A new method of measuring dynamic surface tension

Using a momentum balance, Brown has shown that when a thin, continuous sheet of free-falling liquid which is guided by 2 vertical rods is penetrated by an obstacle, it will disintegrate unless the resulting inequality is satisfied everywhere in the curtain. When this inequality is satisfied, the curtain does not disintegrate, but can be broken and forms an inverted v-shaped free edge. This work reveals that the curtain of liquid parts and forms a free edge if the obstacle is nonwettable and if the inequality is satisfied. However, if the obstacle is wettable, the curtain does not break. New calculations for determining the momentum balance of the dynamic surface tension are presented. The results demonstrate that there is no measurable difference bettween dynamic and static surface tension for pure liquids.