Research Engineer “modeling water and temperature transfers in an anisotropic porous medium using the HPC simulation code of permafrost permaFoam” at Centre National de la Recherche Scientifique (CNRS), Toulouse, France
Number of positions: 1
Date of publication: 8 January 2024
Type of Contract: FTC Technical / Administrative
Contract Period: 10 months
Expected date of employment: 1 March 2024
Proportion of work: Full time
Remuneration: €2782-3142 gross monthly depending on experience.
Desired level of education: Level 7 – (Bac+5 and above)
Experience required: Indifferent
BAP: Life, earth and environmental sciences
Typical job: Research engineer in geo-natural and anthropized environments
Permafrost (or permafrost, soils frozen at depth throughout the year) represent nearly 25% of land in the Northern Hemisphere. Their evolution under the effect of climate change is a major scientific issue which depends on numerous processes still poorly represented in climate models. The ANR HiPerBorea project aims to quantify the impacts of global warming on boreal permafrost through high-resolution mechanistic modeling (e.g., Orgogozo et al., 2019, 2023). The objective is to assess the impact of climate change, as given by the IPCC over a period of 50 to 100 years, on the hydrological and thermal dynamics of boreal watersheds. The approach implemented consists in particular of carrying out digital simulations at the scale of the watershed using the permaFoam code (Orgogozo et al. 2023). The implications of the future of permafrost (part of frozen soil) relate, for example, to the carbon stock it contains or to the stability problems of civil structures induced by its thawing.
As part of this project, the GET laboratories in Toulouse (Géosciences Environnement Toulouse) and LSCE in Saclay (Laboratory of Climate and Environmental Sciences) are offering a research engineer contract on high-performance simulation of the impact of climate change on the hydrology of boreal environments, with a focus on the couplings between surface flows and underground flows. The recruited engineer will begin his activity with the validation of an advanced version of permaFoam already developed elsewhere, an advanced version which allows the anisotropy of the underground environment to be taken into account in the resolution of water transfers, with a tensor form for hydraulic conductivity at saturation. Indeed, such a tensorialized solver is necessary to implement the generalized Richards equation approach for surface-subsurface coupling (e.g., Weill et al., 2009). It will then be 1) to develop within the OpenFOAM digital environment a hydrological module coupling surface hydrological flows (hydrography), subsurface (water tables) and heat transfer in the ground by taking into account the phase change open water-frozen water; 2) to validate the module thus developed on test cases from the literature, and in particular international benchmarks, 3) to apply the model to high latitude experimental sites (boreal environments). The digital environment used is the OpenFOAM “open source” code developed for fluid mechanics applications. This is used by the GET laboratory to simulate permafrost, with the development of the permaFoam cryohydrogeological simulator (Orgogozo et al., 2019, 2023). Due to the strong couplings and strong nonlinearities of the physical processes modeled, fine spatio-temporal discretizations are necessary for this type of numerical simulation, which leads to very significant computational loads. The use of intensive computing methods is therefore essential, and, with this in mind, the use of OpenFOAM allows you to benefit from a cutting-edge environment, kept up to date for massively parallel computing on the largest supercomputers. Thus permaFoam showed excellent parallel performances on test cases with meshes of up to a billion cells (on Olympe of the CALMIP meso-center in Toulouse), using up to 16,000 cores (on IRENE-ROME of CEA national TGCC center). As part of this contract, this computing power will be fully used to add the non-linear coupling between surface flow and sub-surface flow to the permafrost dynamics modeled by permaFoam.
- L. Orgogozo, T. Xavier, H. Oulbani, C. Grenier, 2023. Permafrost modeling with OpenFOAM ®: the permaFoam solver.
- L. Orgogozo, AS Prokushkin, OS Pokrovsky, C. Grenier, M. Quintard, J. Viers, S. Audry, 2019. Water and energy transfer modeling in a permafrost-dominated, forested catchment of Central Siberia: the key role of rooting depth. Permafrost and Periglacial Processes 30: 75-89 (2019) DOI: 10.1002/ppp.1995
- S. Weill, E. Mouche, J. Patin, 2009. A generalized Richards equation for surface/subsurface flow modeling. Journal of Hydrology (2009); 366:9–20. DOI: 10.1016/j.jhydrol.2008.12.007
- Handling and validation of the tensor version of permaFoam
- Development of test cases based on surface-subsurface coupling benchmarks from the literature
- First application tests to the modeling of the Abisko site in Arctic Sweden (https:/ /eu-interact.org/field-sites/abisko-scientific-resarch-station/)
- Promotion of results in the form of publications in scientific journals and conference communications
- First experience with the compilation and use of a scientific numerical code
- Mastery of a compiled programming language
- Ability to use the LINUX environment on a daily basis
- English read, written, spoken (reading and writing documentation, paper of scientific journals, possible participation in international conferences, etc.)
Optional technical skills:
- Experience in the use of calculation infrastructures
- Mastery of the C++ development language
- First experience with OpenFOAM code
The contract is part of the activities of the ANR HiPerBorea project (hiperborea.omp.eu). The work will mainly take place at GET in Toulouse and in collaboration with LSCE in Saclay.
Constraints and risks:
Interactions with the ESI-Group / OpenCFD developer team will be possible to diagnose possible additional needs in terms of implementation.
Application deadline: 29 January 2024