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Ruissellement en conditions de mouillage partiel

Abstract : Many everyday situations and industrial applications involve a fluid flowing over an inclined surface under partial wetting conditions. At low flow rate, stationary dry patches can exist within a flowing film, which may lead to a loss of efficiency of heat exchangers. We made a systematical experimental study involving a film of silicone oil flowing over an inclined plane, which was properly coated in order to obtain a finite static contact angle. We show that stationary dry arches with a well defined and reproducible shape exist within a range of flow rates. They are swept away by the flow above a critical flow rate. We suggest a model for these phenomena, based on a subtle equilibrium between gravity, capillarity and viscosity, which explains the behaviour of the system in a wide range of parameters. At the lowest order, the equilibrium of the liquid ridge which forms near the contact line results from a balance between its weight and capillary forces, and for high contact angles and low inclinations of the plate, secondary effects arising from the curvature of the contact line and hydrostatic pressure within the film become non-negligible and set the stability of the system. We also studied drops running over an inclined plate, which exhibits various flow regimes. Depending on their velocities, drop can be oval, cornered or pearling. We suggest an interpretation of the existence of cornered drops, based on a model of dynamical contact angles. Finally, we present a few qualitative results on the flow of water over an array of tubes similar to those present in some heat exchangers.
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Contributor : Thomas Podgorski <>
Submitted on : Monday, August 4, 2003 - 12:54:43 PM
Last modification on : Monday, December 14, 2020 - 9:52:09 AM
Long-term archiving on: : Tuesday, September 11, 2012 - 9:25:21 PM

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  • HAL Id : tel-00003231, version 1

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Thomas Podgorski. Ruissellement en conditions de mouillage partiel. Dynamique des Fluides [physics.flu-dyn]. Université Pierre et Marie Curie - Paris VI, 2000. Français. ⟨tel-00003231⟩

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