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Highlights • Simulation and shaking table test was done to identify the vibration characteristics of drain pipe. • Natural frequency, mode shape, and transmissibility were determined and compared. • The new design is expected to successfully suppress the vibration response. • Additional design change may be needed for further vibration reduction. Abstract The drain pipe of the steam generators in nuclear power plants is designed to remove the remaining reactor coolant when the nuclear power plant stops. In the normal electricity generating condition of the nuclear power plant, the drain pipe acts as the pressure boundary between the primary coolant system and outside, which forbids the radioactive coolant to be leaked. Therefore, it is important to assure the structural integrity of the drain pipe, which is closely related with the vibration characteristics of the drain pipe. In this paper, the vibration characteristics of the previous and newly designed drain pipes are investigated by simulation and measurement with the shaking table test. The purpose of the new design was to suppress the excessive vibration in the interested low and high frequency ranges, which were observed in the power uprating of plants. From the measured results, in y direction, the first three modal frequencies are increased by 5, 18, and 50 Hz in the low frequency region, and the higher order modes are excluded in the interested high frequency region with the adoption of the new design. Further design modification is required to reduce the high frequency vibration in x direction with other approaches. In general, it is expected from the result that the newly designed drain pipe is more robust to the existing vibration compared with the previous one. [ABSTRACT FROM AUTHOR]

This paper treats the two-phase flow-induced vibration in pipes. A broad range of two-phase flow conditions, including bubbly, dispersed and slug flow, were tested in a clamped-clamped straight horizontal pipe. The vibration response of both transversal directions for two span lengths was measured. From experimental results, an in-depth discussion on the nature of the flow excitation and flow-parameters influence is presented. The hydrodynamic mass parameter is also studied. Experimental results suggest that it is proportional to mixture density. On the other hand, two analytical formulations were developed and tested against experimental results. One formulation predicts the quadratic trend between standard deviation of acceleration and shear velocity found in experiments. The other formulation indicates that the peak-frequency of vibration response depends strongly on void fraction. It provides accurate predictions of peak-frequency, predicting 97.6% of the data within ±10% error bands. [ABSTRACT FROM AUTHOR]

Highlights: [•] A theoretical study on vibration analysis of pipes with FSI is presented. [•] Pipelines with high fluid pressure and velocity can be solved by developed method. [•] Several pipeline schemes are discussed to illustrate the application of the method. [•] The proposed method is easier to apply compared to most existing procedures. [•] Influence laws of structural and fluid parameters on FSI of pipe are analyzed. [ABSTRACT FROM AUTHOR]