In the rapidly evolving automotive industry, electric vehicles have become a focal point for global manufacturers. However, the endurance of electric SUVs remains a critical concern for users. While increasing battery capacity is one approach, it is constrained by current energy storage technology limitations. Alternatively, reducing aerodynamic drag offers a more immediate solution to enhance range. Aerodynamic drag is primarily influenced by the drag coefficient (Cd) and frontal area (A), with the latter being less controllable due to vehicle size constraints. Thus, lowering the drag coefficient is essential. A 10% reduction in aerodynamic drag can improve range by approximately 7% or more, making it a vital aspect of electric SUV development.
Our team focused on optimizing the aerodynamic performance of a pure electric SUV through computational fluid dynamics (CFD) simulations. Using STAR-CCM+ software, we analyzed the vehicle’s exterior and underbody to propose drag reduction strategies that balance aerodynamic principles, styling aesthetics, and engineering feasibility. This approach enabled a systematic development process, resulting in a significant reduction in the drag coefficient and improved续航能力.
The aerodynamic analysis process begins with data input, including computer-aided styling (CAS) and component geometries. We utilized ANSA for preprocessing to generate finite element meshes, which were then imported into STAR-CCM+ as .nas files. A virtual wind tunnel domain was created to simulate driving conditions, with appropriate mesh refinement around the vehicle. The physical model assumed steady-state, three-dimensional, incompressible flow, solving the Reynolds-averaged Navier-Stokes (RANS) equations with the Realizable k-ε turbulence model. The discretization scheme employed a second-order upwind method. Boundary conditions included a velocity inlet at 120 km/h, a pressure outlet at 0 MPa, a slip ground surface matching the inlet velocity, and non-slip walls for the surrounding surfaces. The vehicle body was treated as a wall, with rotating wheels and porous media for radiators and condensers. Temperature and humidity effects were neglected for simplicity. The drag coefficient is defined as:
$$C_d = \frac{F_d}{\frac{1}{2} \rho v^2 A}$$
where \( F_d \) is the drag force, \( \rho \) is air density, \( v \) is velocity, and \( A \) is the frontal area. The overall aerodynamic design follows the “front round, rear sharp” principle, which minimizes frontal pressure and optimizes rear flow separation to reduce drag.
For the electric SUV, we evaluated various exterior and underbody modifications. The front bumper area was initially designed with concave features for stylistic depth, but this caused airflow separation and increased energy dissipation. By applying rounded edges (e.g., R6 mm fillets) and integrating through-flow air curtains, we reduced local positive pressure and improved flow attachment. The air curtain design involved optimizing entry and exit widths, with a Y-direction width of 10–20 mm proving optimal. Additionally, inward adjustments of the bumper grooves and outward extensions to shield the front wheels further minimized drag. These changes collectively enhanced flow continuity and reduced frontal resistance.
The rear section was optimized to manage wake vortices and pressure recovery. Key modifications included sealing a镂空 spoiler, lowering the roof profile, inward-tapering side wings, elevating tail lamp areas, and sharpening the rear bumper’s lower edge. These adjustments promoted earlier flow separation, moving the vortex core away from the vehicle and increasing base pressure. The spoiler extension by 30 mm, for instance, redirected airflow over the surface instead of through gaps, reducing drag significantly. The cumulative effect of these rear-end optimizations was a more stable wake structure and lower pressure drag.
Wheels and wheel arches contribute substantially to overall drag, accounting for up to 25% of the total. We developed aerodynamic wheel rims with reduced镂空 ratios and improved sidewall flatness. Three rim designs were compared: Design A (25.5%镂空), Design B (4.4%镂空), and Design C (6.5%镂空). Design C, with its smoother Y-direction profile, achieved the best drag reduction by minimizing lateral flow disturbances and enhancing attachment. The relationship between镂空 ratio and drag reduction is summarized in Table 1.
| Rim Design | 镂空 Ratio (%) | Drag Reduction (%) |
|---|---|---|
| A | 25.5 | 0.0 |
| B | 4.4 | 0.8 |
| C | 6.5 | 2.4 |
The underbody plays a critical role in managing airflow beneath the electric SUV. We implemented a full-coverage, flat underbody shield comprising front and rear wheel deflectors, bumper guides, battery guards, and side panels. This design streamlined the flow, reducing momentum losses caused by ground interaction and wheel-induced turbulence. Comparative analysis with competitor vehicles revealed that our comprehensive underbody approach effectively minimized separation and vortex formation. The drag reduction from this optimization was substantial, as shown in the velocity vector comparisons, where attached flow along the underbody replaced chaotic interactions with exposed components.
Other detailed optimizations included rounding the hood front edge, smoothing transitions between bumper flaps and underbody guides, expanding side surfaces, widening A-pillars, flaring rocker panel ends, sharpening spoiler tips, and refining护板 mounting holes. Each of these minor adjustments contributed incrementally to drag reduction, as summarized in Table 2. The combined effect of all optimizations exceeded a 30% reduction in drag coefficient, achieving a final Cd below 0.28.
| Optimization Description | Drag Reduction (%) |
|---|---|
| Hood front edge rounding | 0.4 |
| Bumper flap and guide smoothing | 0.8 |
| Side surface expansion | 0.8 |
| A-pillar widening and contouring | 0.8 |
| Rocker panel end flaring | 1.2 |
| Spooler tip sharpening | 1.6 |
| Wheel arch contour inward adjustment | 0.8 |
| 护板 mounting hole slot design | 0.4 |
| Front bumper underbody side recess | 0.4 |
| Rear bumper underbody guide ribs | 0.4 |
The Realizable k-ε turbulence model equations were used to simulate the turbulent flow:
$$ \frac{\partial (\rho k)}{\partial t} + \frac{\partial (\rho k u_i)}{\partial x_i} = \frac{\partial}{\partial x_j} \left[ \left( \mu + \frac{\mu_t}{\sigma_k} \right) \frac{\partial k}{\partial x_j} \right] + P_k – \rho \epsilon $$
$$ \frac{\partial (\rho \epsilon)}{\partial t} + \frac{\partial (\rho \epsilon u_i)}{\partial x_i} = \frac{\partial}{\partial x_j} \left[ \left( \mu + \frac{\mu_t}{\sigma_\epsilon} \right) \frac{\partial \epsilon}{\partial x_j} \right] + C_{1\epsilon} \frac{\epsilon}{k} P_k – C_{2\epsilon} \rho \frac{\epsilon^2}{k} $$
where \( k \) is turbulent kinetic energy, \( \epsilon \) is dissipation rate, \( \mu_t \) is turbulent viscosity, and \( P_k \) represents production terms. These equations helped accurately capture the flow behavior around the electric SUV, enabling precise optimization.
In conclusion, the aerodynamic development of this electric SUV involved a holistic approach integrating CFD simulations with practical design constraints. Through front-end rounding, rear sharpening, wheel rim refinements, underbody shielding, and numerous细节 tweaks, we achieved a drag coefficient reduction of over 30%, culminating in a Cd under 0.275. This outcome not only meets performance targets but also enhances the vehicle’s range, demonstrating the effectiveness of aerodynamic optimization in electric SUV design. Future work may explore dynamic conditions and further integration of active aerodynamic elements to push the boundaries of efficiency.