Solitary traveling waves are prominent features on the surface of a falling liquid film and are known to promote heat/mass transfer. We focus on the little studied case where they are subject to an extremely confined counter-current gas flow, and we identify two novel secondary instabilities. At high gas velocities, a catastrophic instability develops, leading to flooding through wave reversal. At lower gas velocities, an oscillatory instability occurs, producing a high-frequency periodic modulation of the wave height. Conjunction of this self-sustained oscillatory state and vortices forming in the liquid is shown to enhance mixing. Also, we uncover a new hydrodynamic route toward film rupture.

中文翻译：

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超限下降液膜上的孤立波

孤行波是下落的液膜表面上的显着特征，并且已知会促进热量/质量传递。我们专注于研究很少的情况，在这种情况下，它们会受到极度受限的逆流气流的影响，并且我们发现了两个新颖的次级不稳定性。在高气体速度下，会发生灾难性的不稳定性，从而导致通过波逆向泛滥。在较低的气体速度下，会发生振荡不稳定，从而产生波高的高频周期性调制。这种自我维持的振荡状态和液体中形成的涡流的结合显示出可以增强混合。此外，我们发现了一条新的流体动力途径，可以破坏薄膜。