Aerodynamic Simulation Reveals Best Position in a Peloton of Cyclists

July 5, 2018

Professor Bert Blocken, Eindhoven University of Technology (TU/e) and KU Leuven is recognized worldwide for his thorough scientific investigations about elite cycling sport. His research helps to better understand, among others, the best downhill position to adopt by a cyclist, aerodynamic benefits provided by a following car or motorbikes, which are all conditions that impact the result of the race. In a new 2018 project, Professor Bert Blocken conducted the largest numerical simulation ever done in the sport industry and cycling discipline. The goal was to understand the aerodynamic interactions in the entire peloton revealing unexpected results.

The cyclist pushes air in front of him (red) and creates a depression in its back. This air resistance induces the drag.

The simulation results confirm that the best position is in the core of the peloton close its head, row 12 to 14; but the computer models surprisingly calculates that the drag experienced by the athletes in this position is 10 to 20 times less than for an isolated cyclist; so far the scientific community considered that the drag was only 2 or 3 times smaller in the peloton.

While biking, cyclists push air in front of them creating an over pressure (in red) and a depression in its back (blue); this air resistance that the athlete continuously has to fight is known as the drag.

Because of the aerodynamic interactions with the surrounding cyclists, the athlete at the center of the pack is literally entrained by the peloton induced air motion. Using ANSYS Fluent running on a Cray, the largest computer model ever done with 3 billion cells to accurately predict the flow pattern in between each cyclist of the peloton enables Prof Bert Blocken to create a complete map of the drag experienced by all cyclists. Compared to the drag of an isolated cyclist the air resistance experienced at the core of the peloton is reduced by up to a factor 20! (down to 5% of an isolated cyclist): it is approximately 4 times easier to bike at the core of the peloton than alone.

Map of the drag reduction compared to an isolated cyclist; circled in red is the best position with favorable aerodynamic conditions while staying close to the head of the race.

“We are closely collaborating with elite athletes who want to benefit from advanced technology. These results teach them how important it is to stay well sheltered in the peloton as long as possible: you save a lot of energy and remain fresh until the final rush of the race” explains Prof Bert Blocken (TU/e and KU Leuven). He added “These results were so surprising that we also set up a wind tunnel test and successfully validated the numerical results with the largest wind tunnel experiment we have ever done”.

“Supercomputers handle the most challenging simulation, analytics and AI workloads imaginable,” said Dominik Ulmer, director of Operations in EMEA at Cray. “Because Cray systems deliver extreme scalability and performance, they are essential to gaining better understanding of complex problems.”

“In a time when simulation is crucial to accelerate and amplify innovation for High Tech industries, the peloton project and is surprising results illustrate that this simulation technology is truly pervasive and can make a huge difference in a popular sport such as cycling,” concludes Thierry Marchal, Global Industry Director for Sports and Healthcare at ANSYS.

An experimental wind tunnel validation confirms the surprising results revealed by the large CFD computer model. The yellow cyclist identifies one of the very advantageous positions with 5 to 10% calculated drag.

About Professor Bert Blocken

Prof. dr. ir. Bert Blocken is a Civil Engineer holding a PhD in Building Physics. He is Full Professor in the Department of the Built Environment at Eindhoven University of Technology (TU/e) in the Netherlands and part-time Full Professor in the Department of Civil Engineering at KU Leuven in Belgium. His main areas of expertise are urban physics, wind engineering and sports aerodynamics. He developed TU/e’s first Massive Open Online Course (MOOC) entitled “Sports & Building Aerodynamics” on the Coursera platform. He has published 148 articles in international peer-reviewed journals. He has received the 2013 Junior Award from the International Association of Wind Engineering and six best paper awards from the Elsevier ISI journal Building & Environment (2009, 2011 and 2012) and at international conferences. According to the 2016 Academic Ranking of World Universities (Shanghai Ranking) & Elsevier, he is among the 150 most-cited researchers worldwide both in the field of Civil Engineering and in the field of Energy Science & Engineering. He is an Editor of the journal Building & Environment and Associate Editor of the Journal of Wind Engineering & Industrial Aerodynamics. He is member of the editorial board of the journals Building Simulation and Sports Engineering. He has acted as a reviewer for more than 70 different ISI journals. He is currently supervising a team of 4 senior researchers, 25 PhD students and 4 MSc students.

In previous years, the lead researcher professor Bert Blocken and his co-workers also investigated (see figure below):
● The aerodynamic benefit for a first cyclist followed by a second one
● The aerodynamic benefit for a cyclist by a following car
● The aerodynamic benefit for a cyclist by a following motorcycle
● Which cycling hill descent position is aerodynamically superior (focused on the downhill position by Chris Froome in the 2016 Tour de France – Peyresourde descent)

All these studies were performed with the same methods (ANSYS CFD and wind tunnel research); they were published in top scientific journals (see files on USB drive). An article discussing the Peloton study will be published soon in a leading scientific journal.

About TU Eindhoven

Eindhoven University of Technology (TU/e) in the Netherlands is a research university specializing in engineering science & technology. Our education, research and knowledge valorization contribute to science for society (solving the major societal issues and boosting prosperity and welfare), science for industry (the development of technological innovation in cooperation with industry) and science for science (progress in engineering sciences through excellence in key research cores and innovation in education). The research group Wind Engineering & Sports Aerodynamics led by Professor Bert Blocken of the Department of the Built Environment focuses on numerical simulation with Computational Fluid Dynamics (CFD), wind-tunnel testing and field measurements for fundamental and applied research in buildings and city aerodynamics and sports aerodynamics. Visit http://www.urbanphysics.net for more information.

About ANSYS, Inc.

If you’ve ever seen a rocket launch, flown on an airplane, driven a car, used a computer, touched a mobile device, crossed a bridge or put on wearable technology, chances are you’ve used a product where ANSYS software played a critical role in its creation. ANSYS is the global leader in engineering simulation. Through our strategy of Pervasive Engineering Simulation, we help the world’s most innovative companies deliver radically better products to their customers. By offering the best and broadest portfolio of engineering simulation software, we help them solve the most complex design challenges and create products limited only by imagination. Founded in 1970, ANSYS is headquartered south of Pittsburgh, Pennsylvania, U.S.A., Visit www.ansys.com for more information.

About Cray, Inc.

Cray Inc. (Nasdaq:CRAY) combines computation and creativity so visionaries can keep asking questions that challenge the limits of possibility. Drawing on more than 45 years of experience, Cray develops the world’s most advanced supercomputers, pushing the boundaries of performance, efficiency and scalability. Cray continues to innovate today at the convergence of data and discovery, offering a comprehensive portfolio of supercomputers, high-performance storage, data analytics and artificial intelligence solutions. Go to www.cray.com for more information.

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