A fluid-structure interaction scheme for numerical simulation of actively controlled bridges subject to flutter instability is proposed in this work. In order to suppress or attenuate dynamic instabilities induced by ...
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A fluid-structure interaction scheme for numerical simulation of actively controlled bridges subject to flutter instability is proposed in this work. In order to suppress or attenuate dynamic instabilities induced by the wind action on long-span bridges, control systems are proposed considering aerodynamic appendices and winglets attached to the deck structure, where control forces are continuously calculated using optimal control theory. The flow fundamental equations are solved here employing the explicit two-step Taylor-Galerkin method and the arbitrary Lagrangian-Eulerian (ALE) description. Eight-node hexahedral finite elements with one-point quadrature and hourglass stabilization are utilized for spatial discretization. Flow turbulence is modeled using Large Eddy Simulation (LES) and a partitioned coupling scheme is adopted for fluid-structure interactions. The structural system is analyzed considering the sectional model approach and a rigid-body formulation for large rotations. Different control techniques and winglet configurations are investigated using prismatic and bridge cross-sections, where control efficiency is evaluated in terms of displacement reduction and energy required by the control system. Preliminary results are obtained here employing approximate flowconditions to verify the control algorithm, where laminar flows and a two-dimensional LES-type approach are utilized. (C) 2020 Elsevier Ltd. All rights reserved.
In this paper, we present a numerical model capable of solving the fluid-structure interaction problems involved in the dynamics of skeleton-reinforced fish fins. In this model, the fluid dynamics is simulated by solv...
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In this paper, we present a numerical model capable of solving the fluid-structure interaction problems involved in the dynamics of skeleton-reinforced fish fins. In this model, the fluid dynamics is simulated by solving the Navier-Stokes equations using a finite-volume method based on an overset, multi-block structured grid system. The bony rays embedded in the fin are modeled as nonlinear Euler-Bernoulli beams. To demonstrate the capability of this model, we numerically investigate the effect of various ray stiffness distributions on the deformation and propulsion performance of a 3D caudal fin. Our numerical results show that with specific ray stiffness distributions, certain caudal fin deformation patterns observed in real fish (e.g. the cupping deformation) can be reproduced through passive structural deformations. Among the four different stiffness distributions (uniform, cupping, W-shape and heterocercal) considered here, we find that the cupping distribution requires the least power expenditure. The uniform distribution, on the other hand, performs the best in terms of thrust generation and efficiency. The uniform stiffness distribution, per se, also leads to 'cupping' deformation patterns with relatively smaller phase differences between various rays. The present model paves the way for future work on dynamics of skeleton-reinforced membranes.
The structural integrity assessment of the water-cooling re-circulating system of nuclear boiling water reactors (BWR) is a subject of great importance, because the jet-pump assembly system cold down the reactor by ac...
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The structural integrity assessment of the water-cooling re-circulating system of nuclear boiling water reactors (BWR) is a subject of great importance, because the jet-pump assembly system cold down the reactor by accelerating water flow recirculation through the core of the reactor for its appropriate operation without compromising its structural integrity. The analysis becomes even more important when a nuclear reactor has been upgraded to produce more energy by accelerating water flow through the core of the reactor. However, this process will result in loads increment in the jet-pump assemblies causing higher structural stresses which can result in damage and failure in the mechanical components of the re-circulation system, which can cause overheating in the nuclear reactor leading to a catastrophic event. To deal with such problematic, in the present work it was developed a modelling methodology which combines finite element (FEA) and computational fluid dynamics (CFD) modelling to analyse water flow effects on the structural response of jet-pump assemblies in order to predict damage and failure of mechanical components of the re-circulating system. Therefore, FEA and CFD models of a jet-pump assembly were developed, and dynamic modal analyses were performed. Then, the natural frequencies of different vibration modes were obtained in order to identify critical mechanical components of the assembly by integrating dynamic and static analyses. The effect of fluid velocity on the natural frequencies of the assembly was also analysed.
fluid-structure interaction (FSI) during water hammer in a viscoelastic (VE) pipe is studied in the frequency domain. The main aim is to investigate pressure and stress waves using Transfer Matrix Method (TMM) in a ty...
