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High-Fidelity Tetrahedral Mesh Generation from Medical Imaging Data for fluid-structure interaction Analysis of Cerebral Aneurysms

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CMES-COMPUTER MODELING IN ENGINEERING & SCIENCES 2009年第2期42卷 131-149页

作者： Zhang, Yongjie Wang, Wenyan Liang, Xinghua Bazilevs, Yuri Hsu, Ming-Chen Kvamsdal, Trond Brekken, Reidar Isaksen, Jorgen Carnegie Mellon Univ Dept Mech Engn Pittsburgh PA 15213 USA Univ Calif San Diego Dept Struct Engn San Diego CA 92103 USA SINTEF Informat & Commun Technol Dept Appl Math Trondheim Norway SINTEF Hlth Res Dept Med Technol Trondheim Norway Univ Hosp N Norway Dept Neurosurg Tromso Norway

This paper describes a comprehensive and high-fidelity finite element meshing approach for patient-specific arterial geometries from medical imaging data, with emphasis on cerebral aneurysm configurations. The meshes contain both the blood volume and solid arterial wall, and are compatible at the fluid-solid interface. There are four main stages for this meshing method: 1) Image segmentation and geometric model construction;2) Tetrahedral mesh generation for the fluid volume using the octree-based method;3) Mesh quality improvement stage, in which edge-contraction, pillowing, optimization, geometric flow smoothing, and mesh cutting are applied to the fluid mesh;and 4) Mesh generation for the blood vessel wall based on the boundary layer generation technique. The constructed meshes are extensively employed in a fully-coupled fluid-structure interaction analysis of vascular blood flow. This paper presents several case studies of hemodynamics in patient-specific cerebral aneurysms.

关键词： Tetrahedral meshing fluid-structure interaction cerebral aneurysm

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A comparison of FE-BE coupling schemes for large-scale problems with fluid-structure interaction

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INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING 2009年第5期77卷 664-688页

作者： Brunner, Dominik Junge, Michael Gaul, Lothar Univ Stuttgart Inst Appl & Expt Mech D-70550 Stuttgart Germany

To predict the sound radiation of structures, both a structural problem and an acoustic problem have to be solved. In case of thin structures and dense fluids, a strong coupling scheme between the two problems is essential, since the feedback of the acoustic pressure onto the structure is not negligible. In this paper, the structural part is modeled with the finite element (FE) method. An interface to a commercial FE package is set up to import the structural matrices. The exterior acoustic problem is efficiently modeled with the Galerkin boundary element (BE) method. To overcome the well-known drawback of fully populated system matrices, the fast multipole method is applied. Different coupling formulations are investigated. They are either based on the Burton-Miller approach or use a mortar coupling scheme. For all cases, iterative solvers with different preconditioners are used. The efficiency with respect to their memory consumption and computation time is compared for a simple model problem. At the end of the paper, a more complex structure is simulated. Copyright (c) 2008 John Wiley & Sons, Ltd.

关键词： fluid-structure interaction multipole boundary element method FE-BE coupling iterative solvers mortar coupling

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Viscous fluid-thin cylindrical elastic layer interaction: asymptotic analysis

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APPLICABLE ANALYSIS 2014年第10期93卷 2032-2056页

作者： Panasenko, G. P. Stavre, R. Univ St Etienne Univ Lyon Inst Camille Jordan CNRSUMR 5208 F-42023 St Etienne France Romanian Acad Simion Stoilow Inst Math Bucharest 014700 Romania

This article represents a generalization of our previous work. We consider a periodic, non-steady, axially symmetric, creeping flow of a viscous incompressible fluid that fills a cylindrical elastic hollow tube. We study the interaction problem " viscous fluid-thin cylindrical elastic layer" when the thickness of the tube wall, e, tends to zero, while the density and the Young's modulus of the elastic material are of order e-1 and e-3, respectively. We construct a complete asymptotic expansion when e tends to zero. The error between the exact solution and the asymptotic one is evaluated in order to justify the asymptotic construction.

关键词： fluid-structure interaction cylindrical elastic hollow tube axially symmetric flow periodic case asymptotic solution error estimate

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Influence of squeeze-film damping on higher-mode microcantilever vibrations in liquid

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EPJ TECHNIQUES AND INSTRUMENTATION 2014年第1期1卷 1-13页

作者： Bircher, Benjamin A. Krenger, Roger Braun, Thomas Univ Basel Biozentrum Ctr Cellular Imaging & NanoAnalyt Mattenstr 26 CH-4058 Basel Switzerland

