A HYDRODYNAMIC ANALYSIS OF ROLL WAVES ON THIN LIQUID FILMS

The occurrence of thin liquid film flows in modern industrial applications are numerous and important. Despite the prevalence of this special case of two-phase flow in practical transport enhancement processes, a mechanistic understanding of gravity driven liquid film motion is lacking. This is due to the uncertainty associated with the wavy character of the gas-liquid interface.;Unlike periodic disturbances, roll waves exhibit random shape, spacing, and kinematic characteristics at given flow conditions. It is, therefore, inappropriate to attempt hydrodynamic field description in the roll wave regime based solely on the liquid properties and flow rate.;In this dissertation, a new method of analyzing local roll wave motions is developed. Liquid motion is coupled to the free surface shape and kinematics by postulating a relative, phase position weighted, surface contribution. A computational strategy is described, which employs a specific nonlinear function minimization technique in order to provide an approximate solution to the local roll wave hydrodynamics problem. Comparisons with experimental data and predictions of various permanent wave theories are presented.;Although a substantial amount of research has been devoted to the study of film surface kinematics based on an hypothesis that the interface is composed of periodic waves which propogate without deformation, observed film motions invariably exhibit a predominantly evolutionary surface character. At larger flow rates, and further away from the point of initiation, relatively large amplitude, isolated surface disturbances become dominant. These two-dimensional asymmetric waves, which travel at large velocities and carry a substantial portion of the liquid flow, are commonly referred to as roll waves.