  Computational load imbalance is a well-known performance issue in
multiprocessor reacting flow simulations utilizing directly integrated chemical
kinetics. We introduce an open-source dynamic load balancing model named
DLBFoam to address this issue within OpenFOAM, an open-source C++ library for
Computational Fluid Dynamics (CFD). Due to the commonly applied operator
splitting practice in reactive flow solvers, chemistry can be treated as an
independent stiff ordinary differential equation (ODE) system within each
computational cell. As a result of the highly non-linear characteristics of
chemical kinetics, a large variation in the convergence rates of the ODE
integrator may occur, leading to a high load imbalance across multiprocessor
configurations. However, the independent nature of chemistry ODE systems leads
to a problem that can be parallelized easily (called an embarrassingly parallel
problem in the literature) during the flow solution. The presented model takes
advantage of this feature and balances the chemistry load across available
resources. Additionally, a reference mapping model is utilized to further
speed-up the simulations. When DLBFoam it utilized with both these features
enabled, a speed-up by a factor of 10 is reported for reactive flow benchmark
cases. To the best of our knowledge, this model is the first open-source
implementation of chemistry load balancing in the literature.
