FLOODING AND ASSOCIATED PHENOMENA IN FALLING FILM FLOW IN A TUBE

A falling water film was set up in a vertical 1.25-in.bore acrylic resin tube using porous sections for introducing and extracting the liquid. Air was passed upwards through the tube, countercurrent to the liquid flow, and the air flow rate required to carry liquid up beyond the injector (the flooding point'') was determined. An empirical relation for flooding rate was obtained. Measurements were made of liquid film thickness, pressure gradient, and interfacial profile for air flows from zero up to the flooding point. High-speed cine films using a special lighting technique gave qualitative information on the flow structure and were analyzed for surface wave velocity. In relating these measured parameters and the flooding phenomena it became obvious that flooding did not occur as a result of reversal of flow under surface shear. It was more likely to be associated with the coarsening of the liquid surface waves leading to the build-up of liquid at the injector and consequent splashing upwards of the liquid. (auth)