Generation of a Disturbance Wave on a Liquid Film Flowing Down a Heated Inclined Plane

Abstract

An investigation was conducted into the generation of a disturbance wave on a liquid film flowing down a heated inclined plane. Theoretical analysis based on the instability caused by both dynamic and kinematic waves shows that the Marangoni effect due to the surface tension gradient contributes to reduction of the critical flow rate of the liquid on the occurrence of a disturbance wave. Theoretical results also suggest the existence of two boundaries on generation of a disturbance wave at a fixed inclined angle. The flow pattern of a liquid film flowing down a heated brass duct was examined. It was found that one of the boundaries which corresponds to the existence of the disturbance wave is qualitatively consistent with the theoretical result ; the lower boundary, however, could not be observed because liquid film breakdown occurred before the lower critical flow rate was achieved. The measured velocity of a disturbance wave and the wave height are also discussed in comparison with previous results from isothermal liquid film flow.