Abstract
Large Eddy Simulation (LES) of flow around the aerodynamic model ASMO
was performed on the world-class vector-processing parallel computing system "Earth
Simulator". The software "FrontFlow/red" based on the unstructured Finite Volume Method
was utilized in this study. The computational code was intensively optimized on Earth
Simulator and high vectorization and parallelization of more than 95% and 99% respectively
were achieved in the simulations on 256 parallel processors, which made it possible to
complete the large-scale computations (25 million meshes with 150 GB memory) including
the calculation of turbulence statistics in only two or three days. The obtained turbulence
statistics such as the averaged pressure distribution on the vehicle body surface showed good
agreement with existing wind-tunnel experimental data. Reynolds-Averaged Navier-Stokes
simulation (RANS) using the standard k- model with the same grid resolutions as those of
LES was also conducted, and the validity of LES against RANS was discussed in the context
of its accuracy and the CPU time consumed. The most notable feature obtained in LES was
the reproduction of the base pressure of the vehicle body, which, in contrast, RANS results
poorly estimated. The wake structures were analyzed both in terms of averaged and
instantaneous flow fields. As a result, it was shown that LES could be a dominant and
effective turbulence model in the very near future for the computations of the flow around the
vehicle with complex configurations.
Keywords - Vehicle Aerodynamics, CFD, High Performance Computing, Large Eddy
Simulation, Earth Simulator