A two-dimensional (2D) numerical analysis of flow past two and three square rods arranged side-by-side (SBS) using the numerical technique of the lattice Boltzmann method (LBM) is performed. The combined effects of gap spacing (g = g/D) for two rods and, in the case of three rods, the size (d/D) of the middle rod vary with the delay of vortex shedding. The flow across two and three square rods is examined for 0.5D ≤ g/D ≤ 4D and 0.1D ≤ d/D ≤ 1D at a fixed Reynolds number (Re = 160). The results indicate a strong correlation between middle rod size and flow characteristics for small gap spacings (g/D ≤ 1D). It is observed that at a large value of g/D and a small value of d/D, the secondary rod interaction frequency disappears, and the flow is fully controlled by the primary vortex shedding frequency. It is also observed that at g/D ≥ 1, the drag force for the upper and lower rods decreases with the addition of the middle rod. The observed flow regime (FR) without the middle rod (d/D = 0) is the irregular flow regime (FR), occurring at g/D = 0.5 and 1, and modulated antiphase synchronized FRs occur at g/D = 2, 3, and 4. In the presence of the middle rod, the irregular FR occurs at (g/D, d/D) = (0.5, 0.1 ≤ d/D ≤ 1) and (1, 0.1 ≤ d/D ≤ 0.8). While at (g/D, d/D) = (2, 0.1 ≤ d/D ≤ 0.6), (3, 0.1 ≤ d/D ≤ 0.6), and (4, 0.1 and 0.2), the modulated antiphase synchronized FR occurs in the presence of the middle rod.