Quantum Turbulence (QT) is a young research field, but very timely since first applications of large superfluid systems start to emerge. Using liquid helium as a coolant for high-field superconducting magnets is a key frontier technology that is already in use in the Large Hadron Collider (LHC) at CERN and could be possibly used in the higher luminosity upgrade (LH-LHC) and other facilities operating very high magnetic fields (future fusion reactors, accelerators). Other possible applications of superfluid systems, promised to a future technological era, suggest that understanding and simulating QT is a key challenge in low temperature physics and a strategic technological topic for the next decades.
The project is aimed at providing a new state-of-the-art for the mathematical-physical modelling and High Performance Computing (HPC) of QT in superfluid quantum fluids, such as superfluid Helium (He) and atomic Bose–Einstein condensates (BEC). The primary focus of the project is the study of QT in liquid helium. This is a very low temperature system in which two interpenetrating fluids with different behaviors exist: a normal viscous flow, governed by the Navier-Stokes (NS) equation, and an inviscid (zero viscosity) superfluid flow, introducing quantum effects and governed by the Gross-Pitaevskii (GP) equation. QT is a highly multiscale phenomenon, ranging from Angstrom for the superfluid vortex diameter, to centimeters/meters for the size of the cryostat, which explains why mathematical-physical models and simulations covering accurately all scales do not exist nowadays.
Our project is scoped to address theoretically and numerically the critical gap between a close-up view of the interaction between normal-fluid and quantized superfluid vortices and a coarse-grained representation of QT dynamics. The final goal of the project is to offer a unified theoretical and numerical representation of QT, describing accurately all scales present in the system.
The originality of our approach is based upon an ambitious strategy using state-of-the art computational and experimental techniques available in our group. The project is multi-disciplinary: it combines mathematical and physical modelling, numerical analysis and HPC simulation, and, finally, experimental validation of numerical results, in a coherent workflow that brings together 10 (permanent) scientists from 7 laboratories. This includes a solid task-force of 2 research engineers, who will use their important experience in HPC to support coding effort.
This participation ensures the mandatory critical mass required to take up the following challenges: Explore QT in the zero-temperature limit (GP model) using high space and time resolution HPC computations going beyond existing simulations; Couple HPC numerical solvers for superfluid (GP) and normal fluid (NS) to simulate the QT system up to the inter-vortex length scale and beyond; Derive a new global model for QT; Implement this model in a new numerical HPC code, that is intended to become a reference for the global QT problem; Generate new experimental database of QT, especially probed to validate theoretical models and numerical simulations.
The main investigation tool will be based on large numerical simulations using HPC supercomputers. The final goal of the project is to provide a new numerical approach that will be equivalent to the Large-Eddy Simulations (LES) techniques used nowadays as the most evolved numerical investigation tool in dealing with Classical Turbulence (CT) in applications (aerodynamics, combustion, etc). This new QT-LES HPC code is intended to become the reference HPC code for the global QT problem and will be distributed in open-source.
Given the challenging objectives of the project and its unique composition gathering expertise in applied mathematics, scientific computing, HPC programming, theoretical/numerical/experimental physics, our project has no worldwide equivalent.
Monsieur Ionut Danaila (LABORATOIRE DE MATHEMATIQUES RAPHAEL SALEM)
The author of this summary is the project coordinator, who is responsible for the content of this summary. The ANR declines any responsibility as for its contents.
LMRS LABORATOIRE DE MATHEMATIQUES RAPHAEL SALEM
LMFA LABORATOIRE DE MÉCANIQUE DES FLUIDES ET D'ACOUSTIQUE
INEEL Institut NEEL - CNRS
Help of the ANR 577,152 euros
Beginning and duration of the scientific project: December 2018 - 48 Months