Seismic Analysis and Design of a 21,000-Gallon Frac Tank Considering the Fluid-Structure Interaction Effects for a FLEX Response at a Nuclear Power Station

Author(s):  
Christine H. Roy ◽  
Michael Mudlock
2009 ◽  
Vol 131 (3) ◽  
Author(s):  
Jean-François Sigrist ◽  
Daniel Broc

Seismic analysis of steam generator is of paramount importance in the safety assessment of nuclear installations. These analyses require, in particular, the calculation of frequency, mode shape, and effective modal mass of the system eigenmodes. As fluid-structure interaction effects can significantly affect the dynamic behavior of immersed structures, the numerical modeling of the steam generator has to take into account FSI. A complete modeling of heat exchangers (including pressure vessel, tubes, and fluid) is not accessible to the engineer for industrial design studies. In the past decades, homogenization methods have been studied and developed in order to model tubes and fluid through an equivalent continuous media, thus avoiding the tedious task to mesh all structure and fluid subdomains within the tube bundle. Few of these methods have nonetheless been implemented in industrial finite element codes. In a previous paper (Sigrist, et al., 2007, “Fluid-Structure Interaction Effects Modeling for the Modal Analysis of a Nuclear Pressure Vessel,” J. Pressure Vessel Technol., 123, pp. 1–6), a homogenization method has been applied to an industrial case for the modal analysis of a nuclear rector with internal structures and coupling effects modeling. The present paper aims at investigating the extension of the proposed method for the dynamic analysis of tube bundles with fluid-structure interaction modeling. The homogenization method is compared with the classical coupled method in terms of eigenfrequencies, eigenmodes, and effective modal masses.


Author(s):  
T. Liaghat ◽  
F. Guibault ◽  
L. Allenbach ◽  
B. Nennemann

Fluid-structure interaction (FSI) and unavoidable vibrations are important characteristics in the operation of hydropower structures and must be taken into account in the analysis and design of such equipment. Hydrodynamic damping influences the amplitude of vibrations and is directly related to fatigue problems in hydraulic machines which are of great importance. The aim of this study is to investigate the coupled effects of flowing fluid on a simplified hydrofoil by using three-dimensional two-way fluid-structure interaction modeling, in order to determine its importance in predicting vibration amplitudes and damping. The effect of considering different flow velocities is also investigated in the present study. The results of this research are compared with those obtained from experiments done by ANDRITZ [1]. The influences of mesh size and time step are also studied. Our results indicate that considering FSI in predicting the frequencies of the fluctuating fluid forces in practical problems might be ignored if the main concern of the analysis is to check the possibility of resonance. However, FSI must be included in the modeling when we aim to predict the influence of the fluid on the damping behavior in the hydrofoil vibration.


Author(s):  
Marie Pomarede ◽  
Aziz Hamdouni ◽  
Erwan Liberge ◽  
Elisabeth Longatte ◽  
Jean-Franc¸ois Sigrist

Tube bundles in steam boilers of nuclear power plants and nuclear on-board stokehold are known to be exposed to high levels of vibrations under flowing fluid. This coupled fluid-structure problem is still a challenge for engineers, first because of the difficulty to fully understand it, second because of the complexity for setting it up numerically. Although numerical techniques could help the understanding of such a mechanism, a complete simulation of a fluid past a whole elastically mounted tube bundle is currently out of reach for engineering purposes. To get round this problem, the use of a reduced-order model has been proposed with the introduction of the widely used Proper Orthogonal Decomposition (POD) method for a flow past a fixed structure [M. Pomare`de, E. Liberge, A. Hamdouni, E.Longatte, & J.F. Sigrist - Simulation of a fluid flow using a reduced-order modelling by POD approach applied to academic cases; PVP2010, July 18–22, Seattle]. Interesting results have been obtained for the reconstruction of the flow. Here a first step is to propose to consider the case of a flow past a fixed tube bundle configuration in order to check the good reconstruction of the flow. Then, an original approach proposed by Liberge (E. Liberge; POD-Galerking Reduction Models for Fluid-Structure Interaction Problems, PhD Thesis, Universite´ de La Rochelle, 2008) is applied to take into account the fluid-structure interaction characteristic; the so-called “multiphase” approach. This technique allows applying the POD method to a configuration of a flow past an elastically mounted structure. First results on a single circular cylinder and on a tube bundle configuration are encouraging and let us hope that parametric studies or prediction calculations could be set up with such an approach in a future work.


Author(s):  
A. R. M. Gharabaghi ◽  
A. Arablouei ◽  
A. Ghalandarzadeh ◽  
K. Abedi

The dynamic response of gravity type quay wall during earthquake including soil-sea-structure interaction is calculated using ADINA finite element techniques. The main objective of this study is to investigate the effects of fluid-structure interaction on the residual displacement of wall after a real earthquake. A direct symmetric coupled formulation based on the fluid velocity potential is used to calculate the nonlinear hydrodynamic pressure of sea water acting on the wall. The doubly asymptotic approximation (DAA) is used to account for the effects of outer fluid on the inner region. The non-associated Mohr-Coulomb material behavior is applied to model the failure of soil. The full nonlinear effective stress analysis is performed in this study and the soil-pore fluid interaction effects are modeled using porous media formulation. Viscous boundary condition is implemented to model the artificial boundary in direct method analysis of soil-structure interaction system and sliding contact condition was modeled in the interface of wall and surrounding soil. A typical configuration of gravity quay wall is used for analysis and three real earthquakes excitation are applied as base acceleration. The results show that influence of fluid-structure interaction effects on the permanent displacement of a gravity quay wall constructed on relatively non-liquefiable site is not considerable.


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