Étude des transferts de masse et de chaleur dans la grotte de Lascaux : le suivi climatique et le simulateur., 2007, Lacanette D. , Malaurent Ph. , Caltagirone J. P. , Brunet J.

Study of heat and mass flows in Lascaux cave: the climatic monitoring and the simulation tool. The cave of Lascaux, discovered in 1940 and located in the Dordogne area in France, is inscribed on the Unesco World Heritage List. It is considered as one of the major prehistoric caves in the world. Since its discovery, several problems have occurred, due to the huge amount of visitors, and their release of vapour and carbon dioxide by their breath, causing the formation of calcite and the apparition of green algae and mosses. The Ministry of Cultural Affairs had the cave closed in 1963. Since then, prehistorians, archaeologists, geologists, hydrogeologists, have tried hard to maintain the cavity in the most stable state as possible, using remote metering to record the variations in temperature, hygrometry, and carbon dioxide gas pressure. The biological equilibrium remained fragile and, in 2001, colonies of micro-organisms, mushrooms and bacteria developed on the rock edges and on the floor. This attack made the authorities and the Minister of Culture and Communication create the scientific international comity of the Lascaux cave, a multidisciplinary comity (composed of archaeologists, physicists, geologists, hydrogeologists, conservators working altogether) to understand the mechanisms of apparition of the micro-organisms in order to stop their propagation. Among the measures taken by the comity, a better understanding of the flows in the cave has appeared very important, and has induced the creation of a simulation tool, the "Lascaux Simulator". The non intrusive character of simulation is one of the major assets of this method. Thus, the numerical simulation in fluid mechanics is here dedicated to the conservation of the cave of Lascaux. The simulator is based on a computational fluid dynamics code named Aquilon. A three dimensional survey has been leaded in the cave using laser scanning and an accurate topology of the environment is incorporated in the simulator. Starting from this point, governing equations of the fluid mechanics are solved and parameters such as temperature, velocity or moisture content are known in every point of the cavity. Thermal conditions are chosen, basing on the analysis of the calculated and measured temperature data for more than 50 years. In this article, two configurations are chosen, the first one in September 1981, period during which the cave remained in a stable state regarding condensation, and the other one in December 1999; at this time, temperature were reversed, the ground of the cavity was colder than the vaults. This phenomenon implied an inversion of the air flow in the cave. Finally, the removal of the dividing wall of the “Bauer airlock” has been simulated, and it has been showed that the impact on the cavity would be negligible.