This paper describes the development of a tool for predicting the vibration response of elastically mounted bluff bodies (in this case a cylindrical tube or tube arrays) excited by fluid forces in cross-flow. The modelling approach utilizes computational-fluid-dynamics (CFD) to model the transient behaviour of the fluid flow with explicit coupling to a structural model of the bluff body. The structural model represents the inertial, damping and spring characteristics of the bluff body. The paper presents preliminary validation of the model for laminar and turbulent flow in single tube arrangements. Validation against experiment emphasizes comparison with mean and RMS drag and lift values, along with Strouhal number to measure fluid vortex-shedding frequency. The results represent a preliminary step in the development of a methodology to extract force coefficients, obtained directly by coupling CFD and FEA, for introduction into unsteady structural (vibration) response models applicable to large tube arrays.