Numerical simulations of a single vortex superimposed on a uniform flow past a circular cylinder are performed using large eddy simulation (LES), unsteady Reynolds averaged Navier-Stokes equations (URANS) and delayed detached eddy simulation (DDES) for a high Reynolds number flow, Re=1.4x10^6, based on the cylinder diameter and the free stream velocity. The URANS approach fails to accurately predict the unsteady flow field due to excessive dissipation. The LES technique provides a promising tool for obtaining the unsteady wall-pressure fields, aerodynamic coefficients and the acoustic source functions. From the LES results, it was observed that presence of the vortex in the flow field causes an increase of Strouhal number. The influence of vortex-cylinder horizontal miss-distance on the aerodynamic coefficients was also investigated, indicating that the flow field will record to its original state after similar time intervals, about 0.06s.