• International Journal of Aeronautical and Space Sciences
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• v.13 no.2
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• pp.127-153
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• 2012

This paper presents an advanced computational method for the prediction of the responses in the frequency domain of general linear dissipative structural-acoustic and fluid-structure systems, in the low-and medium-frequency domains and this includes uncertainty quantification. The system under consideration is constituted of a deformable dissipative structure that is coupled with an internal dissipative acoustic fluid. This includes wall acoustic impedances and it is surrounded by an infinite acoustic fluid. The system is submitted to given internal and external acoustic sources and to the prescribed mechanical forces. An efficient reduced-order computational model is constructed by using a finite element discretization for the structure and an internal acoustic fluid. The external acoustic fluid is treated by using an appropriate boundary element method in the frequency domain. All the required modeling aspects for the analysis of the medium-frequency domain have been introduced namely, a viscoelastic behavior for the structure, an appropriate dissipative model for the internal acoustic fluid that includes wall acoustic impedance and a model of uncertainty in particular for the modeling errors. This advanced computational formulation, corresponding to new extensions and complements with respect to the state-of-the-art are well adapted for the development of a new generation of software, in particular for parallel computers.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2008.11a
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• pp.571-572
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• 2008

• Journal of the Korea institute for structural maintenance and inspection
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• v.9 no.1
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• pp.271-281
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• 2005

The effects of radiation damping is used to compensate the truncated boundary which is relatively close to the structure-fluid interface in the fluid element surrounding the submerged structures. An efficient ring element is presented to model the shell and fluid element which fully utilizes the characteristics of the axisymmetry. The computational model uses the technique which separate the meridional shape and circumferential wave mode and gets similar result with the exact solution in the eigenvalues and the earthquake analysis. The fluid-structure interaction techniques is developed in the finite element analysis of two dimensional problems using the relations between pressure, nodal unknown acceleration and added mass assuming the fluid to be invicid, incompressible and irrotational. The effectiveness and efficiency of the technique is demonstrated by analyzing the free vibration and seismic analysis using the added mass matrix considering the structural deformation effect.

• Computational Structural Engineering
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• v.6 no.4
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• pp.73-82
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• 1993

Investigated in this paper is the effect of fluid-structure interaction between reactor internal components due to their immersion in a confining fluid on the dynamic responses. A non-linear mathematical model is developed for the dynamic analysis of the reactor internals, which includes lumped masses, stiffnesses and hydrodynamic couplings. The hydrodynamic mass matrix which characterizes the fluid-structure interaction is calculated. Also, the equations of motion containing hydrodynamic mass matrix are presented. The responses of the reactor internals due to seismic and pipe break excitations are obtained for the case of with- and without-hydrodynamic couplings and the different response characteristics are investigated.

• Structural Engineering and Mechanics
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• v.12 no.1
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• pp.101-118
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• 2001

The reliable prediction of elastic vibrations of wetted complex structures, as ships, tanks, offshore structures, propulsion components etc. represent a theoretical and numerical demanding task due to fluid-structure interaction. The paper presented is addressed to the vibration analysis by a combined FE-BE-procedure based on the added mass concept utilizing a direct boundary integral formulation of the potential fluid problem in interior and exterior domains. The discretization is realized by boundary element collocation method using conventional as well as infinite boundary element formulation with analytical integration scheme. Particular attention is devoted to modelling of interior problems with both several separate or communicating fluid domains as well as thin-walled structures wetted on both sides. To deal with this specific kind of interaction problems so-called "virtual" boundary elements in areas of cut outs are placed to satisfy the kinematical conditions in partial connected fluid domains existing in realistic tank systems. Numerical results of various theoretical and practical examples demonstrate the performance of the BE-methodology presented.

• Structural Engineering and Mechanics
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• v.21 no.1
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• pp.101-119
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• 2005

An efficient methodology is presented to evaluate the seismic behavior of a Fluid-Elevated Tank-Foundation/Soil system taking the embedment effects into accounts. The frequency-dependent cone model is used for considering the elevated tank-foundation/soil interaction and the equivalent spring-mass model given in the Eurocode-8 is used for fluid-elevated tank interaction. Both models are combined to obtain the seismic response of the systems considering the sloshing effects of the fluid and frequency-dependent properties of soil. The analysis is carried out in the frequency domain with a modal analysis procedure. The presented methodology with less computational efforts takes account of; the soil and fluid interactions, the material and radiation damping effects of the elastic half-space, and the embedment effects. Some conclusions may be summarized as follows; the sloshing response is not practically affected by the change of properties in stiff soil such as S1 and S2 and embedment but affected in soft soil. On the other hand, these responses are not affected by embedment in stiff soils but affected in soft soils.

