The performance of several aerodynamic technologies, such as trailer skirts, vortex generators, and aerodynamic van trailer obtained from model wind tunnel testing were compared with track test results.
Wind tunnel tests were conducted on 1/8, 1/15 or 1/24 scale models of a tractor in combination with 53-foot semi-trailer. The tests consisted of two phases: setting the initial baseline, and component testing of various configurations. The SAE Fuel Consumption Test Procedures Type II and Type III were used for track test evaluations.
The differences between the track and wind tunnel test results are in some cases explained directly by the some differences between the real scale device and the model. In other situations, the variability and realism of tract testing explain the differences. The wind tunnel results were closer to the track test results for 1/8 scale models than for smaller scale models.
For the trailer skirts, the wind tunnel tests confirmed the influences observed during the track tests, such as longer, wider, and closer to the ground trailer skirts are expected to offer better results.
Wind tunnel tests are conducted in very controlled conditions, and the direct result of the wind tunnel test is the reduction in drag coefficient. However, track tests recreate real conditions, and give fuel savings as a direct result, which is closer to the real life performance of the product. Therefore, track tests are critical to establish the potential return of investment for fleet operators interested in pursuing the implementation of any aerodynamic technologies.