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Tuesday, January 29, 2019

Revealing Results Of Drafting Research

One trailing swimmer drafting off a lead swimmer.

One trailing swimmer drafting between two leading swimmers.

Courtesy of Nature.

Nature is a British scientific journal, one of the world's most respected scientific journals and one of the world's top academic journals that publishes original research across a wide range of fields.

In the field of fluid dynamics, Zhi-Ming Yuan, Mingxin Li, Chun-Yan Ji, Liang Li, Laibing Jia and Atilla Incecik at the University of Strathclyde in Glasgow published research about drafting among swimmer in an article titled Steady hydrodynamic interaction between human swimmers published on January 23rd.

They write, "The main purpose of this study is to find the mechanism of the hydrodynamic interaction between human swimmers and to quantify this interactive effect by using a steady potential flow solver."

The researchers focused on swimmers in the open water and used hydrodynamic models of simplified human-like figures to calculate the benefits of drafting.

When swimming at 2 meters per second - a world-class swimming speed of 50 seconds per 100 meters, they determined that the optimal drafting position is 6.8 meters behind the leader and 1.7 meters to the leader’s side to benefit from a maximum total drag reduction of 30%.

"I understand the theoretical situation that is analyzed and studied by researchers using a model dummy, but since the speed of the average -or even world-class elite - open water swimmer is significantly slower than 2 meters per second and the dynamics of open water conditions are dramatically different than theoretical modeling studied in a laboratory with a mock human torso, I believe the optimal drafting position by a trailing swimmer to a lead swimmer is significantly closer in real-world racing conditions than that was determined by academic researchers," commented Steven Munatones.

"In a competitive race - whether it involves the world's fastest swimmers like Thomas Lurz, David Davies, and Vladimir Dyatchin racing in the world championships - that is shown on left - or in an amateur open water swim [shown above] with competitive masters swimmers like Parks Wesson, Bryan Buck, Bill Ireland, Lyle Nalli, and Ryan Ballance in the Naples Island Swim & SUP, the drafting positions are quite similar - and that tells me swimmers over the years - like migrating birds intuitively know the most optimal position for drafting in competitive situations."

Read the study here.

Munatones added, "Everyone in the open water swimming world - whether drafting in a race or slipstreaming by a boat - understands and appreciates the value of drafting in open water. But how much is drafting worth? How much faster can an athlete race while drafting in the slipstream of another swimmer in competition?

It is one thing to test out and compare the differences of swimming fast in a test lab with the analysis of a researcher. Especially with a dummy model that would create an unnatural wake that is not replicable in real-life conditions. But what is the actual value of drafting in the heat of competition among world-class swimmers?

We compared the times of the world-class swimmers at the 2013 FINA World Championships in Barcelona in both the solo 5 km event and the 5 km team pursuit event. Both courses were held on the same course on different days. While this comparison is not an exact measure where differences in conditions come into play, a comparison does give an indication of the value of drafting among world-class open water athletes.

The 2013 FINA World Championships in Barcelona were held in a harbor under conditions that were similar: low winds, little surface turbulence, and comfortable water temperatures. So the differences in the relative conditions were minimal. On the other hand, the conditions of swimming while facing extreme physicality in a pack is remarkably different than swimming in a team pursuit race where swimmers have the advantage of clean water and pure drafting.

Additionally, while the women generally swam much faster in the team event while drafting off of their faster male teammates, the men were conversely significantly faster in the solo event where they were able to swim at 100%.

Eva Fabian drafting behind leader Megan Rankin in the photo above.

At the extreme ends of the spectrum, Germany's Isabelle Franziska Harle swam nearly 4 minutes faster swimming behind teammates Christian Reichert and Thomas Lurz in the team pursuit event compared with her 5 km solo race among women. This time differential equates to at least 325 meters in distance - light years in the open water swimming world. Conversely, New Zealand's Kane Radford was 2 minutes 24 seconds slower and Chad Ho was 3 minutes in their 5 km team pursuit efforts versus their swims in the solo 5 km.

The differences between men and women among the different countries is below:

Thomas Lurz 52:52.0 (team) vs. 53:32.2 (solo)
Isabelle Franziska Harle 52:54.9 (team) vs. 56:46.2 (solo)

Kalliopi Araouzou 54:03.3 (team) vs. 56:45.3 (solo)

Samuel De Bona 54:03.3 (team) vs. 53:34.9 (solo)
Poliana Okimoto Cintra 54:03.5 (team) vs. 56:34.4 (solo)

Jarrod Poort 54:15.8 (team) vs. 53:34.3 (solo)

Luca Ferretti 54:32.7 (team) vs 53:47.1 (solo)
Rachele Bruni 54:34.0 (team) vs. 56:48.1 (solo)

Andrew Gemmel 54:42.4 (team) vs. 53:38.7 (solo)
Sean Ryan 54:43.1 (team) vs. 53:45.9 (solo)
Haley Anderson 54:44.7 (team) vs. 56:34.2 (solo)

Kane Radford 56:08.6 (team) vs. 53:44.3 (solo)
Cara Baker 56:11.7 (team) vs. 56:46.2 (solo)
Phillip Ryan 56:12.0 (team) vs. 56:17.5 (solo)

Damien Cattin-Vidal 55:25.8 (team) vs. 53:38.4 (solo)
Aurelie Muller 55:26.3 (team) vs. 56:46.5 (solo)

Mark Papp 56:05.8 (team) vs. 53:55.3 (solo)
Anna Olasz 56:09.4 (team) vs. 56:58.4 (solo)

Evgeni Drattcev 56:06.9 (team) vs. 53:38.6 (solo)
Anastasia Azarova 56:08.7 (team) vs. 57:04.3 (solo)

Eric Hedlin 57:10.7 (team) vs. 53:31.6 (solo)
Philippe Guertin 57:08.0 (team) vs. 53:46.4 (solo)

Chad Ho 56:33.4 (team) vs. 53:33.7 (solo)
Daniel Marais 56:34.4 (team) vs. 53:51.0 (solo)
Kyna Pereira 56:34.7 (team) vs. 57:30.8 (solo)

Ivan Alejandro Enderica Ochoa 1:00:30.5 (team) vs. 53:36.7 (solo)
Katia Paola Barros Esquivel 1:00:32.6 (team) vs. 57:26.4 (solo)

Johndry Segovia 58:59.9 (team) vs. 54:02.3 (solo)
Florencia Melo 58:59.4 (team) vs. 1:01:32.5 (solo)

Adel Ragab 1:00:57.2 (team) vs. 54:20.4 (solo)
Youssef Hossameldeen 1:00:57.9 (team) vs. 57:08.5 (solo)
Laila El Basiouny 1:01:02.2 (team) vs. 1:01:52.4 (solo)

Vitaliy Khudyakov 1:00:13.2 (team) vs. 54:24.8 (solo)

Seifeddine Sghaier 59:16.3 (team) vs. 57:10.1 (solo)
Maroua Mathlouthi 59:19.4 (team) vs. 59:51.8 (solo)

Ching Leung Sunny Poon 1:01:26.6 (team) vs. 1:00:05.9 (solo)
Chun Hong Li 1:01:41.5 (team) vs. 1:00:15.9 (solo)

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