How Vortex Generators Make Airplanes Fly Better: The History and Science of These Amazing Devices
Let’s talk Vortex Generators — those nifty little contraptions you’ll spot on aircraft wings. ✨
They’re like the wing’s personal trainers, sculpting airflow for some serious low-speed lift magic. ✈️
But what are they, how do they work, and who invented them? In this article, we’ll explore the history and science of these amazing devices that help airplanes fly better and safer.
What are Vortex Generators?
Vortex Generators (VGs) are small devices that are attached to the surface of an aircraft wing, usually near the leading edge. They are typically rectangular or triangular in shape, and have an angle of attack with respect to the local airflow. Their purpose is to create vortices, or swirling patterns of air, that improve the aerodynamic performance of the wing.
Vortices are regions of rotating fluid that have a lower pressure than the surrounding fluid. They can be seen in nature, such as in tornadoes, hurricanes, and whirlpools. They can also be created artificially, such as by stirring a cup of coffee, blowing bubbles, or spinning a propeller.
Vortices have many applications in engineering and science, such as in wind turbines, submarines, cars, and space vehicles. One of the most common uses of vortices is in aerodynamics, which is the study of how air flows around objects, such as wings.
How do Vortex Generators work?
To understand how VGs work, we need to know a bit about aerodynamics. Aerodynamics is the study of how air flows around objects, such as wings. When air flows over a wing, it creates a difference in pressure between the upper and lower surfaces of the wing. This pressure difference is what generates lift, or the force that keeps the airplane in the air.
However, as the airplane slows down, the airflow over the wing becomes less smooth and more turbulent. This causes the air to separate from the wing surface, creating a region of low pressure behind the wing. This reduces the lift and increases the drag, or the force that opposes the motion of the airplane. This can lead to a stall, or a sudden loss of lift and control.
This is where VGs come in handy. By creating vortices, they mix the high-energy air from outside the boundary layer (the thin layer of air that sticks to the wing surface) with the low-energy air inside the boundary layer. This delays or prevents the airflow separation, and maintains a higher pressure on the upper surface of the wing. This results in more lift and less drag, allowing the airplane to fly at lower speeds and angles of attack without stalling.
The boundary layer is a layer of air right above the surface of your aircraft where skin friction slows down and removes energy from the airflow. As air flows across your wing, the pressure decreases until it reaches the center of lift — about 25% down the wing’s chord. Then, pressure starts to increase again, so the air moves from an area of low pressure to higher pressure — this is called an “adverse pressure gradient”. As the airflow moves towards high pressure, it loses energy. Eventually, when it runs out of energy, the airflow separates from the wing.
The air above the boundary layer isn’t affected by skin friction, so it has more energy than the air in the boundary layer. If you could pull some of that free-stream air into the boundary layer, you could add energy and delay the boundary layer’s separation. That’s what VGs do.
VGs act like tiny wings and create mini wingtip vortices, which spiral through the boundary layer and free-stream airflow. These vortices mix the high-energy free-stream air into the lower energy boundary layer, allowing the airflow in the boundary layer to withstand the adverse pressure gradient longer. Your wing can now operate at a higher angle of attack before airflow separation causes a stall.
Who invented Vortex Generators?
The concept of using vortices to improve aerodynamics dates back to ancient times, when sailors observed that placing feathers on their sails improved their performance. However, it was not until the 20th century that VGs were applied to aircraft design.
One of the earliest pioneers of VGs was Sir George Cayley (1773–1857), a British engineer and inventor who is widely regarded as the father of aerodynamics1. He experimented with various shapes and configurations of wings, and discovered that adding curved surfaces or flaps to the leading edge1 of a wing could generate vortices that increased lift.
Another influential figure was Ludwig Prandtl (1875–1953), a German physicist and engineer who is considered as the founder of modern aerodynamics1. He developed the theory of boundary layers1 and explained how vortices could delay or prevent airflow separation. He also designed several wind tunnels and tested various models of wings with VGs.
The first practical application of VGs was on the Boeing 707, one of the first commercial jet airliners. The engineers at Boeing noticed that at high speeds, the airflow over the highly cambered wing became separated, reducing the effectiveness of the ailerons (the control surfaces that roll the airplane left or right). To solve this problem, they installed VGs on the upper surface of the wing near the ailerons, which restored their control authority.
Since then, VGs have been used on many types of aircraft, from airliners to fighters to gliders. They have also been adapted to other applications, such as wind turbines, cars, submarines, and even space vehicles.
Vortex Generators are truly remarkable inventions that have revolutionized aerodynamics and aviation. They are proof that sometimes, small things can make a big difference. ✨
I hope you enjoyed reading this article. Have a great day! 😊
