Characteristics of Liquid Film Flowing around a Horizontal Circular Cylinder

当液膜沿水平圆柱侧壁流动时，在液膜表面观察到峰值线沿周向的驻波。振幅向下游增长，最后一部分波从膜流中分离出来。对驻波的这种特性进行了理论和实验研究。在波浪发生的位置，离心力、重力、表面张力和粘性力的合力被认为在波浪上是平衡的。这个动态平衡引出了波长的方程。理论计算的波长与实验结果吻合较好。由于液膜向下游加速，离心力变大，上述力不再相互平衡，导致驻波放大。推导了考虑波幅力平衡的动量方程，确定了放大率。放大效应主要取决于惯性力和引力，而不是表面张力。数值计算得到的波廓线与针接触法测得的波廓线基本一致。其次，提出了一个理论模型来描述波分离的机理。波峰内流速随波幅的增大而增大。流量的增量由周围的波槽供给。波槽内的液体在波峰根部与壁垂直，并在波内供给。垂直于壁面的动量由作用在波根上的离心力、重力和表面张力的合力给出。当波被放大到某个临界值时，所产生的液体不能提供足够的量来维持波的放大，一部分波从膜流中分离出来。理论模型得到的三种液体的分离位置与实验结果吻合较好。少

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