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Effect of gas flow on the bending moment acting on a shaft in a sparged vessel stirred by a Pitched Blade Turbine

CHEMICAL ENGINEERING RESEARCH & DESIGN 2014年第11期92卷 2255-2263页

作者： Shi, Daien Cai, Ziqi Liang, Yangyang Eaglesham, Archie Gao, Zhengming Beijing Univ Chem Technol Sch Chem Engn Beijing 100029 Peoples R China Huntsman Polyurethanes B-3078 Everberg Belgium

The bending moment acting on the overhung shaft of a gas-sparged vessel stirred by a Pitched Blade Turbine, as one of the results of fluid-structure interactions (PSI) in stirred vessels, was measured using a moment sensor equipped with digital telemetry. The amplitude and Power Spectral Density of the shaft bending moment were analyzed. It shows that the gas flow has a considerable influence on the characteristics of the bending moment, such as the amplitude mean, distribution, Standard Deviation and peak, and the low-frequency and speed frequency contributions to the fluctuation. The relative mean bending moment initially increases with gas rate till the transition from complete dispersion to loading regimes, approaching a peak, then decreases to a valley and again rises gradually, going through the transition from loading to flooding regimes. The "S" trend of the relative mean bending moment over gas flow rate, depending on the flow regime in gas-liquid stirred vessels, results from the competition among the nonuniformity of bubbly flow around the impeller, the formation of gas cavities behind the blades and the gas direct impact on the impeller as gas is introduced. (C) 2014 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.

关键词： Bending moment Gas-liquid flow Gas sparged stirred vessel fluid-structure interaction

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Dynamic stability of a pipe conveying fluid with an uncertain computational model

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JOURNAL OF fluidS AND structureS 2014年 49卷 412-426页

作者： Ritto, T. G. Soize, C. Rochinha, F. A. Sampaio, Rubens Univ Fed Rio de Janeiro Ctr Technol Dept Mech Engn BR-21945970 Rio De Janeiro Brazil Univ Paris Est Lab Modelisat & Simulat Multi Echelle CNRS UMR 8208 F-77454 Marne La Vallee 2 France Pontificia Univ Catolica Rio de Janeiro Dept Mech Engn BR-22453900 Rio de Janeiro Brazil

This paper deals with the problem of a pipe conveying fluid of interest in several engineering applications, such as micro-systems or drill-string dynamics. The deterministic stability analysis developed by Paidoussis and Issid (1974) is extended to the case for which there are model uncertainties induced by modeling errors in the computational model. The aim of this work is twofold: (1) to propose a probabilistic model for the fluid-structure interaction considering modeling errors and (2) to analyze the stability and reliability of the stochastic system. The Euler-Bernoulli beam model is used to model the pipe and the plug flow model is used to take into account the internal flow in the pipe. The resulting differential equation is discretized by means of the finite element method and a reduced-order model is constructed from some eigenmodes of the beam. A probabilistic approach is used to model uncertainties in the fluid-structure interaction. The proposed strategy takes into account global uncertainties related to the noninertial coupled fluid forces (related to damping and stiffness). The resulting random eigenvalue problem is used to analyze flutter and divergence unstable modes of the system for different values of the dimensionless flow speed. The numerical results show the random response of the system for different levels of uncertainty, and the reliability of the system for different dimensionless speeds and levels of uncertainty. (C) 2014 Elsevier Ltd. All rights reserved.

关键词： fluid-structure interaction Uncertainty quantification Stochastic dynamics Stochastic stability analysis Reliability analysis

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Computation of unsteady viscous flow around a locally flexible Cross Mark airfoil at low Reynolds number

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JOURNAL OF fluidS AND structureS 2014年 46卷 42-58页

作者： Kang, Wei Zhang, Jia-zhong Lei, Peng-fei Xu, Min Northwestern Polytech Univ Sch Astronaut Xian 710072 Shaanxi Provinc Peoples R China Xi An Jiao Tong Univ Sch Energy & Power Engn Xian 710049 Shaanxi Provinc Peoples R China

