On characterizing the wake of side-by-side rectangular prisms at low Reynolds numbers

This study directly solves the incompressible Navier–Stokes equations to investigate the laminar wake dynamics of two identical side-by-side rectangular prisms over ranges of Reynolds numbers, gap ratios, and depth ratios to gain a detailed understanding of bluff-body wake interactions. While canonical side-by-side wake transitions are usually interpreted primarily in terms of Reynolds number and spacing, the present results show that varying prism depth ratio substantially modifies gap-flow acceleration, shear-layer development, mean recirculation, and the resulting flow regimes. Based on the Strouhal number, unsteady vorticity fields, and spectral analysis, the wakes are classified into four principal regimes: steady, merged, separated, and transitional wakes. These regimes contain distinct synchronization sub-states and downstream reorganization patterns. Furthermore, the depth ratio shifts the regime boundaries and alters the transition pathways between canonical wake states. To account for the effect of prism depth ratio on wake development, a corrected Strouhal number scaling is introduced using the local gap velocity and the mean recirculation length and width. This definition links shedding frequency to both the local convective timescale and the shape of the wake formation region. The proposed framework establishes the depth ratio as a key control parameter in the wakes of side-by-side prisms.