Engineers in Sweden hope to improve the efficiency of trucks by using a novel electronic vortex generator to reduce drag.
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.”
Its 55 years since I was associated with vortices in anger (my Degree dissertation was on the Ranque-Hilsch vortex tube-a mechanism on high-speed aircraft -those with a ‘cheap? supply of compressed air- able to develop a refrigeration effect) but along with the associated equations of ‘lift’ I certainly recall it as a fascinating aspect of Engineering and mathematics. We were looking into the effect(s) of these systems at hundreds of miles-per-hour: I am interested to note that some benefitial effects are possible at much lower speeds (say up to 85 mph) Presumablt long-distance train stock would be another candidate? Isn’t the case that advances are now not ‘massive’ but a series of discrete and small steps, which cumulatively give value.
Perhaps the use of PASSIVE vortex generators, like those used on wings of many airplanes (I remember those on the Embraer ERJ-145), would result in more economical results, but the question remains: At which speed range would the devices start to work on terrestrial vehicles?
Could the Total Perspective Vortex help here?
another amateur advertisement embarrassingly empty of coldwar context spawned in sixties MIG interceptors always at altitude ahead of Starfighters, this being Bonn ‘s biggest fear for any confrontation catalysed by Cuban crisis. Revived by BAe as candidate capability post perestroika but perceived as problematic not only for extreme voltages but also impairment impact unless meticulously maintained. Won’t cover costs in lightening lorry diesel demand because backend salient separation dominates drag.
Now if they would just start using the HOD systems for diesel trucks (lorries), they could reduce fuel cost up to 30%. 5% seems trivial in comparison, with how much parasitic electric load???