Offres de Thèses et Postdocs

This thesis will focus on internal tidal waves (at diurnal and semi-diurnal frequencies), and may further extend to other type of ocean internal wave (e.g. near-inertial waves).

In atmospheric clouds, in industrial power plants, and in the pandemic we have been living, a crucial element is the interaction of small particles with the turbulent flow that carries them. Will two ice crystals collide and aggregate to form a snowflake? Will an ocean wave break and splash droplets in the atmosphere? How far will a drop of saliva travel in air? Particle-laden turbulent flows are ubiquitous and extremely challenging to predict: the chaotic motion of the fluid is intertwined with the particles’ ability to exchange momentum and energy at the microscopic scale, while also altering the flow globally.

The objective of this postdoc position is to improve the CYCLONE library developed by RTECH, possibly by incorporating a different type of Immersed Boundary Method (IBM), such as the sharp interface method, which is presently under investigation at Pprime Institute.

Dans le contexte de changement climatique, il est parfois difficile de distinguer les influences anthropiques, de la variabilité naturelle, tant celle-ci est complexe et pourtant si importante qu’elle peut masquer les effets des activités humaines sur le climat. C’est notamment le cas pour la variabilité de la circulation atmosphérique, que les modèles numériques actuels ne reproduisent pas correctement. L’une des raisons est l’impossibilité pour ces modèles de simuler les processus physiques sur l’ensemble des échelles spatio-temporelles où elles se produisent et notamment comment différents processus à différentes échelles interagissent. Le but de la thèse est de comprendre le lien entre les grandes échelles spatio-temporelles des mouvements cohérents de l’atmosphère et les statistiques à l'échelle régionale des différents champs turbulents (vitesse, température, humidité, précipitations), et notamment les événements rares ou extrêmes.

TWe are currently offering two PhD positions: Experimental measuremenst of multiphase flows and numerical simulations of multiphase flows.The official advertisement will be opened soon, but inquiries can be sent to Mrs. Müllner at christina.muellner@tuwien.ac.at

The objective of this postdoc is to study the importance of the fluid miscibility on the RTI dynamics using highly resolved simulations with the pseudo-spectral code STRATOSPEC . A diffuse interface method relying on the Cahn-Hilliart equations will be coupled to the Navier-Stokes solver. To this aim, we propose to assess the efficiency of various semi- or fully implicit numerical methods. Computational resources for the simulations will be provided through the TGCC supercomputers. Different theories and models will be proposed to interpret the results.

The Fluid Mechanics Laboratory of Lille (CNRS-LMFL) is seeking a highly qualified candidate for a post-doctoral research fellowship to participate in ERC Advanced Grant research project NoStaHo which is aimed at an extensively transformative fundamental understanding and theory of non-stationary and/or non-homogeneous turbulence.The candidat will participate in the experimental side of the project by contributing to (i) Particle Image velocimetry and Hot Wire Anemometry measurements and (ii) various ways to analyse the data obtained for a variety of turbulent flows including various types of turbulent wakes, jets and boundary layers.

Turbulence et circulations à résolution décamétrique dans les nuages convectifsDans le cadre de cette thèse, nous souhaitons étudier les processus physiques à l’interface nuageuse à l'aide de simulations à très fine résolution (LES décamétrique) avec le modèle Méso-NH (Lac et al, 2018). L'objectif est de caractériser les circulations au sein des nuages convectifs (du cumulus au cumulonimbus), ainsi que les structures turbulentes associées.

A goal of this research project is to propose solutions to improve the performance of heat exchang-ers by using acombination of active control strategiestomaximise heat-transfer capacityalong the interface fluid/structureandminimise the pressure loss due to friction betweenthe fluid and the wall.

The aim of the PhD project is to understand the dynamics of jets hitting a surface, using a combination of experimental, numerical and theoretical approaches.

L'objectif de ce post-doctorat est de réaliser et d'exploiter des simulations directes de turbulence compressible homogène avec forçage, de façon à mettre en évidence les propriétés inertielles de la circulicité.

