A volcanic plume rises until the atmosphere becomes so thin that the mixture of air and ash loses buoyancy and starts to spread laterally, forming an umbrella. The umbrella spreads and cools for a long time before the ash begins to fall gradually. |
Turbulence is the jittery, swirling behavior of a gas or liquid when flowing next to a wall or around an obstacle. Although most of the flows that surround us in everyday life are turbulent flows over rough walls, these flows have remained one of the least understood phenomena of classical physics. |