FLASH is an astrophysical hydro code originally developed by the University of Chicago under the auspices of the DOE/ASCI program. At CHAMP, we have developed a Reaction Flow Solver (RFS) that couples to FLASH, and is capable of modeling chemically reacting flows with heat release. The RFS was developed and implemented in FLASH at CHAMP using the unsplit hydro method and the Piecewise Parabolic Method (PPM). Diffusive transport of mass, momentum and heat are implemented through a dedicated Diffuse unit that computes the fluxes associated with each transport phenomena. Recently, we have extended the capabilities of the Diffuse unit to be compatible with Adaptive Mesh Refinement (AMR) implemented using PARAMESH.

The capabilities of the RFS are wide-ranging and include a temperature-dependent, multi-species equation of state (EOS), mass, thermal, and viscous diffusion using an implicit solution technique or a flux-based solver, implementation of detailed chemical reaction mechanisms, and an expanded material database that includes temperature-dependent transport and thermodynamic properties. The extended EOS is applicable to temperatures ranging from 298K – 5000K, using multiple coefficients for each species to calculate thermodynamic properties. The expanded material properties database accommodates temperature-dependent thermodynamic or transport properties of a single- or multi-species system. The RFS is implemented in FLASH as a portable wrapper code, that can scan reaction rates and properties for any N species and M reaction mechanism and automatically generate the necessary scripts for compilation.

Figure: Evolution of a non-premixed, Hydrogen-air, Rayleigh-Taylor flame (Isosurfaces of mixture fraction), simulated using FLASH RFS.

Evolution of product (H2O) mass fraction in a sonic jet in a supersonic crossflow simulated using FLASH RFS. The jet is injected vertically and is composed of a mixture of H2 and N2, while the crossflow direction is from left to right and composed of a mixture of O2 and N2.

Related Publications:

  1. N. Attal, P. Ramaprabhu, J. Hossain, V. Karkhanis, M.Uddin, J.R. Gord & S. Roy, “Development and validation of a chemical reaction solver coupled to the FLASH code for combustion applications”, Computers & Fluids, 107, 59-76, (2015). https://doi.org/10.1016/j.compfluid.2014.09.051
  2. N. Attal & P. Ramaprabhu, “Numerical investigation of a single-mode chemically reacting Richtmyer-Meshkov instability”, Shock Waves, 25, 307 – 328, (2015). https://doi.org/10.1007/s00193-015-0571-6
  3. P. Ramaprabhu, N. Attal & H. Varshochi, “Combustion processes in interfacial instabilities”, Book chapter in Developments in Combustion Technology, 2015.
  4. N. Attal & P. Ramaprabhu, “The stability of reacting single-mode Rayleigh-Taylor flames”, Physica D: Nonlinear Phenomena, 404, 132353 (2020). https://doi.org/10.1016/j.physd.2020.132353