Large eddy simulation of a turbulent buoyant helium plume

Abstract

At the Institute for Clean and Secure Energy at the University of Utah we are focused on education through interdisciplinary research on high-temperature fuel-utilization processes for energy generation, and the associated health, environmental, policy and performance issues. We also work closely with the government agencies and private industry companies to promote rapid deployment of new technologies through the use of high performance computational tools.Buoyant flows are encountered in many situations of engineering and environmental importance, including fires, subsea and atmospheric exhaust phenomena, gas releases and geothermal events. Buoyancy-driven flows also play a key role in such physical processes as the spread of smoke or toxic gases from fires. As such, buoyant flow experiments are an important step in developing and validating simulation tools for numerical techniques such as Large Eddy Simulation (LES) for predictive use of complex systems. Large Eddy Simulation is a turbulence model that provides a much greater degree of resolution of physical scales than the more common Reynolds-Averaged Navier Stokes models. The validation activity requires increasing levels of complexity to sequentially quantify the effects of coupling increased physics, and to explore the effects of scale on the objectives of the simulation.In this project we are using buoyant flows to examine the validity and accuracy of numerical techniques. By using the non-reacting buoyant helium plume flow we can study the generation of turbulence due to buoyancy, uncoupled from the complexities of combustion chemistry.We are performing Large Eddy Simulation of a one-meter diameter buoyancy-driven helium plume using two software simulation tools -- ARCHES and Star-CCM+. ARCHES is a finite-volume Large Eddy Simulation code built within the Uintah framework, which is a set of software components and libraries that facilitate the solution of partial differential equations on structured adaptive mesh refinement grids using thousands of processors. Uintah is the product of a ten-year partnership with the Department of Energy's Advanced Simulation and Computing (ASC) program through the University of Utah's Center for Simulation of Accidental Fires and Explosions (C-SAFE). The ARCHES component was initially designed for predicting the heat-flux from large buoyant pool fires with potential hazards immersed in or near a pool fire of transportation fuel. Since then, this component has been extended to solve many industrially relevant problems such as industrial flares, oxy-coal combustion processes, and fuel gasification.The second simulation tool, Star-CCM+, is a commercial, integrated software environment developed by CD-adapco, that can be used to simulate the entire engineering simulation process. The engineering process can be started with CAD preparation, meshing, model setup, and continued with running simulations, post-processing, and visualizing the results. This allows for faster development and design turn-over time, especially for industry-type application. Star-CCM+ was build from ground up to provide scalable parallel performance. Furthermore, it is not only supported on the industry-standard Linux HPC platforms, but also on Windows HPC, allowing us to explore computational demands on both Linux as well as Windows-based HPC clusters.