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Shape optimization of pulsatile ventricular assist devices using FSI to minimize thrombotic risk

COMPUTATIONAL MECHANICS 2014年第4期54卷 921-932页

作者： Long, C. C. Marsden, A. L. Bazilevs, Y. Los Alamos Natl Lab Fluid Dynam & Solid Mech T 3 Los Alamos NM 87545 USA Univ Calif San Diego Dept Mech & Aerosp Engn La Jolla CA 92093 USA Univ Calif San Diego Dept Struct Engn La Jolla CA 92093 USA

In this paper we perform shape optimization of a pediatric pulsatile ventricular assist device (PVAD). The device simulation is carried out using fluid-structure interaction (FSI) modeling techniques within a computational framework that combines FEM for fluid mechanics and isogeometric analysis for structural mechanics modeling. The PVAD FSI simulations are performed under realistic conditions (i.e., flow speeds, pressure levels, boundary conditions, etc.), and account for the interaction of air, blood, and a thin structural membrane separating the two fluid subdomains. The shape optimization study is designed to reduce thrombotic risk, a major clinical problem in PVADs. Thrombotic risk is quantified in terms of particle residence time in the device blood chamber. Methods to compute particle residence time in the context of moving spatial domains are presented in a companion paper published in the same issue (Comput Mech, doi:10.1007/s00466-013-0931-y, 2013). The surrogate management framework, a derivative-free pattern search optimization method that relies on surrogates for increased efficiency, is employed in this work. For the optimization study shown here, particle residence time is used to define a suitable cost or objective function, while four adjustable design optimization parameters are used to define the device geometry. The FSI-based optimization framework is implemented in a parallel computing environment, and deployed with minimal user intervention. Using five SEARCH/POLL steps the optimization scheme identifies a PVAD design with significantly better throughput efficiency than the original device.

关键词： Pulsatile VAD Residence time fluid-structure interaction Isogeometric analysis Optimization SMF

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Minimum mesh design criteria for blast wave development and structural response - MMALE method

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LATIN AMERICAN JOURNAL OF SOLIDS AND structureS 2014年第11期11卷 1999-2017页

作者： Trajkovski, Jovan Kunc, Robert Perenda, Jasenko Prebil, Ivan Univ Ljubljana Fac Mech Engn Chair Modelling Engn Sci & Med Ljubljana 1000 Slovenia Sistemska Tehn Doo Ravne Na Koroskem 2390 Slovenia

The Multi Material Arbitrary Lagrange Euler (MMALE) method is widely used method for numerical investigation of structural response under blast loading. However the method is very demanding for use at the other hand. In this paper are presented the results of the detailed numerical investigation in order to simplify some decisions contributing to the accuracy and efficiency of this model. The influence of mesh properties (particularly mesh size, its biasing and distance of the boundary (DoB) conditions from the deforming structure) on blast wave loading parameters and structural response is investigated in detail and based on the results minimum mesh design criteria is proposed. The results obtained are presented as a function of the scaled distance and additionally related to the radius of the charge. Validation studies were also done successfully.

关键词： Blast wave blast response blast loading fluid-structure interaction

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Dynamic Responses of Composite structures in Contact with Water While Subjected to Harmonic Loads

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APPLIED COMPOSITE MATERIALS 2014年第1期21卷 227-245页

作者： Kwon, Y. W. Naval Postgrad Sch Dept Mech & Aerosp Engn Monterey CA 93943 USA

Composite ship hull structures are in contact with water on the external surfaces and may support vibrating equipment on the internal surfaces. This study examined how the fluid-structure interaction (FSI) coupled with the harmonic excitation could affect the composite structural response. A multiphysics computational technique based on the Finite Element Method (FEM) and Cellular Automata (CA) was developed and applied for this research. A comparison was made on the structural responses with and without FSI for composite beams and plates. Furthermore, metallic structures made of either aluminum or steel were also compared to composite structures to investigate the effect of the coupled FSI and a harmonically vibrating machine. The study showed that FSI could magnify the displacement and stress level in composite structures supporting harmonically vibrating equipment. Analysis of composite structures supporting such equipment without considering the FSI effect would result in non-conservative design leading to pre-mature failure. A parametric study was conducted to determine what parameter could signify the FSI effect on composite structures.

