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A NUMERICAL APPROACH TO THE STANDARD MODEL OF WATER HAMMER WITH fluid-structure interaction

JOURNAL OF THEORETICAL AND APPLIED MECHANICS 2015年第3期53卷 543-555页

作者： Henclik, Slawomir Polish Acad Sci Inst Fluid Flow Machinery Gdansk Poland

In the classic water hammer (WH) theory, 1D liquid flow in a quasi-rigid pipe is assumed. When the pipe is flexible or is fixed to the foundation with elastic supports, the dynamic fluid structure interaction (FSI) should be taken into account for more accurate modelling of the system behaviour. The standard model of WH-FSI for a straight pipe reach is governed by fourteen hyperbolic partial differential equations of the first order, two for 1D liquid flow and twelve for 3D motion of the pipe. This model is presented in the paper and an algorithm for its numerical solution based of the method of characteristics is proposed. Basic boundary conditions (BC) are shortly discussed. The important condition at the junction of two sub-pipes fixed to the foundation with a viscoelastic support is presented in details and a general method of its solution is proposed.

关键词： water hammer transient pipe flow fluid-structure interaction standard model method of characteristics

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A viscoelastic fluid-structure interaction model for carotid arteries under pulsatile flow

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INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING 2015年第5期31卷 e02709页

作者： Wang, Zhongjie Wood, Nigel B. Xu, Xiao Yun Univ London Imperial Coll Sci Technol & Med Dept Chem Engn London SW7 2AZ England

In this study, a fluid-structure interaction model (FSI) incorporating viscoelastic wall behaviour is developed and applied to an idealized model of the carotid artery under pulsatile flow. The shear and bulk moduli of the arterial wall are described by Prony series, where the parameters can be derived from in vivo measurements. The aim is to develop a fully coupled FSI model that can be applied to realistic arterial geometries with normal or pathological viscoelastic wall behaviour. Comparisons between the numerical and analytical solutions for wall displacements demonstrate that the coupled model is capable of predicting the viscoelastic behaviour of carotid arteries. Comparisons are also made between the solid only and FSI viscoelastic models, and the results suggest that the difference in radial displacement between the two models is negligible. Copyright (c) 2015 John Wiley & Sons, Ltd.

关键词： carotid artery viscoelastic model pulsatile flow fluid-structure interaction

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Systolic fluid-structure interaction model of the congenitally bicuspid aortic valve: assessment of modelling requirements

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COMPUTER METHODS IN BIOMECHANICS AND BIOMEDICAL ENGINEERING 2015年第12期18卷 1305-1320页

作者： Kuan, May Y. S. Espino, Daniel M. Univ Birmingham Sch Mech Engn Birmingham B15 2TT W Midlands England

A transient fluid-structure interaction (FSI) model of a congenitally bicuspid aortic valve has been developed which allows simultaneous calculation of fluid flow and structural deformation. The valve is modelled during the systolic phase (the stage when blood pressure is elevated within the heart to pump blood to the body). The geometry was simplified to represent the bicuspid aortic valve in two dimensions. A congenital bicuspid valve is compared within the aortic root only and within the aortic arch. Symmetric and asymmetric cusps were simulated, along with differences in mechanical properties. A moving arbitrary Lagrange-Euler mesh was used to allow FSI. The FSI model requires blood flow to induce valve opening and induced strains in the region of 10%. It was determined that bicuspid aortic valve simulations required the inclusion of the ascending aorta and aortic arch. The flow patterns developed were sensitive to cusp asymmetry and differences in mechanical properties. Stiffening of the valve amplified peak velocities, and recirculation which developed in the ascending aorta. Model predictions demonstrate the need to take into account the category, including any existing cusp asymmetry, of a congenital bicuspid aortic valve when simulating its fluid flow and mechanics.

关键词： bicuspid aortic valve fluid-structure interaction multi-physics modelling congenital malformation

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Novel structural modeling and mesh moving techniques for advanced fluid-structure interaction simulation of wind turbines

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INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING 2015年第3-4期102卷 766-783页

作者： Bazilevs, Y. Korobenko, A. Deng, X. Yan, J. Univ Calif San Diego Dept Struct Engn La Jolla CA 92093 USA

In this paper, we target more advanced fluid-structure interaction (FSI) simulations of wind turbines than reported previously. For this, we illustrate how the recent advances in isogeometric analysis of thin structures may be used for efficient structural mechanics modeling of full wind turbine structures, including tower, nacelle, and blades. We consider both horizontal axis and vertical axis wind turbine designs. We enhance the sliding-interface formulation of aerodynamics, previously developed to handle flows about mechanical components in relative motion such as rotor-tower interaction to allow nonstationary sliding interfaces. To accommodate the nonstationary sliding interfaces, we propose a new mesh moving technique and present its mathematical formulation. The numerical examples include structural mechanics verification for the new offshore wind turbine blade design, FSI simulation of a horizontal axis wind turbine undergoing yawing motion as it turns into the wind and FSI simulation of a vertical axis wind turbine. The FSI simulations are performed at full scale and using realistic wind conditions and rotor speeds. Copyright (C) 2014 John Wiley & Sons, Ltd.

