Splitter-plate proximity-induced transitions in flow-induced vibration of a triangular prism

The effect of a splitter-plate downstream of an elastically mounted equilateral triangular prism on flow-induced vibration is numerically investigated at Reynolds number Re = 100, mass ratio m* = 10, damping ratio zeta = 0.005, cylinder-plate gap G* = 0.3, and various angle of attacks alpha = 0 degrees-60 degrees. The alpha = 0 degrees and 60 degrees correspond to vertex and edge of the cylinder facing the free stream. Under the effect of the splitter plate, a single transition from vortex-induced vibration (VIV) to proximity-induced galloping (PIG) in the vibrational response for an axisymmetric circular cylinder is reported, whereas, for the present non-axisymmetric triangular prisms, the varying alpha exhibits four proximity-induced transitions: VIV to modified VIV at smaller alpha = 0 degrees and 25 degrees, VIV to PIG at alpha = 35 degrees, distinct VIV-galloping to combined PIG-galloping at alpha = 40 degrees, and asymmetric to symmetric-galloping at larger alpha = 60 degrees. The plate results in more symmetric vibration for high alpha >= 35 degrees, while a reduction is observed for alpha <= 25 degrees. The gap-flow leads to onset (alpha = 35 degrees) and enhancement (alpha = 40 degrees) of afterbody re-attachment on the prism, which significantly enhances the galloping instability and vibrational amplitude. A reduction in galloping instability leading to a slight reduction in amplitude is found for alpha = 60 degrees prism. The study shows that the presence of the splitter-plate downstream influences near-wake structure and far-wake vortex shedding modes, which lead to stabilizing and destabilizing near-wake flow and distinct vibrational characteristics-depending on the angle of attack (alpha).