Michael over at
http://groups.yahoo.com/group/lotuseuropa/ has produced 2 highly informational videos that answer several questions about the airflow over the rear deck. His experiment has not only proven that the openings draw air out, but the airflow at the deck level is reverse. This is the same airflow pattern that's experienced in pickup trucks with opening rear windows. Open the window at speed and every bit of garbage lying in your bed is now inside the cabin with you:) What's happening is shown in the first image of Michael's car. Air coming over the roof, and in this case, exiting the deck vents, begins a rotational movement that creates a "roll" of air that travels along with the vehicle and reduces the drag of the air passing over the roof. If the rear window is removed, as it is in Michael's car, a portion of this roll of air can separate and penetrate the cabin (yellow arrow). The yarn hanging from the top of the window opening is visibly seen to "bend" inward by this airflow coming in from the deck lid.
The reason the factory vents above the window draw air out, is due to the flow, moving over the roof and being separated as it leaves the body work, meeting up with the air moving vertically up the window and creating a band of low pressure along the rear edge of the roof. This is the same as the airflow over the wing of an airplane... High pressure below, low above. If the window were in, the yarn would stream out and away from the body.
Therefore, the answer to a ventilating window is to turn the window into an outward swinging "hopper" style window as shown in my 2nd image.
Thank you Michael for your excellent experiment. If this were a science fair project, you'd be going to the nationals.
Addendum: btw... The S2's wings would theoretically prevent the airflow close to the cabin sides from "cheating" and moving off the sides. Michael's yarn at the edges shows this to be happening on the Twink. The S2's wings would serve the same purpose as the wing tips on modern commercial aircraft and the Australian Yacht "wing keel" that broke the America's Cup from America's grip back in the 1980s... I'm thinking now, that Colin Chapman was the true inventor of that idea.
