This article from 2009 my shed some light on what we are seeing.... What McLaren's Barcelona Paint Job Tells Us About Their Testing Troubles | Bleacher Report In short they say it is normal for the teams to spray on some paint when testing to see the real life airflow patterns.
FRANKFURT (Reuters) – Daimler AG's Mercedes-Benz is to gain full ownership of the racing team Mercedes GP by buying the 24.9 percent stake held by team principal Ross Brawn, Germany's auto motor und sport magazine reported on Wednesday. The Mercedes Grand Prix racing team will continue to compete under Brawn's leadership, and cars and engines will continue to be developed and manufactured in England, the magazine said. It said it obtained the information on the sidelines of pre-season tests in Valencia. "We will only inform at a given time when there are facts," a spokesman for Mercedes motorsport told Reuters. Mercedes bought a 75.1 percent stake in the team in November 2009 together with its partner, Abu Dhabi investment company Aabar, which bought a 9.1 percent stake in Daimler in March 2009. The team emerged from the former Honda team after a management buyout led by former Ferrari technical director Ross Brawn. Honda quit the sport for financial reasons.
Flow Viz is a fluorescent powder suspended in a light oil (often paraffin). This is liberally applied by a spray gun to bodywork up stream of the area you want to investigate. As the car laps, the airflow spreads the non drying liquid back along the car, following the same path over the surface as the airflow. By then analysing the patterns the flow Viz leaves, you can see the behaviour of the airflow over the car. Details like direction and attached\non-attached flow can be observed. But this is only surface airflow and this is not the entire story when it comes to aerodynamics, so Flow Viz is only one solution for measuring aero on track.
Look at that front wing! I can't remember ever seeing a more dense and complex mess of shapes and surfaces crammed onto a single wing, and this is the new version without any moving parts! (Keep in mind this is, if I remember correctly, last year's car being used to test this year's wings and they launch the new car tomorrow, 4 Feb.....I think)
No, no, that's not a problem, it's a new performance feature. Ferrari's 2011 secret surprise. Last year it was Red Bull's double diffuser, this year Ferrari's whatever that is.....
It sounds like the new rules indicate a minimum cross section for the area above the drivers head. So if you did do the split, then the beam is so wide it shouldn't be as helpful. If you notice the center beam on the Lotus is a lot wider than on the Mercedes.
Could it be that Ferrar has hired George Barris and he brought along design theory from the Batmobile?
The new McLaren (sort of) and a few snips of an article explaining that "sort of": McLaren play it safe at MP4-26 unveiling (eurosport.yahoo.com)