关键词： fluid-structure interaction Vibrating equipment Multiphysics analysis

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Computational simulation of the interactions between moving rigid bodies and incompressible two-fluid flows

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COMPUTERS & fluidS 2014年 94卷 1-13页

作者： Ghasemi, Amirmandi Pathak, Ashish Raessi, Mehdi Univ Massachusetts Dept Mech Engn Dartmouth NS Canada

We present a two-dimensional computational flow solver for simulation of two-way interactions between moving rigid bodies and two-fluid flows. The fluids are assumed to be incompressible and immiscible. The two-step projection method along with Graphics Processing Unit (GPU) acceleration is employed to solve the flow equations. The fluid-solid interaction is captured by using the fictitious domain method. A consistent mass and momentum scheme is implemented, which allows for simulation of multiphase flows characterized by large density ratios. The evolution of interfaces in the three-phase system is tracked by using the volume-of-fluid method with two scalar functions, representing the solid domain and one of the fluids. A geometrical approach is employed to reconstruct the interfaces in cells containing three phases and capture the intersection of phase interfaces (triple point). The performance and accuracy of the flow solver are assessed through a set of canonical test cases. Then, it is used to simulate the interactions between a free-floating buoy and waves generated by a bottom-hinged paddle in a wave tank. (C) 2014 Elsevier Ltd. All rights reserved.

关键词： Multiphase flow fluid-structure interaction Fictitious domain Multimaterial interfaces CPU acceleration Wave energy conversion

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An analysis of a new stable partitioned algorithm for FSI problems. Part I: Incompressible flow and elastic solids

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JOURNAL OF COMPUTATIONAL PHYSICS 2014年 269卷 108-137页

作者： Banks, J. W. Henshaw, W. D. Schwendeman, D. W. Lawrence Livermore Natl Lab Ctr Appl Sci Comp Livermore CA 94551 USA Rensselaer Polytech Inst Dept Math Sci Troy NY 12180 USA

Stable partitioned algorithms for fluid-structure interaction (FSI) problems are developed and analyzed in this two-part paper. Part I describes an algorithm for incompressible flow coupled with compressible elastic solids, while Part II discusses an algorithm for incompressible flow coupled with structural shells. Importantly, these new added-mass partitioned (AMP) schemes are stable and retain full accuracy with no sub-iterations per time step, even in the presence of strong added-mass effects (e.g. for light solids). The numerical approach described here for bulk compressible solids extends the scheme of Banks et al. [1,2] for inviscid compressible flow, and uses Robin (mixed) boundary conditions with the fluid and solid solvers at the interface. The basic AMP Robin conditions, involving a linear combination of velocity and stress, are determined from the outgoing solid characteristic relation normal to the fluid solid interface combined with the matching conditions on the velocity and traction. Two alternative forms of the AMP conditions are then derived depending on whether the fluid equations are advanced with a fractional-step method or not. The stability and accuracy of the AMP algorithm is evaluated for linearized FSI model problems;the full nonlinear case being left for future consideration. A normal mode analysis is performed to show that the new AMP algorithm is stable for any ratio of the solid and fluid densities, including the case of very light solids when added-mass effects are large. In contrast, it is shown that a traditional partitioned algorithm involving a Dirichlet-Neumann coupling for the same FSI problem is formally unconditionally unstable for any ratio of densities. Exact traveling wave solutions are derived for the FSI model problems, and these solutions are used to verify the stability and accuracy of the corresponding numerical results obtained from the AMP algorithm for the cases of light, medium and heavy solids. (C) 2014 Elsevier Inc

关键词： fluid-structure interaction Partitioned algorithms Added mass instability Incompressible fluid flow Elastic solids

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FSI analysis of the blood flow and geometrical characteristics in the thoracic aorta

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COMPUTATIONAL MECHANICS 2014年第4期54卷 1035-1045页

