Aerodynamic Car Design.

A useful aerodynamic design has to consider both the force pressing the car toward the ground and the drag resisting its motion. Our project focused on increasing the magnitude of downforce relative to drag.

We developed the car in SolidWorks and evaluated its aerodynamic forces through flow simulation. The design combined a shaped front body, rear wing, vortex generators, and rear diffuser, rather than treating each feature as a separate add-on.

A note on the force sign

The executive summary reports lift-to-drag as −2.804045 because the lift force is negative in the model’s coordinate system. For a car, that negative lift is downforce. This page uses the positive magnitude, downforce/drag = 2.804, to make the objective easier to read.

The dimensioned views document the overall side profile, tire clearance, passenger-compartment width, tire width, overall width, and ground plane.

The side cuts preserve space around the tires while changing the surrounding body shape. The front views and ground-plane drawing establish the geometry used for the analysis.

These are the dimensions visible in the surviving deck. They do not provide the complete original constraint list, so exact compliance limits are not inferred from them.

A gentle front profile

The front body uses a gentle concave slope, with areas beside the passenger compartment cut away. The team’s intent was to reduce front drag and limit unwanted low pressure above the compartment.

A rear wing with side panels

The rear wing curves upward to turn the flow and develop downforce. Its side panels were intended to limit lateral escape and help maintain the pressure loading on the wing.

Vortex generators ahead of the wing

Small features behind the passenger compartment were intended to influence the boundary layer and delay separation before the rear wing. Vortex generators act through local mixing; the slides’ description of increasing “laminar flow” is treated here as a design intention to keep the flow attached, rather than a demonstrated laminar-flow result.

A channeled rear diffuser

The underside uses separate channels and a rear diffuser to shape the underbody flow. The presentation records iterative testing of its length, proportions, and rear-edge treatment, with the final version omitting a rear fillet.

The final force results describe the complete model. The deck does not include a separate baseline or a force breakdown for each feature, so it does not establish how much improvement came from any one change.

At the 150 mph benchmark, the simulation reported drag of 712.6079 lbf and signed lift of −1,998.1848 lbf. Taking the magnitude of negative lift gives approximately 2.80 units of downforce for each unit of drag.

How the ratio changed with speed

The largest ratio among these four reported runs was approximately 3.064 at 100 mph. This identifies the best of the sampled operating points; it does not establish a global optimum or a competition result.

Force rises with speed

Both drag and downforce increased across the sweep. The deck reports approximately 3,526 lbf of downforce at 200 mph. More downforce therefore came with increased drag and aerodynamic power demand.

The power cost of drag

The power required to overcome aerodynamic drag follows P = D × V. At 150 mph, the reported drag corresponds to approximately 285 hp of aerodynamic power. This excludes rolling resistance, drivetrain losses, acceleration, and other vehicle loads.

These are modeled forces. The surviving presentation does not provide a mesh-independence study, convergence history, full boundary-condition settings, or measured aerodynamic validation.

The presentation explores a 1/20-scale model in a water tunnel by matching Reynolds number, the ratio of inertial to viscous effects. It uses a full-size reference length of 80 inches and a model length of 4 inches.

For the stated 150 mph air condition, the slide calculates Reynolds number of approximately 9.08 million. Matching it with the specified water properties requires a water speed of about 89.6 m/s, or 200.4 mph.

That demanding result illustrates a practical limitation of matching Reynolds number at this scale. The slide contains calculations, but does not document a completed water-tunnel experiment or measured forces.

Coefficients and reference area

The same slide calculates downforce-coefficient magnitude of 1.418 and drag coefficient of 0.506 using its stated frontal reference area. Coefficients depend on that area definition; their ratio is consistent with the reported downforce-to-drag magnitude.

A fuel-pump reference

The final slide shows a Holley 130 GPH inline fuel pump as a sizing reference. It does not include the associated fuel-demand calculation, engine assumptions, or installed-system results, so a validated component selection is not claimed here.

• Optimize a tradeoff: greater downforce alone does not guarantee a better downforce-to-drag ratio.
• Check more than one operating point: the ratio varied across the four speeds even as the force magnitudes increased.
• Integrate the geometry: the front body, upper surfaces, rear wing, and underbody influence the same flow.
• Keep simulation settings traceable: mesh, convergence, boundary conditions, and force definitions matter when comparing revisions.
• Plan a feasible validation method: scale-model similarity requirements can become demanding before any physical test begins.

The complete 19-slide deck preserves the model dimensions, aerodynamic features, force summaries, plots, scale-model calculations, and fuel-pump reference.