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The local interactions between the flame-front and turbulence control the dynamics, morphology, and propagation of a premixed turbulent flame. To investigate such complex dynamics of a flame–turbulence interaction, we present an experimental exposition of a premixed turbulent Bunsen flame. Several quantities have been evaluated to assess the flame–turbulence interaction. We first measured the statistics of the flowfield adjacent to the flame and compared it with the cold flow. This allowed us to evaluate the effect of the flame on the upstream turbulence. Subsequently, we performed statistical analyses of the local values of various stretch rates and quantified how their distribution changes with turbulence intensity and flame temperature. We also evaluated the pairwise relation among various stretch rates to assess their dependence on each other. Finally, we used flame particles to evaluate the Lagrangian evolution of stretch rates conditioned on flame-fronts. All the analyses presented in this work point out Karlovitz number as a key factor in determining the flame–turbulence interaction. Specifically, we observe a stronger influence of turbulent eddies on flames with increasing Karlovitz number, as evidenced by the reduced effect of flame on upstream flow, wider probability distribution functions of stretch rates, and increased persistence timescales for stretches. 

Abstract We present a phenomenological reduced-order model to capture the transition to thermoacoustic instability in turbulent combustors. Based on the synchronization framework, the model considers the acoustic field and the unsteady heat release rate from turbulent reactive flow as two nonlinearly coupled sub-systems. To model combustion noise, we use a pair of nonlinearly coupled second-order ODEs to represent the unsteady heat release rate. This simple configuration, while nonlinearly coupled to another oscillator that represents the independent sub-system of acoustics (pressure oscillations) in the combustor, is able to produce chaos. Previous experimental studies have reported a route from low amplitude chaotic oscillation (i.e., combustion noise) to periodic oscillation through intermittency in turbulent combustors. By varying the coupling strength, the model can replicate the route of transition observed and reflect the coupled dynamics arising from the interplay of unsteady heat release rate and pressure oscillations.