  Numerical simulations of detonation-containing flows have emerged as crucial
tools for designing next-generation power and propulsion devices. As these
tools mature, it is important for the combustion community to properly
understand and isolate grid resolution effects when simulating detonations. To
this end, this work provides a comprehensive analysis of the numerical
convergence of unsteady detonation simulations, with focus on isolating the
impacts of chemical timescale modifications on convergence characteristics in
the context of operator splitting. With the aid of an adaptive mesh refinement
based flow solver, the convergence analysis is conducted using two kinetics
configurations: (1) a simplified three-step model mechanism, in which chemical
timescales in the detonation are modified by adjusting activation energies, and
(2) a detailed hydrogen mechanism, in which chemical timescales are adjusted
through ambient pressure modifications. The convergence of unsteady
self-sustained detonations in one-dimensional channels is then analyzed with
reference to steady-state theoretical baseline solutions using these
mechanisms. The goal of the analysis is to provide a detailed comparison of the
effects of grid resolution on both macroscopic (peak pressures and detonation
wave speeds) and microscopic (detonation wave structure) quantities of
interest, drawing connections between the deviations from steady-state
baselines and minimum chemical timescales. This work uncovers
resolution-dependent unsteady detonation regimes, and highlights the important
role played by not only the chemical timescales, but also the ratio between
chemical and induction timescales in the detonation wave structure on
simulation convergence properties.
