A concept of volume porosity together with model of moving walls were elaborated and implemented into the COM3D code. Additionally to that a support of real-time data exchange with finite-element code ABAQUS - © Dassault Systèmes provided possibility to perform simulations of the gas-dynamic simultaneously with geometrical adaptation of environmental conditions. Based on the data obtained in the KIT combustion experiments in narrow gaps [1], the authors performed a series of the simulation on the combustion in the corresponding conditions. Obtained numerical results demonstrated good agreement with the observed experimental data. These data were also compared with those obtained in the simulation without wall bending, where simulation showed considerably different combustion regime. Application of the developed technique allows to obtain results unreachable without accounting on wall displacements, which demonstrates massive over-estimation of the pressures observed during flame propagation