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Effect of an impinging shock wave on a partially opened door

SHOCK WAVES 2014年第2期24卷 115-121页

作者： Biamino, L. Igra, O. Jourdan, G. Houas, L. Aix Marseille Univ IUSTI CNRS F-13013 Marseille France Ben Gurion Univ Negev Dept Mech Engn IL-84105 Beer Sheva Israel

The behavior of an aluminum door hanging at the exit of an open shock tube at different angles, from 5 to 85, and thereby providing partially open space for the exiting flow, was investigated experimentally. Experiments were conducted with an incident shock wave Mach number of impinging on the partially opened door. Both pressure measurements in the vicinity of the door, on its center and inside the shock tube, and schlieren visualization were undertaken for studying the door movement and its maximum opening angle relative to its initial position. It was found that for an initial opening angle smaller than 25 the door opened completely while for larger angles its motion is marginal. In addition, for an initial door opening angle of about 10 the lowest pressures were recorded inside the shock tube behind the evolving waves after exiting of the incident shock wave. The present experimental results may be useful to numerical studies of fluid-structure interactions, e.g., in designing safety valves in jet engines. Such a device is needed for preventing rupture in the case when a sudden overpressure pulse is generated inside the aircraft engine compartment.

关键词： Shock wave impact Shock tube environment fluid-structure interaction

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Numerical experiments using a HLLC-type scheme with ALE formulation for compressible two-phase flows five-equation models with phase transition

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COMPUTERS & fluidS 2014年 94卷 112-138页

作者： Daude, F. Galon, P. Gao, Z. Blaud, E. UMR EDF CNRS CEA 8193 LaMSID Clamart France AMA EDF R&D Clamart France CEA SEMT DYN DENDANSDM2S Gif Sur Yvette France

Computation of compressible two-phase flows with single-pressure single-velocity two-phase models in conjunction with the moving grid approach is discussed in this paper. A HLLC-type scheme is presented and implemented in the context of Arbitrary Lagrangian-Eulerian formulation for solving the five-equation models. In addition, the extension to multicomponent cases is also examined. The method is first assessed on a variety of Riemann problems including both fixed and moving grids applications showing its simplicity and robustness. The method is also tested on 2-D moving mesh applications including fluid-structure interactions. The heat and mass transfer modeling is finally examined for two-phase mixtures. Computations using a fractional step approach of water hammer and fast depressurization with flashing are performed. Good agreement is obtained with available experimental data. All computations are performed with the Europlexus fast transient dynamics software. (C) 2014 Elsevier Ltd. All rights reserved.

关键词： Two-phase compressible flows Finite-Volume method HLLC scheme Unstructured grids ALE formulation fluid-structure interaction

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The computational fluid dynamics modelling of the autorotation of square, flat plates

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JOURNAL OF fluidS AND structureS 2014年 46卷 111-133页

作者： Hargreaves, D. M. Kakimpa, B. Owen, J. S. Univ Nottingham Fac Engn Nottingham NG7 2RD England

This paper examines the use of a coupled Computational fluid Dynamics (CFD) - Rigid Body Dynamics (RBD) model to study the fixed-axis autorotation of a square flat plate. The calibration of the model against existing wind tunnel data is described. During the calibration, the CFD models were able to identify complex period autoration rates, which were attributable to a mass eccentricity in the experimental plate. The predicted flow fields around the autorotating plates are found to be consistent with existing observations. In addition, the pressure coefficients from the wind tunnel and computational work were found to be in good agreement. By comparing these pressure distributions and the vortex shedding patterns at various stages through an autorotation cycle, it was possible to gain important insights into the flow structures that evolve around the plate. The CFD model is also compared against existing correlation functions that relate the mean tip speed ratio of the plate to the aspect ratio, thickness ratio and mass moment of inertia of the plate. Agreement is found to be good for aspect ratios of I, but poor away from this value. However, other aspects of the numerical modelling are consistent with the correlations. (c) 2014 The Authors. Published by Elsevier Ltd.

关键词： CFD Autorotation fluid-structure interaction

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Development of a model of a multi-lymphangion lymphatic vessel incorporating realistic and measured parameter values

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BIOMECHANICS AND MODELING IN MECHANOBIOLOGY 2014年第2期13卷 401-416页

作者： Bertram, C. D. Macaskill, C. Davis, M. J. Moore, J. E., Jr. Univ Sydney Sch Math & Stat Sydney NSW 2006 Australia Univ Missouri Sch Med Dept Med Pharmacol & Physiol Columbia MO USA Univ London Imperial Coll Sci Technol & Med Dept Bioengn London SW7 2AZ England

