Hydrodynamics and Heat Transfer of Vertical Falling Liquid Films : Part 1, Classification of Flow Regimes

Abstract

Hydrodynamics of a vertical falling liquid film has been the subjectof not a few papers in which the film is analyzed in the same wayas in the single phase flow without a free surface. A study for improvingthis situation is reported in a series of papers including this oneon an experimental study on the wavy flow of falling films of waterand highly viscous fluids. By analyzing the experimental study itis concluded that the flow of a vertical falling liquid film is classifiedas follows. 1. Purely laminar flow ; there is no wavy motion on theliquid film. 2. First transition region. 3. Stable wavy flow ; thereare stable wavy motions on the liquid film in which turbulence isfound. 4. Second transition region. 5. Fully turbulent low ; theflow becomes shear-flow type, and its wall law is identical withthat of the turbulent boundary layer.