#DrivenBy: Nikolaos Karras

The aerodynamics department of the Mercedes-AMG Motorsport DTM Team approaches the issue from various angles. These include working with 50-percent scale models in the wind tunnel and performing Computational Fluid Dynamics (CFD) simulations. Nikolaos Karras (30) operates in the area of Trackside Aerodynamics using a working Mercedes-AMG C 63 DTM. He and his colleagues put the track-ready version of the car through the full-scale wind tunnel as well performing aerodynamic test drives at small airports in Germany or Southern Europe. The objective is to gather as much data as possible.

Nikolaos, surely your job was done after the homologation of the new car on 1st March?

Nikolaos Karras: Actually, no. For me, that was when things really started happening. Ahead of every event, I draw up a document in which we record what is being tested and the outcomes we have set for ourselves. It’s the same before every race weekend. For example, I record the aero sensitivities of the vehicle. In other words, how would the car behave if the ground clearance were increased or decreased at either the front or the rear? I also participate in groups working on the setup. We use simulations to see which setup would be better in theory. So as you can see, I am involved in all the setup work.

How much of your work consists of computer simulation?

Nikolaos Karras: Everything we test goes through CFD. First we come up with an idea, next we simulate it in CFD, and then the most promising options are tested on scale models in the wind tunnel. The best of these is then transferred to the vehicle. If appropriate, we will test two options against each other. An important point for us is what we call ‘correlation’. We try to correlate the results from the simulation, from the small and the large wind tunnel as well from the race track to ensure that the sequence is giving us a true picture and that we are seeing and reading everything correctly. This is an ongoing process.

How closely do you work with the performance engineers?

Nikoloas Karras: I work very closely with the performance engineers and vehicle managers. That includes Fabien `{`Chenin`}` who is responsible for tyres. Aerodynamics is a vital element in the overall system. If the aero is wrong, you don’t have any downforce and you’re much too slow on the corners. At the start of the season, after completion of the test drives, I create a so-called ‘aero-map’. This is a multi-dimensional aerodynamic model with parameters such as ground clearance, rolling behaviour, wing angles etc. From these, we can calculate the applicable downforce and air resistance, which we then use for our lap time simulation. On a race weekend, I’m looking at all of our cars in equal measure. For example, if one of our drivers complains about understeer or oversteer, I look at his data in comparison to that of the others, and I’m then able to make suggestions for a resolution of the problem.

What personal qualities are particularly important in your job?

Nikolaos Karras: First and foremost, you have to be a perfectionist. If my aero-map is inaccurate, none of the simulations will be correct. That puts you under a good deal of pressure. Consequently, the model has to be constantly correlated against track data and tests. It is therefore crucial that the tests are done well and methodically. There has to be this high level of accuracy and complex data analysis. Also, you need to have a passion for your work. You have to get underneath the car and see if all the aero elements are in place, precisely as specified. So you should not be so precious as to worry about getting your hands dirty. But it’s also a lot of fun working with the mechanics and getting their input. After all, they can see things on the car that I might miss.

You’ve mentioned the importance of passion. Is motor racing more than a profession for you?

Nikolaos Karras: Of course, motor racing is also one of my hobbies. Otherwise, I would be out of place here. This interest began as a child during the Michael Schumacher era. Since I was three years old, I have also played club football. In recent years, I’ve been a member of the Sportfreunde Stuttgart. There is the same kind of family atmosphere there that you find in motorsport. So as you can see, team spirit is important to me, both at work and in my leisure time.

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