Upgrades in fuel economy in transportation require the development of breakthrough technologies to achieve drag reduction. Indeed, a huge portion of the power consumption is caused by aerodynamic forces that opposes to the motion of vehicles such as trucks and cars on highway.

Wide range of flow control strategies are available to achieve drag reduction in road vehicles, one of them being the use of flaps. Many studies were based on the use of fixed flaps (see e.g., Capone et al, 2019). This raises the problem of an optimization process which is only relevant for a given set of operating conditions. This is far from being suited in real-life where these conditions are likely to change. This makes adjustable flaps a more attractive solution (see e.g., Mazellier et al, 2012). This study, which is part of the ANR project COWAVE, aims at exploring recent development in flow control based on genetic programming algorithms to mitigate drag of road vehicles over a wide range of operating conditions.

Here, we present some of the very preliminary results obtained from both experimental and numerical investigations of the flow over a square-back Ahmed body fitted with fixed flaps. In terms of drag reduction and by using different types of flaps, it is found that 10% to 11% reduction were obtained at zero incidence (flaps aligned with the axis of the body), and 13% in the case of an curved flap. In comparison, flap configuration with angle 15 degrees with respect to flow stream direction is found more effective in reducing drag coefficient.

More detailed analysis will be provided within the full paper and during the oral presentation