Fluid-elastic instability characteristics of a U-tube bundle were experimentally investigated in air-water two-phase flow. A total of 39 U-tubes were arranged in a rotated square array with a pitch-to-diameter ratio of 1.633. Vibration responses of four U-tubes were measured with three-axis accelerometers. Two sets of experiments were performed to investigate the onset of fluid-elastic instability, and the damping and hydrodynamic mass of the U-tube. The experiments were performed for a void fraction of 70–95%. Fluid-elastic instability was clearly observed in an out-of-plane mode vibration. The effect of a primary side flow on the vibration of U-tube was investigated separately. The damping ratio of the present U-tube was higher than the damping ratio of the cantilever tubes in the literature. The hydrodynamic mass of the U-tube was generally in accordance with the hydrodynamic mass of the cantilever tubes in the literature. The instability constant of the Connors equation was assessed with a simplified effective gap velocity, and the fluid-elastic instability constant was 8.5.
Fluid-Elastic Instability of Rotated Square Array U-Tubes in Air-Water Flow
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Chu, I., Chung, H. J., and Lee, C. H. (June 12, 2009). "Fluid-Elastic Instability of Rotated Square Array U-Tubes in Air-Water Flow." ASME. J. Pressure Vessel Technol. August 2009; 131(4): 041301. https://doi.org/10.1115/1.3148187
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