There are many reasons for thinking that Formula 1 aerodynamicists have it easy. For a start, this particular guild of tradesmen are only compelled to consider the dynamics of a single fluid (namely air), and perforce have no need to take into account the turbulent mixing which occurs at the boundary between fluids of different densities, due to Rayleigh-Taylor and Richtmyer-Meshkov instabilities. Moreover, at Formula 1 speeds, the airflows under consideration are almost exclusively subsonic, and these conditions permit the simplifying idealisation of incompressible fluid flow. Formula 1 aerodynamicists are thereby deprived of such complex beauty as the hourglass cavities, and supersonic jets produced when small objects, such as mere pebbles, are thrown into water. One can go even further afield, and consider the exotica of radiation hydrodynamics, typical in the astrophysical realm, where the fluids in question absorb and emit radiation, and the humble theoretician must solve both the Boltzmann equation for radiation transport, and the entwined equations of fluid flow.
Despite the ultimately parochial nature of the field, however, Formula 1 aerodynamics remains capable of generating a creative cornucopia in the early months of the year, when a flotilla of new cars are unveiled and testing resumes. Only two days of testing have been completed at Valencia, but already the most exciting development is the new McLaren MP4-25, and to be precise, the diffuser on the McLaren.
It appears that McLaren are using the beam wing, rather than the rear crash structure, as the ceiling for the upper-storey of a triple-diffuser, thereby utilising the entire area between the rear wing endplates. McLaren director of engineering, Paddy Lowe, commented at the unveiling of the car in Newbury last week: "This is the first car in which we have had a clean sheet of paper to really exploit the interpretation [of diffusers] that was developed last year...You will see we have produced a fairly extreme incarnation of that but we won't be alone in that...In certain aspects we have sought guidance from the FIA and they have come out with very clear interpretation, understanding and guidance - and we think that has been made available to all the teams." The question, however, is whether McLaren can feed the upper storey of their diffuser with sufficient airflow to prevent it from stalling.
Lewis Hamilton tested the car on Tuesday, and reported "a night and day difference and feeling compared to the first lap and the first test day in 2009." The latter, however, constitutes a very low baseline for comparison, and Hamilton was half a second slower than Felipe Massa's Ferrari. Moreover, McLaren instantly resorted to using the same fluorescent paint used in 2009 when grappling to understand the MP4-24's intransigent behaviour.
Ferrari, meanwhile, also have a triple diffuser, but appear to be using the rear crash structure
as the upper ceiling, as per the 2009 convention.
The other expected championship contender, Mercedes, seem to currently possess a simple double-diffuser. Whilst the word is that an updated version will appear before the first race in Bahrain, such a device will clearly have less testing time than those on the McLaren and Ferrari. Plenty of fluid flow for thought, then.