With the 2011 Formula 1 season-opener in Bahrain set to kick off in just a few weeks, more and more teams are starting to unveil their latest race cars for the new season.

Already we’ve seen the new Ferrari F150 and the Team Lotus and Sauber cars, but now we get our first glimpse of the latest F1 race car from the Williams team.

Dubbed the Williams Cosworth FW33, the new race car has been presented in an interim livery which will remain until racing starts in Bahrain next month. Also joining the new livery at the first race will be an aero upgrade, which is still in development.

New rules, which were only confirmed by the FIA’s World Motorsport Council in June 2010, forced teams to redesign much of the aero components from their 2010 cars. The ban on double diffusers and the F-duct, for example, forced aerodynamicists to seek new downforce solutions; KERS had to be incorporated into the layout and teams had to prepare for the arrival of a new tire supplier, Pirelli, for the first time in five years.

One of the most controversial rule changes for 2011 is the introduction of a moveable rear wing. The top element of the wing has to be able to lift at the front until the slot gap is 50-mm and it’s hoped that the resultant reduction in drag will increase speeds by up to 10 mph. The wing’s sole purpose is to make overtaking easier, but the real indication of any success won’t come until racing starts.

The Williams team now has 15 days of testing at four different racetracks ahead of the opening race of the season: Valencia, Jerez, Barcelona and Bahrain. Later today Rubens Barrichello will commence a three day test of the FW33 in Valencia, Spain, with Pastor Maldonado set to take over on Wednesday.