**When it comes to designing and developing cars that are not only efficient but also environmentally friendly, one of the most crucial factors is understanding and optimizing the aerodynamics. In the race to reduce fuel consumption and pollutant emissions, we need tools that can accurately predict the aerodynamic performance of vehicles. That's where NablaFlow's AeroCloud comes into play. But, how can we be sure that this advanced CFD (computational fluid dynamics) tool is up to the task? The answer lies in validation.** 
In this blog post, we'll dive into two fascinating validation cases that demonstrate AeroCloud's ability to accurately calculate the drag coefficient of various car models. The first case deals with the widely used DrivAer model, while the second case focuses on a high-performance-type vehicle with modifications to the DrivAer model. These validation studies are vital steps in ensuring the reliability of the simulations and ultimately, the success of the product. So, buckle up and let's explore the world of accurate aerodynamics!
 
## Introducing the DrivAer Model

![Drivaer_Model_picture.png](https://nablaflow-cms-uploads-production.s3.eu-west-1.amazonaws.com/Drivaer_Model_picture_3587aa98d9.png)
_The DrivAer model_

To put AeroCloud's drag coefficient calculations to the test, we turned to the DrivAer model, an open-source benchmark model developed at TU-Munich [1]. This model is based on a combination of two series cars and offers a more detailed geometry than other models commonly used in academia, such as the Ahmed or SAE body. The DrivAer model is also modular, featuring exchangeable rear ends, underbody, and wheel geometries, which makes it an ideal platform for investigating realistic flow features and their nonlinear interactions in various car configurations [1]. This versatility allows us to examine how AeroCloud (pro version) performs across different car configurations, which is essential in understanding its accuracy.

### The Validation Process: Comparing AeroCloud with Real-world Experiments

![landscape.png](https://nablaflow-cms-uploads-production.s3.eu-west-1.amazonaws.com/landscape_2274c10652.png)
_Streamlines over the DrivAer model extracted from the AeroCloud simulation_

To validate AeroCloud's drag coefficient calculations, we compared its results with real-world experimental data from studies conducted at various wind tunnel facilities. These studies include the work of Varney et al. [2], which focuses on the validation of numerical methods, as well as tests conducted at the TUM wind tunnel in Munich [3], where the DrivAer model was developed [1], and the University of Stuttgart Göttingen-type wind tunnel [4]. By examining different car configurations, we could gauge how well AeroCloud was able to capture the aerodynamic behavior of each variant. The goal was to see how closely the simulations matched the experimental results, which would demonstrate the tool's accuracy and reliability.
 
### Delving Deeper: The Numbers Behind AeroCloud's Remarkable Accuracy

To truly appreciate the accuracy of AeroCloud's drag coefficient calculations, let's take a closer look at the actual results from both the wind tunnel tests and AeroCloud's simulations. The bar diagram below visually illustrate the match between experimental and CFD results, in the different highlighted configurations of the DrivAer model.

![Picture 3.png](https://nablaflow-cms-uploads-production.s3.eu-west-1.amazonaws.com/Picture_3_1e354282e3.png)
_Different configuration of the model used in the experiment:_
1. Car 1: Fastback rear end, smooth underbody, no cooling system, no mirrors
2. Car 2: Notchback rear end, smooth underbody, no cooling system, with mirrors
3. Car 3: Estateback rear end, smooth underbody, no cooling system, with mirrors
4. Car 4: Notchback rear end, detailed underbody, no cooling system, with mirrors
5. Car 5: Estateback rear end, detailed underbody, no cooling system, with mirrors
6. Car 6: Notchback rear end, detailed underbody, with engine bay cooling system, with mirrors
7. Car 7: Estateback rear end, detailed underbody, with engine bay cooling system, with mirrors

![Picture 4.png](https://nablaflow-cms-uploads-production.s3.eu-west-1.amazonaws.com/Picture_4_57ba7248d0.png)
_Comparison of drag coefficients for the DrivAer model:  Wind Tunnel Experiments vs. AeroCloud Pro CFD Simulations._
 
 The data in the bar diagram demonstrate that the AeroCloud CFD simulations closely match the experimental results in every case, with only minor deviations in percentage: relative differences within +- 4 %. This exceptional level of agreement between the real-world tests and AeroCloud's predictions is a testament to the tool's accuracy and reliability.
 
