Direct numerical simulation of a laminar diffusion flame established over a horizontal flat plate in micro-gravity environment

Abstract
A numerical study of a laminar diffusion flame established over a horizontal flat plate in micro-gravity environment is performed. Three dimensional, time-dependent numerical solutions to the Navier-Stokes equations are used to simulate the experiments. In the experiment, fuel is injected through the burner and the oxidiser (air) is provided by a forced flow parallel to the surface. The experiments were conducted in a range of oxygen concentration from 23 to 30 % at two different wind velocities of 2.6 and 4 cm/s in a 5 s drop tower. Combustion process is described by a global one-step, finite-rate reaction given by the Arrhenius expression. Direct Numerical Simulation (DNS) is used to provid a detailed description of the transition process of the flame in micro-gravity environment. The model results show that after the imposition of the micro-gravity, a plume region is maintained momentarily due to the dominant inertia. The transition time is about 2.5 s for reducing the overall air flow velocity to that of the forced boundary layer flow. The model results reflect the qualitative features of the experiments.