关键词： horizontal axis wind turbine vertical axis wind turbine sliding interface fluid-structure interaction isogeometric analysis composites thin shells NURBS mesh moving

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Partitioned coupling strategies for fluid-structure interaction with large displacement: Explicit, implicit and semi-implicit schemes

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WIND AND structureS 2015年第3期20卷 423-448页

作者： He, Tao Shanghai Normal Univ Dept Civil Engn Shanghai 201418 Peoples R China Univ Birmingham Sch Civil Engn Birmingham B15 2TT W Midlands England

In this paper the unsteady fluid-structure interaction (FSI) problems with large structural displacement are solved by partitioned solution approaches in the arbitrary Lagrangian-Eulerian finite element framework. The incompressible Navier-Stokes equations are solved by the characteristic-based split (CBS) scheme. Both a rigid body and a geometrically nonlinear solid are considered as the structural models. The latter is solved by Newton-Raphson procedure. The equation governing the structural motion is advanced by Newmark-beta method in time. The dynamic mesh is updated by using moving submesh approach that cooperates with the ortho-semi-torsional spring analogy method. A mass source term (MST) is introduced into the CBS scheme to satisfy geometric conservation law. Three partitioned coupling strategies are developed to take FSI into account, involving the explicit, implicit and semi-implicit schemes. The semi-implicit scheme is a mixture of the explicit and implicit coupling schemes due to the fluid projection splitting. In this scheme MST is renewed for interfacial elements. Fixed-point algorithm with Aitken's.2 method is carried out to couple different solvers within the implicit and semi-implicit schemes. Flow-induced vibrations of a bridge deck and a flexible cantilever behind an obstacle are analyzed to test the performance of the proposed methods. The overall numerical results agree well with the existing data, demonstrating the validity and applicability of the present approaches.

关键词： fluid-structure interaction arbitrary Lagrangian-Eulerian finite element method coupling scheme vortex-induced vibrations large displacement

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Numerical evaluation of blood viscosity affecting pulse wave propagation in a fluid-structure interaction model

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BIOMEDICAL ENGINEERING-BIOMEDIZINISCHE TECHNIK 2015年第1期60卷 11-15页

作者： He, Fan Hua, Lu Gao, Li-jian Beijing Univ Civil Engn & Architecture Sch Sci Dept Mech Beijing 100044 Peoples R China Chinese Acad Med Sci Fuwai Hosp Natl Ctr Cardiovasc Dis Key Lab Clin Trial Res Cardiovasc DrugsMinist Hl Beijing 100037 Peoples R China Peking Union Med Coll Beijing 100037 Peoples R China

High blood viscosity often causes cardiovascular diseases, such as hypertension, atherosclerosis and thrombosis. It is proven that blood viscosity plays an important role in cardiovascular functions. In this paper, pulse wave characteristics with normal and high blood viscosities are presented in detail to evaluate how blood viscosity affects pulse wave propagation. A fluid-structure interaction is employed to solve for pulse wave characteristics. The results show that increased blood viscosity does not change the time delay of wave propagation. However, high viscosity reduces the velocity amplitude, while it enhances the pressure level. This study provides physical insight for evaluating blood viscosity leading potentially to pulse wave changes.

关键词： blood viscosity finite element method fluid-structure interaction pulse wave propagation

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Particle-image velocimetry investigation of the fluid-structure interaction mechanisms of a natural owl wing

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BIOINSPIRATION & BIOMIMETICS 2015年第5期10卷 056009页

作者： Winzen, A. Roidl, B. Schroeder, W. Rhein Westfal TH Aachen Inst Aerodynam D-52062 Aachen Germany

The increasing interest in the development of small flying air vehicles has given rise to a strong need to thoroughly understand low-speed aerodynamics. The barn owl is a well-known example of a biological system that possesses a high level of adaptation to its habitat and as such can inspire future small-scale air vehicle design. The combination of the owl-specific wing geometry and plumage adaptations with the flexibility of the wing structure yields a highly complex flow field, still enabling the owl to perform stable and at the same time silent low-speed gliding flight. To investigate the effects leading to such a characteristic flight, time-resolved stereoscopic particle-image velocimetry (TR-SPIV) measurements are performed on a prepared natural owl wing in a range of angles of attack 0 degrees <= alpha <= 6 degrees and Reynolds numbers 40 000 <= Re-c <= 120 000 based on the chord length at a position located at 30% of the halfspan from the owl's body. The flow field does not show any flow separation on the suction side, whereas flow separation is found on the pressure side for all investigated cases. The flow field on the pressure side is characterized by large-scale vortices which interact with the flexible wing structure. The good agreement of the shedding frequency of the pressure side vortices with the frequency of the trailing-edge deflection indicates that the structural deformation is induced by the flow field on the pressure side. Additionally, the reduction of the time-averaged mean wing curvature at high Reynolds numbers indicates a passive lift-control mechanism that provides constant lift in the entire flight envelope of the owl.

