A geometry of particular interest concerns flows in a Hele-Shaw cell, i.e. a channel whose depth is much smaller than its width and length. This classical problem has been studied in depth, both theoretically and experimentally. While the theoretical solutions predict that the relative velocity of an inviscid bubble should be twice the velocity of the outer fluid, this is never observed in practice. Instead, bubbles travel at lower speeds than the outer fluid. Moreover, complex recirculation patterns are observed for bubbles rising in a quiescent outer fluid [5]. All of these observations point out the effect of an uneven surfactant coverage of the interface and its redistribution due to the fluid motion.

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