检索结果-内蒙古大学图书馆

Characterization of a Bioprosthetic Bicuspid Venous Valve Hemodynamics: Implications for Mechanism of Valve Dynamics

引用

EUROPEAN JOURNAL OF VASCULAR AND ENDOVASCULAR SURGERY 2014年第4期48卷 459-464页

作者： Tien, W. -H. Chen, H. Y. Berwick, Z. C. Krieger, J. Chambers, S. Dabiri, D. Kassab, G. S. 3DT Holdings LLC Res & Dev Indianapolis IN USA Univ Washington Dept Aeronaut & Astronaut Seattle WA 98195 USA Indiana Univ Sch Med Dept Surg Indianapolis IN 46202 USA Indiana Univ Sch Med Dept Cellular & Integrat Physiol Indianapolis IN 46202 USA IUPUI Dept Biomed Engn Indianapolis IN USA COOK Med Res Engn Bloomington IN USA

Background: Chronic venous insufficiency (CVI) of the lower extremities is a common clinical problem. Although bioprosthetic valves have been proposed to treat severe reflux, clinical success has been limited due to thrombosis and neointima overgrowth of the leaflets that is, in part, related to the hemodynamics of the valve. A bioprosthetic valve that mimics native valve hemodynamics is essential. Methods: A computational model of the prosthetic valve based on realistic geometry and mechanical properties was developed to simulate the interaction of valve structure (fluid structure interaction, FSI) with the surrounding flow. The simulation results were validated by experiments of a bioprosthetic bicuspid venous valve using particle image velocimetry (PIV) with high spatial and temporal resolution in a pulse duplicator (PD). Results: Flow velocity fields surrounding the valve leaflets were calculated from PIV measurements and comparisons to the FSI simulation results were made. Both the spatial and temporal results of the simulations and experiments were in agreement. The FSI prediction of the transition point from equilibrium phase to valve-closing phase had a 7% delay compared to the PD measurements, while the Ply measurements matched the PD exactly. FSI predictions of reversed flow were within 10% compared to PD measurements. Stagnation or stasis regions were observed in both simulations and experiments. The pressure differential across the valve and associated forces on the leaflets from simulations showed the valve mechanism to be pressure driven. Conclusions: The flow velocity simulations were highly consistent with the experimental results. The FSI simulation and force analysis showed that the valve closure mechanism is pressure driven under the test conditions. FSI simulation and PIV measurements demonstrated that the flow behind the leaflet was mostly stagnant and a potential source for thrombosis. The validated FSI simulations should enable future valve de

关键词： Bioprosthetic valve Venous flow Chronic venous inefficiency fluid-structure interaction Particle image velocimetry

来源：评论

学校读者我要写书评

暂无评论

Numerical Investigation of the Dynamics of a Flexible Filament in the Wake of Cylinder

引用

Advances in Applied Mathematics and Mechanics 2014年第4期6卷 478-493页

作者： Ru-Nan Hua Luoding Zhu Xi-Yun Lu Department of Modern Mechanics University of Science and Technology of ChinaHefei 230026China Department of Mathematical Sciences Indiana University-Purdue University Indianapolis402 North Blackford StreetIndianapolisIN 46202USA

fluid-structure-interaction problems are ubiquitous,complicated,and not yet well *** this paper we investigate the interaction of a leading rigid circular cylinder and a trailing compliant filament and analyze the dynamic responses of the filament in the wake of the *** is revealed that there exist two flapping states of the filament depending on the cylinder-filament separation distance and the relevant critical distance distinguishing the two states is associated with the Reynolds number and the filament *** is also found that the drag coefficient of the cylinder is reduced but that of the filament may be increased or decreased depending on its *** with a single filament in a uniform flow,the filament of the same mechanical properties flapping in the wake of the cylinder has a lower frequency and a greater amplitude.