Our published model of a lymphatic vessel consisting of multiple actively contracting segments between non-return valves has been further developed by the incorporation of properties derived from observations and measurements of rat mesenteric vessels. These included (1) a refractory period between contractions, (2) a highly nonlinear form for the passive part of the pressure-diameter relationship, (3) hysteretic and transmural-pressure-dependent valve opening and closing pressure thresholds and (4) dependence of active tension on muscle length as reflected in local diameter. Experimentally, lymphatic valves are known to be biased to stay open. In consequence, in the improved model, vessel pumping of fluid suffers losses by regurgitation, and valve closure is dependent on backflow first causing an adverse valve pressure drop sufficient to reach the closure threshold. The assumed resistance of an open valve therefore becomes a critical parameter, and experiments to measure this quantity are reported here. However, incorporating this parameter value, along with other parameter values based on existing measurements, led to ineffective pumping. It is argued that the published measurements of valve-closing pressure threshold overestimate this quantity owing to neglect of micro-pipette resistance. An estimate is made of the extent of the possible resulting error. Correcting by this amount, the pumping performance is improved, but still very inefficient unless the open-valve resistance is also increased beyond the measured level. Arguments are given as to why this is justified, and other areas where experimental data are lacking are identified. The model is capable of future adaptation as new experimental data appear.

关键词： Lumped parameter model fluid-structure interaction Lymph transport Valve hysteresis Intrinsic pumping mode

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fluid-structure interactions of Mechanical Sensors at Nanometer Scales

Fluid-Structure Interactions of Mechanical Sensors at Nanome...

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IEEE Sensors

作者： John Elie Sader Department of Mathematics and Statistics The University of Melbourne Victoria 3010 Australia

ISBN: (纸本)9781479901609

Miniaturization of resonant mechanical structures has driven progress in a wide range of advanced technologies, including sensors for mass detection and imaging with atomic resolution. While the constituent elastic properties of mechanical resonators remain identical to bulk values upon miniaturization to nanometer length scales, operation in fluid environments gives rise to physical phenomena not normally seen at macroscopic levels. Here, we discuss recent work aimed at interrogating and modeling the fluid-structure interaction of nanometer-scale mechanical sensors, in gases and liquids.

关键词： nanomechanics fluid-structure interaction gases liquids cantilevers nanoparticles

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High-order accurate fluid-structure simulation of a tuning fork

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COMPUTERS & fluidS 2014年 98卷 230-238页

作者： Froehle, Bradley Persson, Per-Olof Univ Calif Berkeley Dept Math Berkeley CA 94720 USA

The aeroacoustics of a tuning fork are investigated using a high-order fluid-structure interaction (FSI) scheme. The compressible Navier-Stokes equations are discretized using a discontinuous Galerkin arbitrary Lagrangian-Eulerian (DG-ALE) method on an unstructured tetrahedral mesh, and coupled to a non-linear hyperelastic neo-Hookean model of a tuning fork, discretized using continuous Galerkin finite elements on an unstructured tetrahedral mesh. The fluid and structure are both integrated implicitly in time using a partitioned approach based on an implicit-explicit Runge-Kutta method. We measure radial sound distributions which show good agreement with theoretical predictions and physical experiments in the open literature. In addition we demonstrate how to measure Q factors for several common modes, emphasizing that we can accurately capture the decay rates arising purely from the interaction of the tuning fork with the air and without any damping built into the structure model. (C) 2013 Elsevier Ltd. All rights reserved.

关键词： Aeroacoustics Discontinuous Galerkin fluid-structure interaction Tuning fork

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High-volume fraction simulations of two-dimensional vesicle suspensions

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JOURNAL OF COMPUTATIONAL PHYSICS 2014年 274卷 245-267页

作者： Quaife, Bryan Biros, George Univ Texas Austin Inst Computat Engn & Sci Austin TX 78712 USA

We consider numerical algorithms for the simulation of the rheology of two-dimensional vesicles suspended in a viscous Stokesian fluid. The vesicle evolution dynamics is governed by hydrodynamic and elastic forces. The elastic forces are due to local inextensibility of the vesicle membrane and resistance to bending. Numerically resolving vesicle flows poses several challenges. For example, we need to resolve moving interfaces, address stiffness due to bending, enforce the inextensibility constraint, and efficiently compute the (non-negligible) long-range hydrodynamic interactions. Our method is based on the work of Rahimian et al. (2010) [33]. It is a boundary integral formulation of the Stokes equations coupled to the interface mass continuity and force balance. We extend the algorithms presented in that paper to increase the robustness of the method and enable simulations with concentrated suspensions. In particular, we propose a scheme in which both intra-vesicle and inter-vesicle interactions are treated semi-implicitly. In addition we use special integration for near-singular integrals and we introduce a spectrally accurate collision detection scheme. We test the proposed methodologies on both unconfined and confined flows for vesicles whose internal fluid may have a viscosity contrast with the bulk medium. Our experiments demonstrate the importance of treating both intra-vesicle and inter-vesicle interactions accurately. (C) 2014 Elsevier Inc. All rights reserved.

