Cluster-based reduced-order modeling to capture intermittent dynamics of interacting wakes

Interacting flows are found in a range of aviation-relevant technologies, including flow control devices, engine combustors and augmentors, and aerodynamic control surfaces. The structure and dynamics of interacting jets and wakes, including both large-scale coherent dynamics and turbulent fluctuations, are fundamentally different from that of a single flowfield. The goal of this work is to understand large-scale intermittent dynamics of turbulent interacting wakes and jets using an improved reduced-order modeling strategy called cluster-based reduced-order modeling (CROM) to capture these dynamics. The dynamics of a three-wake system at two spacings is compared to that of a single-wake flowfield using the cluster-based method. The CROM is able to capture the expected dynamics of the single wake and the results are analogous to those from proper orthogonal decomposition (POD). However, CROM reveals a much more complicated set of dynamics in the interacting wake cases, including the existence of two sets of dynamics that intermittently appear and the switching points between them, which the POD was unable to detect. CROM is used to quantify these dynamics and understand the effect of bluff-body spacing on the three-wake flowfields.