A numerical model was developed to evaluate the design and performance of a detonation-flame-arrestor (DFA). The numerical model is based on a detonation test setup per the ISO16852-2016 standard. The simulation domain consisted of a closed-end pipe where ignition is initiated (the unprotected-side), the DFA, and an open-end pipe representing the side protected from detonation and flame. The DFA has three main components, the inlet section, the middle section consisting of the DFA element, and an outlet section. The DFA element was modeled as a porous zone, where the pressure loss was represented as a momentum sink and the heat loss as a heat sink in the governing equations. The parameters for the pressure loss in the element were determined experimentally and represented by the Forchheimer equation, which is an extension of the Darcy law for higher flowrate. The two-dimensional reactive Euler equations and the ideal gas equation of state were used to model the detonation propagation. A 21-step elementary reaction mechanism with 10 species was used to model the stoichiometric hydrogen–oxygen detonation. The experimental methods are presented in detail and test results for two DFA configurations were presented. Numerical simulation for these two DFA configuration was conducted and presented. The simulation results were qualitatively compared to the experimental results. The numerical simulation results in the unprotected side were compared to the experimental data and had a same trend. The effect of the DFA element on the transmission of the detonation is evaluated using simulation and had shown the same result as the experimental data.