Liquid-jet evolution is driven by surface tension, not gravity – Physics World –

Image of a liquid jetCees van Rijn at the University of Amsterdam have shown that surface tension plays a far larger role than gravity in slowing the upward flow and shaping the jet. The team used advanced imaging techniques to provide a clear quantitative explanation for the self-similar evolution of the jets. Their results shed new light on a widely studied area of fluid dynamics, and could lead to a better understanding of how liquids behave in microgravity.

When a raindrop hits a pool of water, the liquid it contains will rapidly move to fill in the impact crater it forms. This generates an upward-moving jet typically several centimetres in height, which rises and falls in under 100 ms. A key feature of these jets is that their shapes remain the same as they rise and fall – a phenomenon called self-similarity.