Physical Insights into Wake Stabilization: Morphological Geometry of a Detached Triangular Splitter Plate for Passive Flow Control of a Circular Cylinder

The unsteady wake of a circular cylinder is governed by global instability and shear-layer interactions, which lead to significant pressure drag and fluctuating forces. This study numerically investigates how the morphological geometry of a detached isosceles triangular splitter plate modulates the near-wake dynamics to achieve passive flow control. Twodimensional unsteady laminar simulations are performed at Reynolds number Re = 100, 150, and 200. To elucidate the underlying fluid physics, this study systematically explores how three geometric parameters—the apex angle (θ), base-length ratio (B/D), and scale factor (k)—alter the shear-layer roll-up and wake stability. The results reveal a clear geometric modulation of the flow: decreasing the apex angle and increasing the base length progressively suppress the shear-layer interaction and delay vortex formation, leading to a significant base-pressure recovery. Consequently, all splitter-plate configurations reduce drag compared to the bare cylinder. The optimal configuration (θ = 20◦ , B/D = 0.75, k = 1.5) disrupts the self-sustained oscillatory mode most effectively, achieving the maximum drag reduction of up to 17.50%. Conversely, excessive scaling (k = 2.0) triggers massive separation and deteriorates wake stability. These findings establish a direct causal link between triangular plate geometry, wake instability suppression, and macroscopic force reduction, providing physical insights for the design of passive flow control strategies.