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Blade dynamical response based on aeroelastic analysis of fluid structure interaction in turbomachinery

ENERGY 2016年 115卷 986-995页

作者： Brahimi, F. Ouibrahim, A. Univ Mouloud Mammeri Lab Energet Mecan & Mat Tizi Ouzou Algeria Univ MHamed Bouguerra Boumerdes Fac Sci Ingn Dept Energet Boumerdes Algeria

The flow around airfoils being an energy tank;instabilities are then possible, leading often to dangerous vibratory levels. In order to predict and control aeroelastic instabilities, this investigation aims to provide a detailed understanding of the flow interaction within the complex geometry of moving blades cascade. Among the working parameters, we consider the effect of the pressure rate on the blades aeroelastic instabilities under an unsteady compressible flow. We investigate the consequences of the airfoil motion onto the aerodynamic performances, the energy transfer between the flow and the structure and the aerodynamic stability. The nonlinear aeroelastic model is based on a dynamic fluid code, a structure code and a weak coupling algorithm. Numerical simulations are conducted in three airfoil situations: fixed, pitching and free motions. The simulation results show that the pressure rate has an effect on the blade aeroelastic instabilities, their amplitude and their type: flutter and limit cycle oscillations (LCOs). The oscillation amplitude and the energy transferred to the airfoil increase more rapidly as the pressure rate increases. These instabilities have significant effects on the aerodynamic loads. Analysing the energy exchange and the aerodynamic work, we note that the aerodynamic stability is very sensible to the pressure ratio. (C) 2016 Elsevier Ltd. All rights reserved.

关键词： Aeroelasticity Energy fluid-structure interaction Instability Turbomachinery CFD

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An overlapping domain technique coupling spectral and finite elements for fluid-structure interaction

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COMPUTERS & fluidS 2015年 123卷 235-245页

作者： Verkaik, A. C. Hulsen, M. A. Bogaerds, A. C. B. van de Vosse, F. N. Eindhoven Univ Technol Dept Biomed Engn NL-5600 MB Eindhoven Netherlands Eindhoven Univ Technol Dept Mech Engn NL-5600 MB Eindhoven Netherlands Ctr Mat Sci DSM Res Geleen Netherlands

In this study the coupled overlapping domain (COD) technique, previously developed within our group, is extended to make it suitable for fluid-structure interaction (FSI) computations with flexible elastic solids. A standard FSI benchmark from literature is implemented to verify the computations of the COD technique. However, in this study the incompressible neo-Hookean material model is applied instead of the compressible St. Venant-Kirchhoff model. The results of the COD technique are compared to the solutions obtained with a full finite element method. The performed computations demonstrate the COD technique accurately computes the solids displacements and the forces on the elastic solid. The results of the COD technique also show a good resemblance with the results obtained by other researchers, even with the use of a different material model. Additionally, the COD technique is applied to compute a rotating elastic beam in a square box filled with fluid. The computations show that the COD technique is capable of computing large deformations and translations, which makes this technique suitable for a wide range of applications without the need for computationally expensive remeshing. (C) 2015 Elsevier Ltd. All rights reserved.

关键词： fluid-structure interaction Spectral elements Finite elements Non-conforming meshes Overlapping domains

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Well-posedness and robust preconditioners for discretized fluid-structure interaction systems

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COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING 2015年 292卷 69-91页

作者： Xu, Jinchao Yang, Kai Penn State Univ Dept Math University Pk PA 16802 USA Penn State Univ Ctr Computat Math & Applicat University Pk PA 16802 USA

In this paper we develop a family of preconditioners for the linear algebraic systems arising from the arbitrary Lagrangian-Eulerian discretization of some fluid-structure interaction models. After the time discretization, we formulate the fluid-structure interaction equations as saddle point problems and prove the uniform well-posedness. Then we discretize the space dimension by finite element methods and prove their uniform well-posedness by two different approaches under appropriate assumptions. The uniform well-posedness makes it possible to design robust preconditioners for the discretized fluid-structure interaction systems. Numerical examples are presented to show the robustness and efficiency of these preconditioners. (C) 2014 Elsevier B.V. All rights reserved.

