Instabilities of a liquid film falling down an inclined plane with or without a counter-current air flow

By Nicolas Kofman
Laboratoire FAST (Université Paris-Sud, Orsay) – Air Liquide (Les Loges en Josas)


Thursday 3rd of April 2014 – 14:00 / Room BM 5204



Falling liquid films in the presence of a counter-current gas flow constitute the state-of-the-art technical solution in distillation columns. Indeed, the wavy dynamics organized by localized structures, or solitary waves, is known to enhance the heat and mass transfer. The optimal operating conditions are generally close to the onset of flooding, for which a sharp increase in the pressure drop and decrease in the efficiency are observed.
Without the gas flow, the 2D wave regime for moderate Reynolds number is relatively well-understood. It is not the same for the 3D evolution of such waves. By using both experimental and numerical tools, I will explain that several 3D modes exist and discuss the related physical mechanisms.
Then I will show experimentally the influence of a counter-current air flow on the waves. Their amplitude, speed and 3D features are found to be strongly affected. The flooding point is characterized by the emergence of waves going upstream.