Speaker: Philippe Peyla, Univ. Grenoble Alpes, LIPhy


Structure and flow properties of colloidal suspensions: combination of in-situ scattering and rheometric techniques

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...)

 

When particles come to life

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.

 

15:30 - 15:50 Coffee break

 

 

 

15:50 - 17:20

Homogenisation of coupled phenomena in heterogeneous materials

 

Speaker: 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.


17:30 - 20:00

Cocktail and Poster Session

All participants are kindly asked to prepare a poster about their work that will be exposed during the cocktail on Monday evening. It will be the opportunity for the participants to present their research, have fruitful scientific discussions and build up connexions.

 

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

 

 

 

Tuesday 17: Numerical and experimental tools and methods

 

8:30 - 9:00 Coffee

 

 

 

9:00 - 10:30

A brief review of turbulence metrology

 

Speaker: Mickaël Bourgoin, CNRS, LMFA (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 - 10:50 Coffee break

 

 

 

10:50 - 12:20

Numerical predictions of turbulent flows

 

Speaker: 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 - 14:00 Lunch break, Galilée Building

 

 

 

 

14:00 - 15:30

Full-field methods and multi-scale approaches in experimental solid mechanics

 

Speaker: Gioacchino Viggiani, Univ. Grenoble Alpes, 3SR


Various advanced modeling approaches have been proposed to describe intriguing phenomena in solid mechanics. However, such models require experimental results, at the appropriate scales, with the appropriate sensitivities and under the appropriate loading conditions, to identify and characterize the important mechanisms controlling the material responses, to provide ground truth and to identify model input parameters. Unfortunately, traditional experimental methods often fall short of providing the necessary data for the increasingly ambitious modeling approaches. To address such shortcomings, new (advanced) experimental methods have been under development in recent years. This lecture summarizes some of the key developments in this area, with specific examples mostly (but not only) from geomechanics.

 

15:30 - 15:50 Coffee break

 

 

 

15:50 - 17:20

Numerical investigations of macroscopic behaviour of heterogeneous materials

 

Speaker: 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 18: High tech lab courses

The participants can attend 2 out of the 8 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. A short description of the lab-courses is given lower on the page.

 

8:30 - 9:00 Coffee

 

 

 

9:30 - 12:30

Practical Sessions

 

12:30 - 14:00 Lunch break, Galilée building

 

 

 

 

14:00 - 18:00

Practical Sessions


 

*** Description of the lab courses ***

 

Lab-Course # 1: Turbulence and particle transport 

 

Teacher: Nicolas Mordant, Univ. Grenoble Alpes, LEGI

 

Teacher: Henda Djeridi, Grenoble-INP, LEGI

 

Teacher: Guillaume Balarac, Grenoble-INP, LEGI

Location: Laboratory LEGI

Building K

1209-2011 rue de la Piscine

University Campus


Turbulence is a canonical example of multi scale phenomenon. This multi scale character is actually at the very center of the phenomenological theory of turbulence by Kolmogorov. During this lab course, the trainees will be initiated to the PIV (Particle Image Velocimetry) measurement technique that provides 2D spatial maps of a flow or to hot wire anemometry. We will focus on the wake behind a simple object like a cylinder. This introduction to major experimental techniques in fluid mechanics (and to their limitations) will be augmented by an initiation to numerical techniques (and the issues associated to them) such as direct numerical simulations, RANS method, or Large Eddy Simulations. View the full description of the Lab-course


Lab-Course # 2: Granular and porous materials  

 

Teacher: Gaël Combe, Grenoble-INP, 3SR

Location: Laboratory 3SR

Building E

175 rue de la passerelle

University Campus


In this practical session, we will perform shear tests on a 2D granular media with the help of the device called 1γ2ε. This unique apparatus allows to apply various loading paths on granular assemblies made of rods. By means of a 80 MPixels camera, discrete kinematics field will be assessed and analyzed. Comparisons between experimental and numerical simulations by means of Discrete Element Modeling will also be performed. The multiscale kinematic behavior will then be discussed. View the full description of the lab-course


Lab-Course # 3: Mechanics of blood circulation  

 

Teacher: Gwennou Coupier, CNRS, LIPhy (Grenoble)

Location: Laboratory LIPhy

Building E

140 avenue de la Physique

University Campus


One of the functions of the vascular system is to bring oxygen to the body via the red blood cells. The vascular system consists of a large number of vessels subdividing themselves in increasingly small vessels, where the distribution in cells is highly heterogeneous. The purpose of this practical work is to measure these heterogeneities in a simplified artificial network, where real blood samples will be injected. The results will then allow comparison with existing models from the literature. View the full description of the lab-course


