Plasma vortex generators could cut lorry fuel costs

Vortex generators are already widely used in the aerospace industry to enhance lift at takeoff and landing.

Typically mounted on the upper side of a wing these mechanical devices – which resemble small fins - operate on a basic aerodynamic principle: if you reduce the separation of the airflow on the leeward side of an airfoil, you can enhance the lift and at the same time reduce the drag.

Now, researchers at Sweden’s KTH Royal Institute of Technology in Sweden hope to exploit the same phenomenon on lorries, and have developed technology that they claim could reduce fuel consumption by up to five per cent.

Intriguingly, unlike conventional vortex generators, the KTH system, which has been developed in collaboration with truck manufacturer Scania, is entirely electronic.

The system uses plasma actuators to apply a high voltage between two electrodes. Surrounding air molecules become ionized and accelerate through the electric field – which results in wind.

Normally, when wind hits a truck at an angle, friction deprives the air of the energy it needs to push all the way around the opposite side of the truck.

As it moves around the corner towards the leeward side of the vehicle, the air in the boundary layer slows down and cannot follow the surface any longer. This separation of the flow forms a bubble filled with eddies and swirls of air.

A vortex generator placed at the front corner slices through the boundary layer right at its head, creating a spiral of air that mixes high velocity air into the boundary layer. This injection of high velocity air towards the surface keeps the air from separating and makes it follow the surface, thereby lowering the drag.

Commenting on the project KTH researcher Julie Vernet said: “Our ultimate goal is to reduce the flow separation that occurs on the front corners of the truck. By adding momentum close to the surface, the size of the separated region is reduced.”