The science of riding a bike

The science of riding a bike

NDN2022 participants are in for a treat as Professor Bert Blocken will reveal some of the aerodynamics secrets which help professional cycling teams perform their best.

Any cycling enthusiast will recognize the names Jumbo Visma and Groupama FDJ. Both these world-class professional cycling teams have acquired assistance from civil engineering professor Bert Blocken.

“A building and the body of an athlete are both non-aerodynamic objects, and from a scientific point of view the associated problems are similar in many ways,” says Bert Blocken.

At the NDN2022, Bert Blocken will provide an insight into the behind-the-scenes science helping professional cyclists gaining the last margins which may well mean the difference between victory and a secondary result.

Sports projects inspire research in buildings

Since the interview is an appetizer for the conference, not all details will be revealed here. Still some pointers:

“For a building you will roughly know in advance how the aerodynamics will work, but athletes’ torsos are different, and you must study them individually to find the optimal positions for each one. Also, factors like the roughness of the clothing, the shape of the wheel, the shape of helmets, etc. are important,” Bert Blocken explains.

Not everybody is a sports enthusiast. Some people might consider science behind cycling performances to be less serious in comparison to, say, calculating the wind tear at the surface of a building.

“The requirements are actually significantly stricter when we do sports projects. For a building, you will normally consider an accuracy of 10 % to be adequate. In professional cycling, this would deem your results worthless. You need 1 % accuracy – at least! In this way, the sports projects push us to the limit as modelers. And the insights which we acquire in the sports projects is something we can bring back to inspire our research in buildings, climate etc.”

“If only I had known then, what I know today”

Also pushed to the limit is the demand for computing power.

“For a cyclist, a lot of the physics happen in a very thin layer of air close to the body surface. We are talking about a layer just a few 10s of microns thick. To model the aerodynamics properly, you will need some 10-100 million data points. This is much more than we need when looking at buildings. When we model the aerodynamics of a building or even a small part of an urban environment, we can usually make do with time at a small local cluster. But when we do sports aerodynamics, we need High-Performance Computing.”

Not surprisingly, Bert Blocken is a keen cyclist himself.

“Well, as a young rider I was quite good. But that was 25 years and 25 kilograms ago!”

With the knowledge he has today, what would he had done differently back in the day?

“Many things. I often think that if only I had known, what I know today. Just to take an example: after a training session, we would usually ride home side-by-side. That is the worst you can do. When two cyclists ride next to each other, they both must put in 8 % extra power to overcome the increased air resistance. That is quite a lot when you are already exhausted from your hard training.”

Massively popular online course

The first scientific interest in cycling aerodynamics came in 2005, when Bert Blocken was approached by physiology professor Peter Hespel, who advises the QuickStep team. Even though Bert Blocken was both highly qualified professionally and had a keen private interest in sports aerodynamics, he still had to overcome resistance as he entered the field.

“In the beginning, some of my colleagues were skeptical.”

This all changed in 2012. First, a national TV station did a program based on his research on cycling aerodynamics. And soon after, Bert Blocken developed Eindhoven University’s first Massive Open Online Course (MOOC) on the Coursera platform. Entitled “Sports & Building Aerodynamics” the first edition of the course attracted more than 20,000 students from a large number of countries. The success of the course – which remains highly popular – put an end to any suggestions that sports aerodynamics would not be serious science.

Participants at the NDN2022 will have the chance to see for themselves. And perhaps even acquire a useful tip or two on how to optimize their own bike riding.

Bert Blocken is a Professor at the Department of the Built Environment at Eindhoven University of Technology (TU/e) in the Netherlands and at the Department of Civil Engineering at KU Leuven in Belgium.

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