Background: The functionality of atomic force microscopy (AFM) and nanomechanical sensing can be enhanced using higher-mode microcantilever vibrations. Both methods require a resonating microcantilever to be placed close to a surface, either a sample or the boundary of a microfluidic channel. Below a certain cantilever-surface separation, the confined fluid induces squeeze-film damping. Since damping changes the dynamic properties of the cantilever and decreases its sensitivity, it should be considered and minimized. Although squeeze-film damping in gases is comprehensively described, little experimental data is available in liquids, especially for higher-mode vibrations. Methods: We have measured the flexural higher-mode response of photothermally driven microcantilevers vibrating in water, close to a parallel surface with gaps ranging from similar to 200 mu m to similar to 1 mu m. A modified model based on harmonic oscillator theory was used to determine the modal eigenfrequencies and quality factors, which can be converted into co-moving fluid mass and dissipation coefficients. Results: The range of squeeze-film damping between the cantilever and surface decreased for eigenfrequencies (inertial forces) and increased for quality factors (dissipative forces) with higher mode number. Conclusions: The results can be employed to improve the quantitative analysis of AFM measurements, design miniaturized sensor fluid cells, or benchmark theoretical models.

关键词： Microcantilever Dissipation Squeeze-film damping Higher eigenmode Photothermal excitation Eigenfrequency Quality factor fluid-structure interaction

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Unsteady fluid-structure interactions of a pitching membrane wing

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AEROSPACE SCIENCE AND TECHNOLOGY 2013年第1期28卷 79-90页

作者： Tregidgo, L. Wang, Z. Gursul, I. Univ Bath Dept Mech Engn Bath BA2 7AY Avon England

Experiments were conducted on rectangular wings with an aspect ratio of two, at a chord Reynolds number Re-c = 46,000, in order to understand how membrane wings behave in a prescribed transient motion. As a reference, high-speed Digital Image Correlation (DIC) and Particle Image Velocimetry (PIV) measurements were performed on stationary membrane wings in the range 0 degrees < alpha < 25 degrees. Four distinct incidence regions were identified based on the mode shape, frequency and amplitude of the surface vibrations. Flow-field measurements indicated that the different regions were caused by the interactions of the leading-edge separated shear layer with the membrane. Then the membrane wing was subjected to transient sinusoidal pitching manoeuvres at starting incidences in each of these regions. The membrane deformation characteristics were seen to vary considerably with starting angle;both in terms of time-averaged and instantaneous quantities. In some cases there was significant time-lag in the response of the membrane. The PIV flow field measurements for this case showed signs of hysteresis between the pitch-up and pitch-down parts of the wing motion, which was not the case for a rigid wing with identical planform. (C) 2012 Elsevier Masson SAS. All rights reserved.

关键词： Membrane wings fluid-structure interaction Low Reynolds number aerodynamics

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2D FSI determination of mechanical stresses on aneurismal walls

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BIO-MEDICAL MATERIALS AND ENGINEERING 2014年第6期24卷 2519-2526页

作者： Veshkina, Natalia Zbicinski, Ireneusz Stefanczyk, Ludomir Tech Univ Lodz Fac Proc & Environm Engn PL-90924 Lodz Poland Med Univ Lodz Dept Radiol & Diagnost Imaging PL-90153 Lodz Poland

In this study, a fluid-structure interaction analysis based on the application of patient-specific mechanical parameters of the aneurismal walls was carried out to predict the rupture side during an abdominal aortic aneurysm (AAA). Realistic geometry of the aneurysm was reconstructed from CT data acquired from the patient, and patient-specific flow conditions were applied as boundary conditions. A newly developed non-invasive methodology for determining the mechanical parameters of the patient-specific aortic wall was employed to simulate realistic aortic wall behaviors. Analysis of the results included time-averaged wall shear stress (TAWSS), oscillatory shear index (OSI), and von Mises stress (VMS). Results of the TAWSS, OSI, and VMS were compared to identify the most probable region of the AAA's rupture. High OSI, which identified the region of wall degradation, coincided with the location of maximum VMS, meaning that the anterior part of the aneurismal wall was a potential region of rupture.

关键词： fluid-structure interaction abdominal aortic aneurysm mechanical parameters of the aortic wall computed tomography computational fluid dynamics

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Wall effect on fluid-structure interactions of a tethered bluff body

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PHYSICS LETTERS A 2013年第34-36期377卷 2079-2082页

作者： Sharma, Sumant Raghav, Vrishank Komerath, Narayanan Smith, Marilyn Georgia Inst Technol Daniel Guggenheim Sch Aerosp Engn Atlanta GA 30332 USA

Wind tunnel experiments have shown an unexplained amplification of the free motion of a tethered bluff body in a small wind tunnel relative to that in a large wind tunnel. The influence of wall proximity on fluid-structure interaction is explored using a compound pendulum motion in the plane orthogonal to a steady freestream with a doublet model for aerodynamic forces. Wall proximity amplifies a purely symmetric single degree of freedom oscillation with the addition of an out-of-phase force. The success of this simple level of simulation enables progress to develop metrics for unsteady wall interference in dynamic testing of tethered bluff bodies. (C) 2013 Elsevier B.V. All rights reserved.

