On Passive Flow Control of Laminar Wake Interference Between Tandem Triangular Cylinders

Numerical simulations were conducted to investigate the effects of the Reynolds number (Re) and gap ratio (G/L) on the flow over two tandem equilateral triangular cylinders. The variations in wake dynamics, aerodynamic coefficients, and Strouhal number (St) were analyzed for Reynolds numbers ranging from 80 to 160 and gap ratios (G/L) from 0 to 6.0. The pisoFoam solver available in the OpenFOAM software, which employs the PISO algorithm, was used to solve the governing flow equations. Analysis of the vorticity contours reveals that the vortex shedding characteristics of the tandem cylinders are strongly influenced by the gap ratio. Distinct vortex shedding from both cylinders is observed only beyond a critical gap ratio, with vortex shedding being delayed up to this critical value. Based on the vorticity patterns, three distinct flow regimes were identified depending on the values of Re and G/L. The vortices shed from the cylinders are found to be periodic and symmetric across the investigated ranges of Re and G/L. The time-averaged drag coefficient remains positive for the first cylinder, while for the second cylinder it transitions from positive to negative with increasing G/L. A higher value of the CL,rms is observed for the second cylinder due to its placement in the wake of the first cylinder. Furthermore, a sudden increase in both the force coefficients and the Strouhal number is observed for both cylinders beyond the critical gap ratio. The Strouhal number values are found to be nearly identical for the two cylinders.