Two-dimensional numerical simulations of the cross-flow around circular cylinders in staggered arrangements have been performed. The part of the water-cooling system rod bundle is investigated. One of the cylinders is free to oscillate in the transverse and longitudinal direction, in response to the fluid loads. The moving cylinder is modelled as a simple mass-spring-damper system. Cylinders are rigid objects. The Navier-Stokes equations and continuity equation are used to describe a fluid. Dynamics of the structure are described by equations of motion. Turbulent incompressible flow with Reynolds number 10 000 is simulated using the Unsteady Reynolds Averaged Navier-Stokes type Low-Re turbulence model. Fluid-structure interaction is modelled by Arbitrary Lagrangian Eulerian framework, which combines the fluid flow formulated using an Eulerian description and a spatial frame with solid mechanics formulated using the Lagrangian description and a material frame. Commercial solver is used for analyzed the process simulation. The numerical results of benchmark cases are compared with literature to check the used methodology.