4394281 Composition for use in a magnetically fluidized bed : Ronald E Rosensweig assigned to Exxon research and engineering co

Abstract

The focus of the present study is to identify and describe the surface waves on films running down a vertical wall, by applying a novel approach in which the time-dependent wave characteristics are not used explicitly. Using time records of film thickness at a station, a “spatial evolution portrait” of a surface wave is obtained by plotting the rate of displacement vs local film thickness. A specific, shell-like, pattern is easily recognized in all these portraits and it is representative of large (roll) waves, independent of film Reynolds number in the range Re = 500 to 13000. This type of representation is helpful in determining the salient features of roll waves and possibly for modeling the form of wavy interfaces. Calculations of the Eulerian surface accelerations provide additional evidence on the development of surface waves. Several statistical quantities of both the rate of displacement and Eulerian acceleration (i.e. maxima, minima, skewness etc.), have been calculated to provide more information on the character of surface motion. Assuming that roll waves travel with a constant phase velocity, the surface slopes are calculated at various Re. All slopes are smaller than ≈ 20°, being steeper at the wave front than at the wave back. Interestingly, it appears that surface slopes are almost independent of film Re.