A numerical method for fluid-structure interaction is presented for the analysis of unsteady viscous flow over a locally flexible airfoil. The Navier-Stokes equations are solved by ALE-CBS algorithm, coupling with a structural solver with large deformation. Following the validation of the method, a numerical example for the flight of micro-air vehicles at low Reynolds number is chosen for the computation. The coupling effect of flexible structure with different elastic stiffness on aerodynamic performance is demonstrated. A noticeable camber effect is induced by the deflection of the structure as the elastic stiffness of the structure goes smaller. Moreover, when the vibrating frequencies of the structure with smaller elastic stiffness have a close correlation with the shedding frequencies, the positive impact of the vibration of local flexible surface on the lift of the airfoil is highlighted, which results from the formation of the coherent vortices. (C) 2014 Elsevier Ltd. All rights reserved.

关键词： fluid-structure interaction Thin-walled structure Aeroelasticity Airfoil Lift enhancement

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Motion-resonant modes of large articulated damped oscillators in waves

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JOURNAL OF fluidS AND structureS 2014年 49卷 705-715页

作者： Renzi, E. Dias, F. Univ Coll Dublin Sch Math Sci Belfield Dublin 4 Ireland Ecole Normale Super CMLA F-94235 Cachan France

Using a semi-analytical approach, we show that an articulated system of large damped oscillators in the open ocean can be resonated by incoming waves at multiple frequencies. As an application, energy extraction from the system is modelled when the oscillators are used as flap-type wave energy converters. A new parameter - the absorption efficiency is introduced to analyse the performance of the system at resonance. This allows us to identify the occurrence of detrimental processes near the resonant frequencies, which reduce the sustainability of the energy conversion process. This result challenges the diffused belief that large flap-type wave energy converters must be designed to resonate, which is based on the use of inappropriate performance descriptors. (C) 2014 Elsevier Ltd. All rights reserved.

关键词： fluid-structure interaction Multiple resonance Wave energy

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Interface Jacobian-based Co-Simulation

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INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING 2014年第6期98卷 418-444页

作者： Sicklinger, S. Belsky, V. Engelmann, B. Elmqvist, H. Olsson, H. Wuechner, R. Bletzinger, K. -U. Tech Univ Munich Chair Struct Anal D-80333 Munich Germany Dassault Syst SIMULIA Providence RI USA Dassault Syst CATIA Gothenburg Sweden

Co-simulation is a prominent method to solve multi-physics problems. Multi-physics simulations using a co-simulation approach have an intrinsic advantage. They allow well-established and specialized simulation tools for different fields and signals to be combined and reused with minor adaptations in contrast to the monolithic approach. However, the partitioned treatment of the coupled system poses the drawback of stability and accuracy challenges. If several different subsystems are used to form the co-simulation scenario, these issues are especially important. In this work, we propose a new co-simulation algorithm based on interface Jacobians. It allows for the stable and accurate solution of complex co-simulation scenarios involving several different subsystems. Furthermore, the Interface Jacobian-based Co-Simulation Algorithm is formulated such that it enables parallel execution of the participating subsystems. This results in a high-efficient procedure. Furthermore, the Interface Jacobian-based Co-Simulation Algorithm handles algebraic loops as the co-simulation scenario is defined in residual form. Copyright (c) 2014 John Wiley & Sons, Ltd.

关键词： partitioned solution strategy multi-code coupling n-code coupling fluid-structure interaction multi-physics interface Jacobian co-simulation

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FSI modeling of the reefed stages and disreefing of the Orion spacecraft parachutes

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COMPUTATIONAL MECHANICS 2014年第5期54卷 1203-1220页

作者： Takizawa, Kenji Tezduyar, Tayfun E. Boswell, Cody Kolesar, Ryan Montel, Kenneth Waseda Univ Waseda Inst Adv Study Dept Modern Mech Engn Shinjuku Ku Tokyo 1698050 Japan Rice Univ Houston TX 77005 USA

