Ongoing research is motivated by the need to better understand the cross-flow and cylinder mechanical interactions leading to vibration processes in close-packed triangular cylinder array. Computational Fluid Dynamics (CFD) simulations have been done with open source OpenFOAM software. Unsteady Reynolds Averaged Navier-Stokes equations for incompressible flows are solved by the finite volume method. Several two-equation turbulence models have been investigated: standard k-epsilon, RNG k-epsilon, and realisable k-epsilon model. Based on the pressure drop comparison between the calculations and the experiment, the RNG k-epsilon turbulence model has been chosen. CFD simulated quasi-steady-state flow serves as an initial condition for further transient modelling. A spring-mounted cylinder(s) is installed in an array of surrounding rigid cylinders. The neighbourhood rods’ influence on the oscillating rod in the bundle system is studied numerically. Oscillations of the cylinder have been described with mass-spring motion equation. Flexible supports allow vibrating the cylinder in both, the longitudinal and transverse direction under the action of unsteady hydrodynamic forces. Dynamic changes of mesh cells ensure that cylinder motion acts on bypassing flow.