Flow around tandem cylinder is solved using UPACS-LES code developed in JAXA. Delayed detached-eddy-simulation (DDES) is used, and order of numerical schemes and grid density are changed to investigate their sensitivities to the near-field flow and far-field noise. The results are compared with the experimental results. It became apparent that near-field flow structures including both steady and unsteady components are sensitive to the numerical scheme and grid density. As spatial resolution is increased, the results tend to converge toward the experimental results. On the other hand, far-field noise is insensitive to the spatial resolution. The dominant noise is generated by the impingement of the upstream cylinder wake on the downstream cylinder, and this large scale feature is already captured by the lowest spatial resolution case which we have calculated. The highest resolution case with long spanwise length (18D) shows good agreement in terms of both tonal and broadband component. © 2011 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.