Hydrodynamic Characteristics of Two Side-by-Side Cylinders at a Pitch Ratio of 2 at Low Subcritical Reynolds Numbers

Isothermal turbulent flow around circular cylinders arranged side-by-side was numerically simulated on a commercial finite-volumes platform, ANSYS^® CFX, version 2020 R2. The turbulence was modeled by using k-<i>ω</i> shear stress transport (k-ω SST). Three different Reynolds numbers were computed, <i>Re_d</i> = 200, 1000, and 3000, which were based on the cylinder diameter, d, the free stream velocity, <i>U</i><i>∞</i>, and the kinematic viscosity of the fluid, ν. Sided cylinders were spaced apart from each other, forming a <i>p/d</i> ratio equal to 2, which was kept constant throughout the computations regardless of changes in the Reynolds number. The drag coefficient, <i>C_d</i>, as well as its time traces, was evaluated along with the different wake topologies experienced by the cylinders (wide wake <i>WW</i> and narrow wake <i>NW</i>). The simulations were able to predict the bistable flow over the cylinders and the Cd changes associated with the wakes. Whenever a new wake topology was identified, the shape drag changed in accordance with the instantaneous pressure distribution. A laminar simulation was carried out for the lowest Reynolds number case, showing that the adopted turbulence model did not affect the dynamic response of the flow. The <i>Re_d</i> = 3000 case was compared to Afgan’s outcomes, whose simulations were carried out in a 3-D mesh using LES (Large Eddy Simulation), showing great agreement with their results.