Curious

Vaping Next to a Truck Is a Lesson in Aerodynamics

Does vaping make you cool? That’s not something we’re going to touch, but we can confirm that doing it next to a moving semi truck certainly is.

In this video, first posted to Reddit, an enterprising vaper lets loose a cloud of “smoke” right as a semi truck roars past. The end result is something akin to a wind tunnel. Caught by the slipstream, the vapor is first pushed back then sucked forward as the pressure wave pushed ahead of the truck passes by. You can catch a glimpse of the chaotic vortexes that vehicles leave in their wake as well, as the cloud is torn apart toward the end of the scene.

Cruising semi trucks generate a high pressure wave in the front and to each side of the vehicle, and a vacuum forms behind this wedge of air. After a truck passes by, air rushes back in to fill the void. The mechanism of action is uniform at first, and then turbulent in the truck’s wake as small vortexes form. This is why the cloud of vapor scoots back and forth as a single unit and then disperses quickly as turbulence takes over.
 


 
It’s also why trucks move a lane over if there’s someone stopped on the shoulder of the highway. The partial vacuum they leave in their wake can be enough to yank an unsuspecting pedestrian right into the highway.

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