Splitter plate-based flow control study for two square cylinders in tandem arrangement

A numerical study is performed to investigate the effectiveness of a splitter plate (SP) for the unsteady wakeregime control of two-dimensional tandem square cylinders (TSC) arranged with large (G/D = 6), intermediate (G/D = 4) and small (G/D = 2) gap-widths. Here, G is the center-to-center distance between the cylinders, and D is their side-length. The numerical simulations are conducted using an in-house developed FFIBLBM (flexible-forcing-immersed-boundary-lattice-Boltzmann-method) solver at Reynolds number (Re) of 100. The TSC arrangement with SP attached to either upstream or downstream cylinders is named TSC-SPU and TSC-SPD, respectively. It is found that the shear-layer characteristics, wake-regime, and flow-induced forces on TSC are highly susceptible to the G/D ratio and SP length. We observed four distinct flow patterns: VS-VS (vortex shedding-vortex shedding), QS-VS (quasi-steady-vortex shedding), S-VS (steady-vortex shedding), and S-S (steady-steady) in the wakes of TSC. Among them, the S-S flow pattern is the controlled wake-regime, with steady and stabilized vortices behind both cylinders, yielding considerably lesser drag on the TSC. Precisely, at large gap-width (G/D = 6), the TSC-SPU configuration only attains the S-S flow type for which the upstream and downstream cylinder experience 11.86% and 97.73% lesser drag, respectively, than the TSC without an attached SP. However, at intermediate gap-width (G/D = 4), both TSC-SPU and TSC-SPD generate the S-S flow type. Still, the TSC-SPU is advantageous in drag reduction, where the drag of the upstream and downstream cylinders is reduced by 1.61% and 7.26%, respectively. On the other hand, the S-S flow type is established for low gap-width (G/D = 2) with TSC-SPD setup for which the drag reduction for upstream and downstream cylinders are 1.85% and 12.76%, respectively.

Automated summary

A numerical study is conducted to investigate the effect of a splitter plate (SP) on the unsteady wake regime of tandem square cylinders arranged with different gap widths. The results show that the length of the SP and the gap width have a significant influence on the shear layer characteristics, wake regime, and flow-induced forces on the cylinders. Four distinct flow patterns are observed, with the controlled wake regime resulting in significantly reduced drag on the cylinders.