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Portail > Offres > Offre UMR5509-AURNAS-002 - Mécanismes de collisions de particules sphéroïdales en turbulence: application à la microphysique des nuages (H/F)

Mechanisms of collisions between spheroidal particles in turbulence: application to cloud microphysics (H/F)

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Français - Anglais

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General information

Reference : UMR5509-AURNAS-002
Workplace : ECULLY
Date of publication : Friday, September 04, 2020
Type of Contract : FTC Scientist
Contract Period : 8 months
Expected date of employment : 1 December 2020
Proportion of work : Full time
Remuneration : between 2643 and 3766 € monthly gross according to experience
Desired level of education : 5-year university degree
Experience required : Indifferent


A postdoctoral position is open at the Laboratoire de Mécanique des Fluides et d'Acoustique (LMFA, Ecole Centrale de Lyon). The project is devoted to the settling of spheroidal (rod-like or disc-like) particles in a homogeneous isotropic turbulent flow. We focus here on objects smaller than the Kolmogorov scale of the flow and of density much larger than that of the fluid [1,2,3]. The main motivations for studying these problems indeed come from cloud microphysics (ice crystals or water droplets in air). Our group has investigated more particularly the collisions of these particles [4,5], which play a major role in the formation of precipitation in cold clouds.

The next step of the project will consist in identifying the physical mechanisms which drive the collisions of these non-spherical objects. The postdoctoral researcher will join this research program. She/he will more specifically analyze by direct numerical simulation the detailed dynamics and distribution of the particles in the flow.

[1] K. Gustavsson, J. Jucha, A. Naso, E. Lévêque, A. Pumir and B. Mehlig (2017). Statistical Model for the Orientation of Nonspherical Particles Settling in Turbulence. Phys. Rev. Lett., 119:254501.

[2] K. Gustavsson, J. Jucha, A. Naso, E. Lévêque, A. Pumir and B. Mehlig (2019). Effect of fluid inertia on the orientation of a small prolate spheroid settling in turbulence. New J. Phys., 21:083008.

[3] M. Z. Sheikh, K. Gustavsson, D. Lopez, E. Lévêque, B. Mehlig, A. Pumir and A. Naso (2020). Importance of fluid inertia for the orientation of spheroids settling in turbulent flow. J. Fluid Mech., 886:A9.

[4] J. Jucha, A. Naso, E. Lévêque and A. Pumir (2018). Settling and collision between small ice crystals in turbulent flows. Phys. Rev. Fluids, 3:014604.

[5] A. Naso, J. Jucha, E. Lévêque and A. Pumir (2018). Collision rate of ice crystals with water droplets in turbulent flows. J. Fluid Mech., 845:615-641.


The selected candidate will contribute to this effort at several levels, by :
- getting familiar with the available code of integration of the Navier-Stokes equations by direct integration (direct numerical simulation, DNS), which can follow the motion of small and very dense spheroidal particles.
- carrying out the required numerical simulations.
- analyzing the results of these simulations.


- The candidate must hold a PhD in Mechanics, Physics or Applied Mathematics, and have a solid knowledge in one or several of the following areas: hydrodynamic turbulence, particle transport in a fluid.
- Previous experience in numerical methods of spectral type and/or to parallel computing will be highly appreciated.
- Experience of scientific English and in the writing of publications for scientific journals is required.
- Experience in the presentation of research results in international conferences is required.
- The candidate must be able to work as part of a team, and to interact with researchers of the same level or more experienced.

Work Context

This position is part of a larger project, “Particles drifting and propelling in turbulent flows”, involving several groups in the Lyon area, and financed by the IDEXLYON.

This project makes possible collaborations and exchanges with the other partners involved: Laboratoire de Physique (École Normale Supérieure de Lyon), Institut Camille Jordan, Centre de Recherche Astrophysique de Lyon, Laboratoire de Géologie de Lyon, and Institut Lumière Matière, bringing together experimental, computational, theoretical, and multidisciplinary approaches. The hired applicant will participate in these collaborations and exchanges, by participating in particular to regular work meetings.

Additional Information

The contract duration will be comprised between 8 and 12 months depending on the candidate's experience.
The date of employment can be discussed, but the contract must end on December 31, 2021 at the latest.

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