Interactions between vertical and horizontal convections: From nuclear safety to the eye of cyclones
Michael LE BARS
IRPHE, CNRS, Aix-Marseille Université
We investigate heat transfer and flow dynamics in a thin cylindrical fluid layer with imposed heat fluxes at the bottom and top boundaries and a fixed temperature along the sidewall. This study is motivated by the In Vessel Retention strategy for severe nuclear accidents, where molten radioactive fuel and reactor materials form a Corium layer that must remain confined within the reactor vessel, cooled from the side to prevent failure. Combining Direct Numerical Simulations, model experiments, and theoretical analyses, we derive scaling laws for the mean temperature, velocity, and temperature differences in the system. Two distinct asymptotic regimes emerge, driven respectively by radial and vertical heat transfers. Realistic conditions combine these two regimes, leading to unexpected dynamics. In particular, experiments at application-relevant Rayleigh numbers reveal a persistent, large-scale radial branch pattern that drifts over time, governing long-term heat flux fluctuations critical for nuclear safety. Through linear stability analysis, we trace the origin of this pattern to a novel 3D instability arising from the interplay of convective and shear instabilities, significantly lowering the instability threshold compared to either mechanism alone. When global rotation is included, the system also serves as a dry model for hurricane-like vortices, enabling experimental and numerical investigations of the mechanisms behind eye formation in cyclones.
IMAGES
Recollision entre électrons en polarisation circulaire (plus de détails...)
CONFÉRENCES
New Challenges in Turbulence Research VII, École de Physique des Houches, 10 Février 2025
New Challenges in Turbulence Research VII, École de Physique des Houches, 10 Février 2025
New Challenges in Turbulence Research VII, École de Physique des Houches, 10 Février 2025