### Exploring the High-Performance Vehicle Validation Case

In a recent study, a new validation case was conducted for the CFD tool NablaFlow's AeroCloud, which focused on a high-performance enclosed-wheels car based on the DrivAer model [5]. This validation case compares the simulation results of the drag and lift coefficients done in AeroCloud with the results presented in the study by Cranfield University, in which the DrivAer geometry was modified to represent a more realistic high-performance enclosed-wheels car [5]. The results further emphasize the tool's accuracy and capability to handle complex aerodynamic scenarios.

The study demonstrated that the high-performance model produced a higher drag coefficient compared to the baseline model, with an increase of about 0.1, as illustrated in the bar diagram below. This was due to the presence of additional aerodynamic devices mounted on the original baseline model. However, the higher drag also corresponded to greater downforce generation, which is typical in motorsport applications.
Interestingly, as the car model approached the ground, the aerodynamic efficiency increased. The study found that the minimum drag occurred at the highest ride height, while the maximum drag was at the lowest ride height, as shown in the bar diagram. Downforce was also found to be more sensitive to ride height changes, especially for the high-performance model equipped with aerodynamic devices designed to generate downforce and enhance ground effect. Refer to the bar diagram below for a visual representation of these findings.

![Picture 5.png](https://nablaflow-cms-uploads-production.s3.eu-west-1.amazonaws.com/Picture_5_738988ca63.png)
_Comparison of drag coefficients for the baseline and the High-Performance model for different elevation levels:  Wind Tunnel Experiments vs. AeroCloud Pro CFD Simulations for the DrivAer model._

One key finding of the study was the impact of various aerodynamic devices on the baseline model. The front splitter was found to create a stagnation point above the plate, resulting in increased pressure on its upper surface and generating downforce. The rear spoiler, on the other hand, led to a larger wake and higher drag due to its effect on the base region. The underbody diffuser was found to increase both drag and downforce, while also causing a strong asymmetry in the wake.

![Picture 6.png](https://nablaflow-cms-uploads-production.s3.eu-west-1.amazonaws.com/Picture_6_2532900614.png)
_Comparison of drag coefficients for the baseline and the baseline with added parts:  Wind Tunnel Experiments vs. AeroCloud Pro CFD Simulations for the DrivAer model_

These insights not only provide a better understanding of how aerodynamic devices and solutions influence high-performance vehicles but also highlight the importance of considering ground effect and ride height changes when optimizing vehicle aerodynamics. By utilizing the data obtained from this study, engineers can make more informed decisions about the design of high-performance cars and improve their overall performance on the track.

### Key Findings

A closer look at the results reveals the most important effects of different car parts and types on the flow:
1. Rear Ends: The Estateback model, characterized by a large slant angle and no boat tailing, exhibited the highest drag due to a larger wake and separation at the sharp trailing edge. The Notchback model showed a slight increase in drag compared to the Fastback, owing to the early separation on the rear windscreen and the resulting longer wake.
2. Underbodies: Models with smooth underbodies produced lower drag, highlighting the significance of underbody paneling in reducing aerodynamic losses.
3. Cooling Systems: The highest drag among all configurations was observed in models with open front grilles. The cooling air flow caused energy loss due to turbulence, friction, and pressure loss across heat exchangers.

Furthermore, the high-performance vehicle validation case demonstrated the effect of various aerodynamic devices on the drag coefficient and downforce generation. The study also highlighted the importance of considering ground effect and ride height changes when optimizing vehicle aerodynamics, which can contribute to better overall performance on the track.
By consistently delivering accurate drag coefficients for different car configurations, AeroCloud proves to be a powerful and dependable tool that can significantly aid in the design and optimization of efficient and eco-friendly vehicles. The consistency between the wind tunnel tests and AeroCloud's simulations showcases the immense value of this cutting-edge technology for the automotive industry.

