CEA |   |   |   |   |   |   | webmail : intra - extra |  Accès VPN-SSL | Contact | Français

PhD subjects

7 sujets IRAMIS

Dernière mise à jour : 25-06-2018


««

• Soft matter and complex fluids

 

Dissipation, cascades and singularities in turbulence

SL-DRF-18-0272

Research field : Soft matter and complex fluids
Location :

Service de Physique de l'Etat Condensé

Systèmes Physiques Hors-équilibre, hYdrodynamique, éNergie et compleXes

Saclay

Contact :

Bérengère DUBRULLE

Starting date : 01-10-2017

Contact :

Bérengère DUBRULLE

CNRS - DRF/IRAMIS/SPEC/SPHYNX

0169087247

Thesis supervisor :

Bérengère DUBRULLE

CNRS - DRF/IRAMIS/SPEC/SPHYNX

0169087247

Personal web page : http://iramis.cea.fr/Pisp/berengere.dubrulle/index.html

Laboratory link : http://iramis.cea.fr/spec/sphynx/

Many phenomena in nature involve motion of viscous flows, which are widely believed to be described by Navier-Stokes equations (NSE). These equations are used for instance in numerical simulations of flows in astrophysics, climate or aeronautics. These equations are the cornerstones of many physical and engineering sciences, and are routinely used in numerical simulations. From a mathematical point of view, however, it is still unclear whether the Navier-Stokes equations are a well-posed problem in three dimensions, i.e. whether their solutions remain regular over sufficient large time or develop singularities.



Historically, the search for singularities in NSE was initiated by Leray who introduced the notion of weak solutions (i.e. in the sense of distribution). This notion was used to prove that the mathematical singular set has a one-dimensional Haussdorff measure equals to zero in space-time. Therefore, if these singularities exist, they must be extremely localized events in space and time. This makes their direct detection an outstanding problem. For some times, the best suggestive evidence of their existence was provided by the observation that the energy dissipation rate in turbulent flows tends to a constant at large Reynolds numbers This observation is at the core of the 1941 Kolmogorov theory of turbulence, and was interpreted by Onsager as the signature of singularities with local scaling exponent h=1/3. Later, it was conjectured that the singularities are organized into a multifractal set. Analysis of measurements of 3D numerical or 1D experimental velocity fields showed that the data are compatible with the multifractal picture, with a most probable h close to 1/3. However, this analysis could not reveal any information on the space-time statistics of (possible) singularities.



A major breakthrough was achieved when Duchon and Robert performed a detailed energy balance for weak solutions of INSE, and compute the contribution stemming from an eventual lack of smoothness. They show that it can be lumped into a single term that quantifies the "inertial" energy dissipation, i.e. the energy dissipated by non-viscous means.

The purpose of this thesis is to test these mathematical results in a numerical turbulent swirling flow to infer properties of the energy dissipation in a turbulent flow.

Thermoelectric phenomena in ionic liquids and nanofluids

SL-DRF-18-0370

Research field : Soft matter and complex fluids
Location :

Service de Physique de l'Etat Condensé

Systèmes Physiques Hors-équilibre, hYdrodynamique, éNergie et compleXes

Saclay

Contact :

Sawako NAKAMAE

Starting date : 01-10-2018

Contact :

Sawako NAKAMAE

CEA - DRF/IRAMIS/SPEC/SPHYNX

0169087538

Thesis supervisor :

Sawako NAKAMAE

CEA - DRF/IRAMIS/SPEC/SPHYNX

0169087538

Personal web page : http://iramis.cea.fr/Pisp/sawako.nakamae/

Laboratory link : http://iramis.cea.fr/spec/SPHYNX

More : https://www.magenta-h2020.eu

Biophysical and dynamical study of chromatin conformation during genome replication

SL-DRF-18-0276

Research field : Soft matter and complex fluids
Location :

Service Nanosciences et Innovation pour les Materiaux, la Biomédecine et l'Energie

Laboratoire Interdisciplinaire sur l'Organisation Nanométrique et Supramoléculaire

Saclay

Contact :

Frédéric GOBEAUX

Patrick GUENOUN

Starting date : 01-10-2018

Contact :

Frédéric GOBEAUX

CEA - DRF/IRAMIS/NIMBE/LIONS

01 69 08 24 74

Thesis supervisor :

Patrick GUENOUN

CEA - DRF/IRAMIS/NIMBE/LIONS

01-69-08-74-33

Personal web page : http://iramis.cea.fr/Pisp/frederic.gobeaux/

Laboratory link : http://iramis.cea.fr/nimbe/lions/

The tridimensional organization of the genome and its dynamics in live cells are decisive to perform its functions. It is crucial to understand them and to identify the parameters controlling them. Current state of the art allows describing the short range (<10 nm) and long range (>250 nm) organization of chromatin conformation in the nucleus. However, there is an intermediate range (10-250 nm) where chromatin organization is difficult to apprehend. This range corresponds to the size of protein complexes that modify chromatin and harness genome replication.



