Direct-forcing immersed boundary modeling of vortex-induced vibration of a circular cylinder

A numerical study of the vortex-induced vibration (VIV) of aflexible supported circular cylinder using the direct-forcing immersed boundary (DFIB) method incorporating the virtual force term is investigated. The use of DFIB method eliminates the requirement of mesh regeneration at each time step, owing to the movement of the cylinder, a practice which is common with body-fitted grid setups. The fluctuating hydrodynamic forces may cause the vibration of the structure due to vortex shedding behind it. In reality, this vibration phenomenon may result in the failure of the structure especially for the so-called lock-in/synchronization phenomenon. The present study shows that a dynamically mounted circular cylinder is allowed to vibrate transversely only or both in the in-line and the transverse directions in a uniformflow at a moderate Reynolds number. The effects of reduced velocity and gap ratio on VIV are discussed. Hydrodynamic coefficients of a freely vibrating cylinder are analyzed in time and spectral domains. The cylinder orbits the slightly oval-shaped and eight-shaped motions in the lock-in regime. Moreover, the 2S and the C(2S) vortex shedding modes can be found at the low amplitude vibration and the large amplitude vibration, respectively. The comparisons against the published data prove the capability of the present DFIB model. This proposed model can be useful for the investigation of VIV of the structures.