This study numerically investigates laminar flow around two prismatic bodies, specifically square cylinders, arranged in tandem. The analysis covered gap ratios ($L/D=2$–7) and Reynolds numbers ($Re$ = 100–200), focusing on quantifying the aerodynamic characteristics and examining the wake flow structures within the established interference regimes. The time-averaged and unsteady parameters, including the drag and lift coefficients, RMS lift, vortex formation length, Strouhal number, recirculation length, wake width, and pressure distribution, were evaluated for both cylinders. A consistent critical spacing of $L/D\approx 4.5$ was observed across all Reynolds numbers, coinciding with the minimum Strouhal number, a sharp increase in unsteady lift, and divergence in wake width between cylinders. Notably, in the range $4.5\lesssim L/D\lesssim 6.5$ at higher $Re$, the DC exhibited a mean drag exceeding that of an isolated cylinder, attributed to base-pressure reduction and accelerated inflow from the upstream wake. A critical spacing in the co-shedding regime produced strong drag amplification on the DC, attaining an overall maximum value of 50.41% at $Re=200$ and $L/D=6.0$. To note, unlike mean drag, mean lift is found to be zero in all interference cases for both cylinders, irrespective of spacing ratio and Re, owing to the symmetry of the time-averaged pressure distribution on either side of the cylinders. Spectral and phase analyses reveal a transition from broadband, desynchronised oscillations to a frequency-locked state, with the phase angle between the cylinders reducing sharply to $\Delta \varphi \approx 0^{\circ }$ at the critical spacing. This indicates complete in-phase synchronisation or symmetry of the vortex-shedding process between the cylinders at the critical spacing. This confirmed the hydrodynamic transition between the coupled and independent shedding modes of the cylinders. The recirculation lengths for the DC reduce to as low as $0.6D$ in the co-shedding regime, highlighting rapid wake recovery. The research presented here offers new insights into force modulation, the evolution of wake structures, and the sensitivity to the Re that occurs when laminar flow occurs between two tandem square cylinders. These findings can be utilised to develop methods for controlling VIV and designing thermal-fluid systems.

An accurate prediction of design wind speed is critical to the estimation of wind loads on any earth-bound civil engineering structure. Concerns have been raised within the Indian design community concerning the precision of design wind speeds as well as the new formulation of the importance factor for cyclonic regions in the current Indian Wind Loading Standard. The current study investigates the extreme wind climate of India by carrying out an independent study of wind speeds at noncyclonic and cyclonic regions, respectively, using measured and simulated data. Further, the results were compared against the existing wealth of knowledge concerning other major international standard formulations, gust factors, and wind speeds of similar climate regions. This study demonstrates that the existing 50-year return period wind speeds in the IS for noncyclonic regions such as Mumbai and Delhi are overconservative resulting in uneconomical structures. Further, the study confirms that the existing 50-year return period wind speeds for cyclonic regions such as Chennai and Kolkata are conservative as well without the use of cyclonic factor ($k_4$ ). The study recommends the removal of the cyclonic factor ($k_4$ ) section from the standard and also recommends a basic wind speed of 39 and $44\mathrm{m}/\mathrm{s}$ respectively for Mumbai and New Delhi.

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Flow interference among bluff bodies can strongly amplify or suppress unsteady aerodynamic forces and induced vibrations thereof. However, the behaviour of tandem square-cylinder interference and its passive control in the laminar regime remains insufficiently quantified, particularly near the known critical tandem spacing ratio (L/D ≈ 4.5). This study systematically analysed and determined how a splitter plate placed downstream of the second cylinder modulates the aerodynamic forces, symmetry of vortex shedding, wake topology, and associated wake metrics in two-dimensional incompressible laminar flows. Unsteady finite-volume numerical simulations were conducted using ANSYS Fluent (2022 R1) at Re = 150. The tandem cylinder spacing (L) was varied over L/D = 2–6 (D, the cylinder side length), and the splitter gap (G) was varied over G/D = 1–6. The splitter plate acted as a strong wake stabiliser at small gaps (G/D = 1), where vortex shedding was largely suppressed and lift fluctuations were minimal (for example, C_l,rms ≈ 0.055), and the DC experienced negative drag (C_d ≈ −0.13), consistent with elongated and weakly rolled-up shear layers and extended recirculation. The splitter plate acted as a sharp control “switch” at a critical splitter gap G/D ≈ 2, where the wake transitioned to unsteady shedding, the Strouhal number (St) jumped to values that remained nearly constant for G/D = 2–6, and the wake metrics indicated earlier roll-up (reduced vortex formation length and recirculation length) and greater lateral spreading (increased wake width). The outcome was influenced by the tandem regimes: for 1.5 < L/D < 4, persistent shielding and negative downstream drag predominated. However, near the critical gap (L/D ≈ 4.5), the restoration of shear-layer impingement at G/D ≥ 2 resulted in a downstream drag surpassing the isolated-cylinder baseline (C_d,SC ≈ 1.49) by approximately 3–8%. In the co-shedding regime, when L/D = 5, there was a notable increase in drag, approximately 12.3% more than that on an isolated cylinder. Conversely, when L/D = 6, the system approached aerodynamic independence without any amplification (approaching the single-cylinder value). The interference metrics showed a maximum combined drag reduction of ~68.6% at L/D = 4.5 and G/D = 1, whereas the upstream cylinder drag was only weakly affected. The results of the present study establish splitter placement as an effective passive control method for suppressing or recovering interference-driven unsteadiness, thereby supporting designs in bluff-body aerodynamics, heat-transfer equipment, and vibration-mitigation systems.