Famous Formula 1 and car designer now owner of Gordon Murray Automotive, on the series of vlog’s hosted by Dario Franchitti is explaining the complex aerodynamics of the T.50 supercar and the backend fan in a short and simple way.
On a sketch Murray is basically showing how aero flow from the top of the car and bottom of the car (groundeffect) ending at the back is creating area of low pressure. That’s why almost all racing cars are using the rear diffuser to assist on reducing the low pressure and vortices created, but further more this much talked fan on T.50 is helping the diffuser even more so to achieve its own purpose.
Here is the short lesson from the genius designer: