Jetting efficiency of bursting bubbles with multiple neighbors

Bubbles bursting at the surface of the ocean produce drops that heavily influence ocean-atmosphere interactions. The jet drop production mechanism involves the collapse of the bubble cavity, leading to the formation of a fast upwards jet, which then destabilizes into drops. As bubbles in the ocean are often found in rafts, we investigate experimentally how this mechanism is modified by the presence of neighboring bubbles of the same size during the collapse. We show that for a large range of conditions (size, surface contamination, etc.) the size of the emitted drops is monotonically reduced as the number of neighboring bubbles is increased, up to six for hexagonal packing. The presence of neighboring bubbles is of primary importance to estimate drop production, as the size can be reduced by a factor up to 5. With the help of multiple high speed views of the collapsing bubble, we show how a change of cavity shape during collapse leads to the selection of smaller and faster drops. We also illustrate that a bubble bursting at the center of hexagonal packing can produce a very thin and fast jet leading to up to 10 small drops.