Coalescence (physics)

When the droplets become too large to be sustained on the air currents, they begin to fall as rain.

Contrast-enhanced ultrasound in medicine applies microscopic bubbles for imaging and therapy.

Coalescence of ultrasound contrast agent microbubbles is studied to prevent embolies[1] or to block tumour vessels.

[3] In cloud physics the main mechanism of collision is the different terminal velocity between the droplets.

The other factors that determine the collision rate are the droplet concentration and turbulence.