Dynamics in the shear layer and vortical structures in the near-field of a fan array wind tunnel

Fan array wind tunnels offer a unique testing environment for repeatable and robust aerodynamic and environmental flow studies. They consist of an array of individually controlled fans that collectively generate programmable, large-scale conditions with variable shear and turbulence statistics. The fans generate an array of jets that merges in the near field, forms a single jet in the far field, and behaves differently from a single jet at the same mass flow rate. The shear layer interactions and vortical features induced by the fans contribute to the near-field dynamics. We employ high-fidelity, large-eddy simulations using curvilinear immersed boundary methods to resolve the geometric details of the fan and shroud and to characterize vortical structures and shear layer turbulent statistics of a fan and its extension to a fan array. Specifically, we examine the coalescence of individual fan jets and the merger of shear layers in the near field into a unified far-field flow. The vortical features induced by the blades affect the mixing and merger length. The velocity profiles and generated thrust are compared with experimental measurements. We compare these results with simulations using an actuator disk model parameterization, which represents the fan as a simplified disk and does not induce similar coherent vorticity into the flow. This offers insights into how the fan geometry influences the overall jet dynamics and structure.