Lab-Course # 4: Dense flows  

 

Teacher: Thierry Faug, IRSTEA (Grenoble)

 

Teacher: Mohamed Naaim, IRSTEA (Grenoble)

Location: IRSTEA

2 rue de la Papeterie

University Campus


The aim of this lab-course is to tackle the problem of the modeling of dense gravitational flows dynamics. Dense avalanches of granular materials will be produced and analyzed with the help of a laboratory inclined plane equipped with advanced instrumentation: granular PIV, fringe projection, etc. The experimental granular avalanche-flows will then be reproduced by numerical simulations based on shallow-flow (Saint-Venant) equations. Emphasis will be placed on comparing the propagation and final stopping of laboratory and numerical avalanche-flows, with the objective to infer the relevant rheological parameters of the studied granular fluid. View the full description of the lab-course


Lab-Course # 5: Investigation of the mechanics of fibrous materials using X-ray microtomography

 

Teacher: Sabine Rolland du Roscoat, Univ. Grenoble Alpes, 3SR

 

Teacher: Laurent Orgéas, CNRS, 3SR (Grenoble)

Location: Laboratory 3SR

Building I

1301 rue de la Piscine

University Campus


The aim of this module is to emphasize the interest of coupling 3D imaging and fine scale fluid flow simulation to estimate the both the microstructures and the permeability of fibrous reinforcements commonly used in fiber reinforced composites or geotextiles. A woven fabric will be subjected to a tensile loading with a mechanical testing machine placed inside a X-ray microtomograph, allowing the 3D in situ observations of the fibrous microstructure of the textile during its deformation. The microstructure will be then finely characterized using 3D image analysis subroutines provided by the freeware ImageJ (Fiji). Therefrom, the permeability of the initial and deformed fibrous reinforcements will be estimated from fluid flow simulation inside the imaged fibrous microstructures using a finite volume CFD software (GeoDict). View the full description of the lab-course


Lab-Course # 6: Biobased fibre reinforced composites

 

Teacher: Julien Bras, Grenoble-INP, LGP2

Location: Laboratory LGP2

461 rue de la Papeterie

University Campus


This practical course is organized in 2 parts. The first one deals with processing of different bio-based materials using different techniques like twin-screw extrusion or thermopressing. Biodegradable polymers and natural fiber will be performed. A 3D converting using thermopressing might be expected. The second part of the practical work will focus onto biocomposites characterization using DMA and DSC in order to check the influence of fibre addition onto end-use materials properties. View the full description of the lab-course


Lab-Course # 7: Wave turbulence

 

Teacher: Nicolas Mordant, Univ. Grenoble Alpes, LEGI

Location: Laboratory LEGI

1209-1211 rue de la Piscine

University Campus


Wave turbulence is a statistical state that aims at describing the nonlinear random ensemble of waves as commonly observed at the surface of the ocean. Here we will experiment on a physical model for wave turbulence: the vibrating elastic plate in which a state of wave turbulence is obtained by shaking a thin steel plate at low frequency. In this lab-course, turbulence will be observed and measured using imaging tools, and a numerical simulation of the vibrating plate will be carried out to further investigate the behaviour of wave turbulence. View the full description of the lab-course


Lab-Course # 8: Rheology of suspensions

 

Teacher: Frédéric Pignon, CNRS, LRP (Grenoble)

 

Teacher: Nicolas Hengl, Univ. Grenoble Alpes, LRP

Location: Laboratory LRP

Building B, 363 rue de la Chimie

University Campus


The purpose of this lab course is to give Master students the opportunity to discover the mechanisms involved in membrane ultrafiltration processes in relation with the rheological behavior of the aqueous filtered suspensions. During the filtration process under shear flow and pressure forces, the filtered particles accumulate near the membrane surface forming a concentrated layer of a few hundred micrometers. The changes from a dilute phase to a concentrated phase induce a change in the rheological behavior of the suspensions which control the performance of the process. The proposed approach is to combine the characterization of the filtration properties of the suspensions, the in-situ visualization of the accumulated layers and the rheometric behavior of the suspensions. The goal is to understand the principal mechanisms governing the ultrafiltration process used in several industrial applications, bio- and agro-industries, chemical industries, pharmaceutical, nuclear, as well as water and sludge treatment. View the full description of the lab-course

 

 

Thursday 19: High tech lab courses

 

8:30 - 9:00 Coffee

 

 

 

9:30 - 12:30

Practical Sessions

 

12:30 - 14:00 Lunch break, Galilée Building

 

 

 

 

