Vortex Streets

Alternating cloud vortices spawn over the Juan Fernandez islands.
This unusual cloud formation occurs when airflow is disrupted by a roughly cylindrical object. In this case, the Juan Fernandez islands provide the disruption.

August 28, 2015

When the path of a fluid is diverted around a solid object, it doesn’t always go smoothly. Turbulent vortices can form as fluid adheres to the object in its path before breaking off and traveling downstream. Within a certain range of flow velocities, the alternating pattern of eddies seen above can form, a phenomenon known as a vortex street.  While they’re not usually visible, these formations occur at smaller scales all the time, on everything from power lines to smokestacks. Many tall cylindrical structures are built with spiral “fins”, specifically to discourage vortex street formation, preventing the structural wear caused by rapid air pressure oscillations.