Experimental and numerical investigations of flow-induced vibration of tube arrays subjected to cross flow

Abstract

Flow-induced vibration of tube array structures is a major concern in nuclear engineering. In this paper, the dynamical behavior of flexible tubes in cross flow is studied. A computational fluid dynamics (CFD) model is developed to investigate the interaction between flow perturbations and tube oscillations. The Large Eddy Simulation (LES) is validated and adopted in the simulations. The motion of tubes in different tube configurations (i.e., single tube, three in line tubes, normal square tube array, and normal triangle tube array with different pitch to diameter ratios) under different flow conditions are analyzed and compared by time trace, power spectral density (PSD), phase plane plot and Poincaré map. Experiments have been conducted using a flexible tube in a closed-loop piping system to compare with the CFD model predictions. It is found that tube undergoes vortex-induced vibration and then fluid elastic instability, limit-cycle oscillation occurs when the inlet flow velocity exceeds a critical point. The central tube in normal square tube array is the most stable among the three configurations. The critical pitch to diameter ratio of tube array under reduced velocity Ur = 6 is about 5.5. The experimental observations are in good agreement with the CFD predictions.