Vortex Shedding - Smarter Every Day 23

Destin is at an airshow and introduces the topic of vortex shedding with live aircraft demonstrations.

When asked why smoke comes out of airplanes, a child responds that it helps the airplane go better.

Destin plans to explain the physics principle of vortex shedding using real aircraft as visual examples.

The explanation begins with the Bernoulli principle and how it relates to airplane flight.

The Bernoulli principle states that where flow is high, pressure is low.

• Air travels farther over the top of the wing than the bottom, creating faster flow on top • This results in low pressure on top and high pressure on the bottom • High pressure below pushes the airplane up, enabling flight

At the wing edge, high and low pressure attempt to meet, creating a discontinuity that nature tries to resolve.

High pressure flowing around the edge creates vortex shedding, with calculable vorticity.

At the wing tip, high pressure on the bottom and low pressure on top cause flow to roll over, creating a vortex.

• Wing tips are kicked up slightly to manage pressure differences • The swept design helps control how vortices shed off the wing end • This design reduces drag by moving vortices away from the vehicle

Nature abhors a vacuum and discontinuity, so it automatically rolls pressure to equalize the difference.

By controlling vortices and getting them off the vehicle quickly, engineers reduce overall drag.

Vortex shedding is not limited to airplane wings but occurs with any object like paddles that have pressure differences.

When paddling a kayak, vortex shedding occurs at the paddle edge where low pressure and high pressure meet.

The vortex appears where the paddle transitions from the high pressure side to the low pressure side, visible in water movement.

Destin demonstrates this concept while on a kayak overlooking a hot air balloon festival with friends.

Asking scientific questions helps viewers understand phenomena rather than simply accepting surface-level explanations.

Without scientific curiosity, people might attribute fighter jet vortex shedding to cultural references like Top Gun rather than physics.

• A-10 Warthog aircraft visibly demonstrate vortex shedding • Fighter jets create distinctive vortex patterns at high speeds • These vortices are fundamental to aircraft aerodynamics

Encouraging scientific inquiry helps people understand the actual mechanisms behind everyday phenomena and technological marvels.