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Evaluation method for In-plane FEI of triangular array tube bundle
Shingo Nishida

Last modified: 2018-06-25


Recently, tube-to-tube wear indications of triangular tube bundle steam generators caused by in-plane fluid elastic instability (FEI) have been reported. Several experiments were conducted to investigate the characteristics of in-plane FEI by our research group. In a series of experiments, particular characteristics were found. For example, critical velocity difference between in-plane and out of plane directions, difference between straight tube bundle test and U-bend tube bundle test etc.. To explain these characteristics, we measured unsteady fluid force acting on tubes under high temperature and pressure steam-water two phase flow conditions close to the steam generators. And stability analysis was conducted using the measured unsteady fluid force. Firstly, stability analyses were conducted to simulate straight tube bundle tests. Analysis results agreed well with experiments and it could explain critical velocity trend against number of flexible tubes and directions of vibration. Secondly, U-tube stability analyses were also conducted by applying unsteady fluid force coefficients for each location of U-bend tube FEM model. From the results, mechanisms of in-plane FEI were explained. We decided Conners’ constant K of in-plane FEI conservatively based on consideration above.


tube bundles;fluid elastic instability;stability analysis

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