A numerical investigation of the flow around a motorbike when subjected to crosswinds

Abstract

Crosswinds have the potential to influence the stability and therefore the safety of a motorbike rider. Numerical computations using both delayed detached-eddy simulations (DDES) and Reynolds-Averaged Navier-Stokes (RANS) were employed to investigate the flow around a motorbike subjected to crosswinds with yaw angles of 15, 30, 60 and 90 degrees. The Reynolds number was 2.2 million, based on the crosswind velocity and the height of the rider from the ground. The aerodynamic force coefficients and flow structures around the motorbike and rider were obtained and analysed. Although both DDES and RANS provided comparable overall aerodynamic forces, RANS failed to predict both the DDES surface pressures at the separation regions and the location and size of the main circulation region. The DDES results showed that the drag coefficients decrease with increasing yaw angles, while the side force coefficients significantly increase. It was found that increasing yaw angles result in stronger vortex shedding around the windshield and helmet.