• International Journal of Fluid Machinery and Systems
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• v.3 no.4
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• pp.342-351
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• 2010

During the operation of a hydro turbine the fluid mechanical pressure loading on the turbine blades provides the driving torque on the turbine shaft. This fluid loading results in a structural load on the component which in turn causes the turbine blade to deflect. Classically, these mechanical stresses and deflections are calculated by means of finite element analysis (FEA) which applies the pressure distribution on the blade surface calculated by computational fluid dynamics (CFD) as a major boundary condition. Such an approach can be seen as a one-way coupled simulation of the fluid structure interaction (FSI) problem. In this analysis the reverse influence of the deformation on the fluid is generally neglected. Especially in axial machines the blade deformation can result in a significant impact on the turbine performance. The present paper analyzes this influence by means of fully two-way coupled FSI simulations of a propeller turbine utilizing two different approaches. The configuration has been simulated by coupling the two commercial solvers ANSYS CFX for the fluid mechanical simulation with ANSYS Classic for the structure mechanical simulation. A detailed comparison of the results for various blade stiffness by means of changing Young's Modulus are presented. The influence of the blade deformation on the runner discharge and performance will be discussed and shows for the configuration investigated no significant influence under normal structural conditions. This study also highlights that a two-way coupled fluid structure interaction simulation of a real engineering configuration is still a challenging task for today's commercially available simulation tools.

• Structural Engineering and Mechanics
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• v.41 no.4
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• pp.559-573
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• 2012

An adaptive modeling and simulation technique is introduced for the effective and reliable fluid-structure interaction analysis using MSC/Dytran for large-scale complex pressurized liquid containment. The proposed method is composed of a series of the global rigid sloshing analysis and the locally detailed fluid-structure analysis. The critical time at which the system exhibits the severe liquid sloshing response is sought through the former analysis, while the fluid-structure interaction in the local region of interest at the critical time is analyzed by the latter analysis. Differing from the global coarse model, the local fine model considers not only the complex geometry and flexibility of structure but the effect of internal pressure. The locally detailed FSI problem is solved in terms of multi-material volume fractions and the flow and pressure fields obtained by the global analysis at the critical time are specified as the initial conditions. An in-house program for mapping the global analysis results onto the fine-scale local FSI model is developed. The validity and effectiveness of the proposed method are verified through an illustrative numerical experiment.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2011.04a
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• pp.553-556
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• 2011

The primary aim of the present study is to propose new design formulae that can be used to evaluate the structural performance of breakwaters installed on container carriers under green water impact loads. A series of numerical analyses for green water impact loads inducing breakwater collapse have been carried out. The well-known fluid-structure interaction analysis technique has been adopted realistically to consider the phenomenon of green water impact loads. The structural behavior of these breakwaters under green water impact loads has also been carried out simultaneously throughout the transient analysis. A verification study of the numerical results was performed using the actual collapse incidents of breakwaters on container carriers. It would be expected that the proposed design formulae, based on the obtained insights, could be used as practical guidelines for the design of breakwaters on container carriers.

• Structural Engineering and Mechanics
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• v.33 no.4
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• pp.407-428
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• 2009

The effects of the uniform and spatially varying ground motions on the stochastic response of fluid-structure interaction system during an earthquake are investigated by using the displacement based fluid finite elements in this paper. For this purpose, variable-number-nodes two-dimensional fluid finite elements based on the Lagrangian approach is programmed in FORTRAN language and incorporated into a general-purpose computer program SVEM, which is used for stochastic dynamic analysis of solid systems under spatially varying earthquake ground motion. The spatially varying earthquake ground motion model includes wave-passage, incoherence and site-response effects. The effect of the wave-passage is considered by using various wave velocities. The incoherence effect is examined by considering the Harichandran-Vanmarcke and Luco-Wong coherency models. Homogeneous medium and firm soil types are selected for considering the site-response effect where the foundation supports are constructed. A concrete gravity dam is selected for numerical example. The S16E component recorded at Pacoima dam during the San Fernando Earthquake in 1971 is used as a ground motion. Three different analysis cases are considered for spatially varying ground motion. Displacements, stresses and hydrodynamic pressures occurring on the upstream face of the dam are calculated for each case and compare with those of uniform ground motion. It is concluded that spatially varying earthquake ground motions have important effects on the stochastic response of fluid-structure interaction systems.