关键词： natural owl wing time-resolved stereoscopic PIV fluid-structure interaction

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FINITE ELEMENT MODELING OF THE HUMAN COCHLEA USING fluid-structure interaction METHOD

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JOURNAL OF MECHANICS IN MEDICINE AND BIOLOGY 2015年第3期15卷

作者： Xu, Lifu Huang, Xinsheng Ta, Na Rao, Zhushi Tian, Jiabin Shanghai Jiao Tong Univ State Key Lab Mech Syst & Vibrat Inst Vibrat Shock & Noise Shanghai 200240 Peoples R China Fudan Univ Zhongsan Hosp Dept Otorhinolaryngol Shanghai 200032 Peoples R China

In this paper, a 3D finite element (FE) model of human cochlea is developed. This passive model includes the structure of oval window, round window, basilar membrane (BM) and cochlear duct which is filled with fluid. Orthotropic material property of the BM is varying along its length. The fluid-structure interaction (FSI) method is used to compute the responses in the cochlea. In particular, the viscous fluid element is adopted for the first time in the cochlear FE model, so that the effects of shear viscosity in the fluid are considered. Results on the cochlear impedance, BM response and intracochlear pressure are obtained. The intracochlear pressure includes the scala vestibule and scala tympani pressure are extracted and used to calculate the transfer functions from equivalent ear canal pressures to scala pressures. The reasonable agreements between the model results and the experimental data in the literature prove the validity of the cochlear model for simulating sound transmission in the cochlea. Moreover, this model predicted the transfer function from equivalent ear canal pressures to scala pressures which is the input to the cochlear partition.

关键词： Finite element model human cochlea fluid-structure interaction basilar membrane intracochlear pressure

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EVALUATION OF THE fluid-structure interaction EFFECTS IN A LEAD-COOLED FAST REACTOR

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NUCLEAR TECHNOLOGY 2015年第1期189卷 1-10页

作者： Lo Frano, R. Univ Pisa DICI I-56126 Pisa Italy

The aim of the study is to investigate the structural effects induced by a beyond design basis earthquake on the main safety relevant structures and components of an isolated liquid metal reactor, such as the European Lead-cooled SYstem (ELSY) or ALFRED projects. An extensive R&D program related to heavy-metal cooled systems was recently carried out as Euratom projects of the 6th and 7th Framework Programmes, addressing many of the most important issues related to the viability of a lead-cooled fast reactor. The importance of seismic effects is mainly related to the high inertial forces of the primary coolant (liquid metal) and associated with the impact of the liquid waves on the reactor structures. The isolation devices considered for the design were represented by means of an iso-elastic approach. Moreover, the influence of isolator failure was also evaluated. The fluid-structure interaction and the sloshing phenomenon, characterized by hydrodynamic and impact forces, were numerically investigated, since an explicit analytical solution for structures of such complex geometry is not possible. Numerical calculations (i.e., dynamic nonlinear analyses) were carried out with appropriate finite element method codes and external coupling. A validation analysis was further performed to check the consistency and adequacy of the method used with respect to the American Society of Civil Engineers (ASCE) 4-98 rules. The accelerations propagated in the reactor building confirmed the favorable effect of the seismic isolation, even with 2% faulted isolators. The results indicated that the stress state, in the reactor internals, is not sufficient to impair their structural integrity, although there is localized plastic deformation.

关键词： fluid-structure interaction beyond-design-basis earthquake lead-cooled fast reactor

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MODELING OF ILIAC ARTERY ANEURYSM USING fluid-structure interaction

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JOURNAL OF MECHANICS IN MEDICINE AND BIOLOGY 2015年第1期15卷

作者： Sabooni, Hatef Hassani, Kamran Bahraseman, Hamidreza Ghasemi Islamic Azad Univ Dept Biomech Sci & Res Branch Tehran Iran Tennessee Technol Univ Dept Mech Engn Cookeville TN 38505 USA

The aneurysm of iliac artery is a rare entity and there are few computational models that have studied the disease. In this study, we have presented the flow patterns in the aneurysmal artery using fluid-structure interaction method. The blood was assumed Newotonian, pulsatile, laminar, incompressible, and homogenous. The geometry of the model was made based on CT images of clinical cases. Using the computational method, we have obtained the velocity and pressure contours, shear rates and vortices for the healthy and aneurysmal artery. The results show that a pressure maximum was found at the midpoint of the dilation. The vortices are formed in the aneurysmal area(26) and shear rates do not change much. However, the rate increased in the neck of aneurysms. Furthermore, the aneurysm with bigger dilation tend to rupture due to more shear rates in the neck and the velocity at peak systole decreases in the aneurysmal area due to increase of the artery diameter. We have compared our results with some available relevant clinical data in discussion section.

关键词： Iliac aneurysm fluid-structure interaction computational

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