Delphine Lacanette

Macroscopic analysis of gas-jet wiping: Numerical simulation and experimental approach

Coating techniques are frequently used in industrial processes such as paper manufacturing, wire sleeving, and in the iron and steel industry. Depending on the application considered, the thickness of the resulting substrate is controlled by mechanical (scraper), electromagnetic (if the entrained fluid is appropriated), or hydrodynamic (gas-jet wiping) operations. This paper deals with the latter process, referred to as gas-jet wiping, in which a turbulent slot jet is used to wipe the coating film dragged by a moving substrate. This mechanism relies on the gas-jet–liquid film interaction taking place on the moving surface. The aim of this study is to compare the results obtained by a lubrication one–dimensional model, numerical volume of fluid–large eddy simulation (VOF-LES) modeling and an experimental approach. The investigation emphasizes the effect of the controlling wiping parameters, i.e., the pressure gradient and shear stress distributions induced by the jet, on the shape of the liquid film. Those...

Contribution of numerical modelling of environmental parameters to the conservation of prehistoric cave paintings: the example of Lascaux Cave

Abstract This study of Lascaux Cave consisted of simulating the evolution of changes in the levels of temperature and humidity both in the air and in the rock. By choosing different models (one-dimensional, three-dimensional, etc.), it was possible to calculate the required variables (temperature, moisture levels, speeds, etc.) at all points inside the cave, to locate zones of high water vapour concentration and to understand the nature of the airflow. The simulations described here provide the first general data on the airflow within the cave and its hygrothermic behaviour. The temperature fields result from natural convection phenomena, which are influenced by the climate outside the cave. From the point of view of air dynamics, we can observe the presence of an overall airflow that starts in the Machine Room (containing the air conditioning system installed in 1958), runs along the ground to the end of each of the branches of the cave, and returns along the cave vault to its starting point. This slow-moving phenomenon suggests the possibility of passive control of the ambient air from the Machine Room. There are localized risk areas where condensation of water vapour can occur, resulting in rapid deterioration of the limestone. Several of these areas are therefore monitored using condensation indicators placed on the cave walls or by visual observation of painted areas. The higher air speeds detected in some areas of the cave result in decay of the prehistoric paintings. The numerical modelling results, confirmed by observations and measurements in situ, should be taken into consideration when managing the conditions within the cave.