Three-dimensional instability-inspired wake control on flow past a square cylinder via spanwise-distributed suction

The square cylinder, a simplified model, is widely used in the analysis of flow fields in practical ocean engineering structures, with research on its wake flow providing significant scientific insights. This study investigates the wake flow around a square cylinder at a Reynolds number of 5000, a transitional flow regime characterized by enhanced vortex shedding and wake structures, with the three-dimensional nature of the wake becoming more pronounced. Traditional two-dimensional control methods are ineffective at this Reynolds number; therefore, a novel three-dimensional, periodically spanwise-distributed suction control strategy is proposed. By comparing five suction scenarios, the optimal control period (λ = 3) is identified, leading to a 25.9 % reduction in mean drag, an 84.7 % reduction in lift coefficient fluctuations, and suppression of the vortex shedding frequency to 0.136. Spectral Proper Orthogonal Decomposition analysis reveals that, at λ = 3, vortex size and intensity are significantly reduced, particularly in the far wake region. These results demonstrate the potential of the proposed suction control strategy to improve flow stability and suppress vortex-induced energy, making it highly effective for optimizing wake structures in complex flow regimes.

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