Critical Regions Driving Unsteady Wake Dynamics in Flow Past Multi-Cylinder Arrays

Large-eddy simulation (LES) is used to determine the time-resolved flow evolution past two cylinders placed side by side. The simulations are conducted at a nominal Reynolds number of Re = 10,000. Complex network analysis is applied to the resulting datasets to identify the location and spatial extent of the flow regions that govern the unsteady wake dynamics. A nominal single-cylinder configuration with well-established reference data is employed to benchmark the LES. For the closely spaced two-cylinder case, an asymmetric time-averaged flow structure with a biased inter-cylinder gap flow is observed. This configuration exhibits a broad and a narrow wake, with the former driving the vortex shedding in the near wake. The widely spaced case presents a symmetric time-averaged flow structure, with vortex shedding from both wakes that interact further downstream. Complex networks are constructed for the single-cylinder case using correlation, mutual information, and transfer entropy to quantify nodal connectivity. These networks exhibit prominent hubs when mapped back into physical space, thereby identifying the wavemaker region that drives the downstream wake dynamics, consistent with prior studies. For the closely spaced two-cylinder case, the network analysis reveals a wavemaker only within the broad-wake region, while a more symmetric wavemaker distribution is observed in the widely spaced case.