Segment V3.2: Free Vortex

(Related to Textbook Section 3.3 - F=ma Normal to a Streamline)

For flow with curved streamlines, centrifugal acceleration causes the pressure on the outside of the bend to be greater than on the inside.

The swirling water draining from an inverted bottle approximates a free vortex. The velocity increase and pressure decrease near the center of the flow produce a hollow air core. Similar flows in the atmosphere can produce tornados. The rotation (swirl) of the parent cloud is enhanced as the air is drawn into the strong updraft at the tornado core. Very high winds and low pressure occur near the core, which is made visible by debris and condensed water vapor. (Tornado video courtesy of NOAA National Severe Storm Lab.)