This paper presents a newly developed high-fidelity fluid-structure interaction simulation tool for geometrically resolved rotor simulations of wind turbines. The tool consists of a partitioned coupling between the st...
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This paper presents a newly developed high-fidelity fluid-structure interaction simulation tool for geometrically resolved rotor simulations of wind turbines. The tool consists of a partitioned coupling between the structural part of the aero-elastic solver HAWC2 and the finite volume computational fluid dynamics (CFD) solver EllipSys3D. The paper shows that the implemented loose coupling scheme, despite a non-conservative force transfer, maintains a sufficient numerical stability and a second-order time accuracy. The use of a strong coupling is found to be redundant. In a first test case, the newly developed coupling between HAWC2 and EllipSys3D (HAWC2CFD) is utilized to compute the aero-elastic response of the NREL 5-MW reference wind turbine (RWT) under normal operational conditions. A comparison with the low-fidelity but state-of-the-art aero-elastic solver HAWC2 reveals a very good agreement between the two approaches. In a second test case, the response of the NREL 5-MW RWT is computed during a yawed and thus asymmetric inflow. The continuous good agreement confirms the qualities of HAWC2CFD but also illustrates the strengths of a computationally cheaper blade element momentum theory (BEM) based solver, as long as the solver is applied within the boundaries of the employed engineering models. Two further test cases encompass flow situations, which are expected to exceed the limits of the BEM model. However, the simulation of the NREL 5-MW RWT during an emergency shut down situation still shows good agreements in the predicted structural responses of HAWC2 and HAWC2CFD since the differences in the computed force signals only persist for an insignificantly short time span. The considerable new capabilities of HAWC2CFD are finally demonstrated by simulating vortex-induced vibrations on the DTU 10-MW wind turbine blade in standstill. Copyright (c) 2016 John Wiley & Sons, Ltd.
Transcatheter aortic valve replacement (TAVR) represents an established recent technology in a high risk patient base. To better understand TAVR performance, a fluid-structure interaction (FSI) model of a self-expanda...
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Transcatheter aortic valve replacement (TAVR) represents an established recent technology in a high risk patient base. To better understand TAVR performance, a fluid-structure interaction (FSI) model of a self-expandable transcatheter aortic valve was proposed. After an in vitro durability experiment was done to test the valve, the FSI model was built to reproduce the experimental test. Lastly, the FSI model was used to simulate the virtual implant and performance in a patient-specific case. Results showed that the leaflet opening area during the cycle was similar to that of the in vitro test and the difference of the maximum leaflet opening between the two methodologies was of 0.42%. Furthermore, the FSI simulation quantified the pressure and velocity fields. The computed strain amplitudes in the stent frame showed that this distribution in the patient-specific case is highly affected by the aortic root anatomy, suggesting that the in vitro tests that follow standards might not be representative of the real behavior of the percutaneous valve. The patient-specific case also compared in vivo literature data on fast opening and closing characteristics of the aortic valve during systolic ejection. FSI simulations represent useful tools in determining design errors or optimization potentials before the fabrication of aortic valve prototypes and the performance of tests.
The present paper approaches fluid-structure interaction by means of a 4-equation model. Experimental data collected from a straight copper pipe-rig lying directly on the lab floor is used for the model validation in ...
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The present paper approaches fluid-structure interaction by means of a 4-equation model. Experimental data collected from a straight copper pipe-rig lying directly on the lab floor is used for the model validation in terms of wave shape, timing and damping. The main focus lies on the friction coupling modelling considering skin and dry friction. For skin friction three approaches are analysed: quasi-steady, Brunone's and Trikha's unsteady friction. For dry friction Coulomb's model is added in the beam momentum conservation equation. Results present a good fitting between experimental and numerical data, showing the dissipative effect of dry friction phenomenon which complement that of skin friction, specially in the short term simulation. (C) 2016 Elsevier Ltd. All rights reserved.