The design and operation of future large wind turbines require an in-depth understanding of the interaction between the rotor and the turbulent wind in the atmosphere. To this end, we will scan the entire wind field in front of, at and close behind two multi-megawatt wind turbines with a high spatial and temporal resolution, using the laser-based scanning technique lidar (light detection and ranging).Our two short-range WindScanners are continuous-wave Doppler wind lidars. They remotely measure the wind speed component along the beam direction (line-of-sight wind speed) at several hundred positions each second. A wind field can be reconstructed using these point measurements and additional meteorological information. In this project, particular focus will lie on wind field reconstructions using novel stochastic methods, which consider statistical features of small-scale turbulence.

IFISC (Institute for Cross-Disciplinary Physics and Complex Systems) offers a postdoc position to work on the research project "Lagrangian transport of marine litter and microplastics in coastal waters: structures of transport and connectivity patterns".

The work of the candidate will aim for the development of the following tasks:1. Implementation of data streaming machine learning techniques within the C++ software developed by the research group, aiming to reconstruct an augmented IBM formalism. The AI learning procedure will be fed by online data generated by the MGEnKF.2. The performance of the code will be assessed via the analysis of progressively more complex scale-resolved turbulent flows. The test cases investigated include the turbulent channel flow and, in case of success, complex test cases such as a radial pump will be investigated. For every test case considered, high fidelity DNS / experimental data are already available from previous analyses of the research group.

Post-doc dans le cadre de l'ERC NoStaHo (Non-stationary and non-homogeneous turbulence)

A one-year post-doctoral position is opened at LEGI, in the EDT team, to conduct experimental research on the influence of surface conditions for spray impact, with applications to spray cleaning. While the appointment is at LEGI, the post-doc will also work at LIPhy, in the MODI team, since this is a collaborative project between researchers at both labs.

OPAALE INRAE, located in Rennes, France, is seeking highly motivated postdoctoral Marie Skłodowska-Curie candidates to work on a cutting-edge project using volumetric velocimetry data to reconstruct high-resolution turbulent flow fields. We are seeking candidates with expertise in machine learning or data assimilation to join our team and use this valuable dataset to train flow reconstruction models.We recently conducted a massive experimental campaign and obtained high-quality data from nearly 200 experiments with various scenarios, including cylinder, step cylinder, flat plate, step plate, wall-bounded cylinder, and more. Our dataset consists of approximately 12 billion trajectories recorded in total for a variety of Reynolds numbers. This is a unique experimental dataset to train machine learning algorithms.

Offre de thèse, Univ. Bristol UK

Large-scale plunging jets encountered in hydroelectric infrastructures directly influence turbine operation and performance through their ability to generate huge bubble clouds and thereby draw air into the pipelines under load. Nevertheless, despite the relevance of applications, something as fundamental as predicting the flow rate of air entrained in a pool by a plunging jet is still an open question.This postdoc project consists on an experimental study that involves LEGI lab, CERG center and EDF, and aims at providing a better understanding of these flows within hydroelectric installations.I this context, a key parameter for the modelling and scale-up of these flows is the ability of a jet to entrain air under the free surface that it impacts and the characterization of its sub-surface dynamics. Other important parameters are the size distribution of the bubbles generated, the entrained air flow rate and the spatial distribution of local quantities of interest.

This project is multidisciplinary and focuses on the development of new Deep Learning models for non-linear multiscale characterization with applications in fluid turbulence, remote sensing images and the combination of both to study ocean dynamics.

La convection thermique turbulente constitue un problème omniprésent dans de nombreuses situations naturelles. Elle peut être modélisée en laboratoire par la cellule de Rayleigh-Bénard. Il s’agit d’une couche de fluide confinée entre deux plaques horizontales. Le fluide est chauffé par le bas, et refroidi par le haut. Les couches limites thermiques se forment au voisinage des plaques. L’instabilité de flottabilité conduit à la germination de structures cohérentes, applées panaches thermiques. Ces panaches et leur interaction donnent naissance à un mouvement global (la circulation grande échelle). Lorsque le forçage est suffisamment intense, l’écoulement peut devenir turbulent, et le comportement global est déterminé par la compétition entre les effets purement inertiels, le forçage thermique local et l’interaction entre panaches.