关键词： fluid-structure interaction Stabilization Robust preconditioners

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Comparison between one-way and two-way fluid-structure interaction simulations of a horizontal tidal current turbine

Comparison between one-way and two-way fluid-structure inter...

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第二届全球华人水动学学术会议

作者： Zhipeng Deng Qiuhao Hu Yifan Dong Ye Li School of Mechanical Engineering Purdue University Mutiple funtional towing tank School of Naval ArchitectureOcean and Civil EngineeringShanghai Jiao Tong University

CFD and FSI methods have been used to predict the performance of tidal current ***,few researches compared the difference of various FSI methods to power efficiency and structural response of turbine *** this study,we first used BEM method to design and optimize *** one-way and two-way FSI methods were realized in ANSYS CFX to compare the *** results showed that one-way FSI method overestimated the power efficiency and underestimated tipvortex strength comparing to two-way ***,blade deformation and stress distribution presented limited variations for different *** also found that the maximum blade displacement and Von-Mises stress amplitude had nearly a linear relationship with TSR,while maximum stress location was unchanged in different working conditions.

关键词： Tidal current turbine fluid-structure interaction method comparison blade deformation stress distribution

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A NURBS-based immersed methodology for fluid-structure interaction

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COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING 2015年 284卷 943-970页

作者： Casquero, Hugo Bona-Casas, Carles Gomez, Hector Univ A Coruna Dept Metodos Matemat La Coruna 15071 Spain

We introduce an isogeometric, immersed, and fully-implicit formulation for fluid-structure interaction (FSI). The method focuses on viscous incompressible flows and nonlinear hyperelastic incompressible solids, which are a common case in various fields, such as, for example, biomechanics. In our FSI method, we utilize an Eulerian mesh on the whole domain and a Lagrangian mesh on the solid domain. The Lagrangian mesh is arbitrarily located on top of the Eulerian mesh in a non-conforming fashion. Due to the formulation of our problem, based on the Immersed Finite Element Method (IFEM), we do not need mesh update or remeshing algorithms. The fluid-structure interface is the boundary of the Lagrangian mesh, but cuts arbitrarily the Eulerian mesh. The generalized- alpha method is used for time discretization and NURBS-based isogeometric analysis is employed for the spatial discretization on both fluid and solid domains. The information transfer between the two meshes is carried out using the NURBS functions, which avoids the use of the so-called discretized delta functions. The higher order and especially the higher continuity of NURBS functions allow us to deal with severe mesh distortion in the Lagrangian mesh in comparison with classical C-0 linear piecewise functions as we prove numerically. Our numerical solutions attain good agreement with theoretical data for free-falling objects in two and three dimensions, which confirms the feasibility of our methodology. (C) 2014 Elsevier B.V. All rights reserved.

关键词： fluid-structure interaction Isogeometric analysis Immersed methods NURBS Variational multiscale Collocation methods

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Numerical modeling and investigation of viscoelastic fluid-structure interaction applying an implicit partitioned coupling algorithm

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JOURNAL OF fluidS AND structureS 2015年 54卷 390-421页

作者： Chen, Xingyuan Schaefer, Michael Bothe, Dieter Tech Univ Darmstadt Ctr Smart Interfaces Inst Math Modeling & Anal D-64287 Darmstadt Germany Tech Univ Darmstadt Grad Sch Computat Engn D-64293 Darmstadt Germany Tech Univ Darmstadt Chair Numer Methods Mech Engn D-64293 Darmstadt Germany Tech Univ Darmstadt Dept Math D-64289 Darmstadt Germany