We propose to monitor cell cultures during genome replication using small angle x-ray scattering. Thanks to a dedicated experimental set-up we will study chromatin conformation dynamics during genome duplication and complement this analysis with numerical simulations (molecular dynamics) so as to correlate chromatin dynamics with that of genome duplication. We will study different cell types to test the generality of our observations.



This project is a collaboration between two teams of physicists and biologists and will consist for the student to reach a dual expertise in both disciplines.

Data-driven model-learning for suspensions of micro-swimmers

SL-DRF-18-0902

Research field : Soft matter and complex fluids
Location :

Service de Physique de l'Etat Condensé

Systèmes Physiques Hors-équilibre, hYdrodynamique, éNergie et compleXes

Saclay

Contact :

Hugues CHATE

Starting date : 01-09-2018

Contact :

Hugues CHATE

CEA - DRF/IRAMIS/SPEC/SPHYNX

0169087535

Thesis supervisor :

Hugues CHATE

CEA - DRF/IRAMIS/SPEC/SPHYNX

0169087535

Laboratory link : http://iramis.cea.fr/spec/SPHYNX/

The past ten years have seen the emergence of Active Matter – composed of particles that convert energy from an ambient source into systematic movement – as a distinct topic in nonequilibrium statistical physics, motivated mainly by the need to understand and imitate individual and collective motility. Experiments are still relatively few, but, increasingly, large datasets obtained in controlled conditions are obtained with the aim of testing theoretical ideas and results. The time is ripe to try to build models from data, aiming at full quantitative agreement so that the effect of experimental control parameters on model parameters is made explicit. This is challenging and important since models, especially continuous ones, typically contain many terms parameters so that there is no one-to-one correspondence with experimental ones.



We will use high-throughput experimental data on bacterial suspensions (‘big data’, from collaborators in Shanghai and Hong Kong) to build quantitative models/theories.



The PhD work will consist of following two main avenues toward the overarching goal of building a direct quantitative link between experiments and theory. The first one, based on traditional model building based on multidimensional optimization of a set of target quantifiers, is already under way. The second one, based on automatic model learning, is more challenging and risky, as it will explore how to use machine-learning techniques to build a model ‘automatically’. The comparison between the results obtained using both routes will be particularly interesting. Analytical work necessary to derive kinetic and hydrodynamic theories from simple interacting swimmers models, including stochastic terms, will be developed in parallel.

Self-assembled metamaterials made by block copolymers

SL-DRF-18-0245

Research field : Soft matter and complex fluids
Location :

Service Nanosciences et Innovation pour les Materiaux, la Biomédecine et l'Energie

Laboratoire Interdisciplinaire sur l'Organisation Nanométrique et Supramoléculaire

Saclay

Contact :

Patrick GUENOUN

Virginie PONSINET

Starting date : 01-10-2018

Contact :

Patrick GUENOUN

CEA - DRF/IRAMIS/NIMBE/LIONS

01-69-08-74-33

Thesis supervisor :

Virginie PONSINET

CNRS - Centre de Recherche Paul Pascal (CRPP)

+33(0)5 56 84 56 25

Personal web page : http://iramis.cea.fr/Pisp/patrick.guenoun/index.html

Laboratory link : http://iramis.cea.fr/nimbe/lions/

Metamaterials are "artificial" materials which are created to reach properties inaccessible to natural homogeneous materials. Optical properties like negative refractive indices could be achieved by an adequate structuring of materials at a scale lower than the wavelength of the light. In this PhD work, we shall obtain such a structuration by combining the self-assembly of copolymers on surfaces and the insertion of gold nanoparticles in the copolymer matrix. The copolymer matrix of copolymers provides the nanostructuration and the desired geometry thanks to microphase separation on top of the substrate whereas the gold nanoparticles presence confers the expected optical properties. This PhD thesis project in collaboration between LIONS at CEA Saclay (U. P. Saclay) and the Paul Pascal Research Center (CRPP) in Bordeaux will benefit from both environments to lead an experimental study which will consist in preparing surfaces where cylindrical or bicontinuous phases of copolymers will be directed perpendicularly to the substrate. After synthesis in the laboratory and insertion of gold nanoparticles in the structures, the optical properties of the obtained material will be measured and analyzed for modeling.