### The Verdict: AeroCloud Delivers Remarkable Accuracy

After comparing the drag coefficients calculated by AeroCloud with those obtained from real-world experiments for both the DrivAer model and the high-performance vehicle validation case presented in [5] by the Cranfield University, we found that the tool's results were in excellent agreement with the experimental data. This indicates that AeroCloud is highly accurate in predicting the aerodynamic behavior of various car configurations, making it a reliable and powerful tool for designing and optimizing vehicles.

### AeroCloud's Impact on the Automotive Industry

As a testament to the effectiveness of AeroCloud, our tool has been used in the development of the world's fastest electric cars, such as Automobili Estrema's Fulminea. The high-performance vehicle validation case showcases the versatility and adaptability of AeroCloud for various automotive applications, further establishing its credibility in the industry. To learn more about how AeroCloud is helping shape the future of sustainable and high-performance vehicles, check out our previous [blog post](https://nablaflow.io/en/blog/the-need-for-speed-and-sustainability-nablaflow-joined-the-supercars-race-towards-a-greener-future): "The Need for Speed and Sustainability: NablaFlow Joined the Supercars' Race Towards a Greener Future."

With the continuous advancements in AeroCloud's capabilities, we strive to deliver even greater accuracy and reliability to our clients. Our dedication to addressing the challenges faced by the automotive industry, and our commitment to pushing the boundaries of CFD technology, make AeroCloud a driving force for innovation and sustainability.


Use [this link](https://aerocloud.nablaflow.io/s/v5/06fac561-c1e7-4c9c-aed0-c3ae15f72b68/ML5UNpRcbW7xsfnrau6NrkBRo1Hyq0) to access the interactive result page of an example sport car! 


Author of the article: [Trond-Ola Hågbo](https://www.linkedin.com/in/trond-ola-hågbo-2854b4136/).

Author of the study: [Micol Sala](https://www.linkedin.com/in/micolsala/).

References:

[1] Chair of Aerodynamics and Fluid Mechanics. (2022). Geometry - DrivAer Model. Technical University of Munich. Retrieved from https://www.aer.mw.tum.de/en/research-groups/automotive/drivaer/

[2] Varney, Max & Passmore, Martin & Wittmeier, Felix & Kuthada, Timo. (2020). Experimental Data for the Validation of Numerical Methods: DrivAer Model. Fluids. 5. 236. 10.3390/fluids5040236.

[3] Mack, Steffen & Indinger, Thomas & Adams, Nikolaus & Blume, Stefan & Unterlechner, Peter. (2012). The Interior Design of a 40% Scaled DrivAer Body and First Experimental Results. 10.1115/FEDSM2012-72371.

[4] James, Taryn & Krueger, Lothar & Lentzen, Manfred & Woodiga, Sudesh & Chalupa, Karel & Hupertz, Burkhard & Lewington, Neil. (2018). Development of a Full-Scale DrivAer Generic Realistic Wind Tunnel Correlation and Calibration Model. SAE International Journal of Passenger Cars - Mechanical Systems. 11. 10.4271/2018-01-0731.

[5] Soares, Renan & Knowles, Andrew & Goñalons, Sergio & Garry, Kevin & Holt, Jennifer. (2018). On the Aerodynamics of an Enclosed-Wheel Racing Car: An Assessment and Proposal of Add-On Devices for a Fourth, High-Performance Configuration of the DrivAer Model. 10.4271/2018-01-0725.


Picture 3.png

Urban Wind Engineer at NablaFlow, Trond-Ola, has a strong background in energy, climate, and environment, and he is currently completing his Ph.D. studies in computational fluid dynamics.

Trond-Ola has spent several years at NablaFlow researching and developing tools to simulate wind flow within the atmospheric boundary layer, focusing on urban areas. These tools form the core of ArchiWind. Trond-Ola has a passion for nature and the environment and believes that ArchiWind can be used to tackle emerging urban wind challenges related to extreme weather events powered by climate change. These include pedestrian wind comfort and safety, city ventilation related to heat waves and pollution, and urban wind power production.

Trond-Ola Hågbo

How can we be sure that AeroCloud is up to the of understanding and optimizing the aerodynamics? The answer lies in validation. 