作者： Suito, Hiroshi Takizawa, Kenji Huynh, Viet Q. H. Sze, Daniel Ueda, Takuya Okayama Univ Grad Sch Environm & Life Sci Okayama 7008530 Japan Waseda Univ Waseda Inst Adv Study Dept Modern Mech Engn Shinjuku Ku Tokyo 1698050 Japan Stanford Univ Sch Med Stanford CA 94305 USA St Lukes Int Hosp Dept Radiol Tokyo 1048560 Japan

We present a fluid-structure interaction (FSI) analysis of the blood flow and geometrical characteristics in the thoracic aorta. The FSI is handled with the sequentially-coupled arterial FSI technique. The fluid mechanics equations are solved with the ST-VMS method, which is the variational multiscale version of the deforming-spatial-domain/stabilized space-time (DSD/SST) method. We focus on the relationship between the centerline geometry of the aorta and the flow field, which influences the wall shear stress distribution. The centerlines of the aorta models we use in our analysis are extracted from the CT scans, and we assume a constant diameter. Torsion-free model geometries are generated by projecting the original centerline to its averaged plane of curvature. The flow fields for the original and projected geometries are compared to examine the influence of the torsion.

关键词： Blood flow Aortic aneurysms Wall shear stress fluid-structure interaction Space-time techniques Sequential coupling

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Computational aeroelastic investigation of a transonic limit-cycle-oscillation experiment at a transport aircraft wing model

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JOURNAL OF fluidS AND structureS 2014年 49卷 223-241页

作者： Stickan, Bernd Dillinger, Johannes Schewe, Guenter DLR Inst Aeroelast D-37073 Gottingen Germany

Aeroelastic measurements of a three-dimensional wing model, the so-called Aerostabil wing, were conducted in the Transonic Windtunnel Gottingen. This clean, backward-swept wing allowed the experimental investigation of limit cycle oscillations in a certain transonic parameter range. In this paper, a detailed insight into the observed physical phenomena, especially the measured limit cycle oscillations, is presented by means of CFD-CSM coupled simulations. These simulations on the basis of a detailed structural finite element model reveal the specific properties of the Aerostabil wing and furthermore allow investigating the unstable behavior of this windtunnel model for transonic flow settings. The aerodynamic characteristics include a two-shock system and large flow separation areas, further increasing the complexity of the aeroelastic problem. A structural single degree-of-freedom system is used for the prediction of the experimental stability range and the limit cycle oscillation investigations. Due to the good agreement of simulation and experiment the limit cycle oscillations can be explained by means of nonlinear aerodynamic effects. (C) 2014 Elsevier Ltd. All rights reserved.

关键词： Aerostabil Limit-cycle oscillations fluid-structure interaction Transonic flow Single degree-of-freedom flutter Unsteady aerodynamics Static aeroelasticity

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Force-moment line element method for Stokes flow around a slender body

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ENGINEERING ANALYSIS WITH BOUNDARY ELEMENTS 2014年 44卷 120-129页

作者： Jiang, H. Wu, Y. T. Yang, B. Zhao, Y. -P. Univ Texas Arlington Dept Mech & Aerosp Engn Arlington TX 76019 USA Univ Georgia Nanoscale Sci & Engn Ctr Dept Phys & Astron Athens GA 30602 USA

We present a higher-order line element method for Stokes flow around a slender body by taking into account effects of both net force and couple moment densities along its center line. The numerical technique is based on a line integral equation, which in turn is derived by reducing from a boundary integral equation of Stokes flow. The line integral equation of velocity gradient is employed along with that of velocity to close the formulation. Numerical examples of rigid slender bodies are presented to demonstrate the capability and validity of the present method, including passive motion of a slender body suspended in a simple shear flow and active motion of a slender body driven by a body moment. In the first case, it is shown that the moment density due to shear rigidity mismatch between the fluid and solid can be finite. Meanwhile, the transverse net force density is rather induced by a small velocity lag due to the impeding moment density component. Effects of slip and no-slip interfacial conditions are examined, showing their important role in determining the slender-body hydrodynamics. The present force-moment line element method provides a capable tool for solving the problems of strong and weak interactions between a slender body and a viscous fluid at low Reynolds number. (C) 2014 Elsevier Ltd. All rights reserved.

