Sports Coupe Aerodynamic Performance Analysis

The current configuration specifies zero angle of attack and sideslip, with an air density of approximately 1.225 kg/m³. Its Mach number is about 0.098 and its 4.2341 m reference length gives a Reynolds number of approximately 9.66×10⁶. The analysis uses incompressible unsteady external-flow evidence under the conditions below.

Freestream speed

120 km/h (33.33 m/s)

Incidence / sideslip

0° / 0°

Air density

1.225 kg/m³

Reference area / length

1.8559 m² / 4.2341 m

Configured Ma / Re

0.098 / 9.66×10⁶

Statistics window

Final 25% · 4,575 samples

Reference area affects coefficient normalization. Compare force values and coefficients together so a changed reference quantity is not mistaken for better performance. Moving-ground and wheel-rotation settings have not been fully confirmed in the available material. Their influence on underbody and wheel-region flow requires consistent-condition checks; road-equivalent boundaries cannot be assumed.

Use the full-vehicle streamlines to establish spatial relationships, then inspect the scaled sections for velocity changes. These views represent the selected exported flow field, not an established average over the load-statistics window. Mean-load conclusions rely on the separate load statistics.

Full-vehicle streamlines show flow dividing around the nose, roof and sides, then merging and bending behind the rear body. Color represents velocity magnitude, but this rendering has no readable quantitative scale, so it supports inspection of paths and local structures. A streamline represents direction in the selected flow field; this static image does not establish shedding frequency or a local drag contribution.

The longitudinal section uses velocity magnitude in m/s. Higher speeds occur near the roof, with a continuous low-speed region behind the vehicle and a distinct underbody path. Local acceleration and the downstream momentum deficit therefore need to be assessed together. Velocity magnitude alone does not determine reverse flow; inspect vectors or the streamwise velocity component before identifying recirculation.

The horizontal section shows nonuniform velocity around the wheels and along the body sides, connecting those disturbances to the rear wake. A wheel-region or side-body change may therefore affect downstream flow as well as the local field. Compare designs at the same section position, color range and sampling convention to examine the extent and recovery of the low-speed region.

The Q-criterion isosurface highlights local rotating structures near body edges and wheel regions. It helps locate areas for closer inspection, but its appearance depends on the threshold and sampling instant. This rendering does not decompose aerodynamic loads; component drag requires pressure and viscous-force integration over the relevant surfaces.

Mean drag in the final statistics window is 561.03 N. Its fluctuation RMS is 17.87 N, approximately 3.19% of the mean. The mean drag coefficient is 0.4442, reported as exported for this baseline. It is not a direct ranking across vehicles or reference-area conventions.

Associating the reported drag with the configured 33.33 m/s speed gives P = D × U ≈ 18.70 kW of power to overcome aerodynamic resistance. This is an aerodynamic power scale at that speed; it excludes rolling resistance, drivetrain losses and accessory loads, and does not establish driving range.

Mean lift is −10.35 N, acting downward under the positive-Z convention. Lift fluctuation RMS is 49.18 N, substantially larger than the absolute mean. A near-zero average can therefore conceal significant variation within the window. Integrated load alone does not establish axle balance, and RMS alone cannot recover peak loads or prove whether instantaneous lift crosses zero.

The statistics use the final 25%, with window coordinates 13,726–18,300. Their mapping to seconds is not established, so no frequency is inferred. Fluctuation RMS measures variation about the mean, not numerical error or a confidence interval. Selecting a late window does not itself prove statistical convergence.

The available evidence describes flow features and load statistics at one condition, without a matched geometry-variant comparison. Hold reference quantities and boundary treatment fixed, check mean loads over longer windows, and assess mesh and time-step sensitivity. Those checks distinguish a design effect from variation in the numerical evaluation.