14:00 - 18:00

Practical Sessions


20:00

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 20: Advanced tools & methods for the study of multiscale problems

Invited lectures

Investigations of (hydro)mechanical behaviour of granular geomaterials from the intra-grain scale to the sample scale using x-ray and neutron imaging and diffraction

 

Speaker: Stephen Hall, Univ. Lund


Geomaterials are complex multiscale materials with deformation mechanisms occurring over a range of scales. In granular geomaterials, e.g., sands and sandstones, the basic building blocks are the grains that interact with each other at contacts across which forces are transferred. The grains also move relative to each other during shearing, dilation or compaction. How the grains interact and how force transfer across contacts is organised during these processes control the overall material response. At a scale above the grain scale, strains, when the system is regarded as a continuum, generally localise, e.g., in to shear bands, a few grains wide, depending on the grain interactions. The organisation of such localised features and the deformation or damage associated with them will impact on the macroscopic properties and behaviours. For example, shear-bands in rocks can provide conduits or barriers to fluid flow that have implications for processes such as CO2 sequestration. New tools are required to probe these complex, coupled, multi-scale processes and interactions within the body of bulk samples and whilst the samples are contained under realistic experimental conditions. X-ray and neutron scattering and imaging techniques provide many possibilities for such investigations due to the ability to penetrate deep into materials. Both x-rays and neutrons have their advantages and disadvantages for different types of studies, due to different interaction mechanisms with different components of the study material and experimental system. Furthermore, when used in combination x-rays and neutron can reveal many new features of material behaviour. In this presentation an overview will be provided of the possibilities of using X-ray and neutron scattering and imaging techniques to probe geomaterial properties and processes with illustrations from different recent experiments.


Investigation of turbulent sheet flows under unidirectional flow forcing

 

Speaker: Julien Chauchat, Grenoble-INP


During this seminar I will present some recent research activities concerning the modeling of intense bed-load transport usually denoted as sheet-flow. This sediment transport regime is especially important for the morphological evolution of natural systems like rivers or sandy beaches. Our overall objective is to provide a better understanding and modeling of the physical processes involved at fine scales. In order to achieve this goal we have developed a one-dimensional two-phase flow model of this problem in which the particle-particle interactions are modeled based upon the recent mu(I) dense granular flow rheology and we have developed a new experimental setup to acquire High Resolution measurements of velocity and concentration profiles under such flow conditions. The measurements have been obtained using the Acoustic doppler Concentration and Velocity Profiler (ACVP) developed by D. Hurther at LEGI.

After a brief introduction of the dense granular flow rheology mu(I), I will present the two-phase flow model and some first results that illustrate the relevancy of the granular rheology for modeling sheet flow. In the last part I will report on the sheet flow experiments. The new dataset tends to show that a liquid granular regime (mostly frictional) caped by a gaseous one (mostly collisional) is observed. The turbulent measurements show that a log layer exists however the Von Karman is reduced by a factor of two under sheet flow conditions and that the turbulent Schmidt number is around 0.44 for a settling velocity to bed friction velocity ratio around unity. Last but not least, a very strong intermittency has been observed in the sheet flow layer in terms of both sediment flux and bed interface position. This intermittency is most probably linked with the large scale coherent shear stress structures of the boundary layer. This observation is not compatible with the hypotheses made in turbulence averaged two-phase flow model and requires eddy resolving simulations (LES) to further understand the complex couplings between the turbulent boundary layer and the sediment bed dynamic.


FEMxDEM double scale integrated approach in geomechanics 

 

Speaker: Jacques Desrues, Univ. Grenoble Alpes


Recently, multi-scale analysis using a numerical approach of the homogenisation of the microstructural behaviour of materials to derive the constitutive response at the macro scale has become a new trend in numerical modelling in geomechanics. Considering rocks as granular media with cohesion between grains, a two-scale fully coupled approach can be defined using FEM at the macroscale, together with DEM at the microscale [1,2,3]. In this approach, the micro-scale DEM boundary value problem attached to every Gauss point in the FEM mesh, can be seen as a constitutive model, the answer of which is used by the FEM method in the usual way. A first major advantage of two-scale FEM-DEM approach is to allow one to perform real-grain-size micro-structure modelling on real-structure-size macroscopic problems, without facing the intractable problem of dealing with trillions of grains in a fully DEM mapped full-field problem. A second one is that using this approach, microscale related features such as the inherent and induced anisotropy of the material, or material softening/hardening with strain, naturally flow from the microscale DEM model to the macroscale FEM model. Arguably, multi-scale numerical approaches may suffer from computational cost penalty with respect to mono-scale one. However, high performance computing using parallel computation schemes offers solutions to mitigate the computational cost issue. An implementation of the FEM-DEM method in a well-established, finite strain FEM code is presented, and representative results are discussed, including aspects related to strain localisation in this context. High Performance Computing implementation and performances are illustrated.