Orion spacecraft main and drogue parachutes are used in multiple stages, starting with a "reefed" stage where a cable along the parachute skirt constrains the diameter to be less than the diameter in the subsequent stage. After a period of time during the descent, the cable is cut and the parachute "disreefs" (i.e. expands) to the next stage. fluid-structure interaction (FSI) modeling of the reefed stages and disreefing involve computational challenges beyond those in FSI modeling of fully-open spacecraft parachutes. These additional challenges are created by the increased geometric complexities and by the rapid changes in the parachute geometry during disreefing. The computational challenges are further increased because of the added geometric porosity of the latest design of the Orion spacecraft main parachutes. The "windows" created by the removal of panels compound the geometric and flow complexity. That is because the Homogenized Modeling of Geometric Porosity, introduced to deal with the flow through the hundreds of gaps and slits involved in the construction of spacecraft parachutes, cannot accurately model the flow through the windows, which needs to be actually resolved during the FSI computation. In parachute FSI computations, the resolved geometric porosity is significantly more challenging than the modeled geometric porosity, especially in computing the reefed stages and disreefing. Orion spacecraft main and drogue parachutes will both have three stages, with computation of the Stage 1 shape and disreefing from Stage 1 to Stage 2 for the main parachute being the most challenging because of the lowest "reefing ratio" (the ratio of the reefed skirt diameter to the nominal diameter). We present the special modeling techniques and strategies we devised to address the computational challenges encountered in FSI modeling of the reefed stages and disreefing of the main and drogue parachutes. We report, for a single parachute, FSI computation of both reefed stag

关键词： fluid-structure interaction Orion spacecraft parachutes Orion main parachutes Orion drogue parachutes Modeled geometric porosity Resolved geometric porosity Parachute reefed stages Parachute disreefing

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MULTISCALE MODELLING OF SOUND PROPAGATION THROUGH THE LUNG PARENCHYMA

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ESAIM-MATHEMATICAL MODELLING AND NUMERICAL ANALYSIS-MODELISATION MATHEMATIQUE ET ANALYSE NUMERIQUE 2014年第1期48卷 27-52页

作者： Cazeaux, Paul Hesthaven, Jan S. Univ Paris 06 Lab JL Lions UMR 7598 F-75005 Paris France Inria Projet REO F-78153 Le Chesnay France Brown Univ Div Appl Math Providence RI 02912 USA

In this paper we develop and study numerically a model to describe some aspects of sound propagation in the human lung, considered as a deformable and viscoelastic porous medium (the parenchyma) with millions of alveoli filled with air. Transmission of sound through the lung above 1 kHz is known to be highly frequency-dependent. We pursue the key idea that the viscoelastic parenchyma structure is highly heterogeneous on the small scale e and use two-scale homogenization techniques to derive effective acoustic equations for asymptotically small e. This process turns out to introduce new memory effects. The effective material parameters are determined from the solution of frequency-dependent micro-structure cell problems. We propose a numerical approach to investigate the sound propagation in the homogenized parenchyma using a Discontinuous Galerkin formulation. Numerical examples are presented.

关键词： Mathematical modeling periodic homogenization viscoelastic media fluid-structure interaction Discontinuous Galerkin methods

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Passive control of marine hydrokinetic turbine blades

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COMPOSITE structureS 2014年第1期110卷 133-139页

作者： Motley, Michael R. Barber, Ramona B. Univ Washington Dept Civil & Environm Engn Seattle WA 98195 USA

Marine hydrokinetic (MHK) turbine blades are generally constructed from fiber reinforced polymer composites and are subject to large, highly dynamic fluid forces. The bend-twist deformation coupling behavior of these materials can be hydroelastically tailored to improve system performance over the expected life of the turbine by way of rapid, passive pitch control that can increase lifetime power generation, reduce hydrodynamic instabilities, and improve load shedding and structural performance. There are practical concerns, however, that make the design of these devices complex. Constraints on system components such as the rated power of the generator system, maximum rotational speed, or material degradation can affect the extent to which passive control can enhance performance. Using a previously validated boundary element method-finite element method solver, this paper examines the capabilities of passive pitch adaptation under both instantaneous and long-term variable amplitude loading to better describe potential benefits while considering practical design and operational restrictions. (C) 2013 Elsevier Ltd. All rights reserved.

