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Simulation breaks 1 billion computational cell barrier

An Italian research team headed by Ignazio Maria Viola, a member of the engineering group that worked with the Luna Rossa Challenge team for the 2007 America's Cup yacht racing competition, conducted a landmark simulation, using Ansys software, during August 2008 to investigate the aerodynamics of an America's Cup yacht. As the use of simulation becomes increasingly mission-critical in creating 'winning' products - and at the same time reducing cost and cycle time - resolving this scale of problem becomes imperative in order to address the simulation of full systems or subsystems.

Computational cells are an essential element in the engineering simulation process. To perform a simulation, the surface area and/or volume of the geometry under consideration is broken down into hundreds of thousands, or millions, of smaller domains known as cells. Equations are solved to predict fluid flow or stress within each cell to produce an overall total simulation solution. The higher the cell count, the more detailed and comprehensive the simulation can be. Just 15 years ago, simulations of 60,000 cells were considered groundbreaking. More recently, simulations using hundreds of millions of cells have been performed by leaders in the industry. Exceeding 1 billion cells for a simulation has been the latest stretch goal for those pushing the envelope in engineering simulation.

For the 1 billion cell simulation, engineers from two prominent Italian engineering organisations worked alongside Dr Viola to perform the study. Raffaele Ponzini represented CILEA (the inter-university consortium for information and communication technologies, named Consorzio Interuniversitario Lombardo per L'Elaborazione Automatica), an organisation that made available its supercomputer Lagrange, ranked among the most powerful in the world, to power the simulation. Giuseppe Passoni represented the Politecnico di Milano (Polytechnic of Milan), an institution internationally renowned for its expertise in fluid dynamics. In addition, the Regione Lombardia (regional government in Lombardy, Italy) provided finance for the project.

Simulation of an America's Cup racing yacht has the potential to include some of the most complex physics effects possible, with hydrodynamic and aerodynamic fluid flow and stiffness among the structural physics involved. The 1 billion cell-plus simulation case focused on the aerodynamic impact of wind on the America's Cup racing yacht sailing downwind, with a particular emphasis on the mainsail and an asymmetrical spinnaker. A reconstructed fluid dynamics geometry was used for the study based on work done using a wind tunnel at the Politecnico di Milano. The supercomputer used was CILEA's HP Cluster Platform 3000BL with Linux, a system equipped with 208 HP ProLiant BL460c server blades and Intel Xeon 3.166 GHz quad-core central processing units (CPUs). Total peak performance of the system approached 22 teraflops (22 thousand billion floating point operations) per second; the system has recently been ranked number 135 on the Top500 list of supercomputers.

The huge analysis was completed in 170 hours, a little more than a week, achieved by the parallel processing performance of the software on the highly scaled computing resource. This time frame is considered commercially viable when the value of the complex problem solution is mission critical. The simulation results were compared to experimental wind tunnel testing data to benchmark the accuracy, with good agreement being found.

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