LAUSR

Abstract Flow-induced vibration (FIV) of a circular cylinder with an attached rigid splitter plate is studied. A stabilized finite element formulation is utilized to solve the incompressible flow equations in two-dimensions. Three regimes of FIV are identified for the range of reduced speed ( 1 ≤ U ∗ ≤ 70 ) studied: vortex-induced vibration (VIV), steady flow and galloping. The effect of mass ratio, 2 ≤ m ∗ ≤ 1000 , is studied for the R e = 150 flow (Reynolds number is based on diameter of the cylinder, D ) and splitter plate of length, L p = 3 . 5 D . In contrast to an isolated cylinder, the peak response of the cylinder with splitter plate is associated with a significantly smaller amplitude and the lock-in occurs over a wider range of U ∗ . The U ∗ for the onset of lock-in increases with increase in m ∗ . The end of lock-in, however, is independent of m ∗ . In addition, unlike the isolated cylinder, the transition from desynchronization to lock-in is gradual, except for very large m ∗ . Although galloping occurs for all m ∗ , its onset is strongly dependent on m ∗ . The end of lock-in regime of VIV is immediately followed by onset of galloping for small m ∗ . For this range of m ∗ , the galloping is strongly influenced by vortex shedding. A steady regime, wherein the vibration is completely suppressed for a certain range of U ∗ , occurs beyond the lock-in regime for moderate m ∗ . However, galloping eventually ensues and revives the unsteadiness at large U ∗ . For very large m ∗ , the steady flow regime is replaced by a desynchronization region. In general, the onset of galloping is delayed to larger U ∗ with increase in m ∗ . The effect of the length of the splitter plate ( L p ∕ D = 1 . 5 , 2.5 and 3.5) on FIV is studied for m ∗ = 10 . The steady flow regime is observed only for L p = 3 . 5 D . Increase in L p leads to a small increase in the peak amplitude and range of lock-in during VIV. The effect on galloping is more significant; the amplitude of vibration, at a given U ∗ , decreases with increase in L p . The frequency of vibration decreases, during both VIV and galloping, with increase in L p . The effect of R e , within the laminar regime, is studied. Its effect on the amplitude of vibration is found to be similar to that of L p .