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fluid-structure interaction (FSI) during water hammer in a viscoelastic (VE) pipe is studied in the frequency domain. The main aim is to investigate pressure and stress waves using Transfer Matrix Method (TMM) in a typical reservoir-VE pipe-valve (RPV) system. Both major coupling mechanisms namely Poisson and junction are taken into account. The generalized Kelvin-Voigt model simulates VE behavior during water hammer, which is generated by a quick closing/opening of downstream valve. The effect of viscoelasticity is modeled by Volterra integrals (in time) which are written as the products of transforms of the creep function and pressure (or stress) in the Laplace domain. The developed formulation is adopted to solve two well-known FSI problems from literature, and both demonstrate favorable agreement with available analytical and experimental data. To investigate the sole/simultaneous effect of Poisson and/or junction coupling and viscoelasticity, a hypothetical case study is considered and the corresponding results are closely investigated. The robust performance of the Transfer Matrix Method (TMM) allows for deducing the drop of pressure amplitudes due to viscoelasticity, frequency shift of Poisson coupling, and remarkable discrepancy of odd frequencies (relative to classical model) induced by junction coupling. This research is of crucial importance when frequency-response-based methods are utilized for defect detection of unrestrained pipes. (C) 2020 Elsevier Ltd. All rights reserved.
Stenosis can disrupt the normal pattern of blood flow and make the artery more susceptible to buckling which may cause arterial tortuosity. Although the stability simulations of the atherosclerotic arteries were condu...
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Stenosis can disrupt the normal pattern of blood flow and make the artery more susceptible to buckling which may cause arterial tortuosity. Although the stability simulations of the atherosclerotic arteries were conducted based on solid modeling and static internal pressure, the mechanical stability of stenotic artery under pulsatile blood flow remains unclear while pulsatile nature of blood flow makes the artery more critical for stresses and stability. In this study, the effect of stenosis on arterial stability under pulsatile blood flow was investigated. fluid-structure interaction (FSI) simulations of artery stenosis under pulsatile flow were conducted. 3D idealized geometries of carotid artery stenosis with symmetric and asymmetric plaques along with different percentages of stenosis were created. It was observed that the stenosis percentage, symmetry/asymmetry of the plaque, and the stretch ratio can dramatically affect the buckling pressure. Buckling makes the plaques (especially in asymmetric ones) more likely to rupture due to increasing the stresses on it. The dominant stresses on plaques are the circumferential, axial and radial ones, respectively. Also, the highest shear stresses on the plaques were detected in ? - z and r - ? planes for the symmetric and asymmetric stenotic arteries, respectively. In addition, the maximum circumferential stress on the plaques was observed in the outer point of the buckled configuration for symmetric and asymmetric stenosis as well as at the ends of the asymmetric plaque. Furthermore, the artery buckling causes a large vortex flow at the downstream of the plaque. As a result, the conditions for the penetration of lipid particles and the formation of new plaques are provided.
Printed circuit heat exchangers (PCHEs), with supercritical carbon dioxide (sCO(2)) as the working fluid, are being considered for use as recuperators and condensers in Brayton cycles for Next Generation Nuclear Plant...
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Printed circuit heat exchangers (PCHEs), with supercritical carbon dioxide (sCO(2)) as the working fluid, are being considered for use as recuperators and condensers in Brayton cycles for Next Generation Nuclear Plant (NGNP) projects as well as other power generation and heat transfer applications. A few experimental and numerical structural assessments of these PCHEs have been conducted, but all have been somewhat limited due to the difficulty measuring actual stresses in an operating PCHE and the computer resources needed to accurately conduct a fluid-structure interaction (FSI) examination using finite element analysis (FEA). This paper examines a previous pseudo two-dimensional (2D) study of a sodium-sCO(2) PCHE, linear elastic model and multilinear elastic hardening model results are included. Next, previously unperformed, three-dimensional (3D) one-way coupled FSI studies of two notional zigzag-channel, sCO(2) PCHEs are conducted. All results are evaluated against the stress intensity limits set forth by the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code (BPVC) Sections III and VIII. Most of the examined PCHEs meet the requirements for general use but exceed the maximum allowable stress intensities for application as nuclear components.
