Understanding Prevailing Physics in Automotive Aerodynamics Applications—Detached Eddy Simulation vs Reynolds-Averaged Navier–Stokes Approach

<div>This study presents a structured approach to the aerodynamic evaluation of commercial heavy-duty vehicles by categorizing the underlying flow physics into three primary phenomena: pressure-induced separation, geometry-induced separation, and flow diffusion. Furthermore, the study gives insights into the benefits of Detached Eddy Simulations (DES) over traditional Reynolds-Averaged Navier–Stokes (RANS) approaches by analyzing the flow behavior in cases that correspond to these phenomena. Fundamental insights on pressure and geometry-induced separation were developed through simulations of flow over a sphere and a rectangular cylinder at a Reynolds number of 2.8 × 10<sup>6</sup>. Additionally, flow diffusion was investigated using a coaxial jet interacting with surrounding fluid at a Reynolds number of 2.1 × 10<sup>4</sup>. These cases were analyzed using three turbulence modeling techniques: <i>k</i>-<i>ε</i>, <i>k</i>-<i>ω</i> SST, and DES.</div> <div>To demonstrate the practical relevance of these phenomena, a comprehensive aerodynamic performance study was conducted on a commercial heavy-duty truck. This final analysis integrates all three flow behaviors, showcasing their combined impact on vehicle aerodynamics. The study emphasizes the effectiveness of the DES approach in capturing complex flow structures with enhanced accuracy. Furthermore, this study provides meshing guidelines for near-wall and wake dominant regions, to be implemented in DES-based simulations. The findings aim to support future research by offering a robust framework for applying advanced turbulence models in real-world aerodynamic evaluations.</div>