Numerical Investigation of the Flow Past Two Cylinders in Tandem Arrangement with OpenFOAM

The flow past two cylinders in tandem arrangement is of fundamental importance in many engineering applications such as heat exchangers, offshore structures, and power transmission lines. This study presents a comprehensive numerical investigation using open‑source tools: Gmsh for mesh generation and OpenFOAM for the finite‑volume solver. A distance‑based refinement strategy is employed to resolve the flow accurately, with characteristic mesh sizes as low as ( 0.001,mathrm{m} ) around the cylinders. The methodology is validated against the well‑known Schäfer–Turek single‑cylinder benchmark at ( Re = 100 ), showing satisfactory agreement for force coefficients and Strouhal number. The main analysis focuses on a tandem configuration at ( Re = 1.0times10^5 ) (fully turbulent regime) with an upstream cylinder of diameter ( D_1 = 0.1,mathrm{m} ) and a downstream cylinder of diameter ( D_2 = 0.15,mathrm{m} ) spaced ( 1.0,mathrm{m} ) centre‑to‑centre. The results reveal strong wake interaction, with the downstream cylinder experiencing higher mean drag ( (overline{C}_D = 0.997) ) and significantly larger lift fluctuations (( C_L’ = 0.340 )) than the upstream cylinder (( overline{C}_D = 0.947 ), ( C_L’ = 0.129 )). Both cylinders shed vortices at the same frequency ( f = 6.443,mathrm{Hz} ), yielding Strouhal numbers ( St = 0.644 ) (upstream) and ( St = 0.966 ) (downstream). Detailed line profiles and probe data show a pronounced velocity deficit, elevated turbulence levels, and pressure recovery in the wake. The fully reproducible open‑source workflow and the comprehensive dataset provide a valuable reference for future studies on bluff‑body interactions.