Aerodynamic Analysis and Cab Geometry Optimization of an Electric Heavy-Duty Truck

Sammanfattning

This thesis investigates the influence of cab geometry and aerodynamic add-ons onthe aerodynamic performance of a heavy-duty electric truck using computationalfluid dynamics. A parameterized 3D-CAD tractor-trailer model was developed inSTAR-CCM+ and evaluated using steady Reynolds-Averaged Navier–Stokes simulations with the SST k-ω turbulence model. Two cab geometries were studied:a baseline flat-front cab and a more streamlined electric-truck cab. For each cabgeometry, configurations with a large side skirt and a side extender were simulatedto assess the effect of add-ons on the tractor-trailer gap and underbody flow. Atwo-stage cab optimization was then performed using the SHERPA algorithm, firston a simplified model and then on the complete Model 1 configuration.The results show that cab geometry has a strong influence on both the front pressure distribution and the effectiveness of the add-ons. For Model 1, the combinedlarge side skirt and side extender reduced the drag coefficient from 0.407 to 0.391,corresponding to a reduction of approximately 3.9%. For the more streamlinedModel 2, the same add-on configuration reduced the drag coefficient from 0.411 to0.364, corresponding to a reduction of approximately 11.4%. The complete Model 1optimization reduced the drag coefficient from 0.391 to 0.373, giving an additionalreduction of approximately 4.6% relative to Model 1 configuration 3. The accumulated drag and pressure-coefficient results indicate that this improvement mainlyoriginates from the optimized cab-front shape, while the downstream flow remainsstrongly affected by the side skirt, side extender, and trailer arrangement.The work provides a foundation for continued research on aerodynamic analysisand optimization of zero-emission heavy-duty vehicles. The parameterized modeland CFD workflow can be further refined to include additional design concepts,experimental validation, and more realistic operating conditions such as crosswind.