Direct numerical simulation is performed for the stoichiometric hydrogen-air mixture with decaying homogeneous isotropic turbulence of which the Reynolds number based on Taylor micro scale is 97.1. Initial distributions of species are assumed to be uniform. A detailed kinetic mechanism is used to represent the hydrogen-air reactions. The flame ignites from the high temperature kernel at the center of the computational domain, and then propagates with the distortion by the turbulent motion. In this study, the propagation characteristics of a hydrogen-air premixed flame in a constant volume vessel are investigated. The contribution of reaction S_(d, R), normal diffusion S_(d.N) and tangential diffusion S_(d.T) to the local flame displacement speed S_d is studied. As the pressure increases in the vessel, the mean S_d also increases. The contribution of S_(d.T) to S_d is significant due to the existence of high negative mean curvature just after the flame ignition. However, this contribution decreases and becomes negligible as the global diameter of the flame increases. The mean S_d as a function of wall normal distance is also investigated and it is found that S_d is almost constant away from the wall, and decreases drastically approximately 1 thermal flame thickness away from the wall.
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