Calcific aortic valve disease (CAVD) is characterized by calcification accumulation and thickening of the aortic valve cusps, leading to stenosis. The importance of fluid flow shear stress in the initiation and regula...
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Calcific aortic valve disease (CAVD) is characterized by calcification accumulation and thickening of the aortic valve cusps, leading to stenosis. The importance of fluid flow shear stress in the initiation and regulation of CAVD progression is well known and has been studied recently using fluid-structure interaction (FSI) models. While cusp calcifications are three-dimensional (3D) masses, previously published FSI models have represented them as either stiffened or thickened two-dimensional (2D) cusps. This study investigates the hemodynamic effect of these calcifications employing FSI models using 3D patient-specific calcification masses. A new reverse calcification technique (RCT) is used for modeling different stages of calcification growth based on the spatial distribution of calcification density. The RCT is applied to generate the 3D calcification deposits reconstructed from a patient-specific CT scans. Our results showed that consideration of 3D calcification deposits led to both higher fluid shear stresses and unique fluid shear stress distribution on the aortic side of the cusps that may have an impact on the calcification growth rate. However, the flow did not seem to affect the geometry of the calcification during the growth phase.
In this work the effect of the gravity force on the fluid-structure interaction (FSI) simulation of a large horizontal axis wind turbine (HAWT) is analyzed in detail. FSI simulations with and without gravity are carri...
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ISBN:
(纸本)9788494690990
In this work the effect of the gravity force on the fluid-structure interaction (FSI) simulation of a large horizontal axis wind turbine (HAWT) is analyzed in detail. FSI simulations with and without gravity are carried out and compared in order to highlight the effect of gravity force on the loads and performance of the analyzed HAWT.
Taking the assembled pipeline as research object, the deformation of sealing rubber ring was analyzed under water hammer pressure. A calculation method of pressure wave speed with fluid-structure interaction (FSI) in ...
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ISBN:
(纸本)9781538610091
Taking the assembled pipeline as research object, the deformation of sealing rubber ring was analyzed under water hammer pressure. A calculation method of pressure wave speed with fluid-structure interaction (FSI) in assembled pipeline was proposed. The influences of sealing rubber ring on pressure wave speed were researched. The computational results show that the attenuation effect of sealing rubber ring on pressure wave speed with FSI is less than that of pressure wave speed without FSI. The attenuation ratio of sealing rubber ring to pressure wave speed enhances with the increase of the bulk modulus of the transmission medium in assembled pipeline. Owing to the influence of sealing rubber ring, pressure wave speed reflects a trend of rise first and then fall as the ratio between the thickness of pipe wall and the inner diameter of pipe increases.
作者:
Mao, WenbinLi, KeweiSun, WeiGeorgia Inst Technol
Tissue Mech Lab Wallace H Coulter Dept Biomed Engn 206 Technol Enterprise Pk387 Technol Circle Atlanta GA 30313 USA Emory Univ
206 Technol Enterprise Pk387 Technol Circle Atlanta GA 30313 USA Graz Univ Technol
Inst Biomech Stremayrgasse 16-2 A-8010 Graz Austria
Computational modeling of heart valve dynamics incorporating both fluid dynamics and valve structural responses has been challenging. In this study, we developed a novel fully-coupled fluid-structure interaction (FSI)...