A numerical framework is proposed to couple the finite element (FE) and lattice Boltzmann methods (LBM) for simulating fluid-structure interaction (FSI) problems. The LBM is used as an efficient method for solving the...
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A numerical framework is proposed to couple the finite element (FE) and lattice Boltzmann methods (LBM) for simulating fluid-structure interaction (FSI) problems. The LBM is used as an efficient method for solving the weakly-compressible fluid flows. The corotational FE method for beam elements is used to solve the thin plate deformation. The two methods are coupled via a direct-forcing immersed boundary (IB) method with a sub-iteration scheme. A virtual structure method has been developed to improve the computational accuracy. Validations of the proposed coupling method have been carried out by testing a vortex-induced vibration problem. The numerical results are in good agreement with [Li and Favier (2017), "A non-staggered coupling of finite element and lattice Boltzmann methods via an immersed boundary scheme for fluid-structure interaction," Comput. fluids 143, 90-102]. The proposed method does not require heavy linear algebra calculation, which is suitable for parallel computation.
作者：
Zhang, PengCarretto, AlessiaPorfiri, MaurizioNYU
Dept Mech & Aerosp Engn MetroTech Ctr 6 Tandon Sch Engn Brooklyn NY 11201 USA Univ Genoa
Dept Civil Chem & Environm Engn Via Montallegro 1 Genoa 16145 Italy NYU
Dept Biomed Engn Tandon Sch Engn MetroTech Ctr 3 Brooklyn NY 11201 USA
Predicting the response of air-backed panels to impulsive hydrodynamic loading is essential to the design of marine structures operating in extreme conditions. Despite significant effort in this area of research, the ...
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Predicting the response of air-backed panels to impulsive hydrodynamic loading is essential to the design of marine structures operating in extreme conditions. Despite significant effort in this area of research, the lack of full-field measurement techniques of structural dynamics and flow physics hinders our understanding of the fluid-structure interaction. To fill this gap in knowledge, we designed a laboratory-scale experiment to elucidate fluid-structure interaction associated with impulsive hydrodynamic loading on a flexible plate. A combined experimental approach based on digital image correlation (DIC) and particle image velocimetry (PIV) was developed to afford spatially- and temporally-resolved measurements of the plate deflection and fluid velocity. From the velocity field measured through PIV, the hydrodynamic loading on the structure was estimated via a pressure-reconstruction algorithm. Experimental results point at a strong bidirectional coupling between structural dynamics and flow physics, which influence temporal and spatial patterns in counter-intuitive ways. While the plate deflection follows the fundamental in-vacuum mode shape of a clamped plate, the pressure exhibits a complex evolution. Not only does the location of the peak loading on the plate alternates between the clamp and the center as time progresses, but also the time evolution of the peak loading anticipated the peak displacement of the plate. This study contributes a new methodological approach to study fluid-structure interaction in three dimensions, offering insight in the physics of air-backed impact that could inform engineering design and scientific inquiry. (C) 2020 Elsevier Ltd. All rights reserved.
In the present work we study the spider’s hair flow-sensing system by using fluid-structure interaction (FSI) numerical simulations. We observe experimentally the morphology of Theraphosa stirmi ’s hairs and charact...
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Primary Objective: Closed brain injuries are a common danger in contact sports and motorized vehicular collisions. Mild closed brain injuries, such as concussions, are not easily visualized by computed imaging or scan...
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Primary Objective: Closed brain injuries are a common danger in contact sports and motorized vehicular collisions. Mild closed brain injuries, such as concussions, are not easily visualized by computed imaging or scans. Having a comprehensive head/brain model and using fluid-structure interaction (FSI) simulations enable us to see the exact movement of the cerebrospinal fluid (CSF) under such conditions and to identify the areas of brain most affected. Research Design: The presented work is based on the first FSI model capable of simulating the interaction between the CSF flow and brain. Methods and Procedures: FSI analysis combining smoothed-particle hydrodynamics and high-order finite-element method is used. Main Outcomes and Results: The interaction between the CSF and brain under rapid acceleration and deceleration is demonstrated. The cushioning effect of the fluid and its effect on brain are shown. Conclusions: The capability to locate areas (down to the exact gyri and sulci) of the brain the most affected under given loading conditions, and therefore assess the possible damage to the brain and consequently predict the symptoms, is shown.
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