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Compressible/Incompressible Advanced reactive turbulent simulations with Overset

Scientific area

Multiphysics, multiscale Navier-Stokes solver for turbulent reacting flows in complex geometries.

Short description

CIAO performs Direct Numerical Simulations (DNS) as well as Large-Eddy Simulations (LES) of the Navier-Stokes equations along with multiphysics effects (multiphase, combustion, soot, spark, …). It is a structured, finite difference code, which enables the coupling of multiple domains and their simultaneous computation. Moving meshes are supported and overset meshes can be used for local mesh refinement. A fully compressible as well as an incompressible/low-Mach solver are available within the code framework. Spatial and temporal staggering of flow variables are used in order to increase the accuracy of stencils. The sub-filter model for the momentum equations is an eddy viscosity concept in form of the dynamic Smagorinsky model with Lagrangian averaging along fluid particle trajectories. While the fully compressible solver uses equation of states or tabulated fluid properties, a transport equation for internal/total energy, and a low-storage five-stage, explicit Runge-Kutta method for time integration, the incompressible/low-Mach solver uses Crank-Nicolson time advancement and an iterative predictor corrector scheme. The resulting Poisson equation for pressure is solved by HYPRE’s multi-grid solver. The momentum equations are spatially discretized with central schemes of arbitrary order and various different schemes are available for the scalar equations (WENO, HOUC, QUICK, BQUICK, …).

CIAOSimulation of the primary breakup of a multiphase jet using CIAO’s multiphase methods.


  • 458,752 cores on BlueGene/Q (JUQUEEN)

Weak and strong scaling of CIAOWeak scaling plot (left) with 37,000 cells per core per simulation and strong scaling plot (right) with 17 billion total cells per simulation.

Programming language and model

  • Fortran
  • MPI
  • I/O with MPI, HDF5 or VisIt

Tested on platforms

  • BlueGene/Q
  • x86 (LRZ SuperMUC, BSC MareNostrum III, RWTH Compute Cluster)

Application developers and contact

Mathis Bode, Tobias Falkenstein, Heinz Pitsch
Institute for Combustion Technology
RWTH Aachen University

Seongwon Kang
Department of Mechanical Engineering
Sogang University

(Text and images provided by the developers)