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Simulation of Water Circulation Improves Safety of Swimming Pools
Posted Fri May 05, 2006 @08:52AM
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Application Since the 1980’s there have been at least 147 incidents documented of suction entrapment in swimming pools, including 36 deaths. Suction entrapment occurs when a swimmer, usually a small child, is trapped by the suction forces created by the water rushing out of the drain at the bottom of the pool. In some cases swimmers have been trapped underwater until they drowned and in others they have suffered serious injuries to various parts of their bodies.

The swimming pool industry has made serious progress in improving the safety of drains and this has reduced but not eliminated some of the injuries and deaths.


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Now Ray Cronise, Co-Founder of Trilogy Pools, has come forward to state that the premise under which drains were included on the vast majority of pools that have been built is faulty. He concludes that the deaths and injuries caused by suction entrapment can be completely eliminated, without any negative effects, by sealing the drains in existing pools and not building drains in new pools.

Cronise’s ideas strike at the heart of one of the main principles of swimming pool design. “The pool industry has long used drains because of the belief that they are required in order to provide circulation throughout the pool so that contamination will not remain in stagnant areas but will rather quickly pass through the filter where it can be removed,” Cronise said. He approaches the problem from a different direction, asking whether the drain is necessary and even questioning whether there is any advantage to having a drain in the first place.

With a technical background that includes both undergraduate and graduate degrees in chemistry, Cronise knew that advancements in the last several decades have made it possible to simulate the flow of fluids with a great deal of accuracy. Cronise and Dave Schowalter, a lead consulting engineer with Fluent, the largest developer of computational fluid dynamics (CFD) software, worked together to simulate the flow of water through computer models of swimming pools. The simulation involved placing contaminants in various areas of the pool and tracking the amount of time needed to remove them using the pool’s circulation system both with and without drains.

The simulation showed that the contaminant concentration was actually higher at most of the monitoring points in the pool with a drain during the first 1000 seconds of the simulation. But at about the 1000 second point, the contamination in the pool with a drain dropped to the level of the pool without a drain and the two pools showed essentially identical results from that point on. The simulation showed that inlets and skimmers alone are sufficient to clear contamination to levels of about 0.0015 within about 1000 seconds. After that point, the circulation system continues to reduce the level of contamination to about 0.001 after 6000 seconds.

"The circulation of water is something that is nearly impossible to see and very difficult to measure so in many cases pool designers have been using drains simply because the pools that were built in the past have used them," Cronise concluded. "But CFD simulation clearly shows that drains not only are not necessary, but they do not improve the circulation in a pool or enable its ability to clear contamination. The number of injuries and deaths caused by drains in pools is not large compared with other hazards, yet future deaths and injuries can be prevented at no additional cost simply by getting rid of the drains."

The Senate Subcommittee on Consumer Affairs, Product Safety and Insurance is scheduled to discuss pool safety on May 3rd at 2:30. Proponents of reducing pool hazards, including representatives of safety and industry organizations as well as concerned citizens, are prepared to provide both oral and written testimony. Information regarding the hearing will be posted on the US Senate Committee website.

About Trilogy Pools

Trilogy is located in Fayetteville, TN, and is a leading composites manufacturer focused on the pool and spa market. Its products are sold throughout the country through a network of pool builders. Trilogy has taken a leadership role in pool safety and has continued to participate in voluntary standards development including IAF/ANSI standards for residential and public pools as well as the draft IAF standard for entrapment avoidance. Trilogy founders have served on the Association of Pool and Spa Professionals Builders Council, Builders Education Committee and Technical Council. In addition, the company has participated significantly with the American Composites Manufacturing Association (ACMA) serving on the Technical Committee, Composites Manufacturing Magazine Steering Committee, and as a contributing editor to CM Magazine.

About Fluent

Fluent is the world's largest provider of computational fluid dynamics (CFD) software and consulting services. Fluent's software is used for simulation, visualization, and analysis of fluid flow, heat and mass transfer, and chemical reactions. It is a vital part of the computer-aided engineering (CAE) process for companies around the world and is deployed in nearly every manufacturing industry. Using Fluent's software, product development, design and research engineers build virtual prototypes and simulate the performance of proposed and existing designs, allowing them to improve design quality while reducing cost and speeding time to market. Fluent's corporate headquarters are located in Lebanon, New Hampshire, USA, with offices in Belgium, England, France, Germany, India, Italy, China, Japan and Sweden. Its CFD software is also available around the world through joint ventures, partnerships, and distributors in Korea, Australia, Brazil, China, Taiwan, the Czech Republic, Middle East, and most European countries.

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