Evaluating Aerodynamics Through Different Vehicle Models
Abstract
As you are walking around anywhere you live, you notice how all cars are shaped differently. Most cars have round edges with barely to no sharp ends. Cars are shaped in a specific way to be able to reduce drag or in other words, improve aerodynamics. With a Windtunnel, testing has shown how different vehicle models affect the air passing through. Some results that were found is that, when a car wants to drive at a higher rate of speed, a rounder surface would be useful since the air around the car will keep the car on the ground. With this result, it was easy to see how much drag was being produced which makes the car use more energy to move forward. When placing a vehicle with a sharper body shape, it was harder for it to have stability through the track and beat the optimal time due to air not being able to flow. In conclusion, studies show that a rounder body would help a car drive smoothly without getting much wind resistant.
Introduction
Has the question ever risen to you as to why cars are sort of circular shaped or have distinct body shapes that differ from other vehicle models? The simple answer to this question is to improve the aerodynamics of the car. Aerodynamics is the understanding of how air passes through an object. With a less rounder car, the air wouldn’t flow around the vehicle as smooth as the manufacturer would like. One of the first vehicles with a rounded exterior came around 1963 by German engineers who worked for Porsche creating the first Porsche 911 (Stromberg 2016) For example, A Mercedes G Wagon is more square shaped. Which increases the Drag efficiency of the vehicle. Causing the car to go slower, and even use more fuel to power the engine. With a more rounder car like the Honda Accord, The car is able to push through the air more efficiently and use less fuel (George 2009).
Methods and Materials
To evaluate aerodynamics through different vehicle models, different simulation tests will be run in a wind tunnel to measure the air around the vehicle being blown by. This will help with understanding the reaction between the air and the body of the vehicle shape and the fuel consumption between each vehicle. A closed course was used to track each lap around the course until the vehicle is completely low on fuel. This will help with understanding which body shapes help drivers save more money(what-when-how.com). The various vehicles being used will be listed below:
- Race Car
- Passenger Car
- Convertible
- Trailers
- Truck
- Bus
To be able to get a calculation the air resistance formula was used. This formula will be able to calculate the drag coefficient produced by the car. The smaller the drag the more aerodynamic the vehicle will be (what-when-how.com). The formula is as follows:
Results
After seeing the vehicles run tests and making the proper calculations. The drag coefficient was lesser in rounder vehicles than it was in sharper vehicles. For each vehicle, they were in the wind tunnel for 30 minutes enduring different wind speeds. Rounder vehicles were able to handle as wind speed increased. Being able to see the stream line of wind, it was going around the car and flowing according to the body style. Sharper bodies disrupted the flow in the air. It was harder for the wind to go around the vehicle due to the air being pressed into some sort of wall. (Haynes Manual)
Figure 1: One of the team members released a white stream so we can see how the air is interacting with a model Chevy Cruze
Figure 2: As you can see the square really disrupts the air. Blocking it from passing through
Figure 3: With the circle, air is able to flow past it smoothly causing less drag compared to the square.
It also slows down the wind which in a vehicle will make the engine use more fuel to push through. For the circle you can see how the air just goes around it. It may slow down the air a little bit but it will not be enough to create a big enough drag coefficient the square makes. (George 2009)
| Types of Vehicles | Cd (dimensionless) |
| Racing Car | 0.25 – 0.30 |
| Passenger Car | 0.30 – 0.60 |
| Convertible | 0.40 – 0.65 |
| Bus | 0.60 – 0.70 |
| Pickup Truck | 0.80 -1.00 |
| Trailers | 1.25-1.35 |
Figure 3: As you can see a vehicle with less obstruction towards the air flow has a lower drag coefficient than those with more obstruction towards air flow
Discussion
The purpose of this lab report is to bring to attention of how important the body style of a car is. How the car you drive might feel faster compared to others. I want to help people understand that a rounder vehicle would be a better choice than choosing a square body vehicle. It was concluded that rounder shaped vehicles tend to be more pleasing with air flow. When looking through a racing car, passenger car, convertible, and a bus, they did not reach 1.00 Cd. Meaning, they produced less drag than trailers and trucks. With less drag they are able to stick to get better traction at high speeds and save more fuel. This is due to the cars maximizing downforce (Trochalidis 2019). For example, if you apply a 2% reduction in drag coefficient, then you are also reducing fuel consumption by approximately 1% (Morgan 2015). Manufacturers have found ways in combating this to help reduce fuel consumption in trucks. They have added fold out flaps to the rear of the trailers and side skirts between the wheels of the trailer to improve air flow. For the pickup trucks they open the tailgate to fuel consumption. With a closed gate the air gets trapped in the truck bed making the vehicle use more power and fuel (Mcintosh 2018). When going out testing the vehicles on the track, we noticed that the vehicles with better aerodynamics were able to use their fuel efficiently.
