Numerical Study on Coupled Combustion of PMMA Counter-Directional Flame Spread at Variable Slope

This paper investigates the dual effects of slope variation and flame interaction on counter-directional flame propagation through numerical simulations of polymethylmethacrylate (PMMA) plates. Critical flame propagation parameters, including flame morphology, flame spread speed, mass loss rate, and radiative heat flux density, were analyzed using the Fire Dynamics Simulator (FDS v6.7.5) software. By comparing counter-directional flames and unilateral flames under varying slope conditions, we evaluated how flame interactions influence flame spread speed and mass loss rate, as well as the role of the view factor in radiative heat flux distribution. Numerical results revealed that the counter-directional fire propagation process on slopes could be divided into four distinct stages based on variations in flame spread rate and mass loss rate. Moreover, we propose a novel method to quantify flame interaction intensity on slopes using flame spread time. These findings enhance the mechanistic understanding of slope-dependent counter-directional flame propagation.