Selection of the Saffman-Taylor Finger Width in the Absence of Surface Tension: an Exact Result

Abstract

Using our exact time-depending solutions, we solve the Saffman-Taylor finger selection problem in the absence of surface tension by showing that an arbitrary interface in a Hele-Shaw cell evolves to a single uniformly advancing finger occupying one half of the channel width. This result contradicts the generally accepted belief that surface tension is indispensable for the selection of the one-half-width finger.