  We present the development and benchmarking of an in-house fluid-structure
interaction (FSI) solver. An implicit partitioned approach is utilized to
couple a sharp-interface immersed boundary (IB) method based flow solver and a
finite-element method based structural solver. In the present work, the
coupling is accelerated using a dynamic under-relaxation scheme. The revised
coupling is around two to three times faster and numerically stable, as
compared to the one that uses a constant under-relaxation parameter. The solver
is validated against two FSI benchmarks in which a thin, finite thickness,
elastic splitter plate is attached to the lee side of a circular or square
rigid cylinder, subjected to laminar flow. In these two-dimensional benchmarks,
the flow induces a wave-like deformation in the plate, and it attains a
periodic self-sustained oscillation. We employ the FSI solver to analyze the
flow-induced vibration (FIV) of the plate in a uniform laminar free-stream flow
for a wide range of mass ratio and bending stiffness at Reynolds number ($Re$)
of 100, based on the diameter of the cylinder. At the given $Re$,
two-dimensional numerical simulations show that the FIV of the plate
effectively depends only on the mass ratio and bending stiffness. The largest
displacement of the plate vibration is found to occur in the lock-in region,
where the vortex shedding frequency of the coupled fluid-structure system is
close to the natural frequency of the splitter plate. We briefly discuss wake
structures and phase plots for different cases of mass ratio and bending
stiffness.
