Vibration characteristics of a downstream cylinder with rounded corners in an equilateral triangular arrangement at Reynolds number of 180

In this study, we numerically investigate the vibration response of a cylinder arranged in an equilateral triangle with two stationary upstream cylinders at a low Reynolds number of Re = 180. We concentrate on three different rounded corner arrangements: four rounded corners (FRCs), upwind rounded corners (URCs), and leeward rounded corners (LRCs). In addition, we examine three dimensionless rounded corner radii: 0.1, 0.3, and 0.5. The results indicate that as the dimensionless radius increases, the influence of the corner position on the dimensionless amplitude and frequency becomes more pronounced. Furthermore, the dimensionless amplitude and dimensionless frequency curves exhibit significant variations under the different corner arrangements. Within the reduced velocity range (Vr) of 2–5, rounded corners are observed to reduce both the lift and drag coefficients. An increase in the dimensionless radius for a given corner configuration acts to decrease both the lift and drag coefficients. Frequency-domain analysis of the lift coefficient and dimensionless displacement indicates that the observed frequency peaks caused by mutual interference are produced by irregular vortex shedding due to the mutual extrusion and merging of shear layers. At Vr = 4, the FRC, URC, and LRC configurations with a corner radius of 0.5 all exhibit the 2S vortex shedding mode. As Vr increases, the vortex shedding mode for LRCs with a corner radius of 0.5 progressively becomes irregular. At Vr = 16, the vortex shedding mode for LRCs with a corner radius of 0.5 is the regular 2P + 2S mode.