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

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 alpha = 0 degrees-60 degrees with 5 degrees increment, where alpha = 0 degrees and 60 degrees 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 (alpha = 0 degrees-20 degrees), intermittent galloping (alpha = 25 degrees), separated vortex-induced vibration (VIV) and galloping (alpha = 30 degrees-35 degrees), and galloping (alpha = 40 degrees-60 degrees). 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 alpha = 60 degrees, and the distinctions from soft galloping are deliberated.