Automotive Aerodynamics

Automotive aerodynamics is the study of the aerodynamics of road vehicles. Its main goals are reducing drag and wind noise, minimizing noise emission, and preventing undesired lift forces and other causes of aerodynamic instability at high speeds. Air is also considered a fluid in this case. For some classes of racing vehicles, it may also be important to produce downforce to improve traction and thus cornering abilities.

Rail Car

Rail Car Body

To start the rail car body we begin with a basic wedge shape.

We the form the curve of the car and define the cockpit using a loft.

Next we add wheel sendoffs and fenders.

Finally we add some fillers and color the body.

Wheel Assemblies

Thin wheel rim.

Thin wheel tire.

Thick wheel rim.

Rear wheel tire.

Drawing

Without Dimensions

With Dimensions

Additional Parts

CO2 Cartridge

Front Axle

Washer

Rear Axle

Flow Simulation

With Thick Wheels

With Thin Wheels

Data

Fat Wheels

Thin Wheels

Personal Car

The Design

First Draft

Second Draft

I started with a basic block

Added variable fillets to smooth out the sharp edges.

Channel cut in bottom for string

Final Design

I added a rear fender to help deflect air from the rear tires.

I extruded a fin down the middle.

I smoothed the fin with fillets.

Final design

Flow Sims

Flow Sim 1

Flow Sim 2

Surface Plot 1

Flow Trajectories 1

Flow Animation

Surface Plot 2

Flow Trajectories 2

Flow Animation 2

Between the two flow simulations we can see that more air passes over the car generating downforce. The rear fenders also help to divert air away from the tires, preventing dirty air from forming.

Printing and Post-Processing

Test print of back wheels

Completed Test Print

The final car printed vertically without support so the only post processing was adding wheels.

Race Day

The cars were raced on a 60 foot long track using 12oz CO2 cartridges.

Finished Car with axles and wheels

Race 1

In race 1 my car won and achieved a time of 1.080 seconds. It reached a top speed of 65.57 miles per hour.

Race 2

In race 2 I won again with a time of 1.060 seconds, a small improvement over my first race. It reached a max velocity of 66.30 miles per hour.

Race 3

In race 3 my car won, achieving a time of 1.024 seconds, my best yet. 67.64 miles per hour.

Race 4

Race 4 was incredibly close, with a time difference of 0.001 seconds. My car's time was 1.070 while the other car had a time of 1.069. My car reached a top speed of 65.93 miles per hour.

Speed Calculations

Overall my car had an average speed of 66.36 miles per hour.

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