Robust mode analysis of three-bluff-body combustion flow

Studies of combustion flows behind bluff-body configurations help optimize stability and efficacy of propulsion engines. However, theoretical and computational analyses of these systems are difficult in realistic configurations, especially for strongly driven flows. The advent of high-resolution, high-frequency imaging opens a new avenue to study these systems through data-analytic approaches. We use a recently introduced methodology, robust mode analysis (RMA), to study a series of combustion flows behind a three-bluff-body configuration. RMA identifies periodically evolving spatial structures in a flow common between multiple, nominally identical realizations of a flow and, hence, can be used to discard noise and other irregular flow facets. Our experiment records the flow in two spatial perspectives and through a set of time-series pressure measurements. Periods of robust modes, computed through the three recordings, are shown to be consistent for the entire set of experiments. A method to quantify the proximity of spatial structures of modes from different imaging viewpoints is introduced. It is used to compare robust modes in the two imaging views, to identify quasi-periodically evolving flow constituents, and to construct bifurcation diagrams for each constituent.