Computational Fluid Dynamics

In this project, we used Computational Fluid Dynamics (CFD) in ANSYS to improve the aerodynamic performance of a modern car, specifically focusing on reducing drag and lift forces. Starting with an initial design of the Audi Quattro, we analysed airflow behaviour and made modifications such as reshaping the side mirrors, refining the body and adding a spoiler.

These changes led to a significant 20.68% reduction in drag and a 56.87% decrease in lift, ultimately improving the car's speed and stability. The project demonstrates how CFD can optimise vehicle design for better efficiency.

Project Overview

In this project, I teamed up with two engineers, and together we set out to tackle the aerodynamic challenges of modern car design.

Our mission?
To make cars faster, sleeker and more aerodynamic using the power of Computational Fluid Dynamics (CFD).

We started by picking a car model—because who doesn’t want to design a car?—and our choice was the iconic Audi Quattro. Using ANSYS, we dove into the world of airflow, drag and lift forces.



Our goal?
To tweak, refine and reimagine the car’s design to reduce those forces holding it back. And if we happened to make it look cooler along the way, that was just a bonus.

But it wasn’t just about looking good. We had to back it all up with data. Our CFD analysis revealed where the design could be improved and we didn’t stop there. From reworking the side mirrors to adding a spoiler and reshaping the body, every detail was designed with one thing in mind: reducing drag and increasing speed.


The final result?
A car that was not only more aerodynamic but also faster, thanks to a 20.68% reduction in drag. We even managed to decrease lift forces by 56.87%, making the car more stable at higher speeds. All in all, a win for both engineering and style.

Softwares and Tools Utilised

  • Week 1
    Project Planning and Initial Design
    The project kicked off by defining the primary goal: improving car aerodynamics using CFD to reduce drag and lift. We selected the Audi Quattro as the focus vehicle and began setting up the software, choosing the relevant CFD and wind tunnel parameters for the upcoming simulations.
  • Week 2
    Initial Design and Simulation
    We created a CAD model of the Audi Quattro and ran the first round of CFD simulations on the unmodified design. The initial results revealed significant drag (343.04N) and lift (103.76N), providing a baseline for future improvements.
  • Week 3
    First Design Iteration (Side Mirrors)
    The first modification targeted the side mirrors, redesigning them with tapered edges to reduce drag. After simulating this change, we observed a 1.97% decrease in drag, though lift increased slightly due to the higher velocity over the mirrors.
  • Week 4
    Second Design Iteration (Body Shape)
    We streamlined the car's body by chamfering and filleting sharp edges, reducing surface area exposed to airflow. This modification led to a substantial 13.53% decrease in drag and a noticeable reduction in lift, making the car more aerodynamic.
  • Week 5
    Third Design Iteration (Spoiler Addition)
    A spoiler was added to the car’s rear to minimize turbulence and further reduce drag. The CFD analysis showed an 11.90% reduction in drag and improved airflow around the car, though lift forces also slightly increased due to changes in airflow.
  • Week 6
    Final Design and Presentation
    We combined all the improvements—side mirror redesign, streamlined body shape and the spoiler—into a final optimised design. The final CFD simulation showed an impressive 20.68% reduction in drag and a 56.87% decrease in lift, significantly enhancing the car's aerodynamic performance. My group made a presentation showcasing the changes in the model alongside the simulation and performance increase.
Now that we've raced through the timeline, let's shift into the details of the CFD work—where the airflow smooths out and the aerodynamic enhancements really take shape.

Presentation

Initial Design and Car Selection:

To kick things off, we had the task of picking the car we’d put through its aerodynamic paces. After some deliberation (and a few debates about which car looked cooler), we landed on the Audi Quattro—an absolute classic with plenty of room for improvement in the drag department.

Using its real-world dimensions as a reference, we created a detailed CAD model that closely replicated the car’s shape and features. This model served as the baseline for our simulations, where we aimed to identify areas with high drag and lift forces. The initial design’s performance data provided valuable insights into how airflow interacted with the car, setting the stage for future modifications.

Shaft Design:

With our shiny new Audi Quattro CAD model ready, it was time to put it through its paces in the virtual wind tunnel. We set up the boundary conditions to mimic real-world driving conditions. The wind tunnel was configured to simulate a steady airflow at 65 km/h, perfect for testing how air moved around the car. We defined all the nitty-gritty details like the pressure, airflow direction and mesh size to make sure the simulation was as accurate as possible. By recreating the chaos that a car experiences on the road, we started to see where the trouble spots were—mainly high pressure on the front and turbulent air swirling around the back. Turns out, cars don’t love a windstorm as much as you’d think!

Design Improvements:

Armed with our initial results, it was time to make some tweaks. First, those bulky side mirrors had to go—so we streamlined them, tapering the edges to reduce drag. Then, we tackled the car’s sharp body lines, smoothing and chamfering them to create a more aerodynamic shape. Finally, we added a spoiler to minimise turbulence at the rear. Each change made the car sleeker and more efficient, cutting down drag and lift bit by bit, transforming it from a drag-heavy box into a streamlined machine!

Final Design:

After all the tweaks and adjustments, we brought everything together for the final design.

We combined the sleeker side mirrors, streamlined body and the newly added spoiler to create an optimised version of the car.

The result? A major reduction in drag and lift, making the car faster and more stable. The final design not only looked more aerodynamic but performed far better in the simulations. With a 20.68% drop in drag and a 56.87% cut in lift, we had transformed the Audi Quattro into a true road warrior!

And there you have it—from initial designs to streamlined aerodynamics. We’ve refined every detail, and now, this car is ready to slice through the air with maximum efficiency!

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