A comparison of subcycling algorithms for bridging disparities in temporal scale between the fire and solid domains

• Time-sampled and time-averaged subcycling algorithms for fire safety applications.
• Sequential coupling between fire dynamics and solid heat transfer models.
• Application involving a steel beam exposed to a heptane pool fire.
• Time-averaging proven to increase accuracy and computational efficiency.

This paper explores two subcycling algorithms for exchanging surface flux data over disparate time scales between a computational fluid dynamics fire simulation and a conduction heat transfer model. The study specifically aims to evaluate the adequacy of a traditional time-sampled algorithm in comparison to a proposed time-averaged algorithm. A numerical study is carried out on a steel beam exposed to a heptane pool fire. The subcycling algorithms are assessed based on accuracy and the rate of convergence. The results show that the time-averaged algorithm offers greater accuracy and converges more rapidly than the time-sampled algorithm due to its ability to provide an energy-equivalent representation of the fire boundary conditions. The improved convergence rate provided by the time-averaged algorithm allows the time step in the conduction heat transfer analysis to be relaxed significantly. Reducing the step size in the heat transfer model directly corresponds to significant time savings, which is of great importance in the analysis of large-scale systems.