关键词： Dynamic wall effect Bluff body fluid-structure interaction Instability Sling load

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A structured mesh boundary motion approach for simulating wind effects on bluff bodies with changing boundaries

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JOURNAL OF WIND ENGINEERING AND INDUSTRIAL AERODYNAMICS 2014年 126卷 118-131页

作者： Wei, Daniel Spence, Seymour M. J. Kareem, Ahsan Jemcov, Aleksandar Univ Notre Dame Dept Civil & Environm Engn & Earth Sci NatHaz Modeling Lab Notre Dame IN 46556 USA Univ Notre Dame Dept Aerosp & Mech Engn Notre Dame IN 46556 USA

In a number of computational fluid dynamics based wind engineering applications the possibility to move the boundary of the structure without having to re-mesh the computational domain represents a significant computational advantage. Examples of such applications are aerodynamic shape optimization, mesh generation around complicated geometric forms and simulations around bodies with time dependent rigid/deformable boundaries. Strategies for solving this type of problem have been widely investigated in both a general context-e.g. dynamic mesh, adaptive mesh refinement or embedded boundary method as well as more specific cases such as aerospace applications and fluid-structure interaction problems. This paper focuses on developing an efficient method for morphing the kind of structured meshes often encountered in civil engineering applications that are characterized by complicated bluff bodies. In particular a coupled parametric user-defined boundary motion and dynamic mesh approach is proposed specifically for solving fluid simulation problems around such bodies. The method is focused on providing an efficient means for updating structured wall clustered boundary meshes, important for reliable turbulent flow simulations, where the aim is the estimation of the effects of small/local deformations of the boundary. A novel algorithm is also developed to protect/repair the mesh during boundary motion when folding, and therefore loss of mesh validity, is likely to occur. The effectiveness of the proposed approach is demonstrated on a number of structural engineering applications such as turbulent flows around chamfered corners of tall buildings, rapid mesh generation around geometrically more involved bluff bodies and forced oscillations of bridge decks. (C) 2014 Elsevier Ltd. All rights reserved.

关键词： Wind effects on structures CFD and bluff bodies Sharp cornered bodies Automated mesh procedures Dynamic meshing Boundary motion fluid-structure interaction

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Modified immersed finite element method for fully-coupled fluid-structure interactions

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COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING 2013年 267卷 150-169页

作者： Wang, Xingshi Zhang, Lucy T. Rensselaer Polytech Inst Dept Mech Aerosp & Nucl Engn Troy NY 12180 USA

In this paper, we develop a "modified" immersed finite element method (mIFEM), a non-boundary-fitted numerical technique, to study fluid-structure interactions. Using this method, we can more precisely capture the solid dynamics by solving the solid governing equation instead of imposing it based on the fluid velocity field as in the original immersed finite element (IFEM). Using the IFEM may lead to severe solid mesh distortion because the solid deformation is been over-estimated, especially for high Reynolds number flows. In the mIFEM, the solid dynamics is solved using appropriate boundary conditions generated from the surrounding fluid, therefore produces more accurate and realistic coupled solutions. We show several 2-D and 3-D testing cases where the mIFEM has a noticeable advantage in handling complicated fluid-structure interactions when the solid behavior dominates the fluid flow. (C) 2013 Elsevier B.V. All rights reserved.

关键词： Immersed finite element method fluid-structure interaction Compressibility

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Partitioned solution of an unsteady adjoint for strongly coupled fluid-structure interactions and application to parameter identification of a one-dimensional problem

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STRUCTURAL AND MULTIDISCIPLINARY OPTIMIZATION 2013年第1期47卷 77-94页

作者： Degroote, Joris Hojjat, Majid Stavropoulou, Electra Wuechner, Roland Bletzinger, Kai-Uwe Univ Ghent Dept Flow Heat & Combust Mech B-9000 Ghent Belgium Tech Univ Munich Chair Struct Anal D-80333 Munich Germany

Unsteady fluid-structure interaction (FSI) simulations are generally time-consuming. Gradient-based methods are preferred to minimise the computational cost of parameter identification studies (and more in general optimisation) with a high number of parameters. However, calculating the cost function's gradient using finite differences becomes prohibitively expensive for a high number of parameters. Therefore, the adjoint equations of the unsteady FSI problem are solved to obtain this gradient at a cost almost independent of the number of parameters. Here, both the forward and the adjoint problems are solved in a partitioned way, which means that the flow equations and the structural equations are solved separately. The application of interest is the identification of the arterial wall's stiffness by comparing the motion of the arterial wall with a reference, possibly obtained from non-invasive imaging. Due to the strong interaction between the fluid and the structure, quasi-Newton coupling iterations are applied to stabilise the partitioned solution of both the forward and the adjoint problem.

关键词： Adjoint Coupled Partitioned fluid-structure interaction Quasi-Newton

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