Flow Characteristics Around Staggered D-Type Cylinders Near a Flat Wall: A 2D Numerical CFD Investigation

This study presents a 2-D numerical investigation of fluid flow characteristics around staggered D-type cylinders (θs =36⁰) placed near a flat wall at a high Reynolds number (5.3 × 10⁴). Using ANSYS Fluent with the k–ω SST turbulence model, the effects of spacing ratio (L/D), stagger angle (α), and gap ratio (G/D) were systematically examined. The results demonstrate that the upstream cylinder governs the global pressure distribution and wake dynamics, while the downstream cylinder experiences significant shielding effects that reduce aerodynamic loading. At short spacing (L/D = 1.5), strong wake interference and irregular vortex shedding dominate, leading to highly unstable flow. Conversely, for L/D ≥ 3, independent and more stable wake structures emerge behind each cylinder. The gap ratio (G/D) further modulates base pressure and flow separation, with smaller gaps intensifying wall–wake interactions. These findings provide new insights into wake interference mechanisms of modified bluff bodies and are directly relevant for engineering applications such as heat exchangers, offshore structures, and drag-reduction devices.