CIAO performs DNS and LES with multiphysics effects (multiphase, combustion, soot, spark, …). It is a structured, arbitrary order, finite difference code with compressible and incompressible/low-Mach solvers. Moving meshes are supported and overset meshes can be used for local mesh refinement. Spatial and temporal staggering is used 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.The compressible solver uses a low-storage five-stage, explicit Runge-Kutta method for time integration. The low-Mach solver uses Crank-Nicolson time advancement along with an iterative predictor corrector scheme. The Poisson equation for the pressure is solved by the multi-grid HYPRE solver. Momentum equations are spatially discretized with central schemes of arbitrary order, while for scalar equations various different schemes (WENO, HOUC, QUICK, BQUICK, …) are available. Temperature and species equations are advanced by utilizing a Strang operator splitting. The chemistry operator uses a time-implicit backward difference method (CVODE).
YALES2 aims at the solving of two-phase combustion from primary atomization to pollutant prediction on massive complex meshes. It is able to handle efficiently unstructured meshes with several billions of elements, thus enabling the Direct Numerical Simulation and Large-Eddy Simulation of laboratory and semi-industrial configurations. The recent developments are focused on the dynamic mesh adaptation of tetrahedral-based massive meshes for fronts and interfaces.
Nek5000 is a computational fluid dynamics code that employs the spectral element method, ahigh-order weighted residual technique, for applications in a wide range of fields including fluid flow, thermal convection, conjugate heat transfer, combustion and magnetohydrodynamics. It features state-of-the-art, scalable algorithms that are fast and efficient on platforms ranging from laptops to the world’s fastest computers. Nek5000, which is actively developed and improved for more than 30 years at Argonne National Laboratory (ANL), was extended for the direct numerical simulation of low Mach number reactive flows at the Swiss Federal Institute of Technology Zurich and is been used to investigate gas-phase and catalytic combustion in a number of laboratory-scale setups of fundamental and applied interest including internal combustion engines. Nek5000 won a Gordon Bell prize for its outstanding scalability on high-performance parallel computers and the 2016 R&D 100 Award. It is part of the Center for Efficient Exascale Discretizations (CEED) co-design effort, and its user community involves hundreds of scientists and engineers in academia, laboratories and industry.
OpenFOAM is a C++ object-oriented numerical simulation platform, which has a modular code-design suitable to be extended with new functionalities through additional libraries. OpenFOAM uses the unstructured grid formulation with a collocated cell-centred variable arrangement, which allows handling arbitrarily complex geometries and it can be applied in different fluid dynamic problems. For turbulent reacting and multi-phase flows, OpenFOAM provides a wide runtime-selectable flexibility in terms of turbulence models, e.g. RANS and LES, with several turbulence closures, and combustion models, such as tabulated chemistry with presumed PDF, ATF (TU Darmstadt in-house extension), and finite-rate chemistry.
Multi-phase problems as liquid sprays can either be treated using a fully coupled Lagrangian point-particle method or within an Eulerian framework as Volume of Fluid Method. OpenFOAM can be easily coupled with external libraries, as for example the Quadrature-based Method of Moments (QMOM) library developed at TU Darmstadt to account for the soot particle size distribution.