Flow interactions and aerodynamic characteristics of equilateral three-square cylinder arrangements at high Reynolds numbers

The aerodynamic behavior of a single square column is well-established, yet real-world offshore and coastal structures—such as multi-legged platforms or tower assemblies—often comprise multiple columns with complex flow interactions. This study examines the aerodynamics of equilateral arrangements of three square cylinders, representative of such structural configurations, through three-dimensional numerical simulations at high Reynolds numbers. Comparisons with an isolated cylinder are made to assess Reynolds number effects on vortex patterns, wake dynamics, surface pressure distributions, reattachment locations, and force coefficients under a fixed wind direction. Results show that the Reynolds number governs the direction of wake biasing: at Re = 1.4 × 10 6 , 8.2 × 10 6 , and 9.6 × 10 6 , the flow deflects toward cylinder BLDG2, whereas between Re = 2.7 × 10 6 and 6.8 × 10 6 , it shifts toward BLDG3. This biasing leads to amplified wind pressure fluctuations on the inner face of the corresponding cylinder. Vorticity in the z -direction is strongly Reynolds-number-dependent, peaking at Re = 9.6 × 10 6 across near-ground, mid-, and top-height regions. The drag coefficient is highest for the biased cylinder, and the crosswind lift coefficient minimizes at Re = 4.1 × 10 6 . These findings offer relevant insights for the design and analysis of multi-column offshore structures subjected to wind and wave loads. • Comprehensive 3D numerical simulations validated by wind tunnel experiments. • Analysis of vortex shedding, wake reattachment, and force coefficients under varying Re. • Clear implications for optimizing building spacing and mitigating wind-induced vibrations.