What are vortex rings?

What are vortex rings?

These rings (also called smoke rings) are moving portions of fluid that are moving relative to the surrounding fluid. They form a remarkably stable structure. The inner edge of the ring heads forward, while the outer edge head backward and the ring pulls itself through the air. Fluid dynamicists study these sorts of objects.

What is the difference between “thickness” and viscosity? Is viscosity just a …

What is the difference between “thickness” and viscosity? Is viscosity just a fancy word for thickness?

Viscosity is a measurable quantity—a liquid has a specific viscosity as measured in units of poise or pascal-seconds. Thickness refers to the same characteristic as viscosity, but isn’t a specific quantity. It’s certainly correct to say that a thick liquid is a liquid with a large viscosity.