Transition of FIV for a circular cylinder with splitter plates

Abstract

A flow-induced vibration (FIV) investigation to show the transition from vortex-induced vibration (VIV) to galloping for a circular cylinder equipped with a rear rigid splitter plate was undertaken in a water tunnel at Reynolds number of 1100-7700. The length of the splitter plate is in a range of L∗=0-4.0 (L∗ = L/D, L is the plate length, D is the cylinder diameter). The dependence of oscillation characteristics, vortex evolution, force coefficients, mean added mass and effective added mass on L∗ is illustrated in detail. In the investigated L∗, five oscillation patterns are identified successively: VIV, combined VIV–galloping, separated weak VIV (WVIV)–galloping, WVIV and weak galloping, WVIV and desynchronized. For L∗ = 0.4–1.8, severe galloping is observed at high reduced velocities. The oscillation can be well suppressed when L∗>3.2. The transition from VIV to galloping, indeed, is the competition of vortex shedding and free shear layers attachment. At low reduced velocities, the oscillation is always synchronized with the vortex shedding. Beyond a critical plate length (0.4D), however, galloping is found at high reduced velocities, despite of the interference of vortex shedding. Harmonic force component at three times the oscillation frequency is identified in the galloping dominated region for L∗ = 0.4–1.8. Although it has little energy transfer to the oscillation, considerable negative effective added mass is induced.