Numerical study of motorbike aerodynamic wing kit

Abstract This study aims to design the configuration of an aerodynamic wing kit (AWK) on a racing motorbike to achieve the highest downforce-to-drag ratio. The numerical study involves a motorbike traveling in a straight line, where the AWK improves performance and safety by generating downforce to prevent lift. The geometry of the AWK uses a NACA 4412 airfoil with a span of 0.6 m. The computational mesh is generated using SnappyHexMesh and installed on a simplified motorbike to minimize the mesh skewness. The Navier–Stokes equations are solved with OpenFOAM computational fluid dynamics using the Reynolds-averaged Navier–Stokes k-ω SST and large eddy simulation (LES) turbulence models. Case 1 compares a motorbike with and without a dummy, both equipped with the AWK, varying the angle of attack (AoA) from 0 to −41°. Case 2 studies the single wing at different wind speeds (i.e. 20, 60 and 100 m/s) to determine the highest downforce-to-drag ratio at an AoA of −37°. These results serve as the basis for Case 3, which investigates non-parallel wing configurations with a fixed upper wing and a rotating lower wing. In Case 4, where both upper and lower wings rotate simultaneously as parallel wings, the peak downforce-to-drag ratio occurs at an AoA of −41°. Finally, Case 5 modifies the AoA of −41° of the parallel wing of Case 4 to a closed-wing version to comply with Fédération Internationale de Motocyclisme safety regulations. With the LES turbulence model, unsteady and complex turbulence structures can be visualized using the Q-criterion. A comparison of the time-averaged lift coefficient between the wingless and closed-wing configurations shows an increase in downforce of approximately 360%. Subsequently, the popularity of AWK will contribute to the safety of racing motorbike driving.