Improving Aerodynamic Performance of a Truck: a Numerical Based Analysis

Sammanfattning: With a change in EU-legislation regarding the dimensions of heavy trucks [1] coming up, specifically allowing aerodynamic devices fitted to the back of trailers, the transportation industry is set to largely decrease its environmental impact in the near future. These aerodynamic devices have been researched for quite some time [2] but have not yet gained widespread market acceptance, partly because of the transportation industry’s complex owner structures and partly because of size regulations of the past. Though with this new legislation and other expected new EU-legislation on CO2 emissions, development of these aerodynamic devices looks set to become a field of intense study. The study explores different options regarding the influence of changing the rear shape of a generalized ground transportation system (GTS), a simplified model of a truck geometry. By changing the rear shape the drag force induced by the oncoming air flow was reduced, and the overall coefficient of drag (CD) value lowered. There is also an investigation as to how an added suction slot, and that slots location, affects the CD. Computational Fluid Dynamics (CFD) in the form of the commercial computer software STAR-CCM+ was used to simulate the flow around the GTS, and the results were verified with similar studies and experiments [3] on the same geometry. RANS equations and Menter k-! SST turbulence model was used for all simulations. The results show that CD can be lowered by 21% compared to a baseline case. Further on the added suction slots can reduce drag, but depending on slot location also can add to the drag force experienced by the GTS.