Study on Fluid-Elastic Instability of Tube Bundles in Cross Flow Based on Spatiotemporal Coherence

Abstract The flow-induced vibration (FIV) of tube bundles of steam generator is a complex fluid-structure interaction with coupling of multibody. With the impact of the surrounding tubes, the vibration of the tube is excited by forces with different frequencies, and the vibration of tube bundles turns to be nonlinear. At the same time, due to the existence of asymmetry in the support of the tube bundle, resulting in different intrinsic frequencies in the streamwise and transverse directions of the tube bundle, which can result in the difficulty in perdition of fluid elastic instability (FEI). In this work, the fluid elastic instability of tube bundle with different frequency ratios Rf is investigated through water tunnel experiment and numerical simulation. The target tube arrays are rotated triangular arrays with pitch ratio of 1.33 and 1.41. The effects of frequency ratios on the amplitude and frequency response of the tube bundle are analyzed, while the coherence is induced into the analysis of the route to instability. The results show that the critical velocity can be affected by frequency ratios Rf, but the effect of Rf differs in tube arrays with different pitch ratios. The evolution of Lyapunov exponents shows the nonlinearity of the vibration can be influenced by Rf. The method and results of this work can be helpful in the prediction critical velocity of FEI in tube bundles in cross flow.