Simulation and Verification of the Driving Resistance of Refrigerated Trucks with Flow Deflectors at Different Vehicle Speeds

Air resistance is an important factor affecting the energy consumption of refrigerated-truck transportation. This study combined computational fluid dynamics (CFD) with particle image velocimetry (PIV) to investigate the effects of a cab-mounted flow deflector and vehicle speed on the aerodynamic resistance of a refrigerated truck. A three-dimensional model of the truck was simulated at 50, 70, and 90 km/h with and without the flow deflector. A geometrically scaled PIV model was tested at corresponding model-scale wind speeds and compared with scaled CFD results. The flow deflector reduced the drag coefficient by 14.0–15.0% over the tested speed range, reaching 15.0% at 90 km/h. The downforce increased with vehicle speed, while the reference-area drag coefficient decreased gradually with speed. The mean relative error between the PIV and CFD velocities at ten measurement positions was 4.72% ± 1.63% (mean ± standard deviation), supporting the reliability of the model within the measured front-body region. These results provide a reference for reducing the aerodynamic resistance and energy consumption of refrigerated trucks.