关键词： fluid-structure interaction immersed boundary-lattice Boltzmann method

来源：评论

学校读者我要写书评

暂无评论

Modified Ghost fluid Method as Applied to fluid-Plate interaction

引用

Advances in Applied Mathematics and Mechanics 2014年第1期6卷 24-48页

作者： Liang Xu Tiegang Liu China Academy of Aerospace Aerodynamics Beijing 100074China LMIB and School of Mathematics and Systems Science Beijing University of Aeronautics and AstronauticsBeijing 100191China

The modified ghost fluid method(MGFM)provides a robust and efficient interface treatment for various multi-medium flow simulations and some particular fluid-structure interaction(FSI)***,this methodology for one specific class of FSI problems,where the structure is plate,remains to be *** work is devoted to extending the MGFM to treat compressible fluid coupled with a thin elastic *** order to take into account the influence of simultaneous interaction at the interface,a fluid-plate coupling system is constructed at each time step and solved approximately to predict the interfacial ***,ghost fluid states and plate load can be defined by utilizing the obtained interfacial states.A type of acceleration strategy in the coupling process is presented to pursue higher *** one-dimensional examples are used to highlight the utility of this method over looselycoupled method and validate the acceleration ***,this method is applied to compute the underwater explosions(UNDEX)near thin elastic *** of strong shock impacting on the thin elastic plate and dynamic response of the plate are *** results disclose that this methodology for treatment of the fluid-plate coupling indeed works conveniently and accurately for different structural flexibilities and is capable of efficiently simulating the processes of UNDEX with the employment of the acceleration strategy.

关键词： fluid-structure interaction modified ghost fluid method compressible flow thin elastic plate underwater explosions.

来源：评论

学校读者我要写书评

暂无评论

Interface handling for three-dimensional higher-order XFEM-computations in fluid-structure interaction

引用

INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING 2009年第7期79卷 846-869页

作者： Mayer, Ursula M. Gerstenberger, Axel Wall, Wolfgang A. Tech Univ Munich Inst Computat Mech D-85747 Garching Germany

Three-dimensional higher-order extended finite element method (XFEM)-computations still pose challenging computational geometry problems especially for moving interfaces. This paper provides a method for the localization of a higher-order interface finite element (FE) mesh in an underlying three-dimensional higher-order FE mesh. Additionally. it demonstrates. how a subtetrahedralization of an intersected element can be obtained, which preserves the possibly curved interface and allows therefore exact numerical integration. The proposed interface algorithm collects initially a set of possibly intersecting elements by comparing their 'eXtended axis-aligned bounding boxes'. The intersection method is applied to a highly reduced number of intersection candidates. The resulting linearized interface is used as input for an elementwise constrained Delaunay tetrahedralization, which computes an appropriate subdivision for each intersected element. The Curved interface is recovered from the linearized interface in the last step. The output comprises triangular integration cells representing the interface and tetrahedral integration cells for each intersected element. Application of the interface algorithm currently concentrates on fluid-structure interaction problems on low-order and higher-order FE meshes, which may be composed of any arbitrary element types such as hexahedra, tetrahedra, wedges, etc. Nevertheless, other XFEM-problems with explicitly given interfaces or discontinuities may be tackled in addition. Multiple structures and interfaces per intersected element can be handled without any additional difficulties. Several parallelization strategies exist depending on the desired domain decomposition approach. Numerical test cases including various geometrical exceptions demonstrate the accuracy, robustness and efficiency of the interface handling. Copyright (C) 2009 John Wiley & Sons, Ltd.

关键词： three-dimensional higher-order extended finite element method (XFEM) fluid-structure interaction interface localization exact numerical integration constrained Delaunay tetrahedralization surface-surface intersection

来源：评论

学校读者我要写书评

暂无评论

Combining numerical and clinical methods to assess aortic valve hemodynamics during exercise

引用

PERFUSION-UK 2014年第4期29卷 340-350页

作者： Bahraseman, H. G. Hassani, K. Khosravi, A. Navidbakhsh, M. Espino, D. M. Fatouraee, N. Kazemi-Saleh, D. Islamic Azad Univ Sci & Res Branch Dept Biomech Tehran Iran Baqiyatallah Univ Med Sci Atherosclerosis Res Ctr Tehran Iran Iran Univ Sci & Technol Dept Mech Engn Tehran Iran Univ Birmingham Sch Mech Engn Birmingham B15 2TT W Midlands England Amirkabir Univ Dept Biomed Engn Tehran Iran

Computational simulations have the potential to aid understanding of cardiovascular hemodynamics under physiological conditions, including exercise. Therefore, blood hemodynamic parameters during different heart rates, rest and exercise have been investigated, using a numerical method. A model was developed for a healthy subject. Using geometrical data acquired by echo-Doppler, a two-dimensional model of the chamber of aortic sinus valsalva and aortic root was created. Systolic ventricular and aortic pressures were applied as boundary conditions computationally. These pressures were the initial physical conditions applied to the model to predict valve deformation and changes in hemodynamics. They were the clinically measured brachial pressures plus differences between brachial, central and left ventricular pressures. Echocardiographic imaging was also used to acquire different ejection times, necessary for pressure waveform equations of blood flow during exercise. A fluid-structure interaction simulation was performed, using an arbitrary Lagrangian-Eulerian mesh. During exercise, peak vorticity increased by 14.8%, peak shear rate by 15.8%, peak cell Reynolds number by 20%, peak leaflet tip velocity increased by 47% and the blood velocity increased by 3% through the leaflets, whereas full opening time decreased by 11%. Our results show that numerical methods can be combined with clinical measurements to provide good estimates of patient-specific hemodynamics at different heart rates.

关键词： echo-Doppler flow fluid-structure interaction hemodynamics natural aortic valve

来源：评论

学校读者我要写书评

暂无评论

Comparison of uniform and spatially varying ground motion effects on the stochastic response of fluid-structure interaction systems

引用

STRUCTURAL ENGINEERING AND MECHANICS 2009年第4期33卷 407-428页

作者： Bilici, Yasemin Bayraktar, Alemdar Adanur, Sueleyman Karadeniz Tech Univ Dept Civil Engn TR-61080 Trabzon Turkey

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.

关键词： spatially varying earthquake motion stochastic analysis Lagrangian approach fluid finite element fluid-structure interaction

来源：评论

学校读者我要写书评

暂无评论

Hemodynamic Effects of Endoleak Formation in Abdominal Aortic Aneurysm Patients with Stent-Graft Implants

引用

JOURNAL OF MEDICAL AND BIOLOGICAL ENGINEERING 2014年第6期34卷 554-558页

作者： Lu, Yueh-Hsun Chen, Chia-Yuan Menon, Prahlad G. Liu, Kuan-Ting Lin, Hsing-Hung Taipei City Hosp Zhongxing Branch Dept Radiol Taipei 103 Taiwan Taipei Vet Gen Hosp Dept Radiol Taipei 112 Taiwan Natl Yang Ming Univ Sch Med Taipei 112 Taiwan Natl Taiwan Univ Sci & Technol Dept Mech Engn Taipei 106 Taiwan Sun Yat Sen Univ Carnegie Mellon Univ Joint Inst Engn Dept Elect & Comp Engn Pittsburgh PA 15213 USA

Endoleaks may evolve and become severe post-surgical complications in patients with abdominal aortic aneurysms (AAAs). After endovascular aortic aneurysm repair (EVAR), endoleaks may induce EVAR failure. Therefore, the early detection and management of endoleak development could help reduce the need for reoperation. An endoleak is characterized by blood flow that leaks into the cavity between the stent-graft (SG) and aneurysm sac. Comprehensive hemodynamic analysis can identify the relationship of flow-induced wall stress and endoleak formation. Given this hypothesis, a numerical analysis of fluid-structure interaction was performed in this study. SG geometry and AAA flow dynamics were incorporated using the physiological conditions of three patient-specific models of AAA after EVAR. Endoleak locations were well matched to the local peak locations of von Mises stress in the aneurysm bulges of these patients. Further investigation on the associated blood flow structures could provide insights on the physical relationship between hemodynamic force and endoleak formation. The presented analytical procedure offers a reliable alternative for endoleak prediction and detection. This method may be used for post-EVAR patient care with sophisticated imaging techniques such as magnetic resonance, computed tomography, and digital subtraction angiography.

关键词： Endoleak Abdominal aortic aneurysm Stent-graft Hemodynamics fluid-structure interaction

来源：评论

学校读者我要写书评

暂无评论

Numerical Study on Vortex Induced Vibration of a Flexible Plate Behind Square Cylinder with Various Flow Velocities

引用

Journal of Shanghai Jiaotong university(Science) 2014年第4期19卷 488-494页

作者：胡世良鲁传敬何友声 Department of Engineering Mechanics Shanghai Jiaotong University MOE Key Laboratory of Hydrodynamics Shanghai Jiaotong University

The vortex induced vibration(VIV) of a flexible plate behind the square head with various flow velocities is simulated. The closely coupling approach is used to model this fluid-structure interaction *** fluid governed by the incompressible Navier-Stokes equations is solved in arbitrary Lagrangian-Eulerian(ALE)frame by the finite volume method. The structure described by the equations of the elastodynamics in Lagrangian representation is discretized by the finite element approach. The numerical results show that the resonance occurs when the frequency of vortex shedding from square head coincides with the natural frequency of plate. And the amplitude of both the structure motion and the fluid load keeps increasing with the time. Furthermore, it is also found that in particular range of flow velocity the vibration of the plate would reach a periodical state. The amplitude of plate oscillating increases with the growth of velocity, while the frequency is locked.

关键词： fluid-structure interaction closely coupling approach vortex induced vibration(VIV) resonance

来源：评论

学校读者我要写书评

暂无评论

Effect of the Inner Material and Pipe Geometry on the Flow and Induced Radiated Noise

引用

TRANSACTIONS OF THE KOREAN SOCIETY OF MECHANICAL ENGINEERS B 2014年第5期38卷 423-430页

作者： Lee, Su-Jeong Lim, Hee-Chang Pusan Natl Univ Sch Mech Engn Busan South Korea

Noise and vibration, which occur in a pipe, are usually caused by the interaction between the turbulent flow and nearby wall. Although it can be estimated by a simple case of expanded pipes having complex turbulent flow, the radiated noise is highly dependent upon the size, shape, and thickness of the given model. In addition, the radiated noise propagates and has serious interference and destabilization effects on the surrounding systems, which can lead to fatigue fracture and failure. This study took advantage of the variety of commercial programs, such as FLUENT (flow solver), NASTRAN (dynamic motion solver of complex structures) and VIRTUAL LAB (radiated noise solver) based on the boundary element method (BEM), to understand the underlying physics of flow noise. The expanded pipe has separation and a high pressure drop because of the abrupt change in the cross-section. Based on the radiated noise calculations, the noise level was reduced to around 20 dB in the range of 100-500 Hz.

关键词： Pulsating Flow Pressure Drop Radiated Noise fluid-structure interaction FFT

来源：评论

学校读者我要写书评

暂无评论

Numerical Model of Full-Cardiac Cycle Hemodynamics in a Total Artificial Heart and the Effect of Its Size on Platelet Activation

引用

JOURNAL OF CARDIOVASCULAR TRANSLATIONAL RESEARCH 2014年第9期7卷 788-796页

作者： Marom, Gil Chiu, Wei-Che Crosby, Jessica R. DeCook, Katrina J. Prabhakar, Saurabh Horner, Marc Slepian, Marvin J. Bluestein, Danny SUNY Stony Brook Dept Biomed Engn Stony Brook NY 11794 USA Univ Arizona Biomed Engn GIDP Tucson AZ USA ANSY S Fluent India Pvt Ltd Pune Maharashtra India ANSY S Inc Evanston IL USA Univ Arizona Dept Biomed Engn Tucson AZ USA Univ Arizona Sarver Heart Ctr Tucson AZ USA

The SynCardia total artificial heart (TAH) is the only Food and Drug Administration (FDA) approved device for replacing hearts in patients with congestive heart failure. It pumps blood via pneumatically driven diaphragms and controls the flow with mechanical valves. While it has been successfully implanted in more than 1300 patients, its size precludes implantation in smaller patients. This study's aim was to evaluate the viability of scaled-down TAHs by quantifying thrombogenic potentials from flow patterns. Simulations of systole were first conducted with stationary valves, followed by an advanced full-cardiac cycle model with moving valves. All the models included deforming diaphragms and platelet suspension in the blood flow. Flow stress accumulations were computed for the platelet trajectories and thrombogenic potentials were assessed. The simulations successfully captured complex flow patterns during various phases of the cardiac cycle. Increased stress accumulations, but within the safety margin of acceptable thrombogenicity, were found in smaller TAHs, indicating that they are clinically viable.

关键词： Total artificial heart Computational fluid dynamics fluid-structure interaction Thrombogenic potential Mechanical circulatory support devices

来源：评论

学校读者我要写书评

暂无评论

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案：

请选择收藏分类：

通借通还

建议与咨询 留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案： 新增检索档案 确定 取消

请选择收藏分类： 新增自定义分类 确定 取消

通借通还

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

请选择保存的检索档案：

请选择收藏分类：