2134/13447 Valeria Di Sarli Valeria Di Sarli Almerinda Di Benedetto Almerinda Di Benedetto G. Russo G. Russo Simon Jarvis Simon Jarvis Edward Long Edward Long Graham Hargrave Graham Hargrave Large eddy simulation and PIV measurements of unsteady premixed flames accelerated by obstacles Loughborough University 2013 Large eddy simulation Particle image velocimetry Unsteady propagation Premixed combustion Obstacles Sub-grid scale turbulence Mechanical Engineering not elsewhere classified 2013-10-28 14:31:27 Journal contribution https://repository.lboro.ac.uk/articles/journal_contribution/Large_eddy_simulation_and_PIV_measurements_of_unsteady_premixed_flames_accelerated_by_obstacles/9576527 In gas explosions, the unsteady coupling of the propagating flame and the flow field induced by the presence of blockages along the flame path produces vortices of different scales ahead of the flame front. The resulting flame/vortex interaction intensifies the rate of flame propagation and the pressure rise. In this paper, a joint numerical and experimental study of unsteady premixed flame propagation around three sequential obstacles in a small scale vented explosion chamber is presented. The modelling work is carried out utilising Large Eddy Simulation (LES). In the experimental work, previous results [Patel, S.N.D.H., Jarvis, S., Ibrahim, S.S., Hargrave, G.K., Proceedings of the Combustion Institute 29, 1849-1854 (2002)] are extended to include simultaneous flame and Particle Image Velocimetry (PIV) measurements of the flow field within the wake of each obstacle. Comparisons between LES predictions and experimental data show a satisfactory agreement in terms of shape of the propagating flame, flame arrival times, spatial profile of the flame speed, pressure time history and velocity vector fields. Computations through the validated model are also performed to evaluate the effects of both large scale and sub-grid scale (sgs) vortices on the flame propagation. The results obtained demonstrate that the large vortical structures dictate the evolution of the flame in qualitative terms (shape and structure of the flame, succession of the combustion regimes along the path, acceleration-deceleration step around each obstacle, pressure time trend). Conversely, the sgs vortices do not affect the qualitative trends. However, it is essential to model their effects on the combustion rate to achieve quantitative predictions for the flame speed and the pressure peak.