关键词： fluid-structure interaction Turbine Passive control Fatigue Tidal energy Adaptive composites

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Modeling of flow-induced sound in porous materials

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INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING 2014年第1期98卷 44-58页

作者： Beck, S. C. Langer, S. Tech Univ Carolo Wilhelmina Braunschweig Inst Konstrukt Tech D-38106 Braunschweig Germany

The impact of flow on a structure plays a crucial part when considering structural behavior, for example, in aviation. As structural vibrations (also denominated as structural sound) propagate within a structure, sound radiation is a likely consequence. To reduce the emission of noise, the use of poroelastic material is investigated. The approach consists in applying a poroelastic layer on the surface submitted to flow, as such utilizing the damping properties of poroelastic material. To predict flow-induced sound, a computational model has been developed to account for (1) flow-induced sound immission into a structure;(2) sound propagation;and (3) possible resulting sound radiation. Consistent formulation of the interactions between the components-that is, flow, poroelastic material, elastic structure, and acoustic fluid-allows to apply different simulation techniques for each component and thus to exploit each method's advantages. The key aspect of this work is the formulation of the interface conditions to couple flow with poroelastic material. The proposed and implemented coupling conditions are studied. The given example shows a possible application and demonstrates the effectiveness of poroelastic material to reduce flow-induced sound emission. Copyright (c) 2014 John Wiley & Sons, Ltd.

关键词： poroelastic material fluid-structure interaction coupling conditions

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Multiscale modeling and uncertainty quantification in nanoparticle-mediated drug/gene delivery

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COMPUTATIONAL MECHANICS 2014年第3期53卷 511-537页

作者： Li, Ying Stroberg, Wylie Lee, Tae-Rin Kim, Han Sung Man, Han Ho, Dean Decuzzi, Paolo Liu, Wing Kam Northwestern Univ Dept Mech Engn Evanston IL 60208 USA King Abdulaziz Univ Distinguished Sci Program Comm Jeddah 21413 Saudi Arabia Northwestern Univ Evanston IL 60208 USA Northwestern Univ Robert H Lurie Comprehens Canc Ctr Inst Bionanotechnol Med IBNAM Dept Biomed Engn Chicago IL 60208 USA Univ Calif Los Angeles Sch DentDiv Oral Biol & Med Jonsson Comprehens Canc CtrDept BioengnDiv Adv Jane & Jerry Weintraub Ctr Reconstruct Biotechnol Los Angeles CA 90024 USA Methodist Hosp Res Inst Dept Translat Imaging Houston TX 77030 USA

Nanoparticle (NP)-mediated drug/gene delivery involves phenomena at broad range spatial and temporal scales. The interplay between these phenomena makes the NP-mediated drug/gene delivery process very complex. In this paper, we have identified four key steps in the NP-mediated drug/gene delivery: (i) design and synthesis of delivery vehicle/platform;(ii) microcirculation of drug carriers (NPs) in the blood flow;(iii) adhesion of NPs to vessel wall during the microcirculation and (iv) endocytosis and exocytosis of NPs. To elucidate the underlying physical mechanisms behind these four key steps, we have developed a multiscale computational framework, by combining all-atomistic simulation, coarse-grained molecular dynamics and the immersed molecular electrokinetic finite element method (IMEFEM). The multiscale computational framework has been demonstrated to successfully capture the binding between nanodiamond, polyethylenimine and small inference RNA, margination of NP in the microcirculation, adhesion of NP to vessel wall under shear flow, as well as the receptor-mediated endocytosis of NPs. Moreover, the uncertainties in the microcirculation of NPs has also been quantified through IMEFEM with a Bayesian updating algorithm. The paper ends with a critical discussion of future opportunities and key challenges in the multiscale modeling of NP-mediated drug/gene delivery. The present multiscale modeling framework can help us to optimize and design more efficient drug carriers in the future.

关键词： Drug delivery Multiscale modeling Coarse-grained molecular dynamics fluid-structure interaction Immersed molecular electrokinetic finite element Molecular mean-field theory

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