Race cars are more known to be good on fuel usage especially because they are made to stick to the ground. Those cars have wings on the back of the car called a spoiler.. Which helps the car gain more traction on the road. This has been implemented on various vehicles to be able to help them use less fuel. They get different names like roofline, lip spoilers, and boat- spoilers (Jorgensen 2019).
While the aerodynamics was evaluated and have been solved there are still many possible questions that will arise. My investigation can be taken more deeper with professionals and engineers. Seeing how Formula 1 engineers would study vehicles and aerodynamics would be interesting. They bring in some variables. Add different body panels to see what could improve the air flow, see if a heavier car is better than a lighter car. Many experiments can be done to figure out the best way to help air flow around different vehicles. For future research we can even discover how to properly build flying cars for the future.
Appendix
- Drag: A force moving against the direction of the object in motion
- Downforce: A combination of air resistance and gravity that increases the vehicle’s stability
- Windtunnel: A tunnel used to blow air into a stationary object to study air movement
- Porsche: German car manufacturer
References
George, Patrick E. “How Aerodynamics Work” HowStuffWorks, HowStuffWorks, 17 Mar. 2009, auto.howstuffworks.com/fuel-efficiency/fuel-economy/aerodynamics.htm.
Trochalidis, Constantinos. “The Effects of Aerodynamics On Cars” DriveTribe, DriveTribe, 29 Sept. 2019, drivetribe.com/p/the-effects-of-aerodynamics-on-S5nweq-XQASk_m9ebAmeBw?iid=OB8zwyFNSd6TlsZuJzTOJA.
Patton, Phil. “Edgy, Yet Still Aerodynamic” The New York Times, The New York Times, 19 Dec. 2008, www.nytimes.com/2008/12/21/automobiles/21AERO.html.
Nair, Deepak. “Why Do Cars Have Rounded Corners and Ridges in the Bodywork?” Quora.com, 8 Aug. 2017, www.quora.com/Why-do-cars-have-rounded-corners-and-ridges-in-the-bodywork.
Mcintosh, Jil | January. “How It Works: Aerodynamics” How It Works: Aerodynamics, 7 Feb. 2019, driving.ca/auto-news/news/how-it-works-aerodynamics.
Jorgensen, Webster. How Better Aerodynamics Lead to Fuel Savings, 19 Jan. 2019, www.rtsinc.com/guides/how-better-aerodynamics-lead-fuel-savings.
Stromberg, Joseph. “Why Cars Went from Boxy in the ’80s to Curvy in the ’90s.” Vox, Vox, 11 June 2015, www.vox.com/2015/6/11/8762373/car-design-curves.
Sickels, David, et al. “Investing in Aerodynamics to Improve Fuel Efficiency.” Fleet Equipment Magazine, 23 Apr. 2021, www.fleetequipmentmag.com/truck-trailer-aerodynamics-fuel-efficiency/.
“How Does Aerodynamics Affect the Fuel Economy?” Haynes Manuals, 27 Mar. 2019, haynes.com/en-us/tips-tutorials/aerodynamics-and-how-they-affect-fuel-economy.
Staff, Crankshaft. “Body Shape (Automobile).” Whatwhenhow RSS, 2020, what-when-how.com/automobile/body-shape-automobile/.
