Statistics and topology of local flame-flame interactions in turbulent flames

Flame-flame interaction events occur frequently in turbulent premixed flames and change the local structure and dynamics of flames. It is essential to understand these flame-flame interaction events to develop high-fidelity combustion models for use in modern combustion devices. In this study, we experimentally investigate the topology of flame-flame interaction events in single- and multi-flame configurations. A dual-burner experiment is probed with high-speed OH-planar laser-induced fluorescence and stereoscopic-particle image velocimetry to obtain simultaneous flame front locations and velocity fields. A non-rigid image registration technique is implemented to track the topological changes occurring in these flames. In both single- and dual-flame configurations, small-scale interactions occur more frequently compared to large-scale interactions, and statistics show that most of the reactant-side interactions contribute to large flame surface destructions than the product-side interactions. It is also found that turbulence length- and velocity-scales can play an important role in facilitating the interaction events and pocket formations from these events. Filamentarity is used to quantify the two-dimensional shape of these interactions and comparisons are made between the orientation and shape of interaction events and the local turbulence in the flowfield. Alignment between the orientation of the interaction shapes and the principal strain rates show that compressive fluid forces drive both types of interaction events. (C) 2019 The Combustion Institute. Published by Elsevier Inc. All rights reserved.