Abstract

Sustainability and efficiency drive vehicle development and are becoming an increasingly important selling point. Throughout this paper, an ordinary sedan car body is modified using a single rear wheel to form a tricar. Therefore, we examine potentials for aerodynamic drag reduction of the DrivAer?s bodywork. Morphing of the geometry takes place behind the B-pillar. Drag coefficients are obtained through stationary CFD calculations utilizing a realizable k-epsilon-turbulence model in OpenFOAM®. Employing genetic optimization and the efficient global optimization (EGO) algorithm of the Dakota optimization software, a low drag/negative lift objective function leads to a set of shape parameters defining the car?s stern in Blender®. Either a B-spline control net, section cuts or proportional editing are used as shape design tools with different amounts of parameters in a set. The lattice modifier of Blender® uses B-splines to interpolate the deformations from a control net on to the geometry surface. A further method is based on (multiple) vertical cuts along the x-axis which are translated and scaled. A smooth transition between those cuts is achieved through Blender®?s bevel modifier and a relative offset width. With the method of proportional editing in Blender®, there is just one vertical cut at the far end of the car. This cut can be scaled and translated while proportional editing adapts the geometry in the defined influence area to create a smooth transition. Results reveal that the stern is becoming extremely small and, therefore, a big proportion of the rear tyre is uncovered causing turbulences. A second optimization via a wing shaped wheel fairing is constructed and parametrized to solve this issue. Efficiency potentials are quantified though the WLTP-Cycle calculations applying the achieved drag coefficients. Finally, we demonstrate that the drag is reduced by more than 25% and the energy demand can be reduced by up to 22%.