Vortex-induced vibrations (VIV) and galloping effects are studied for the case of two cylinders in tandem arrangement. Both cylinders are allowed to move in X and Y directions and rigidity is kept the same for both directions. The cross-flow around moving cylinders is computed using a specifically designed numerical method which has been thoroughly validated through systematic comparisons between numerical and available experimental results. The motion of cylinders is computed with a 4th order explicit Runge-Kutta method. The coupling between flow and structural computations is semi-implicit in the sense that the potential part of the flow is implicitly taken into account by the structural solver. This confers the required stability to the coupling procedure. After validation results, we present configurations for center-to-center distances L/D=2 and 4 and reduced velocities ranging from 3 to 10 at laminar Reynolds number of 200.


Flow-Induced Vibrations of structures are a phenomenon well known to civil engineers since it may generate structural fatigue or threaten the integrity of the overall structure in extreme situations. For arrays of offshore risers, both VIV and fluidelastic instabilities, such as wake galloping, have been observed. If VIV for single circular cylinders are well documented, VIV, interference and galloping phenomena studies for arrays of cylinders remain sparse since Zdravkovitch (1985). Since then we may notice, for example, the investigation of Assi et al. (2006) concerning flow-induced vibration interference for a Cylinder free to move in the Y direction while the front cylinder is kept fixed. To our knowledge, there exists no numerical study of flow-induced vibration cylinder arrays. In this paper we study VIV, interference and galloping phenomena occurring when two circular cylinders in tandem arrangement are placed in a uniform cross-flow. These configurations are evaluated numerically.

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