PhD thesis, starting in October 2023, for three years.Multi-scale interactions in the atmosphere. Application to the prediction of heat waves and urban heat islands

Hyperpycnal sediment-laden river plumes in lakes: flow-sediment-bathymetry interactions

Deux postes d'AGPR en physique ouverts à l'ENS-Paris à partir de septembre 2013 pour une durée de 3 ou 4 ans

Cette thèse propose l'étude des extrêmes dans la couche limite atmosphérique urbaine ainsi que leur impact sur le vol des drones, à l'aide du code de simulation météo mésoNH et d'outils dédiés, à l'ONERA Lille et au LMFL.

At very high Rayleigh numbers, a very intense heat transfer regime appears for which the triggering mechanisms are still poorly understood. Using HPC numerical simulations and physics-guided machine learning techniques, we seek to extract from data physical information bringing to light the multi-scale interactions between different turbulent flow structures.

How do rain droplets form in clouds? How pollutants, viruses or volcano ashes disperse in the atmosphere? Where can they fall and at which speed? How plankton dynamics is affected by sea conditions? What are the consequences on the trophic chain? What are the optimal parameters for a wastewater treatment plant, for an engine, a chemical reactor? All these questions find answers in the study of inertial particles in turbulence. Such particle laden flows are ubiquitous but so complex to study due to the very large number of intertwined control parameters and the lack of theoretical predictions.

The present project aims at exploring the role of the surrounding turbulence on both the dynamics and the multi-stability of a pendulum in the wind.

Unité de Mécanique de Lille is looking for a PhD student to work on the project “Lagrangian transport of microplastics in nonhomogeneous upper-ocean turbulent flows“.

We are looking for a highly motivated Post-Doc for a project at the frontier of fundamental fluid mechanics and mechanical engineering, coupling numerical and experimental approaches.

A PhD position is open at LEGI to work on simulations of quantum turbulent flows (observed for instance in superfluid helium) at the absolute zero, where they are described as a collection of interacting vortex filaments. The main objective is to investigate the possible similarities between quantum and classical turbulence, in order to strengthen the link between both systems.

Theoretical/numerical study on the interactions between a vortex and a fluid interface. Application (motivation letter and detailed CV) should be sent to the contacts before 21 june 2023.

This doctoral thesis aims to study in depth the physical mechanisms governing the expansion of a wind turbine wake within a turbulent background. To this end, the work will be based on the combination of high-quality experiments and high-fidelity simulations. Particular attention will be paid to the influence of the characteristic quantities of the external turbulence on the aerodynamic performance of the wind turbine, on the expansion of its wake and its dynamics. The physical analysis of experimental and numerical data will be used to formulate new models of wake expansion that are more relevant than those currently used for the design of wind farms.

Depuis le vote de la Loi sur les Opérations Spatiales en 2008, différents outils CNES ont été développés pour l’analyse des risques associés à la rentrée atmosphérique de structures spatiales telles que des lanceurs ou satellites. Différentes stratégies sont employées en fonction de l’objectif de l’outil, du temps de calcul disponible et le degré de fidélité nécessaire. L’ensemble des phénomènes physiques doivent être modélisés avec précision, ceci afin de garantir que les débris retombant au sol ne présentent pas un risque pour la population.La dégradation de satellites étant très complexe, à la fois dépendante des propriétés matériaux dde l’objet et de la précision des flux thermique à la paroi de la structure, son étude pour une modélisation précise est encore au stade de la recherche. En collaboration avec R.Tech et le laboratoire LMFL, 2 objectifs sont visés :1 améliorer les outils numériques du CNES2 Mettre sur pied une expérience sol de dégradation d’une maquette satellite

The student will take part of the joint ANR research program MUFDD (Modelling Urban Flows using Data-Driven methods) between IMFT, LHEEA (Ecole centrale of Nantes) and PPRIME (Poitiers), to support the experimental activities carried out at IMFT. The work will focus on isothermal street canyon urban canopy configuration. Experiments will be performed in the large, 26 m long and 1.1 m wide, hydraulic flume of IMFT with optical access for laser optical measurements (LDV, PLIF, TomoPIV).

In the context of the CNRS Chair in Physical Hydrodynamics, we would like to recruit a PhD student to work at Institut Pprime on theoretical and numerical work related to black-hole laser instabilities and undulations in open channel flows.https://emploi.cnrs.fr/Offres/Doctorant/UPR3346-NADMAA-083/Default.aspx

We have a number of post-doctoral and doctoral positions on ocean modeling to fill in our Odyssey team at Inria (Rennes, France).

