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CONVERGE code optimization yields three-fold increase in engine simulation speed

Researchers at the US Department of Energy’s Argonne National Laboratory are partnering with Convergent Science, Inc. (CSI), to speed up a key piece of modeling and simulation software to ensure those cycles are used as effectively as possible, reducing product development time and resulting in better engines and savings for consumers.

The research is part of Argonne’s Virtual Engine Research Institute and Fuels Initiative (VERIFI), which is working with CSI to optimize the company’s CONVERGE code, a CFD (computational fluid dynamics) program widely used in industry to conduct modeling and simulation for engine design. (Earlier post.) While the effort has been ongoing for more than two years, it has recently moved into a code optimization phase that is showing dramatic gains.

The latest round of optimization yielded a three-fold increase in speed, which correlates directly into faster design of better engines, said Janardhan Kodavasal, a postdoctoral appointee who led the optimization work along with with Marta Garcia Martinez, an assistant computational scientist, and Kevin Harms, a senior software developer at the Argonne Leadership Computing Facility.

The scale of the speed gains were recently demonstrated when researchers ran the largest engine simulation to date on more than 4,000 computer cores.

Using high-performance computer-generated models, VERIFI researchers demonstrated that in gasoline compression ignition, varying the start of injection (SOI) timing produces significant differences in the reactivity of the the fuel mixture, delaying ignition. Such high-resolution modeling was made possible by optimizing the CONVERGE for parallel read/write processes. Source: VERIFI.

Engine designers use modeling and simulation software to test new designs and tweak existing plans in a virtual space, drastically reducing time to market. When the project first started, simulations ran on systems with 50 cores. VERIFI quickly scaled up those numbers to 1,000 cores, and recently conducted an engine simulation on 4,096 cores.

The VERIFI work is focused on a key aspect of engine design—the extraordinarily complicated fluid dynamics and combustion characteristics that are at the heart of all internal combustion engines.

CONVERGE is a multipurpose computational fluid dynamics (CFD) code with innovative features including a fully coupled automated mesh created at runtime and Adaptive Mesh Refinement (AMR). CONVERGE eliminates all user meshing time; automates the setup of moving boundaries; eliminates the deforming mesh issues typically associated with moving boundaries; creates perfectly orthogonal cells, resulting in improved accuracy and simplified numerics; and maintains the true geometry, independent of the mesh resolution.

CONVERGE is also fully equipped with a detailed chemistry model and a genetic optimization tool.

Using high performance computing and X-ray radiography data from Argonne’s Advance Photon Source, VERIFI was able to gain unprecedented insight into the performance of fuel injectors in engines. Once that modeling was completed, it was incorporated into CONVERGE and is currently being used by industry partners in engine design.

The latest phase involved optimizing the CONVERGE code for greater efficiency. One of the key breakthroughs came in the area of load balancing. The varying levels of complexity in the chemistry of ignition meant that some cores weren’t actively engaged in computation, while other cores handling more complex parts of the simulation were working overtime. By balancing the computational load evenly over all the cores, great gains in efficiency were achieved.

Another important development came when the team tweaked CONVERGE to use parallel read/write processes, which allow simultaneous file writing by processors, rather than having to wait for one action to complete before taking another. This resulted in a speed up of more than 100 times in writing large data files generated by the software.

In the end, the advances mean that engine designers can try out more designs in shorter times, yielding more efficient, reliable engines with less cost.

VERIFI and CSI will be presenting the findings of the work in a forthcoming ASME paper.

VERIFI research is funded by the Vehicles Technology Office of DOE’s Office of Energy Efficiency and Renewable Energy.


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