Influence of increase in static pressure on bulk nanobubbles.

The concentration and size distribution of bulk nanobubbles (ultrafine bubbles) of air in liquid was measured before and after increasing the static pressure. It was found that, after pressurization, the number concentration decreased and the size increased. The effect of pressurization is to compress the bubbles and decrease the distance between solids on the bubble surface, which act as nucleation sites for bubble growth and coalescence when the static pressure is returned to atmospheric pressure.