The flow past a bluff body creates an unstable wake in the form of a K ́rm ́n alley, characterized by the shedding of vortices at a well-defined frequency. In return, these vortices exert periodic in-line and cross-flow forces on the bluff body. If the shedding frequency is close to the natural frequency of the body, such oscillations excite large structural vibrations known as vortex-induced vibrations (VIVs). The control of VIV amplitudes is of practical interest for many engineering amplications, for instance low vibration amplitudes help improve the stealth of military aircrafts and to prevent fatigue damage on the risers used in offshore petroleum production. Conversely, large vibration amplitudes of a cylinder in water streams are valuable in the perspective of renewable energy production, for instance, electrical energy can be produced if the oscillation of the cylinder periodically displaces a magnet inside a coil. As a first step towards the control of such vibration amplitudes, we present here a dedicated flow-structure solver developed in the open-source OpenFOAM suite. The solver combine an implicit predictor-corrector method classically used to solve the incompressible Navier-Stokes equations and a state of the art Immersed Boundary Method (IBM). For flows with moving boundaries, the IBM indeed offers an attractive alternative to more classical (but more costly) remeshing strategies. We will discuss the dynamics of several test cases pertaining to 2D flow past fixed cylinders and moving cylinders subjected to forced cross-flow oscillations, for which preliminary results at Reynolds numbers in the range Re=30-500 are in good agreement with reference data reported in the literature.