Until the recent operating experience of steam generator tube degradation at San Onofre Nuclear Power Plant, in-plane fluid-elastic instability has not been observed even though the computed fluid-elastic instability margin may not met. The criterion is established in the literature. Two way coupled fields multi-physics modeling is investigated as an additional approach to address the phenomenon before the design is finalized. It is established in the literature that in order to model the damping controlled fluid elastic instability, a finite time delay between tube vibration and fluid perturbation must be realized. The phase lag between tube vibration and flow perturbation due to damping must be adequately captured by the model. The effects of tube frequency, turbulence level, location, and mean gap velocity on the relative phase values must also be captured. This approach will allow the time delay between tube vibration and flow perturbation due to damping, as well as turbulence, and stiffness to be intrinsically modeled.The simulation of fluid-elastic instability has been investigated using multi-physics software and by benchmarking against an experiment that utilized an air-water two-phase cross-flow and straight tube bundle with a pitch-todiameter ratio of 1.633. The experiments have been performed for the specific mass flux and void fraction. The present study compares the flow pattern, tube vibration model response, and the fluid-elastic instability for the tube bundle. 
The numerical methods used in this work are based on constitutive equations which intrinsically satisfy the equations for unsteady flow defined ,&nbsp;upon which out-of-plane FEI is governed. However this numerical method can be applied to in plane FEI of which there is a dearth of empirical results. We will introduce the applicability of the method to in-plane FEI in a future paper once we have based lined it against out of plane FEI empirical results. This a novel approach to address FEI in steam generators, heretofore not found in the literature.

Two Way Coupled Fields Multi-Physics Modeling Is Investigated as an Additional Approach to Address Fluid Elastic Instability

Paper Proceedings: https://asmedigitalcollection.asme.org/PVP/PVP2021/volume/85314

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