关键词： Boundary element method fluid-structure interaction Integral equation technique Line element method Simple shear flow Slender body Stokes flow

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Aeroelastic study of flexible flapping wings by a coupled lattice Boltzmann-finite element approach with immersed boundary method

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JOURNAL OF fluidS AND structureS 2014年 49卷 516-533页

作者： De Rosis, Alessandro Falcucci, Giacomo Ubertini, Stefano Ubertini, Francesco Univ Bologna Dept Agr Sci DIPSA I-40127 Bologna Italy Univ Naples Parthenope Dept Technol I-80143 Naples Italy Univ Tuscia Sch Ind Engn Dept Econ & Enterprise DEIM I-01100 Viterbo Italy Univ Bologna Dept Civil Environm & Mat Engn DICAM I-40136 Bologna Italy

In this paper, the behavior of two-dimensional symmetric flapping wings moving in a viscous fluid is investigated. Harmonic motion is applied to idealize flying organisms with flexible wings and extensive testing is carried out to investigate the resultant flight behavior related to the ability to take-off or accelerate the flapping wing system away from a starting location. Special attention is paid to analyze the effect of the main mechanical parameters, as well as the effect of lateral wind on flight performances. Moreover, aiming to investigate the possible benefits of flying in flocks, a couple of synchronously flapping wings is considered in addition to the single arrangement. The numerical simulations are performed by solving the fluid-structure interaction problem through a strongly coupled partitioned approach. fluid dynamics are modeled at the mesoscopic scale by the lattice Boltzmann method. The resulting macroscopic quantities are derived, as usual, based on the statistical molecular-level interpretation. Wings are modeled by geometrically nonlinear, elastic beam finite elements and structure dynamics is solved by the time discontinuous Galerldn method. fluid-structure interface conditions are handled using the immersed boundary method. The resultant numerical approach combines simplicity and high computational efficiency. A Monte Carlo simulation strategy is employed to characterize the flight behavior subjected to lateral wind. Various scenarios are discussed. (C) 2014 Elsevier Ltd. All rights reserved.

关键词： fluid-structure interaction Lattice Boltzmann method Flapping wings Immersed boundary

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Seismic response analysis of residual heat removal pump considering transient fluid excitation force in 1000-MW nuclear power plants

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JOURNAL OF VIBROENGINEERING 2014年第2期16卷 965-976页

作者： Deng, Xin Yuan, Shouqi Si, Qiaorui Li, Yalin Pei, Ji Yuan, Jianping Jiangsu Univ Natl Res Ctr Pumps Zhenjiang 212013 Peoples R China

To prevent nuclear leakage accidents at nuclear power plants because of earthquakes, a new method for seismic response analysis that considers the transient fluid excitation force was used. The inherent modal analysis was based on a newly developed three-dimensional residual heat removal pump model. The equivalent static method and response spectrum method were used to analyze the seismic response at half of the safe shutdown earthquake (SSE) seismic load according to the square root of the sum of the squares algorithm;the actions of gravity, the operation load, the piping load under accident conditions, the SSE seismic load, and the fluid excitation force were considered simultaneously. The fluid excitation force was applied to the rotor system by the fluid-structure interaction method. The seismic response of the rotor with and without the fluid excitation force was analyzed. The deformations caused by the seismic load and fluid excitation force of the impeller surface fitted with a wear ring and the trailing edge of the impeller were analyzed. This study revealed that the primary vibration mode of the residual heat removal pump was translational vibration in the horizontal direction. The total deformation of the trailing edge of the impeller was far below the unilateral clearance between the impeller and diffuser, and the total deformation of the impeller surface fitted with the wear ring met the requirements for seismic response analysis. There was no rub and disturbance between the rotor and stator. The requirements for pump operation under a seismic load were guaranteed to be met. The deformation of the trailing edge of the impeller on the shroud was larger than that on the hub. At different positions of the impeller passage, the deformations of the trailing edge of the impeller on the shroud and hub were basically the same;only the phase of the deformation changed. The results proved that the residual heat removal pump sufficiently meets the RCC-M 2000 standa

关键词： seismic response analysis residual heat removal pump fluid-structure interaction transient fluid excitation force

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