We investigate the interaction between a viscoelastic Oldroyd-B fluid and an elastic structure via simulations applying an implicit partitioned coupling algorithm. Simulations are done for a flow through a channel with a flexible wall and a lid-driven cavity flow with flexible bottom. In addition, we make use of a mass-spring-dashpot prototype model to study the dynamic interaction problem. Both the simulation results and the analysis of the prototype model show that there are obvious differences in the fluid-structure interaction if the fluids are viscoelastic instead of purely viscous. These differences appear in the deformation of the solid at stationary state and in the equilibrium position, amplitude, frequency as well as phase shift of the oscillation. Moreover, we investigate the influence of numerical and physical parameters on the implicit partitioned coupling algorithm for simulation of viscoelastic fluid-structure interaction problems. (C) 2014 Elsevier Ltd. All rights reserved.

关键词： Viscoelastic fluids fluid-structure interaction Numerical simulation Mass-spring-dashpot model Implicit partitioned coupling algorithm Lid-driven cavity

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Low-density lipoprotein accumulation within a carotid artery with multilayer elastic porous wall: fluid-structure interaction and non-Newtonian considerations

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JOURNAL OF BIOMECHANICS 2015年第12期48卷 2948-2959页

作者： Deyranlou, Amin Niazmand, Hamid Sadeghi, Mahmood-Reza Ferdowsi Univ Mashhad Dept Mech Engn Mashhad Iran Ferdowsi Univ Mashhad Biomed Engn Res Ctr Mashhad Iran Univ Isfahan Dept Biomed Engn Esfahan Iran

Low-density lipoprotein (LDL), which is recognized as bad cholesterol, typically has been regarded as a main cause of atherosclerosis. LDL infiltration across arterial wall and subsequent formation of Ox-LDL could lead to atherogenesis. In the present study, combined effects of non-Newtonian fluid behavior and fluid-structure interaction (FSI) on LDL mass transfer inside an artery and through its multilayer arterial wall are examined numerically. Navier-Stokes equations for the blood flow inside the lumen and modified Darcy's model for the power-law fluid through the porous arterial wall are coupled with the equations of mass transfer to describe LDL distributions in various segments of the artery. In addition, the arterial wall is considered as a heterogeneous permeable elastic medium. Thus, elastodynamics equation is invoked to examine effects of different wall elasticity on LDL distribution in the artery. Findings suggest that non-Newtonian behavior of filtrated plasma within the wall enhances LDL accumulation meaningfully. Moreover, results demonstrate that at high blood pressure and due to the wall elasticity, endothelium pores expand, which cause significant variations on endothelium physiological properties in a way that lead to higher LDL accumulation. Additionally, results describe that under hypertension, by increasing angular strain, endothelial junctions especially at leaky sites expand more dramatic for the high elastic model, which in turn causes higher LDL accumulation across the intima layer and elevates atherogenesis risk. (C) 2015 Elsevier Ltd. All rights reserved.

关键词： fluid-structure interaction Non-Newtonian Low-density lipoprotein transport Multi layer model Porous media

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Computational fluid-structure interaction simulation of airflow in the human upper airway

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JOURNAL OF BIOMECHANICS 2015年第13期48卷 3685-3691页

作者： Pirnar, Jernej Dolenc-Groselj, Leja Fajdiga, Igor Zun, Iztok Univ Ljubljana Fac Mech Engn Lab Fluid Dynam & Thermodynam Ljubljana 1000 Slovenia Univ Med Ctr Ljubljana Div Neurol Inst Clin Neurophysiol Ljubljana Slovenia Univ Med Ctr Ljubljana Dept Otorhinolaryngol & Cervicofacial Surg Ljubljana Slovenia

