3D thermal modeling of Lascaux Cave: Dynamics of air circulation and implications for its microclimate

Understanding the thermal dynamics of painted caves, such as the Lascaux Cave, is essential for predicting and preventing deterioration of walls and artworks, particularly through processes such as condensation. As a first step, heat conduction within the surrounding rock mass was investigated. Given that even small temperature gradients can significantly influence thermal convection in shallow and confined caves, high precision in thermal characterization is required. As shown in a prior work, this issue is addressed by considering a heterogeneous rock mass with spatially varying thermal properties and determining their optimal values. The present paper focuses on the subsequent step: modelling the natural convection occurring within the cavity. A numerical model was developed to simulate the natural convection in the cavity and applied to the onset of convection on 15 May 2021. Model predictions were compared against in situ measurements from 22 temperature sensors. The analysis reveals the occurrence of two distinct convections: (i) within the Great Fissure, and (ii) between the Great Hall of the Bulls and adjacent chambers. At greater depths, the thermal gradients are insufficient to induce significant velocity fields, thereby preserving the stratified temperature structure. Despite preliminary discussions on wall condensation, future work should address more accurately the modelling of condensation processes on the cave walls.