A UK Apache Helicopter conducts a maneuver on approach to land at Duxford airfield as part of Helitech 2011. During such maneuvers, the rotor disk is highly loaded, and the vorticity in the core of the tip vortices is particularly strong. This leads to a lowering of the pressure hence temperature of the air in the vortex core. If the temperature falls below the dew point of the air, the water vapor condenses, spectacularly visualizing the rotor tip path, as shown here.
Photo taken by Dr. Nicholas Bojdo.
License: Creative Commons Attribution-ShareAlike
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