- Copyright 2015 by the International Society of Offshore and Polar Engineers (ISOPE). In this paper, we present numerical simulations of free span pipelines under vortex-induced vibrations (VIV) and pipe-soil interactions. Pipeline is simplified as a tensioned beam with uniformly distributed tension. The flow field around the pipeline is computed by numerically solving the unsteady Navier-Stokes equations. Fluid domain is discretized using an overset grid system including embedding, overlapping and matching grids. Simulation results are compared to experiments for validation in two cases: one for an isolated pipeline in uniform current without boundary effect, and the other for a free span pipeline lying on soil bottom. General agreements are observed.