AeroCloud validated with DrivAer model

**For decades, the world has worked towards a goal of increasing global sustainability. With growing pressures on the environment, cities, product industry and climate conditions, we have to work harder and nimbler with new ideas to foster sustainable innovation.**
 
When we talk about the future, we should not focus only on predictions but also on solution-oriented scenarios. We believe in sustainability as our core value to help ensure a better future for all of us.
At NablaFlow, we believe that sustainability is not just about natural resources and pollution. It's also about the conditions we create in developing our habitats and how we handle product creation in all industries.

## Simulation driven design improves the product life cycle
In order to ensure a more sustainable future, we can, for example, take into account issues like energy usage and resources and time spent on product processing. When making future-focused decisions it might be useful to take the time to consider impact of our activities on the planet and the finite resources available.

![Picture 1.svg](https://nablaflow-cms-uploads-production.s3.eu-west-1.amazonaws.com/Picture_1_312128d82d.svg)
 
More and more great-performing organizations use [aerodynamic simulations](https://nablaflow.io/en/aerocloud) within their different design phases. According to one of the [Aberdeen Group’s reports](https://www.aberdeen.com/), the design engineers can create 27% fewer prototypes since they adopted CFD simulation tools within their workflow. The direct impact on their overall time spent on the design workflow decreased by 29%.  Besides the time spent on design phase, the engineers relying on simulations during the different design phases, have noticed an increase in their product quality, meeting the deadlines easier, cutting cost and improve their revenue.

## Urban climate CFD modelling helps generate more climate friendly cities and habitats
High performant computing [CFD innovative](https://nablaflow.io/en/archiwind) solutions can help cutting down on the resources spent on creating wind and thermal-proofed cities, while also generating more value and faster. Not only do we now have the technology to help us build a better future for the next generation, but we can also benefit from its cost-effectiveness and fast implementation. To help improve life standards for all. According to the researcher [Parham A. Mirzaei](https://www.sciencedirect.com/science/article/abs/pii/S2210670721001293), “urban climate is recognized as one of these challenges, impacting on the daily life, health, comfort, economic and social behavior of city inhabitants”.

![Picture 2.svg](https://nablaflow-cms-uploads-production.s3.eu-west-1.amazonaws.com/Picture_2_0734b7c298.svg)
 
The urban climate can be influenced by many factors and can be unsteady, but each city or area has its own pattern. Some places can be predominantly windy, but other cities can be overheated. Urban climate CFD models and simulations can help find design and planning solutions for improvement. CFD can resolve the transfer of heat and mass and their interaction with individual obstacles such as buildings and other landscape design elements.

## Commitment and alignment to the UN Sustainable Development Goals
 
![Picture 3.png](https://nablaflow-cms-uploads-production.s3.eu-west-1.amazonaws.com/Picture_3_21229e8e02.png)
 
As the world is fast changing, it is our responsibility to ensure that it changes in the direction of a more sustainable future, and we believe that simulation technology can help us on the way there. Our commitment has been also inspired by the [UN Sustainable Development Goals](https://sdgs.un.org/goals). Our mission aligns with several of them, including:
- [SDG 9](https://sdgs.un.org/goals/goal9) Build resilient infrastructure, promote inclusive and sustainable industrialization and foster innovation;
- [SDG 11](https://sdgs.un.org/goals/goal11) Make cities and human settlements inclusive, safe, resilient and sustainable;
- [SDG 12](https://sdgs.un.org/goals/goal12) Ensure sustainable consumption and production patterns;
- [SDG 17](https://sdgs.un.org/goals/goal17) Strengthen the means of implementation and revitalize the Global Partnership for Sustainable Development.

To ensure a more sustainable future, we can help enhance inclusive and sustainable urbanization, sustainable human settlement planning and management, and help improve the production pattern in many countries by building strong international partnerships and democratize the access to CFD simulations.
 
Here is how we envision the future of CFD simulations and its support for the energy transition:
- Reduce operations’ costs and waste;
- Stimulate the industrial degrowth
- Access faster, more consistent and reliable results for prototypes and solutions;
- Reduce emissions, time to market and time to scale;
- Generate more energy efficient products;
- Help build more climate friendly cities.

