Many thanks to Juha Kivekas for consultation on this piece
|A number of years ago I wrote a piece describing vortex lift and the possibility of its application on the Toyota GT-One. Since that time I've had the opportunity to speak with a number of aerodynamacist about the idea. More recently, in email conversations with Juha Kivekas, I've have come to some different conclusions regarding the principle in general and the Toyota GT-One specifically. To recap, my thought was that the Toyota GT-One was utilizing the strake detail (image left) to generate a vortex that would travel the length of the cockpit and flow under the wing enhancing the low pressure side efficiency.|
|Vortex lift is seen in a number of applications in aircraft and in nature. This principle is what makes, of all things, insects able to fly. Aerodynamic theory states that as an aerodynamic surface gets smaller, it becomes less efficient at generating lift. An insect's wing generates a vortex on the top surface (the low pressure side) which greatly increases the surface's ability to produce lift. Modern supersonic combat aircraft use this idea to increase subsonic aerodynamic performance. The strakes near the cockpit of a F-16 or F/A-18 generate vortices that run over the top side of the wing creating more efficient lift by inducing higher speed and therefore lower pressure. But these vortices aren't present in normal flight, and are only generated when the aircraft achieves a high angle of attack while either maneuvering or landing. Juha Kivekas points out, "in these conditions the flow stays attached at the incredible angles because of the vortex energy mix phenomenon". Or, stated more simply, flow separation is delayed by the rotating vortices which mixes the boundary layer flow and the main stream flow imparting energy to the more stagnant boundary layer.|
lift itself isn't unique as it is used through out motorsports,
to enhance bottom side downforce generation (image, Lola Champ Car
One problem is that vortices come with an inherent drag penalty that
dramatically reduce their effectiveness, especially
when used in
the top side flow regime. Vortices are also very fragile in
nature and therefore difficult to utilize. Which gets us back
the Toyota GT-One. The location of the strake on the GT-One
of a low pressure area created by the shape of the cockpit.
generated would not have a particularly long life as it would probably
be very small to start with and would easily reattach due to that
point. Secondly, the vortex length necessary to effect the
would be problematic as longitudinal vortices burst very
Given the distance and the environment (various low pressure areas
by the cockpit, bodywork, etc.), it is doubtful that any vortex
at the front of the car would survive to effect the rear.
Though ultimately vortices could be used for the benefit of top side race car aerodynamics, specifically in drag reduction. Juha Kivekas sums it up best, "It certainly is possible to use longitudinal vortices to fill the wake of the cockpit bulge. This could be done using delta wings on the sides of the cockpit. And actually there have been studies on lorries where angled delta wing were used near the trailing edge of the cab and have been found to increase base pressure; that is, to reduce drag. The vortices steal energy from the main flow and mix it into the wake flow and thus reduce the effective length of the wake. This is Mother Nature's explanation, we simply call it reduced drag."