Liquid Films Flowing Concurrently with Air in Horizontal Duct : 1st Report, Flow Pattern

Abstract

An isothermal thin water film, flowing concurrently with an air stream in a horizontal duct was investigated. In this paper the flow patterns are classified visually into six regimes according to the wave properties. Then, a detailed area plot for these flow patterns with the air and the water flow rates as the axes is obtained especially in the region of low water flow rate including the zone where the dry patches occurred on the bottom surface of the duct. On the other hand, the time varying film thickness was measured. Then four maps for the isoplathes of wave characteristics such as the averaged, the maximum and the minimum film thicknesses and the amplitude of the waves were drawn on the flow map. The relation of these two maps is strong ; i.e., comparison of these maps shows that the flow patterns can be classified more roughly into three zones ; the first zone for flow with dry surface, the second zone where statistically similar waves to each other with small amplitudes are observed on the interface, and the last zone where large amplitude waves travell on these small waves with higher sped than the small ones.