Scaling of added mass and added damping of cylindrical rods by means of FSI simulations

In this work, the effects of different working fluids on the dynamics of vibrating rods in fluid flows is investigated by means of Fluid–Structure Interaction (FSI) simulations. Different fluids with a wide range of density and viscosity are considered. For each of these fluids, FSI simulations are performed to extract the modal parameters of the system. The turbulent fluid flow is modeled by means of the URANS (Unsteady Reynolds-averaged Navier–Stokes) approach, whereas the rod is modeled as an elastic solid. The two-way coupling FSI solver implemented in the commercial code STAR-CCM+ is used to perform the numerical simulations. The computed modal parameters are first used to evaluate the added mass and the added damping of the rod for the different fluid flows. Subsequently, a correlation that predicts the variation of the added mass and added damping with the fluid density and fluid viscosity is proposed. It is found that the added mass varies linearly with the fluid density and is independent of the fluid viscosity. The added mass coefficient for the system considered in this work is close to the unitary value. The added damping is a non-linear function of both fluid density and viscosity. Finally, a Rayleigh damping model to include added damping effects in a structural solver is proposed. The proposed correlation predicts very well the added mass effects. The added damping effects are also predicted reasonably well, especially for lower values of fluid density and viscosity.