Laminar Flow Around Two Circular Cylinders: Impact of a Wake Splitter Plate

A numerical analysis of laminar flow past two tandem circular cylinders (diameter, D) with a detached wake splitter plate was conducted at a Reynolds number of 160. Five inter-cylinder spacing ratios (L/D) were considered in the range 2 to 6, and at each L/D ratio a splitter plate was placed at six different downstream positions (G = 1D–6D) relative to the trailing edge of the downstream cylinder. The novelty of the present study resides in the parametric investigation of a detached splitter plate positioned downstream of two tandem circular cylinders over a wide range of geometric configurations, together with the introduction of interference drag and lift metrics to quantify wake-control effectiveness. A finite volume method was employed to solve the unsteady Navier–Stokes equations. Computations showed that wake behind the tandem cylinders strongly depends on the values of L/D and G/D. At the lower values of L/D (2–3), the presence of the splitter plate enhanced the downstream cylinder drag inversion and suppressed the vortex-shedding phenomenon from the upstream cylinder. At the critical spacing ratio (L/D = 4), the splitter plate induced abrupt changes in the wake behaviour in the shear-layer reattachment and co-shedding regimes, significantly affecting the wake parameters, and fluctuating forces of both cylinders. At large values of L/D (5–6), the two cylinders produce largely independent, periodic vortex shedding instead of synchronised or suppressed shedding seen at closer L/D ratios. In these cases, the splitter plate mainly serves to stabilise the local wake behind the downstream cylinder, causing very little variation in the wake parameters and reducing the sensitivity of both the drag and lift coefficients to the plate position. To evaluate these effects clearly, the concept of interference drag and lift is introduced. Results show that the interaction between the wake, the downstream cylinder, and the splitter plate can create a bias in the interference lift. Depending on the configuration, this interaction may either suppress the lift or zoom it. The case of L/D = 2 and G/D = 2 displays amplified lift oscillations on both the upstream and downstream cylinders relative to the tandem-cylinder arrangement without a splitter plate, suggesting that the splitter plate can enhance flow-induced forces under specific configurations. In the present study, cylinders are rigid and stationary, and the amplified response is presented as a favourable precondition for energy harvesting rather than a demonstrated benefit, with quantitative assessment via a flexibly mounted or elastically coupled configuration left for future work. The results provide useful insights into passive wake-control strategies for bluff-body configurations encountered in fluid engineering applications, where mitigating wake-induced fluctuations and modifying aerodynamic loads can contribute to improved operational efficiency and structural reliability under unsteady flows.