A vortex generator (VG) is an aerodynamic device consisting of a small vane or angled plate mounted on an aircraft's wing or other surfaces. These low-aspect-ratio blades, set perpendicular to the skin, create mini wingtip vortices that inject small-scale turbulence into the slow-moving boundary layer. By energizing this layer, the flow remains adhesive to the surface, prevents separation, and can even re-attach flow when positioned ahead of a separation point.
Expert behind this article
Jim Goodrich
Jim Goodrich is a pilot, aviation expert and founder of Tsunami Air.
What is a vortex generator on an aircraft?
A vortex generator is an aerodynamic device consisting of a small vane usually attached to a lifting surface like an aircraft wing. Vortex generators act like tiny wings.
A vortex generator on an aircraft is a small angled plate installed on an outer surface of an aerodynamic body. The plate is usually a wedge or T-shaped tab. These tabs create vortices of air across localized portions of wings on aircraft, mixing high energy free stream air into the lower energy boundary layer so that the airflow can withstand adverse pressure gradients longer.
On jets, vortex generators are positioned in front of the flaps on airliners and along the leading edge of the wing on STOL aircraft. They are also mounted on the engine nacelle where nacelle strakes - small delta patterned or triangular panel sheets - induce longitudinal vortices. Helicopter applications follow the same aerodynamic principle: a small vane attached to a lifting surface energizes the boundary layer to keep airflow attached.
Regardless of location - wing leading edge, flap ahead, tail, or nacelle - the device is an aerodynamic device that protrudes through about 80% of the laminar boundary layer, creating mini wingtip vortices that spiral through the boundary layer and free stream airflow.
What is the purpose of a vortex generator?
A vortex generator is designed to create controlled vortices. Aerodynamicists install vortex generators to achieve flow-separation prevention. The primary function is to control the airflow over the wing.
The vortices mix high-energy free-stream air into the lower-energy boundary layer, re-energizing sluggish flow and keeping it attached to the airfoil. By maintaining attached airflow, the vortex generator allows the aircraft to maintain pitch control at high speeds and high angles of attack.
How does a vortex generator work?
For a vortex generator to work, small angled plates are installed on an outer surface of an aerodynamic body like an aircraft wing. These plates stand at an angle to the local airflow, causing the air to swirl and create a vortex behind each plate.
The swirling motion of the vortices energizes the low-energy laminar boundary layer by drawing energetic, rapidly moving outside air into the slow-moving boundary layer. This process creates a vortex generator work effect that increases the mean streamwise momentum by pulling high momentum fluid from the freestream.
As the vortices mix high-energy free-stream air into the lower energy boundary layer, they effectively delay flow separation and maintain a smoother airflow over the surface. This activity of the small angled plates installed on the outer surface of an aerodynamic body helps preserve lift and enhance the aircraft's overall performance. The continuous vortices maintain momentum in the boundary layer, which contributes significantly to the overall flow dynamics around the airfoil.
A vortex generator keeps the boundary layer energized, so the airflow stays tied to the wing and control surface. When the flow would otherwise split up from the wing side, the small blades add a swirl that delays separation. With the aircraft outfitted with vortex generators, I could be nearing stall, yet the aircraft would stay steady.
Jim GoodrichPilot, Airplane Broker and Founder of Tsunami Air
What are the benefits of vortex generators?
The benefits of vortex generators are that they energize the boundary layer, allowing airflow to withstand the adverse pressure gradient longer and delaying flow separation. This directly improves stall characteristics, so while they do not prevent stall, they give the wing a gentler, more controllable stall and lower stalling speed. The same energized boundary layer increases lift. When vortices mix high-energy free-stream air into the lower-energy boundary layer, the wing or blade produces more lift at the same angle of attack.
Installation of vortex generators brings about a slight reduction in stalling speed of an airplane, which in turn reduces the required one-engine-inoperative climb performance and extends the safety margin during flight operations. For turbine blades, the same mechanism raises the lift coefficient of the blade, increasing power output of wind turbines and reducing stress on the blade, which extends blade life.
Vortex generators reduce drag on the blade, leading to slightly better fuel consumption rates under certain conditions. On aircraft, vortex generators refine overall flight characteristics by increasing control authority at low speed: elevator, rudder and aileron effectiveness all rise, so controllability remains high even when the aircraft is flown slowly or at high angles of attack.
Vortex generators can reduce noise. On the Airbus A320, small vortex generators placed on fuel-tank pressure-equalisation vents cut the whistling sound heard in the cabin. Across applications, the same devices that delay separation and refine lift also increase overall aerodynamic efficiency, giving designers a simple, lightweight tool to enhance performance, safety and economy.
What are the types of vortex generators?
Vortex generators are of several types, yet the most common type is the vane type. Vortex generators are typically rectangular or triangular, but they are also trapezoidal. Beyond shape, installations are grouped by vortex sense: the first approach with all of the VGs parallel is called a corotating installation, in which all generators shed vortices that are rotating in the same sense. The paired equal and opposite angle installation is called a counterrotating installation, in which each pair of generators sheds a pair of vortices that rotate in opposite directions.
Recent developments add adaptive capability. Smart VGs are Shape Memory Alloy Reconfigurable Technology vortex generators. NASA and Boeing conducted flight tests of these Shape Memory Alloy Reconfigurable Technology Vortex Generators, and the Boeing 777 200 ecoDemonstrator wing had three standard VGs swapped with Smart VGs.
What is the difference between a vortex and a vortex generator?
A vortex is a naturally occurring swirling motion within a fluid whereas a vortex generator is the specialized device used to create controlled swirling motions in fluid flow. When vortex generators create vortices, the resulting mini wingtip vortices spiral through the boundary layer and free-stream airflow, acting like miniature tip vortices that draw energetic, rapidly moving outside air into the slow-moving boundary layer. By doing so, the devices postpone separation, and boost stability and efficiency.
