Collaborative research: simulation and analysis of turbulent jet noise using arbitrary-order Hermite methods

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Hagstrom and Colonius This award is funded under the American Recovery andReinvestment Act of 2009 (Public Law 111-5). The investigators, with their students and postdocs, pursue an interdisciplinary project with three primary aims. The first aim is the development, optimization, and dissemination of novel computational methods based on arbitrary-order Hermite approximations that efficiently utilize petascale facilities to solve complex, multiple-scale, time-dependent systems of partial differential equations. Secondly, Hermite methods are applied to the direct simulation of turbulent jet noise at Reynolds numbers more than an order of magnitude beyond those currently available, paving the way for future simulations under flow conditions relevant to engineering design. The final goal is the development and application of post-processing techniques to use the simulation data to discover the basic physical mechanisms responsible for the jet noise, improve the inputs to engineering models, and inform strategies for noise reduction. The unique properties of Hermite methods make them ideal for high-resolution simulations on high-performance computing platforms. This is the first instance where they are fully exercised to attack a difficult problem. The methods themselves can be profitably used in any application requiring high accuracy, and a library of optimized building blocks along with templates for their application is created and made freely available to the scientific community. To understand jet noise is an immense scientific challenge. The radiated sound, which carries only a minuscule fraction of the flow energy, results from both small-scale turbulence and the complex dynamics of larger-scale coherent structures. The efficient utilization of the next generation of high-performance computing systems is hindered by the heterogeneous nature of the hardware. This project is focused on new methods that are both flexible enough for complex architectures, and powerful enough to deliver high-resolution approximations. Jet noise is an environmental problem subject to increasingly severe regulation throughout the world. To meet the ambitious noise reduction goals under discussion, a greatly enhanced understanding of the basic physics is needed. The simulations and follow-up analysis to be completed by the investigators bring us much closer to the goal of discovering the subtle physical mechanisms responsible for the acoustic radiation and to the rational design of methods to suppress it.