Characteristics of Liquid Film Flowing around a Horizontal Circular Cylinder

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When the liquid film flows around the sidewall of horizontal circular cylinder, the standing wave with its peak line in the circumferencial direction is observed on the film surface. The amplitude grows downstream and finally a part of wave separates from the film flow. A theoretical and experimental study was conducted to investigate such behavior of the standing wave.At the position of wave occurrence, the resultant of centrifugal force, gravitational force, surface tension and viscous force is considered to be balanced on the wave. This dynamic balance leads an equation for the wave length. The wave length obtained from the theory agrees well with experiment. Since the liquid film is accelerated downstream and the centrifugal force becomes greater, the above forces no longer balance each other, which causes the amplification of the standing wave. The momentum equation considering the force balance on the wave amplitude was derived to determine the amplification rate. The amplificati … More on is dependent mainly on the inertial and gravitational forces and not on the surface tension. The wave profiles calculated numerically roughly agreed with those measured by the needle contact method. Next, a theoretical model was proposed to represent the mechanism of the wave separation. The flow rate inside the wave peak increases as the wave amplitude grows. The increment of the flow rate is supplied from the surrounding wave trough. The liquid in the wave trough is turned normal to the wall at the root of wave peak and is supplied inside the wave. The momentum normal to the wall would be given by the resultant of centrifugal force, gravitational force and surface tension acting on the wave root. When the wave is amplified to some critical value, the resultant cannot supply enough amount of liquid to maintain the wave amplification and a part of wave separates from the film flow. The positions of separation obtained by the theoretical model agreed well with those of experiment for three kinds of liquids. Less