The Peloton Project: Largest-ever sports simulation yields surprising results

[Jef_Dawson]

In partnership with Cray and simulation software vendor ANSYS, Prof. Bert Blocken conducted the first aerodynamic simulation and wind tunnel test of a full peloton of 121 cyclists and, in the process, set a world record in CFD simulation.

Aerodynamics in a cycling peloton aren’t what you might expect

A peloton is the main field or group of riders in a road bicycle race like the Tour de France. While it can take different shapes, the peloton’s overall purpose is to take advantage of the effects of slipstreaming, or drafting, behind other riders in the group. Air resistance is the biggest mechanical component preventing cyclists from going faster on flat road, and slipstreaming can save up to 50 percent of their energy.

Or that was the assumption, at least

The reality is that almost no information exists on aerodynamic resistance for riders in cycling pelotons. Systematic computer simulations or measurements have never been reported before.

Professor Bert Blocken of Eindhoven University of Technology (Netherlands) and KU Leuven (Belgium) set out to fill the information gap.

In partnership with Cray and simulation software vendor ANSYS, Prof. Blocken conducted the first aerodynamic simulation and wind tunnel test of a full peloton of 121 cyclists and, in the process, set a world record in CFD simulation.

With almost 3 billion calculation cells, the Peloton Project simulation was the largest ever in sports and the largest using commercial CFD software anywhere.

Simplified mathematical models commonly assumed the resistance to be reduced to 50 or 70 percent that of an isolated rider. In fact, those numbers are 10 times too high. Teams used them to set strategy such as determining when a cyclist should try to escape the peloton. And it could explain why so few breakaways actually succeeded.

Professor Blocken’s study, for the first time, systematically investigated drag reductions in two pelotons of 121 cyclists each. The simulations were validated by four wind tunnel tests, including one with a peloton of 121 models.

The results showed that the drag of all riders in the peloton decreased compared to that of an isolated rider—but in the mid-rear section of the group, the reduction plunged to between 5 and 10 percent the drag of an isolated rider.

That’s up to 10 times less than previous assumptions, and it benefits almost half the cyclists in a peloton.

The Peloton Project by the Numbers

• 3 world-renowned universities (TU Eindhoven, KU Leuven and U Liège)
• 2 leading global companies (ANSYS and Cray)
• 3 model-building partners (Custom Company, FlexForm and Tenax)
• 4 wind tunnel tests
• 2 x 54 supercomputing hours
• 13,824 parallel processes
• More than 49,000 GB of memory
  
  

More About the Peloton Project

• Tour de France: How to cycle as fast as a pro (BBC)
• Video: What’s the one way to help you cycle faster? (BBC)
• Aerodynamic Simulation Reveals Best Position in a Peloton of Cyclists (HPCwire)
• Research quantifies advantage of riding in a peloton during bicycle races (The Engineer)
• Racing cyclist in peloton saves more energy than previously thought (De Ingenieur)
• Cycling’s Best Performance Enhancer: Riding in the Peloton (The Wall Street Journal – subscription required
  
  

This blog originally published on cray.com and has been updated and published here on HPE’s Advantage EX blog.

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Jeff Dawson
Hewlett Packard Enterprise

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