The flow past a rigid-fixed cylinder and a self-oscillating cylinder is simulated at Re=5000. The finite-volume based CFD package OpenFOAM is used for flow computations for a rigid-fixed cylinder. Extensive mesh convergence and time-step studies are conducted for a cylinder span of 2D (twice the diameter). Spanwise-pressure correlations and spectral calculations are conducted using longer cylinder span lengths: 4D, 8D and 16D. As the cylinder span size increases, better spanwise correlations are obtained. For a self-oscillating cylinder, the numerical approach that tightly couples DDES and FEA based on a fixed point iteration is used to predict the amplitude response and drag in a lock-in condition. The results of the rigid-fixed and self-oscillating cylinder computations compare favorably with experimental data.