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The Physics of Soccer

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Event like the FIFA World Cup brings about countless physics challenges. From minute details like ensuring the material used for players’ jerseys is appropriate for the comfort of the athlete to ensuring the structural integrity of the stadium, physics plays a key role. The nature of most of these sport related problems is such that traditional methods of testing are not only impractical but also quite unreliable. Events of such magnitude just cannot be physically replicated for testing. Therefore, engineering simulation has an important role to play in improving the quality and safety of sporting events.

Hosting the 2014 FIFA World Cup is a matter of immense pride for any nation. Therefore, maintaining the integrity of the stadium, which is at the center of all the action, is crucial whether you view it from a security or a prestige point of view. In Brazil, tens of thousands of football fans can focus on the action on the pitch without having to be concerned about the structural integrity of the Estadio Nacional Mane Garrincha stadium in Brasilia stadium, thanks to engineering simulation technology from Ansys.

Simulation allows for incorporation of various design considerations that would have been unthinkable only a few decades ago. For example, in semi-open stadium design, two of the biggest challenges are limiting swirling wind on the field to avoid affecting play and protecting spectators from wind driven rain. Historically stadium designers largely ignored these factors because they were unable to determine how their design would perform till the venue had been built. But simulation is changing that. A team from Eindhoven University of Technology has conducted 3-D studies of stadium design using Ansys Fluent CFD software to demonstrate the important effects of the architecture on both wind flow and wind-driven rain.

The complexity is quite difficult to fathom. The stadium was originally built in 1974 and was refurbished to include a new facade, metal roof and stands — as well as a lowered pitch that offers unobstructed views from every seat. The stadium has capacity to hold over 72,000 spectators at a time. It is practically impossible to conduct a physical test to verify if the stadium can take this load. Now, if we add the impact of external factors such as wind and rain to mix along with the very real possibility of this 72,000 strong crowd performing the Mexican wave, any engineer would be worried if he was responsible for ensuring the structural integrity of the stadium, without the ability to test it out.

Ensuring Safety of the Stadium

Novacap, a Brazilian state company involved in construction in Brasilia, worked with Paulo de Mattos Pimenta, professor at the University of Sao Paulo to validate the stadium’s structural integrity from a wind-loading perspective. For the first time multiphysics simulation was used as the primary tool for validating the design of a major stadium in Brazil for wind loads. ”The implementing of multiphysics analysis using Ansys confirmed that the fierce Brazilian winds won’t impact the safety for spectators and teams in the stadium. Based on the analysis results, I recommended several changes, such as increasing the number of cables and cable tension,” Pimenta said.

Conducting wind tunnel analysis was an option; but the problem was that they can throw up several discrepancies when compared to real-life conditions. Besides, these tests were costly and time consuming, because they used scale models. Instead, simulation specialists at Ansys channel partner ESSS used Ansys computational fluid dynamics software to predict airflow around the stadium and pressure on the stadium roof. The specialists also used Ansys finite element analysis software to study the combined effects of wind, stadium infrastructure and a traditionally rowdy crowd. Because of tight deadlines, the validation had to be completed in 15 days, 90 percent less time than is needed to build a scale model and perform wind-tunnel testing.

A vibration analysis revealed that the stadium was properly designed and this combination of loads will not endanger the stability of the building. Numerical results were validated with experimental data from a wind tunnel. Virtual stadium design enables engineers to study wind blowing from various directions and at different speeds. Once the stadium models were created, comprehensive investigations could be performed at almost no extra cost to ensure the stadium would endure any wind conditions.

Based on the test results, several changes were recommended such as increasing the number of cables and cable tension. Engineers completed the analysis in two weeks, about one-tenth the time required for traditional wind-tunnel validation – for 66 percent lower costs compared to physical testing methods.

It has been exciting to be associated with the FIFA World Cup, one of the most exciting sporting events in the world. It demonstrated the growing breadth of industries where simulation is revolutionizing the design process by reducing the need for costly physical tests. Using engineering simulation for sporting events is not unusual though. Most iconic football and Olympic stadiums (at least since the French World Cup in 1998) have been analyzed with simulation software. So, while sports and physics may seem to reside in separate universes, they do collide at some point.

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