It is important for us to do this work because we want to help future generations have a place to live that is healthy and sustainable. We believe that we all have the responsibility to take action now so that future generations can enjoy a healthy planet and have access to clean air and water for years to come.
We strongly believe that the future can be bright and sustainable. That's why we are dedicated to helping industries build a more sustainable future for their organizations and the planet.


26365342314_f6b1651884_b.jpg

Co-founder and CEO of NablaFlow, Luca has a background in Aerospace Engineering and holds a Ph.D. in Sports Aerodynamics. He comes from the Professional Sports world, which has been helping athletes from the Norwegian Federations and from the professional cycling team Ineos Grenadiers (former Team Sky). Wave surfer with a strong connection to the ocean and the environment, Luca has also worked for the past 10 years generating research (national and international) projects to help Norway's green transition from Oil&Gas to Offshore Wind by applying his knowledge to push the boundaries of surfing. Currently leading NablaFlow, he is working on twisting how Aerodynamics are applied to a number of fields: urban pedestrian comfort, drone paths, high-performance sports, wind energy, product design, and surfboard design with the power of CFD.

Luca Oggiano 

Wind simulations can help the shift towards a greener development and sustainable innovation

We are committed to help ensure a more sustainable future 

**Trondheim, one of Norway’s windiest municipalities, recently enlisted the help of NablaFlow to investigate the possibility of extending the use of Granåsen Ski Centre to also include a big jump to facilitate freestyle skiing and snowboarding Big Air events.**

Located in Trondheim, Granåsen Ski Centre is known for hosting World Cup and Continental Cup ski jumping competitions as well as world-class biathlon and cross-country skiing competitions. The Centre has one normal-sized hill (K-90) and one large hill (K-124). The proposed plan would require the removal of parts of the existing forest and reshaping of the terrain to form the big jump and necessary landing and entry area.
However, the modification to the surrounding area of the ski jumping facilities could  affect the wind conditions, potentially worsening the conditions for the jumpers. Therefore, Trondheim kommune wanted to be informed on the likelihood and extent of the possible implications.

![Streamlines coming from the simulation run with ArchiWind, crossing the Ski Centre Area](https://nablaflow-cms-uploads-production.s3.eu-west-1.amazonaws.com/8_330e75c7e8.png)
_Streamlines coming from the simulation run with ArchiWind, crossing the Ski Centre Area_

NablaFlow conducted a CFD (Computational Fluid Dynamics) investigation of the impact of the proposed modification to the forest and terrain on the wind velocities and turbulence at the ski jumping facility. The firm used their ArchiWind tool and developed and applied some project-specific extensions to their fully automated platform to include the modeling of the effect of the forest on the wind conditions.
Simulation results showed that the big air jump would affect the local wind conditions around the big air jump but not notably in the ski jumping arena. The information obtained from the simulations allowed Trondheim kommune to make an informed decision on implementing the proposed plan. It also ensured satisfactory similar wind conditions at the ski jumping arena after implementing the modification to the forest and terrain neighboring the ski jump arena compared to before the project.

![Comparison of the wind velocity before (left) and after (right) the construction of the Big Air Jump. These images are referring to only one of the 16 wind directions taken into account for the wind analysis.](https://nablaflow-cms-uploads-production.s3.eu-west-1.amazonaws.com/7_42af5e1d70.png)
_Comparison of the wind velocity before (left) and after (right) the construction of the Big Air Jump. These images are referring to only one of the 16 wind directions taken into account for the wind analysis._

In conclusion, the study undertaken by NablaFlow for Trondheim kommune allowed for a thorough investigation into the potential effects of extending the use of Granåsen Ski Centre while ensuring the preservation of satisfactory wind conditions for ski jumping competitions.

9.png

How NablaFlow's CFD Investigation Provided Valuable Insight for Trondheim Kommune's Decision Making Process.

Frequently Asked Questions

Latest Blogs

Unleashing the Power of Accurate Aerodynamics: A Journey to Validate AeroCloud's Drag Coefficient

We are committed to help ensure a more sustainable future with the help of CFD simulations

Investigating the Possibility of a Big Jump for Freestyle Skiing and Snowboarding at Granåsen Ski Centre