Le projet de thèse se situe dans le cadre du dispositif COFRA (COnvention de Formation par la Recherche des Administrations). Il implique un partenariat entre le Rectorat de l'Académie de Rennes d'une part et deux laboratoires de recherche de l'Université de Rennes : Institut de Physique (IPR) et Laboratoire de Génie Civil et Génie Mécanique (LGCGM) d'autre part.

L'ébullition est un phénomène complexe impliquant à la fois une dynamique complexe et des effets thermiques forts. Une bonne compréhension des différents régimes d'écoulement (bulle, poche, annulaire) est nécessaire pour modéliser correctement ce phénomène dans le cadre d'étude de conception ou de sûreté industrielle. L'objectif de la thèse est d'identifier les conditions d'écoulement amenant un essaim homogène de bulles à se déstabiliser. Il convient de caractériser ce type de transition pour mieux comprendre des effets d'accumulation locale de bulles pouvant amener à de la coalescence, par exemple. Cette étude se fera via des simulations numériques directes et une méthode de capture d'interface Front-Tracking permettant le suivi lagrangien des bulles.

As part of the BANG project, funded by the French National Research Agency, we are exploring the validity of the Navier-Stokes equation as a fluid model by studying phenomena occurring below the Kolmogorov scale, using multi-scale tools and advanced visualization techniques, namely 4D particle tracking velocimetry (4D-PTV), in a large-scale turbulence experiment called Giant Von Karman (GVK) built at the CEA.

L’objectif de ce postdoc est de caractériser théoriquement et numériquement le couplage d’écoulements de sillages turbulents pour plusieurs corps présentant différentes géométries. Les approches seront multiples et permettront de comparer les modèles développés récemment avec des modèles classiques et des simulations numériques directes. Des comparaisons expérimentales seront réalisées dans le cadre du projet SILTURB à l’aide d‘expériences dédiées réalisées à l’UME de l’ENSTA. Les résultats de ces études ont pour objectif de proposer des modèles de fermeture nouveaux implémentables dans les codes CFD

Nous recrutons un(e) Ingénieur(e) R&D Post Doc en CDD, dans le cadre d’une étude collaborative avec les laboratoires LEMTA et IJL de l’Université de Lorraine, l'IRT M2P et l’entreprise Metalor Technologies International.MOTS CLES : MECANIQUE DES FLUIDES – ATOMISATION – MODELISATION PHYSIQUE ET NUMERIQUE DES ECOULEMENTS DIPHASIQUES

We have developed an airborne platform called the Max Planck CloudKite (MPCK). It has been deployed over the Atlantic Ocean during the EUREC4A research cruise and in northern Finland inside the Arctic Circle. Our instruments perform autonomous measurements in the atmosphere, including particle image velocimetry and holography. In the next phase of our investigations, we will simultaneously measure with high resolution aerosols, wind speed and atmospheric thermodynamics as a function of altitude. These measurements will be complemented by most advanced microphysical cloud measurements. In collaboration with our colleagues at the Fraunhofer Institute for Integrated Circuits IIS, we are developing SMART Integrated Electronic Sensors (SMARTIES) to quantify atmospheric transport and mixing through many neutrally buoyant and biocompatible floaters.

The ForWind – Center for Wind Energy Research, Institute of Physics at the University of Oldenburg, jointly with Siemens Gamesa, invites applications for a PhD position (m/f/d)in the “Model Development for the Atmospheric Boundary Layer” as a part of the AptWind Marie Skłodowska-Curie Doctoral Network. The PhD candidate will be employed 50 % of the time (envisaged period: April 2023-September 2024) at the University of Oldenburg in Germany and 50 % (envisaged period: October 2024-March 2026) at Siemens Gamesa in Den Haag/The Hague, The Netherlands.

Trends such as larger wind farms and larger wind turbine rotors require high fidelity models such as large-eddy simulation (LES) to predict and understand the underlying aerodynamic and meteorological phenomena. Within this PhD project you will be part of a research group that focuses on fluid mechanics of individual wind turbines and wind farms. The project is concerned with the development of new modelling capabilities of an established numerical model.

The post holder will work at the Department of Low Temperature Physics, within a project focusing on the experimental study of wall-bounded flows of liquid helium-4.