Numerical Investigation of a Dual-Function Active Flap for Aerodynamic Braking and Battery Cooling in Electric Vehicles

Electric vehicles (EVs) require improved aerodynamic efficiency and effective thermal management to enhance driving range, safety, and component reliability. This study presents a numerical investigation of a dual-function active flap system mounted above the front wheel arches of a generic EV. The proposed system is designed to increase aerodynamic drag during emergency braking while simultaneously redirecting airflow through an internal duct to assist battery cooling. Steady-state Computational Fluid Dynamics (CFD) simulations were performed using the standard k–εturbulence model to evaluate aerodynamic performance for flap deployment angles ranging from 60° to 80°, together with a baseline configuration. Aerodynamic forces, pressure distributions, velocity contours, and streamline patterns were analysed to assess braking effectiveness and airflow behaviour. A scaled 3D-printed baseline vehicle was also tested in a subsonic wind tunnel to provide experimental validation of the numerical model. The results demonstrate that flap deployment substantially increases aerodynamic drag, with an optimum braking configuration identified at approximately 75°, where additional deployment produced negligible drag improvement. Flow visualisation confirmed that increased drag results primarily from enhanced flow separation and wake development, while the cooling simulations demonstrated the feasibility of directing airflow toward the battery compartment. The proposed concept provides a foundation for integrating active aerodynamics with battery thermal management in future electric vehicle designs.