Further updates on W02 pushed diffuser development into a new step to cope better with new aerodynamic needs of the chassis . The new diffuser not only has a new shape but is also built differently allowing the abomination of the metallic cables which increased rear floor-diffuser stiffness , offering a cleaner path and less obstacles to airflow .
The crucial central zone of the diffuser is modified to the former boxy launch version .Nevertheless it is not identical to launch spec as changes took place especially on the engine starter holes. Additionally the longer fences which separate the central zone from the side tunnels now have a leaning inwards attachment on the diffuser roof to restrict as possible mixing of the flow coming from the centre with the one coming from the sides tunnels leading to wicker vortexes formations and thus less drag .
The power of the diffuser to pull air from under the floor is also strengthened by the higher square tab fence under the rear crash structure which extends up to the light .
As regards the exhaust pipes,they are placed since China a bit outwards combined also with new rear floor fences , both causing diffuser roof to regain back the side tabs but of a smaller width this time compared to launch spec . The side tabs prevent strong mixing of hot air from exhausts, which aim now closer to the wheels , with cool air coming from under the floor . Any interaction between the two flows will create powerful vortexes which will be affected further by the wheel rotation leading to serious drag increase . Finally the endplates are supported on additional pillars onto the diffuser , not only to increase stiffness decreasing vibrations but also to isolate airflow coming under the beam wing from that coming close to the wheels .
During early testing W02 showed poor performance , being unable to challenge top teams ,thus Mercedes launched major updates before season kick start in Melbourne including new bargeboards , exhaust layout , front and rear wing , nose vanes , sidepod panels and rear end major modifications among of which a new diffuser .
Barcelona test on March , used in Melbourne
Speaking for the new diffuser it features double small vertical fences now and a new less boxy central zone to extract air from under the floor more efficiently . The new central zone forced the team to put under change the little hole which permit mechanics to enter the engine starter . Moreover the tab fence across the diffuser edge was restricted in length being cut off thoroughly from the sides ,a change triggered by the new exhaust layout, the new nose vanes ,the revised sidepod panels and bargeboards which in total changed the way air flows around the car body and towards the diffuser . Finally the beam wing which had a raised lower section close to the endplates is now flat, a changed linked to the increase in number of the rear brake winglets (will be analyzed in another post) and an additional winglet is placed over the rear structure to generate more downforce (all changes in yellow color pointed with red arrows) .
All changes paid off as the pace was improved but yet could not match the top teams both in qualify and race conditions .
All 2011 diffusers must be single decked and look alike to the designs raced back in 2009 before the arrival of the multiple deck diffusers . Mercedes W02 diffuser has two sets of vertical fences of different height , which act like splitters dividing the structure into two side tunnels and a central section . The central section is built wider so as to extract stronger the air flowing under the floor and close to the plank sides to increase downforce production . The diffuser roof is surrounded by a high tab fence to pseudo increase the dimensions of the diffuser opening . I said “pseudo” because the actual size of the diffuser remains the same but airflow with the tab presence feels the diffuser to be larger than actually is .
Finally the engine starter (in yellow) is reachable to mechanics via a rectangular hole in the centre also defined in size by 2011 rules .