Materials Synthesis and Integration in Water Quality Monitoring Sensors

SL-DRF-18-0286

Research field : Soft matter and complex fluids
Location :

Service Nanosciences et Innovation pour les Materiaux, la Biomédecine et l'Energie

Laboratoire Innovation, Chimie des Surfaces Et Nanosciences

Saclay

Contact :

Jean-Christophe GABRIEL

Starting date : 01-10-2018

Contact :

Jean-Christophe GABRIEL

CEA - DRF/IRAMIS/NIMBE/LICSEN

0438780257

Thesis supervisor :

Jean-Christophe GABRIEL

CEA - DRF/IRAMIS/NIMBE/LICSEN

0438780257

Personal web page : http://inac.cea.fr/Phocea/Pisp/index.php?nom=jean-christophe.gabriel

Laboratory link : http://iramis.cea.fr/nimbe/licsen/

More : https://www.linkedin.com/in/jcpgabriel

The present PhD subject comes in the context of two projects funded by the ANR in 2017 on the theme of Sensors for the environment (4WATER project). The water crisis is the # 1 risk for its impact on society after the "World Economic Forum" (01/2015). In the 4WATER project, the development of new low cost and multi-target matrix sensors is proposed. These MOSFETs sensitive to the different types of ions chosen, in a microelectronic approach, under the form of MOSFET transistors that are sensitive to various ions relevant to appreciate the water potability. This device will constitute a permanent and inexpensive multianalytical solution to monitor surface drinking water resources.



During the thesis work, the student will have to synthesize materials/chemicals by various synthetic methods and will have to solubilize them (ink formulations) so as to be able to perform deposition using an ink jet printer. This component will be integrated into water quality sensors and tested. Depending upon the remaining time and dynamism of the student, physico-chemical studies of the fluid complex, obtained from the synthesized materials and inks, will be performed in collaboration with partners' scientists. The student will be exposed to a multidisciplinary environment and will have to perform experiments in various fields such as inorganic chemistry, physical chemistry, micro-nanofabrication in clean rooms, nano-characterization, and electric/electronic testing. This PhD is therefore an excellent opportunity to build up a CV whether from the point of view of knowledge & knowhow acquisitions or regarding the footprint in the scientific world as well as through collaboration with an industrial partner.

Optical measurements of dissipation and energy fluxes in turbulent flows

SL-DRF-18-0872

Research field : Soft matter and complex fluids
Location :

Service de Physique de l'Etat Condensé

Systèmes Physiques Hors-équilibre, hYdrodynamique, éNergie et compleXes

Saclay

Contact :

Sébastien AUMAÎTRE

Starting date : 01-10-2018

Contact :

Sébastien AUMAÎTRE

CEA - DRF/IRAMIS/SPEC/SPHYNX

01 69 08 74 37

Thesis supervisor :

Sébastien AUMAÎTRE

CEA - DRF/IRAMIS/SPEC/SPHYNX

01 69 08 74 37

Personal web page : http://iramis.cea.fr/Pisp/sebastien.aumaitre/

Laboratory link : http://iramis.cea.fr/spec/sphynx/

The aim of this proposal is the study of power fluctuations in turbulent flow. The usual theoretical approaches have shown that the stationarity of the flow, implying the balance of the power injected large scales with the power dissipated at small scales, constrains the power spectrum of the velocity. However, one needs to go beyond to explain the complexity and the intermittency of turbulent flow. One can consider the statistical properties of the fluctuations of powers involved in turbulent flow. Especially one can explore the correlations implied by the stationarity on the fluctuations of injected and dissipated power and theirs consequences on the structure of the flow. The challenge is to estimate the fluctuations of dissipated power resolved in time. To do so, we would like to develop an innovative optical technics implying diffusive wave spectroscopy and ultra-fast image acquisition. This technics will be complemented by usual measurement technics in order to estimate simultaneously the injected power and to probe the structure of the flow.

 

Retour en haut