关键词： Stokes flow Suspensions Particulate flows Vesicle simulations Boundary integral method fluid membranes Semi-implicit algorithms fluid-structure interaction Spectral collision detection Fast multipole methods

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Effect of geological medium on seismic signals from underground nuclear explosion events - A case study for Baneberry site

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SADHANA-ACADEMY PROCEEDINGS IN ENGINEERING SCIENCES 2014年第1期39卷 221-266页

作者： Singh, R. K. Sikka, S. K. Kakodkar, Anil Bhabha Atom Res Ctr Bombay 400085 Maharashtra India

Seismic signals due to any underground nuclear explosion events are known to be influenced by the local geology of the test site and the yield level. In this paper, transient three-dimensional finite element code SHOCK-3D developed for the simulation of underground nuclear explosion events has been used to obtain synthetic acceleration signals for Baneberry site (Nevada) single and composite rock media. At this site an underground nuclear test of 10 kT conducted on 18th December 1970 at source depth of 278 m resulted into venting as reported by Terhune et al with 2D simulation results and later by us through 3D simulation in Ranjan et al. First, the reasons of the venting for this event are summarized. After the successful validation of the 3D numerical model for Baneberry site rock media, parametric studies are carried out for 1 and 8 kT yields at 100 m depth (Scaled Depths of Burst SDOB similar to 100 and 50 m/kT(1/3), respectively) for homogeneous and composite Paleozoic and Tuff media of Baneberry site. It is demonstrated that the near source local geological formations and associated nonlinear effects significantly influence the seismic signals. With this study the seismic decoupling of the source by an order of magnitude has been illustrated. Finally, it is concluded that the seismic signals alone, in the absence of in-depth information of the local geology of the specific test site, are not appropriate measures of the source strength.

关键词： Underground nuclear explosion transient finite element fluid-structure interaction Baneberry event nuclear yield estimation nuclear event discrimination

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Numerical modal analysis of composite structures coupled with water

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COMPOSITE structureS 2014年第Sep./Oct.期116卷 325-335页

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

Dynamic characteristics of polymer composite beam and plate structures were studied when the structures were coupled with water. The effect of fluid-structure interaction (FSI) on natural frequencies, mode shapes, and dynamic responses was examined for polymer composite structures using multiphysics-based computational techniques. Composite structures were modeled using the Finite Element Method. The fluid was modeled as an acoustic medium using the Cellular Automata and finite element techniques. Those techniques were coupled so that both fluid and structure could interact bi-directionally. In order to make the coupling easier, the beam and plate finite elements have only displacement degrees of freedom but no rotational degrees of freedom. Then, the numerical modal analysis technique was applied to the composite structures with and without FSI, respectively, so that the effect of FSI can be examined by comparing the two results. The study showed that the effect of FSI is significant on dynamic properties of polymer composite structures. Some previous experimental observations were confirmed using the numerical modal analysis. Published by Elsevier Ltd.

关键词： fluid-structure interaction Modal analysis Multiphysics analysis

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Multiscale methods for gore curvature calculations from FSI modeling of spacecraft parachutes

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COMPUTATIONAL MECHANICS 2014年第6期54卷 1461-1476页

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

There are now some sophisticated and powerful methods for computer modeling of parachutes. These methods are capable of addressing some of the most formidable computational challenges encountered in parachute modeling, including fluid-structure interaction (FSI) between the parachute and air flow, design complexities such as those seen in spacecraft parachutes, and operational complexities such as use in clusters and disreefing. One should be able to extract from a reliable full-scale parachute modeling any data or analysis needed. In some cases, however, the parachute engineers may want to perform quickly an extended or repetitive analysis with methods based on simplified models. Some of the data needed by a simplified model can very effectively be extracted from a full-scale computer modeling that serves as a pilot. A good example of such data is the circumferential curvature of a parachute gore, where a gore is the slice of the parachute canopy between two radial reinforcement cables running from the parachute vent to the skirt. We present the multiscale methods we devised for gore curvature calculation from FSI modeling of spacecraft parachutes. The methods include those based on the multiscale sequentially-coupled FSI technique and using NURBS meshes. We show how the methods work for the fully-open and two reefed stages of the Orion spacecraft main and drogue parachutes.

关键词： Spacecraft parachutes Gore curvature fluid-structure interaction Multiscale methods Sequentially-coupled FSI NURBS meshes Orion main parachutes Orion drogue parachutes Reefed stages

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