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. In this challenge, you will not only learn about how build and design a race car but will also realize how the design the surface of a car can help minimize drag and improve its motion through the air for better performance.

Research

For the research, we watched videos in class as well as doing research on our own. The following images depict notes from all types of research as well as images of my design.

Research - Rail Car Build

To begin the designing of our cars, we first followed a tutorial to gain a general understanding of how this process will work. We used multiple features to develop this car and then ran it though the Flow Simulation within SolidWorks to see how well the car performed in regards to lift and drag.

The main body of the car.

After making the main body, a cockpit area was made using the loft feature.

After this, fenders were added onto the car. Then, various fillets were made to smooth up the part. A hole for the C02 cartridge was also added as well as decals.

An image of the final car in an assembly with all wheels and axles present.

The final rendered image of the tutorial car.

Research - Rail Car Flow Sim

After using the Flow Simulation, the goals that were identified are given values. The specific goals here are lift and drag.

This image depicts the surface plot feature within SolidWorks. This feature allows us to see the pressure on the surface of the car.

Finally, the flow trajectories were calculated. This allows for the flow of air over the car to be seen. The colored objects represent the pressure in that area. The key in the upper left hand corner shows what pressure the colors represent.

Research - Rail Car Accessories

In addition to the tutorial rail car, we also had to follow tutorials for the various other parts within the assembly. These are pictured below. For my car I used the front tires only as they were smaller. I also used the axles created in this tutorial however I needed some different sizes for the actual car. The cartridge was also used to simulate reality so that the flow sim and look of the car was more accurate.

The revolved wheel (left), the tire for it (right), and the final wheel/tire assembly (below). After revolving the wheel, other holes and bumps were added. For my car I used the wheel without the tire.

Revolving the wheel for the back set of wheels.

Revolving the tire for the back wheels.

Adding text to the rear wheels.

The final rear wheel assembly.

The two axles that were made are pictured below. The front axle is 56 mm long while the rear axle is 44 mm long.

This is the washer that was made through the tutorials. It goes between the wheel and the car body.

This is the C02 cartridge that was made to be put into the cars within SolidWorks. It allows for the car and flow simulations to be as realistic as possible.

Custom Car

To begin, I created my sketch planes and sketches so I can loft between them. After everything was set up, I used the loft feature to connect the sketches and create the body of my car.

After the loft, I mirrored the feature so as to have a completed car body (left). After this step, many fillets, and the shelling of the part to allow the air to pass through and hopefully increase aerodynamics, I got the main body shown on the right. Then, as also seen in the right image, the first cut into the body is made. This was done to relieve inside pressure as it was very high and causing more drag.

I then added back the second hole which is directly in front of the cartridge. This was added to further alleviate pressure within the inside of the body. It was taken away and replaced with the front hole earlier as the front hole didn't have add as much drag as the back hole. This was because in the back the air would hit the front of the cartridge holder which would act as a wall whereas further forward the air did not behave this way.

In this step I add the final feature, the fin. This was done mainly to satisfy design requirements. My initial design was not tall enough or long enough and this fin solved both of these issues.

Following are different views of the final car body. They show the shell, main car, and the inside of the car so as to better see how it was made and what design features/choices were made.

Flow simulation of my first car. On the outside, flow isn't terrible but on the inside, all the arrows are red meaning there is a lot of pressure and more drag.

This image depicts the high pressure which is present within the body at this stage.

After designing and attempting to relieve some of the high pressure, I got to my final design. This is the outside air flow on my car body.

This is the flow inside my final design. When looking at the inside compared to the first iteration, it is evident that the holes did in fact relieve some inside pressure and increased my cars aerodynamics.

In addition to the flow trajectories, we used the surface plot feature which projects the pressure onto the surface of the car. This is the surface plot on the outside of my final design.

The surface plot on the inside of my final design.

This is the surface plot of the first design.

Below is the lift and drag numbers of the first car.

In the middle of the screen are the goals that SolidWorks was told to calculate. They turn out to be the lift and drag (force) acting on the car. This is the data for the final car.

The final render of my car (left) and the scale used for the pressure.

This is the engineering drawing of my final car.

Percent Improvement

Values

Initial - Drag: -63.8698 p Lift: 1.86517 p

Final - Drag: -29.4046 p Lift: -6.45158 p

Drag % Improvement:

((-63.8698 p - (-29.4046 p))/-63.8698 p) * 100 = 53.96% Improvement

Lift % Improvement:

((1.86517 p - (-6.45158 p))/1.86517 p) * 100 = 445.9% Improvement (In this case, % to change to negative lift, or downforce)

Test Print

Pictured below is the test print I did to check how well the cartridge would fit into it's hole as well as how well the axles would fit. After testing and talking with others, I decided to decrease the diameter of the axle holes so as to make them fit better with less wiggle room. On the left is the finished parts on the printer and on the right is the test print within the slicer program.

Final Product

An image of the car body being printed.

An image of the final body completed and on the build plate.

The part being printed.

An image of some of the parts used in the final car. Wheels were changed multiple times as well as a few other things throughout testing so as to make the car faster.