Flow dynamics in a variable-spacing, three bluff-body flowfield

This work explores the wake dynamics of systems with three bluff bodies with variable spacing. Studies of single-wake systems have shown that coherent wake vortices have a regular and predictable periodicity. A growing literature of dual-wake studies has shown that multi-wake systems are more stochastic than single-wake systems, and their dynamics are highly dependent on the spacing between the wakes. Here, we expand on this literature by investigating three-wake systems and find that the coherent dynamics of the wakes are highly intermittent. We use proper orthogonal decomposition to extract the most energetic modes of the three-wake system at six bluff-body spacings that span a range of dynamical “regimes.” After describing the time-dependent behavior of the interacting wakes in these regimes, we use a statistical approach to describe the relative phase between oscillations in each of the wakes, identifying regimes where oscillations are more or less random. Interestingly, the wake oscillations are less random when the bluff bodies are positioned very close and relatively far from each other. In between these two extremes, an intermediary regime is identified where the wake oscillations are almost completely random; this finding parallels data from the dual-wake literature. Finally, we discuss the implications of the observed behaviors and possible future directions for this work.