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Computational modeling of heart valve dynamics incorporating both fluid dynamics and valve structural responses has been challenging. In this study, we developed a novel fully-coupled fluid-structure interaction (FSI) model using smoothed particle hydrodynamics (SPH). A previously developed nonlinear finite element (FE) model of tran-scatheter aortic valves (TAV) was utilized to couple with SPH to simulate valve leaflet dynamics throughout the entire cardiac cycle. Comparative simulations were performed to investigate the impact of using FE-only models vs. FSI models, as well as an isotropic vs. an anisotropic leaflet material model in TAV simulations. From the results, substantial differences in leaflet kinematics between FE-only and FSI models were observed, and the FSI model could capture the realistic leaflet dynamic deformation due to its more accurate spatial and temporal loading conditions imposed on the leaflets. The stress and the strain distributions were similar between the FE and FSI simulations. However, the peak stresses were different due to the water hammer effect induced by the fluid inertia in the FSI model during the closing phase, which led to 13-28% lower peak stresses in the FE-only model compared to that of the FSI model. The simulation results also indicated that tissue anisotropy had a minor impact on hemodynamics of the valve. However, a lower tissue stiffness in the radial direction of the leaflets could reduce the leaflet peak stress caused by the water hammer effect. It is hoped that the developed FSI models can serve as an effective tool to better assess valve dynamics and optimize next generation TAV designs.
This investigation focuses on studying the effect of flow conditions and the geometric variation of the microcantilever's bluff body on the microcantilever detection capabilities within a fluidic device using a fi...
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This investigation focuses on studying the effect of flow conditions and the geometric variation of the microcantilever's bluff body on the microcantilever detection capabilities within a fluidic device using a finite element fluid-structure interaction model. Such parameters include inlet velocity, flow direction, and height of the microcantilever's supporting system within the fluidic cell. The transport equations are solved using a finite element formulation based on the Galerkin method of weighted residuals. For a flexible microcantilever, a fully coupled fluid-structure interaction (FSI) analysis is utilized and the fluid domain is described by an Arbitrary-Lagrangian-Eulerian (ALE) formulation that is fully coupled to the structure domain. The results of this study showed a profound effect of the magnitude and direction of the inlet velocity and the height of the bluff body on the deflection of the microcantilever. The vibration characteristics were also investigated in this study. This work paves the road for researchers to design efficient microcantilevers that display least errors in the measurements. (C) 2016 Elsevier Ltd. All rights reserved.
fluidstructureinteraction (FSI) analysis is of great significance with the advance of computing technology and numerical algorithms in the last decade. This multidisciplinary problem has been expanded to engineering...
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fluidstructureinteraction (FSI) analysis is of great significance with the advance of computing technology and numerical algorithms in the last decade. This multidisciplinary problem has been expanded to engineering applications such as offshore structures, dam-reservoirs and other industrial applications. The motivation of this research is to investigate the fundamental physics involved in the complex interaction of fluid and structural domains by numerical simulations and to tackle the multiple surface interactions of a one-way coupling FSI GBS engineering case. To solve such problem, the partitioned method has been adopted and the approach is to utilise the advantage of the existing numerical algorithms in solving the complex fluid and structural interactions. The suitability has been validated for both strong and weak coupling methods which are the distinctive partitioned coupling approach. Therefore, with the computational platform of ANSYS FEA, the coupled field methods were adopted in this numerical analysis. Comparisons were made with the results obtained to justify the ability of both strong and weak methods in resolving the one-way coupling example with the potential applications in the field of ocean and marine engineering. (C) 2016 Elsevier Ltd. All rights reserved.
The reefing ratio for the first stage of a parachute limits the reefing ratio for the subsequent stages, so its minimal effective value is very important. In this paper, an empirical formula is derived to calculate th...
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The reefing ratio for the first stage of a parachute limits the reefing ratio for the subsequent stages, so its minimal effective value is very important. In this paper, an empirical formula is derived to calculate the minimal effective reefing ratio. The empirical parameters are obtained by the arbitrary Lagrangian-Eulerian/fluid-structure interaction (ALE/FSI) method. By using the FSI method, the typical flow and structure fields of effective and ineffective reefed parachutes are revealed. The numerical results including drag characteristics and final shape are very consistent with wind tunnel tests. The curves of the empirical parameters with reefing ratios are obtained. The minimal effective reefing ratio obtained by the empirical formula is consistent with that of the numerical results, which shows that the empirical formula has high accuracy.
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