Computational methods for simulating multiphase turbulence

 

Speaker: Olivier Desjardins, Cornell Univ.


Multiphase flows are ubiquitous in environmental and engineering applications. One category of flow of great importance in energy conversion devices is the formation of a liquid spray, a process called atomization. Due to their nonlinear and multiscale nature, such liquid-gas flows present a significant modeling challenge, especially when novel control strategies such as electro-hydrodynamics are considered. In addition, flow variables exhibit discontinuities across the phase interface, leading to numerical difficulties. Another category of flow of importance for energy conversion is dense particle-laden flows, as found in fluidized bed reactors. These flows are strongly multiscale, and momentum coupling between the gas carrier phase and finite-sized particles can lead to the production of gas-phase kinetic energy fluctuations, leading to cluster-induced turbulence which needs to be modeled.

With the advent of more powerful computing resources, simulating such flows from first principles is becoming viable. As with single-phase flows, numerical methods need to be carefully designed to guarantee convergence under grid refinement, primary conservation of key quantities such as mass and momentum, and excellent parallel performance. We will discuss how such properties can be obtained in the context of various multiphase turbulent flows, including atomizing liquid jets and fluidized beds, as well as three-phase flows.


Shake-The-Box – Dense Lagrangian particle tracking for turbulence research 

 

 

Speaker: Andreas Schroeder, German Aerospace Center (DLR)


Shake-The-Box (STB) is a novel time-resolved 3D Lagrangian particle tracking method for densely seeded flows. The STB algorithm has been developed at DLR Göttingen in the past three years and uses the prediction of 3D particle distributions for each subsequent time-step as a mean to seize the temporal domain for accurate track reconstructions based on time series of particle images from few camera projections. Exploiting the temporal information enables the processing of densely seeded flows (up to and beyond 0.1 particles per pixel with a nearly complete suppression of ghost particles). Such high particle trajectory densities are a necessary precondition for interpolating the corresponding time-resolved 3D velocity vector field onto a regular grid using Navier-Stokes-constraints. Such a non-linear data assimilation method named FlowFit has been developed at our group in parallel to STB and tested already successfully: For example, unsteady 3D pressure distributions have been calculated from interpolated 3D acceleration fields.

 

The STB method has been applied to wall bounded turbulence in air and water and to a m³-scale experiment using Helium–Filled-Soap-Bubbles (HFSB) as tracers. The results demonstrate that with STB valuable data for turbulence characterization with outstanding temporal and spatial resolution especially in (wall bounded) shear flow can be obtained.

Figure caption: Dense Lagrangian tracks (~300,000 per time step) colour coded by velocity and iso-contours of Q-values from STB measurements (and Flow-Fit interpolation) in a large scale thermal plume using HFSB 


Multiscale characterisation of soft biological systems using AFM  

 

 

Speaker: Claude Verdier, CNRS


We present different approaches developped with the Atomic Force Microscope to study tissues [1], single cells [2] and the cell membrane with its embedded proteins [3]. At the tissue level, examples will be presented allowing to see the effect of tension on tissue growth, in the particular case of muscle tissues [1].

At the cellular level, a specific technique for measuring dynamic indentation [2] allows to obtain cell viscoelastic properties, and we will see how it can be helpful to characterize cancer cells spread on various substrates with different elasticity or under specific biological conditions. Finally, AFM can be used for measuring cell-cell interactions. By carefully looking at the force signals, we can obtain forces corresponding to nanoscopic events, such the breaking of receptor-ligand bonds. This has been used to understand how cells interact with the endothelium during the metastasis process.

 

[1] S. Chiron, C. Tomczak, A. Duperray, J. Laine, G. Bonne, T. Eschenhagen, C. Verdier, C. Coirault, Dynamic interplay between human myoblasts and 3D fibrin-based matrix, PLOS One, 7(4), e36173 (2012)

[2] Y. Abidine, V.M. Laurent, R. Michel, A. Duperray, L.I. Palade, C. Verdier, Physical properties of polyacrylamide gels probed by AFM and rheology, Europhys. Letters, 109, 38003 (2015)

[3] V.E.J. Sundar Rajan, V.M. Laurent, C. Verdier, A. Duperray, Unraveling the ligand-receptor interactions between bladder cancer cells and the endothelium using AFM, submitted (2016)