have demonstrated that drops of liquid placed on an inclined plane oscillating vertically are able to climb uphill. In the present paper, we show that a two-dimensional shallow-water model incorporating surface tension and inertia can reproduce qualitatively the main features of these experiments. We find that the motion of the drop is controlled by the interaction of a 'swaying' (odd) mode driven by the in-plane acceleration and a 'spreading' (even) mode driven by the cross-plane acceleration.

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... Both modes need to be present to make the drop climb uphill, and the effect is strongest when they are in phase with each other.