Mathis Bode

Multi-scale Coupling for Predictive Injector Simulations

Predictive simulations of full fuel injection systems for e.g. diesel engines could be very important for reducing emissions of current engines but are still rare. Beside the numerical issues arising from discontinuities across the liquid-gas-interface, different scales relevant for the nozzle internal flow, primary breakup in the vicinity of the nozzle, and secondary breakup and evaporation further downstream make efficient simulation of the full injection system challenging. This paper introduces a multi-scale coupling approach for overcoming this issue leading to efficient and predictive injector simulations. After a brief description of the numerical methods used in this study, the coupling among nozzle internal flow, primary breakup, and secondary breakup with evaporation is introduced and analyzed with respect to computing efficiency and physical accuracy. Finally, the simulation framework is applied to the “Spray A” case of the Engine Combustion Network.

Extreme-Scale In Situ Visualization of Turbulent Flows on IBM Blue Gene/Q JUQUEEN

Extracting and analyzing detailed information from large simulations is of crucial importance for science. However, with the increasing problem size of current simulations, the process of visualizing and understanding big simulation raw data becomes more difficult and needs additional effort. More precisely, the gap between compute and I/O performance is widening with current supercomputers. Thus, the classical approach of visualizing simulation results in a post-processing step is limited or even impossible for extreme-scale scenarios. One promising technique to overcome this issue is in situ visualization, which visualizes and analyzes simulation data during simulation runtime. Within this work, in situ visualization using VisIt/Libsim has been added to the CIAO code framework for interactive- and batch-mode visualization on JUQUEEN, an IBM Blue Gene/Q system with 458 752 cores. Full-system runs are demonstrated and early results of performance measurements of an extreme-scale multiphase case are discussed.