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Danish swimmer Pernille Blume wins an Olympic gold medal on the 50m freestyle with a time of 24.07. Blume is the first Danish swimmer in 68 years to win Olympic gold. Less than an hour later, Blume wins an Olympic bronze medal as a part of the 4x100m medley relay alongside Rikke Møller Pedersen, Jeanette Ottesen and Mie Ø. Nielsen. Here the fabulous four also broke the European record with a time of 3:55.01.

npr.org
Phelps Helps U.S. Men Win Relay Gold In Rio; Manuel Helps Women Snare Gold
Michael Phelps wins his 23rd career gold. American Simone Manuel picked up a silver medal and a gold, as she swam an individual race and anchored the women's medley.

Both the men’s and women’s medley relay teams repeated their golden races of the London 2012 games, with the women’s relay bringing Team USA its 1,000th gold medal in the Summer Olympic Games (dating back to 1896).

For Phelps, the win brought his 23rd gold medal and his 28th Olympic medal overall.

We also saw newly minted Olympic champion Simone Manuel – who made history this week as the first African-American woman to win a gold medal in swimming — grab a silver in the 50m freestyle before diving back in the pool later to anchor the women’s medley relay.

Photo: Al Bello/Getty Images

Querido Ex

Vi que você se envolveu com alguém de olhos claros e me desculpe pelos meus olhos castanhos escuros. Você conheceu uma pessoa mais alta do que eu e me desculpe pelos meus 1,50m. Você namorou uma pessoa forte e me desculpe por não ter tanto porte assim e ser fraca ao ponto de chorar ao te ver bem sem mim. Começou a namorar uma quarta pessoa, ou talvez uma quinta. Escreveu uma frase de uma música – que deveria ser nossa e não foi – como legenda nas fotos. Terminou o namoro. A tua vida era sempre a mesma. O mesmo ciclo. O mesmo final para todas as pessoas que se envolvessem contigo. Achei que me ausentar e me afastar do amor e negar as oportunidades que ele me dava era uma boa opção para não me magoar de novo. Foi uma péssima opção.

Só quero te dizer que não precisa me ligar outra vez, nem tentar se explicar. Eu já encontrei todas as explicações para o que você fez, já entendi que a culpa não foi minha e que me ausentar para o amor é um erro. Te disseram que eu estou bem, você me viu com outro alguém, então me ligou a pedir para me ver, disse que queria conversar, pediu permissão para se explicar, mandou mensagem a pedir para tentar outra vez, disse que se arrependeu de tudo o que fez e que andava sentindo a minha falta. Mas é que agora, agora, eu me sinto amada, de verdade, me sinto feliz. Me disseram que um dia eu ia rir de tudo isto, e não é que eu estou a rir agora?

Statistical analysis suggests possible current in the Rio Olympics swimming pool

Several news outlets, beginning with The Wall Street Journal, are reporting that the swimming pool in Rio may have had a current that biased athletes’ performances. This is based on a statistical analysis of athlete performances across the meet, conducted by Indiana University’s Joel Stager and his coworkers. According to WSJ, Stager et al. analyzed times of athletes in the preliminary, semifinal, and final races of the 50m, 800m, and 1500m events and found consistent evidence that swimmers in the higher numbered lanes swam faster when moving toward the starting block and swimmers in the lower numbered lanes swam faster when moving toward the turn end of the pool. A separate analysis by Barry Revzin at Swim Swam came to similar conclusions about the direction and magnitude of lane effect in Rio.

Past questions about lane bias

This is not the first time questions have been raised about a current-induced bias in competition pools. In fact, Stager and his colleagues published an analysis in 2014 that suggested a similar bias in the pool used for the 2013 World Championships in Barcelona. That pool was a temporary pool built specifically for the competition by Myrtha Pools and was disassembled immediately after, before Stager et al.’s analysis was published. 

A more recent paper by Stager and his colleagues found that lane bias seems to be more prevalent in temporary pools than in permanent ones. The Rio Olympics pool, like the 2013 Worlds pool, is a temporary pool also built by Myrtha Pools. 

Myrtha Pools responds to the criticism 

Myrtha responded to both WSJ and Swim Swam by sharing videos (1, 2) of their current test, which was conducted before the competition and on Day 3 of competition. The videos show a floating object in one of the outside lanes; neither video shows any noticeable movement of the object.

Fluid dynamics and swimming pool design

Competitive swimming pools are complicated recirculating systems that can contain special structures intended to minimize interactions between competitors. Myrtha has built many special event pools in recent years, including ones where the results did not show a bias. According to their website, Myrtha has fluid dynamicists on staff and uses computational fluid dynamics (CFD) to analyze pool performance during design, although they only show examples of freeform pools - not competition pools. 

In fact, I have found remarkably few CFD analyses of swimming pools in the literature. Most papers seem to focus on distribution of disinfectants in pools or in predicting evaporation rates - both practical problems but ones with limited relevance to this particular question.

So, is there a current in the Rio pool?

It’s tough to say with certainty that there is a current in Rio’s pool. The performance analyses by Stager et al. and by Revzin do show anomalies in the times of athletes in Rio based on their swim lane, and they show that those anomalies do not exist in many other recent competitions. 

I also do not think Myrtha’s current test constitutes evidence of a lack of current. Their floating object is only indicative of conditions at the air-water interface. Swimmers ride lower in the water and spend significant time completely underwater. Lane markers may also damp any flow effects near the surface. 

I think introducing dye underwater in the pool would do more to reveal any flow that may exist, and this would be a worthwhile test to conduct prior to the deconstruction of the Rio Olympic pool. Additionally, it would be wonderful to see a CFD analysis of the swimming pool, but this would require significant detail about the pool’s design (inlet and outlet locations, etc.) some of which is likely proprietary information.

Neither dye visualization nor CFD simulation will change the results of this competition, but it may help reveal underlying issues in temporary pool designs so that any bias can be avoided in future competitions. 

(Image credit: Rio City Government)

Special thanks to @MicahJGreen for bringing this story to my attention and to Dave B. for his assistance.