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 ͑scraper͒, electromagnetic ͑if the entrained fluid is appropriated͒, or hydrodynamic ͑gas-jet wiping͒ 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-LES͒ 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 profiles obtained experimentally and numerically for a jet impinging on a dry fixed surface are compared. The effect of the substrate motion and the presence of the dragged liquid film on these actuators are analyzed through numerical simulations. Good agreement is found between the film thickness profile in the wiping zone obtained from the VOF-LES simulations and with the analytical model, provided that a good model for the wiping actuators is used. The effect of the gas-jet nozzle to substrate standoff distance on the final coating thickness is analyzed; the experimental and predicted values are compared for a wide set of conditions. Finally, the occurrence of the splashing phenomenon, which is characterized by the ejection of droplets from the runback film flow at jet impingement, thus limiting the wiping process, is investigated through experiments and numerical simulations.

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It is currently debated if either thermal erosion of the lithosphere or dynamical support is the source of topography and geoid anomalies. The origin of tins controversy lies probably in the difficulty to model simultaneously these two effects. For this purpose we have studied the time dependent behavior of two‐dimensional convection with a temperature and pressure dependent viscosity. The use of a control volume method allows us to define a rigid zone simulating the mechanical lithosphere. The interface between the lithosphere and the convective mantle is determined by a viscosity cutoff. First, some experiments model the rise of a plume below the lithosphere in order to observe the evolution of the uplift and thus to appreciate the various processes involved in the swell formation. Before the plume reaches the base of the thermal lithosphere, an uplift a few hundred meters in amplitude develops which can only be ascribed to a pure dynamical support. The major uplift occurs when the ductile part of the lithosphere, the convective boundary layer, is squeezed by the plume. The reheating of the mechanical lithosphere takes place after this transient stage of dynamical erosion. However, this late process is very slow but can magnify the amplitude of the swell if the lithosphere stays long enough above the plume. These results shed some light on the different mechanisms occurring during the swell formation, but the configuration modeled does not correspond to the one expected for actual hotspot swells. They feature plume rising up to the lithosphere while natural situations correspond to lithosphere drifting above preexisting plumes. An experiment with a moving lithosphere was run and shows that thermal erosion does not affect significantly a moving lithosphere even for relatively slow drifting velocities (few centimeters/year). Indeed, the thermal structure of the lithosphere is not modified above the 800°C isotherm except for a motionless plate. In this case the resulting swell should be greater: this could explain why Azores, Crozet or Cap Verde swells are so high. On the other hand, the shape of a swell over a moving lithosphere is strikingly reminiscent of the Hawaiian swell.