Numerical Investigation on the Effect of Lateral Skirts Device on the Flow Dynamics around a Semi-trailer Truck

Society of automative engineers (SAE) guidelines for computational fluid dynamics (CFD) and wind-tunnel tests on semi-trailer trucks were complied with to investigate the influence of adding a lateral skirts device-in the lower trailer part-on the improvement of the total drag force and the airflow structure around the truck. A reduced-scale (1:28) semi-trailer truck moving at three various speeds (i.e., 50 km/h, 75 km/h, and 100 km/h) is considered in this study. A reasonable agreement between experimental and numerical results was achieved in terms of the drag force parameter with a highest relative error of about 13% obtained in the case of the lowest speed (i.e., 50 km/h) of a truck without skirts. The numerical results yielded an average drag coefficient value of 0.48, which is reduced to 0.45 when the skirt device is added to the vehicle model. The airflow field analysis showed that the skirt device isolates and channels the flow toward the back in the lower part of the trailer, thus protecting the relatively structured flow from lateral disturbances that induce high turbulence which, in turn, generates an increase in the aerodynamic drag force.