Fluid-structure interaction among three tandem circular cylinders oscillating transversely at a low Reynolds number of 150

The flow-induced vibration (FIV) of three tandem circular cylinders is numerically investigated using OpenFOAM based on the finite-volume method. The one-degree-of-freedom dynamic response of three tandem circular cylinders with a spacing ratio ranging from 2 to 6 is analysed at a low Reynolds number of 150 over a reduced velocity range of 2–16. The results of hydrodynamic coefficients, response amplitude, vibration frequency, wake structure, and decomposition of vorticity are discussed in this study. Although the streamwise spacing ratio is constant, the dynamic evolution of the crossing angles among three cylinders leads to the switching of wake interference mode. The two-layered vortices are merged into secondary vortices in the far wake, and the energy of secondary vortices is higher than the two-layered vortices. The upstream cylinder exhibits a similar trend as an isolated cylinder in terms of the variations of hydrodynamic coefficients and response amplitude with the reduced velocity. In contrast, the middle and downstream cylinders experience a significantly lower drag due to the shielding effect. Particularly at small spacing ratios, the drag on the middle cylinder becomes negative. At the same time, the lift coefficient and response amplitude are higher than those of an isolated cylinder at high reduced velocities. The three tandem cylinders intermittently form a triangular configuration during the oscillation.