Obstructive sleep apnoea syndrome (OSAS) is a breathing disorder in sleep developed as a consequence of upper airway anatomical characteristics and sleep-related muscle relaxation. fluid-structure interaction (FSI) simulation was adopted to explain the mechanism of pharyngeal collapse and snoring. The focus was put on the velopharyngeal region where the greatest level of upper airway compliance was estimated to occur. The velopharyngeal tissue was considered in a way that ensures proper boundary conditions, at the regions where the tissue adheres to the bone structures. The soft palate with uvula was not cut out from the surrounding tissue and considered as an isolated structure. Both, soft palate flutter as well as airway narrowing have been obtained by 3D FSI simulations which can be considered as a step forward to explain snoring and eventual occlusion. It was found out that during the inspiratory phase of breathing, at given elastic properties of the tissue and without taking gravity into consideration, velopharyngeal narrowing due to negative suction pressure occurs. Furthermore, soft palate flutter as the main attribute of snoring was predicted during the expiratory phase of breathing. The evaluated flutter frequency of 17.8 Hz is in close correlation with the frequency of explosive peaks of sound that are produced in palatal snoring in inspiratory phase, as reported in literature. (C) 2015 Elsevier Ltd. All rights reserved.

关键词： Upper airway OSAS Snoring Segmentation of CT data fluid-structure interaction

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Effects of Dynamic fluid-structure interaction on Seismic Response of Multi-Span Deep Water Bridges Using Fragility Function Method

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ADVANCES IN STRUCTURAL ENGINEERING 2015年第4期18卷 525-541页

作者： Pang, Yutao Kai, Wei Yuan, Wancheng Shen, Guoyu Tongji Univ State Key Lab Disaster Reduct Civil Engn Shanghai 200092 Peoples R China

This paper employs the fragility function method to study the effects of dynamic fluid-structure interaction on seismic response of multi-span deep water bridges. Currently, two approaches are widely used to study the dynamic fluid-structure interaction effect of structures: the analytical 'added mass' method and full-scale two- or three dimensional finite element modeling. This paper offers a computationally economical yet adequate procedure. In this procedure, Morrison equation is employed to calculate the added mass for piles and columns, and a water-foundation coupling system is modeled to calculate the added mass for pile cap. In this water-foundation coupling system, a pile beam-element was adopted to avoid the thorough water domain modeling. A typical multi-span continuous composite girder bridge in China lying in deep water environment is used as a case study. The uncertainty of modeling parameters is considered using an experimental design method. The limit state functions are derived through a simple fuzzy model. Fragility functions of pier column and pile foundation are developed using nonlinear time history analysis. Fragility curves conditioned on different parameters in fuzzy models and different water depth are then compared to illustrate the effects of fuzziness and seismic hydrodynamic pressure. In general, for bridges with only pile surrounding water, the influence of water on potential damage of bridges is small and can be practically negligible. However, for the cases which the pile cap is under the water, increasing the water depth can generally increase the damage probability. It is concluded that for deep water bridges, the influence of dynamic fluid-structure interaction can be harmful to bridge responses, which aggravates with water depth by increasing the displacement of pile cap and introducing larger seismic demands on pier columns.

关键词： deep water bridges fragility function fluid-structure interaction finite element uncertainty

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Efficient shape optimization for fluid-structure interaction problems

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JOURNAL OF fluidS AND structureS 2015年 57卷 298-313页

作者： Aghajari, Nima Schaefer, Michael Tech Univ Darmstadt Inst Numer Methods Mech Engn D-64293 Darmstadt Germany

An approach for the shape optimization of fluid-structure interaction (PSI) problems is presented. It is based on a partitioned solution procedure for fluid-structure interaction, a shape representation with NURBS, and sequential quadratic programming approach for optimization within a parallel environment with MPI as direct coupling tool. The optimization procedure is accelerated by employing reduced order models based on a proper orthogonal decomposition method with snapshots and Kriging. After the verification of the PSI optimization, the functionality and efficiency of the reduced order modeling as well as the corresponding optimization procedure are investigated. (C) 2015 Elsevier Ltd. All rights reserved.

关键词： fluid-structure interaction Shape optimization Reduced order modeling

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