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A NURBS-based immersed methodology for fluid-structure interaction

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

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ENERGY 2016年第Part1期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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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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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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ANALYSIS OF A fluid-structure interaction PROBLEM RECAST IN AN OPTIMAL CONTROL SETTING

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SIAM JOURNAL ON NUMERICAL ANALYSIS 2015年第3期53卷 1464-1487页

作者： Kuberry, P. Lee, H. Clemson Univ Dept Math Sci Clemson SC 29634 USA

fluid-structure interaction (FSI) simulation presents many computational difficulties, particularly when the densities of the fluid and structure are close. A previous report [P. Kuberry and H. Lee, Comput. Methods Appl. Mech. Engrg., 267 (2013), pp. 594-605] has suggested that recasting the FSI problem in the context of optimal control may significantly reduce computation time. This paper introduces a Neumann type control along with detailed analysis for the stability and existence of an optimal solution for a given time step. The existence of Lagrange multipliers is proved, and an optimality system is derived. A gradient-based optimization algorithm is then presented with numerical results confirming its effectiveness in computing an accurate solution.

关键词： optimal control fluid-structure interaction finite element method

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A discrete-forcing immersed boundary method for the fluid-structure interaction of an elastic slender body

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JOURNAL OF COMPUTATIONAL PHYSICS 2015年 280卷 529-546页

作者： Lee, Injae Choi, Haecheon Seoul Natl Univ Dept Mech & Aerosp Engn Seoul 151744 South Korea Seoul Natl Univ Inst Adv Machines & Design Seoul 151744 South Korea

We present an immersed boundary (IB) method for the simulation of flow around an elastic slender body. The present method is based on the discrete-forcing IB method for a stationary, rigid body proposed by Kim, Kim and Choi (2001) [25]. The discrete-forcing approach is used to relieve the limitation on the computational time step size. The incompressible Navier-Stokes equations are implicitly coupled with the dynamic equation for an elastic slender body motion. The first is solved in the Eulerian coordinate and the latter is described in the Lagrangian coordinate. The elastic slender body is modeled as a thin and flexible solid and is segmented by finite number of thin blocks. Each block is moved by external and internal forces such as the hydrodynamic, elastic and buoyancy forces, where the hydrodynamic force is obtained directly from the discrete forcing used in the IB method. All the spatial derivative terms are discretized with the second-order central difference scheme. The present method is applied to three different fluid-structure interaction problems: flows around a flexible filament, a flapping flag in a free stream, and a flexible flapping wing in normal hovering, respectively. Computations are performed at maximum CFL numbers of 0.75-1. The results obtained agree very well with those from previous studies. (C) 2014 Elsevier Inc. All rights reserved.

关键词： Immersed boundary method fluid-structure interaction Elastic slender body Discrete forcing CFL number

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APPLICATION OF fluid-structure interaction TO NUMERICAL SIMULATIONS IN THE LEFT VENTRICLE

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TRANSACTIONS OF THE CANADIAN SOCIETY FOR MECHANICAL ENGINEERING 2015年第4期39卷 749-766页

作者： Doyle, Matthew G. Tavoularis, Stavros Bougault, Yves Univ Toronto Dept Mech & Ind Engn Toronto ON Canada Univ Ottawa Dept Mech Engn Ottawa ON K1N 6N5 Canada Univ Ottawa Dept Math & Stat Ottawa ON Canada

Numerical simulations of blood flow and myocardium motion for an average canine left ventricle (LV) with fluid-structure interaction were performed. The temporal variations of the LV cavity pressure and wall stress during the cardiac cycle were consistent with previous literature. LV cavity volume was conserved from one period to the next, despite sub-physiological ejection volumes and brief periods of backflow during early filling. This study improves on previous ones by presenting details of the models and results for both the fluid and solid components of the LV.

关键词： biomechanics cardiovascular system left ventricle fluid-structure interaction

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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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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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Time-integration for ALE simulations of fluid-structure interaction problems: Stepsize and order selection based on the BDF

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COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING 2015年第Oct.1期295卷 172-195页

作者： Hay, A. Etienne, S. Garon, A. Pelletier, D. Ecole Polytech Dept Genie Mecan Montreal PQ H3C 3A7 Canada

We present an adaptive algorithm for time integration of fluid-structure integration problems. The method relies on a fully coupled procedure to solve FSI problems in which a naturally GCL-compliant ALE formulation for the finite-element spatial discretization is used. The main originality of the proposed solution procedure is that time integration is performed using automatic order and stepsize selections (hp-adaptivity) based on the Backward Differentiation Formulas (BDF). The stepsize selection is based on a local error estimate, an error controller and a step rejection mechanism. It guarantees that the solution precision is within the user targeted tolerance. The order selection is based on a stability test and a quarantine mechanism. The selection is performed to ensure that no other methods within the family of 0-stable BDF methods would produce a solution of the targeted precision for a larger stepsize (and thus a lower computational time). To improve efficiency, the time integration procedure also relies on a modified Newton method and a predictor. The time adaptive algorithm behaviors and performances are assessed on the vortex-induced translational and rotational vibrations of a square cylinder and on the wake-induced vibrations of 3 cylinders in an in-line arrangement. The algorithm yields substantial CPU time savings (compared to constant stepsize and order integration) while delivering solutions of prescribed accuracies. (C) 2015 Elsevier B.V. All rights reserved.

关键词： Time integration Adaptivity fluid-structure interaction Arbitrary Eulerian Lagrangian Vortex induced vibration Wake induced vibration

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