Experimental study on flow-induced vibrations of an equilateral triangular prism with a high mass ratio

Abstract

The mass ratio exerts a significant influence on the vibration responses exhibited by a bluff body in cross flows. In this investigation, the flow-induced vibration (FIV) of a transversely oscillating equilateral triangular prism, characterized by a high mass ratio (m* = 23.15), is experimentally examined to enhance our comprehension of these influences at elevated m*. Various angles of attack (AoA), ranging from α = 0°–60° with 5° increment, where α = 0° and 60° correspond to scenarios of one vertex facing upstream and downstream, respectively. The reduced velocity ranged from Ur = 3.0 to 31.0. The vibration responses are categorized into four regimes according to amplitudes and spectral characteristics: no vibration (α = 0°–20°), intermittent galloping (α = 25°), separated vortex-induced vibration (VIV) and galloping (α = 30°–35°), and galloping (α = 40°–60°). The implications of high m* are profound in the intermittent galloping regime, characterized by random and intermittent vibration responses, which is uniquely observed in the FIV of a triangular prism with a high mass ratio. Additionally, for FIV at high m*, the onset of galloping occurs at a notably lower Ur, and the restart of the prism's vibration in separated VIV and galloping regime is initiated by lower harmonic synchronization. Hard galloping is discerned exclusively at α = 60°, and the distinctions from soft galloping are deliberated.