SUMMARY

Even the simplest swirling shear flows possess an astonishing degree of complexity. From this complexity arises both major challenges and unique opportunities for advancement in the study of fluid mechanics through their investigation. Beyond this scientific relevance, swirling jets and wakes have proven crucial for enabling the increased efficiencies and drastically-reduced emissions seen in modern combustion systems. However, the enhanced mixing and flame stability characteristics offered by swirling flow configurations are constrained by a relatively limited understanding of their physics, and this continues to press the combustion industry against the limits of reliable performance.

Prior studies of turbulent swirling flows have identified the triple decomposition as an effective means to isolate large-scale coherent flow structures from chaotic turbulent motions, and subsequently investigated their dynamics separately. Several studies have extracted coherent motions from measurements or simulations of non-reacting swirling jets and demonstrated agreement between the dominant modes from the decomposition and predictions from hydrodynamic global modes. Such work has indicated that, in certain cases, the evolution of coherent structures is predominantly linear with respect to the mean flow, and numerous studies on the hydrodynamics of non-reacting swirling shear flows have been performed. However, the presence of thermal stratification from combustion both modifies existing instability mechanisms and adds several new ones that remain largely unexplored.

The proposed research expands upon previous work by extending the study of swirling jet dynamics to reacting flows. Specifically, this work would explore how dilatation and baroclinic effects induced by thermal stratification from combustion interact to alter a flow's dynamic behavior.