Nakagawa, M., Kallweit, S., Michaux, F., and Hojo, T., "Typical Velocity Fields and Vortical Structures around a Formula One Car, based on Experimental Investigations using Particle Image Velocimetry," SAE Int. J. Passeng. Cars - Mech. Syst. 9(2):754-771, 2016, doi:10.4271/2016-01-1611.
This paper presents typical flow structures around a 60%-scale wind-tunnel model of a Formula One (F1) car, using planar particle image velocimetry (PIV). The customized PIV system is permanently installed in a wind tunnel to help aerodynamicists in the development loop. The PIV results enhance the understanding of the mean velocity field in the two-dimensional plane in some important areas of the car, such as the front-wheel wake and the underfloor flow. These real phenomena obtained in the wind tunnel also help maintain the accuracy of simulations using computational fluid dynamics (CFD) by allowing regular checking of the correlation with the real-world counterpart. This paper first surveys recent literature on unique flow structures around the rotating exposed wheel, mostly that on the isolated wheel, and then gives the background to F1 aerodynamics in the late 2000s. It subsequently describes features of the PIV system that is used in the development loop and discusses improvements to the efficiency of the preparation and operation processes. Typical velocity fields behind the rotating front wheel and the underfloor of two F1 car models, one before and one after a regulation change in 2009, are then analyzed. Finally, important vortical structures around the 2009 car are highlighted from the results obtained in the development loop. These results show the initial effect of the regulation change on the flow structures, and how the 2009 car was developed to overcome the initial deficit in downforce.