Sandia RAPTOR turbulent combustion code selected for next-gen Summit supercomputer readiness project
RAPTOR, a turbulent combustion code developed by Sandia National Laboratories mechanical engineer Dr. Joseph Oefelein, was selected as one of 13 partnership projects for the Center for Accelerated Application Readiness (CAAR). CAAR is a US Department of Energy program located at the Oak Ridge Leadership Computing Facility and is focused on optimizing computer codes for the next generation of supercomputers.
Developed at Sandia’s Combustion Research Facility, RAPTOR, a general solver optimized for Large Eddy Simulation (LES, a mathematical model for turbulence), is targeted at transportation power and propulsion systems. Optimizing RAPTOR for Summit’s hybrid architecture will enable a new generation of high-fidelity simulations that identically match engine operating conditions and geometries. Such a scale will allow direct comparisons to companion experiments, providing insight into transient combustion processes such as thermal stratification, heat transfer, and turbulent mixing.
Unlike conventional LES codes, RAPTOR is a DNS [direct numerical simulation] solver that has been optimized to meet the strict algorithmic requirements imposed by the LES formalism. The theoretical framework solves the fully-coupled conservation equations of mass, momentum, total-energy, and species for a chemically reacting flow. It is designed to handle high Reynolds number, high-pressure, real-gas and/or liquid conditions over a wide Mach operating range. It also accounts for detailed thermodynamics and transport processes at the molecular level, and is sophisticated in its ability to handle a generalized model framework in both the Eulerian and Lagrangian frames.
A noteworthy aspect of RAPTOR is it was designed specifically for LES using non-dissipative, discretely conservative, staggered, finite-volume differencing. This eliminates numerical contamination of the subgrid models due to artificial dissipation and provides discrete conservation of mass, momentum, energy, and species, which is an imperative requirement for high quality LES.— Oefelein (2013)
Ultimately, this work will help inform new design concepts of internal combustion engines and gas turbines, which have the potential to provide significant increases in fuel efficiency with minimal emissions.
|Instantaneous particle distribution superimposed on the corresponding turbulent velocity field. The calculations were performed using RAPTOR. Oefelein (2013). Click to enlarge.|
Summit, a high-performance computing system set to be delivered to Oak Ridge National Laboratory (ORNL) in 2017 with availability in 2018, will support DOE’s Office of Science in its broad science and energy mission, advancing knowledge in critical areas of government, academia and industry.
The CAAR program is focused on optimizing application codes for Summit’s hybrid architecture comprising IBM POWER CPUs, NVIDIA GPU accelerators and the NVLink high-speed interconnect technology—expected to provide at least five times the performance of the OLCF’s current leadership system, Titan.
Leading up to the delivery of Summit, the CAAR application teams, with technical support from the IBM/NVIDIA Center of Excellence at ORNL, will redesign, port and optimize their software to Summit’s architecture, and demonstrate the effectiveness of their application on Summit through a scientific grand-challenge project.
RAPTOR was chosen as a partnership project for its importance in discerning the complex fuel injection and combustion processes in modern engines and because it has demonstrated good scaling properties for operation on massively parallel supercomputers.—Joseph Oefelein
|LES reveals how fuel from a state-of-the-art injector mixes with air inside an engine cylinder. Image credit: Joseph Oefelein and Daniel Strong, Sandia National Laboratories, 2011. Click to enlarge.|
Future supercomputers will use increasingly complex arrangements of multicore processors and graphics processor units to minimize electrical power consumption. With each new generation of supercomputers, scientists must adapt their complex codes to leverage advances in computational power and speed.
The readiness projects were chosen based on a computational and scientific review conducted by the OLCF in consultation with the ALCF, NERSC, IBM and NVIDIA. The application teams represent a broad range of computational algorithms and programming approaches in a diverse range of scientific disciplines including astrophysics, biophysics, chemistry, climate modeling, combustion engineering, materials science, nuclear physics, plasma physics and seismology.
In addition to RAPTOR, the modeling and simulation applications selected for the CAAR program and their principal investigators include:
- Climate simulation code ACME, Dr. David Bader, Lawrence Livermore National Laboratory
- Relativistic chemistry code DIRAC, Prof. Lucas Visscher, Free University of Amsterdam
- Astrophysics simulation code FLASH, Dr. Bronson Messer, Oak Ridge National Laboratory
- Plasma physics code GTC, Dr. Zhihong Lin, University of California-Irvine
- Cosmology simulation code HACC, Dr. Salman Habib, Argonne National Laboratory
- Electronic structure application LS-DALTON, Prof. Poul Jørgensen, Aarhus University
- Biophysics simulation code NAMD, Prof. Klaus Schulten, University of Illinois at Urbana-Champaign
- Nuclear physics application NUCCOR, Dr. Gaute Hagen, Oak Ridge National Laboratory
- Computational chemistry code NWCHEM, Dr. Karol Kowalski, Pacific Northwest National Laboratory
- Materials science application QMCPACK, Dr. Paul Kent, Oak Ridge National Laboratory
- Seismology application SPECFEM, Prof. Jeroen Tromp, Princeton University
- Plasma physics code XGC, Dr. C.S. Chang, Princeton Plasma Physics Laboratory
Joseph C. Oefelein (2013) “Large Eddy Simulation of Complex Thermophysics in Advanced Propulsion and Power Systems” 8th US National Combustion Meeting