A dynamic load and stress analysis of a wind turbine is carried out using transient fluid-structure interaction simulations. On the structural side, the three 50 m long commercial glass-fiber epoxy blades are modelled...
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A dynamic load and stress analysis of a wind turbine is carried out using transient fluid-structure interaction simulations. On the structural side, the three 50 m long commercial glass-fiber epoxy blades are modelled using shell elements, accurately including the properties of the composite materials. On the fluid side, a hexahedral mesh is obtained for every blade and for the hub of the machine. These meshes are then overlaid to a structured background mesh through an overset technique. The displacements prescribed by the structural solver are imposed on top of the rigid rotation of the turbine. The atmospheric boundary layer (ABL) is included using the k-epsilon turbulence model. The computational fluid dynamics (CFD) and computational solid mechanics (CSM) solvers are strongly coupled using an in-house code. The transient evolution of loads, stresses and displacements on each blade is monitored throughout the simulated time. The ABL induces oscillating axial displacements in the outboard region of the blade. Furthermore, the influence of gravity on the structure is accounted for and investigated, showing that it largely affects the tangential displacement of the blade. The oscillating deformations lead to sensible differences in the torque provided by each blade during its rotation. (C) 2019 Elsevier Ltd. All rights reserved.
Composite materials are increasingly used in hydrodynamic lifting surfaces due to their higher specific strength and favorable fatigue properties. A set of parametric studies are performed to investigate the influence...
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Composite materials are increasingly used in hydrodynamic lifting surfaces due to their higher specific strength and favorable fatigue properties. A set of parametric studies are performed to investigate the influence of fiber orientation on the vibration characteristics and load-dependent bend-twist coupled behavior of composite hydrofoils in viscous flow. A 3-D Reynolds-averaged Navier-Stokes (RANS) solver is coupled with a 3-D finite-element method (FEM) to predict the fluid-structure response of cantilevered composite hydrofoils made of unidirectional carbon fiber reinforced polymer (CFRP). Fiber orientation changes the modal characteristics of composite hydrofoils, as well as the hydroelastic response. The bending-up and nose-down material bend-twist coupling leads to lower hydrodynamic load coefficients with increasing flow speed, as well as delayed separation, stall, and static divergence. The opposite trend is observed when the fiber orientation results in a bending-up and nose-up material bend-twist coupling. Material failure index contours show that the fiber orientation affects the location of failure. These parametric studies provide guidance for future design and optimization of composite hydrodynamic lifting surfaces.
A novel method for complex fluid-structure interaction (FSI) involving large structural deformation and motion is proposed. The new approach is based on a hybrid fluid formulation that combines the advantages of purel...
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A novel method for complex fluid-structure interaction (FSI) involving large structural deformation and motion is proposed. The new approach is based on a hybrid fluid formulation that combines the advantages of purely Eulerian (fixed-grid) and arbitrary Lagrangian-Eulerian (ALE) moving mesh formulations in the context of FSI. The structure, as commonly given in Lagrangian description, is surrounded by a fine resolved layer of fluid elements based on an ALE-framework. This ALE-fluid patch, which is embedded in a Eulerian background fluid domain, follows the deformation and motion of the structural interface. This approximation technique is not limited to finite element methods but can also be realized within other frameworks like finite volume or discontinuous Galerkin methods. In this work, the surface coupling between the two disjoint fluid subdomains is imposed weakly using a stabilized Nitsche's technique in a cut finite element method (CutFEM) framework. At the fluid-solid interface, standard weak coupling of node-matching or nonmatching finite element approximations can be utilized. As the fluid subdomains can be meshed independently, a sufficient mesh quality in the vicinity of the common fluid-structure interface can be assured. To our knowledge, the proposed method is the only method (despite some overlapping domain decomposition approaches that suffer from other issues) that allows for capturing boundary layers and flow detachment via appropriate grids around largely moving and deforming bodies. In contrast to other methods, it is possible to do this, eg, without the necessity of costly remeshing procedures. A clear advantage over existing overlapping domain decomposition methods consists in the sharp splitting of the fluid domain, which comes along with improved convergence behavior of the resulting monolithic FSI system. In addition, it might also help to save computational costs as now background grids can be much coarser. Various FSI-cases of rising co
In this paper, we present a method for the analysis of the motion behaviour and also the structural response ? stresses and deformations ? of a floating wind turbine. A partitioned approach is chosen to solve the flui...
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In this paper, we present a method for the analysis of the motion behaviour and also the structural response ? stresses and deformations ? of a floating wind turbine. A partitioned approach is chosen to solve the fluid-structure interaction problem. Therefore, our C++ library comana, developed to couple various solvers, is enhanced to couple the fluid solver pan MARE and the structural solver ANSYS. Initially, a simple elastic finite element model is used in the coupled analysis. This finite element model is described, and some results of the coupled simulation are presented. In order to use a more detailed finite element model without drastically increasing the computation time, superelements can be employed. This procedure is described and applied to an example, a floating buoy in waves, to demonstrate its applicability in fluid-structure interaction simulations.
The Jones eigenvalue problem first described in [D. S. Jones, Quart. T. Mech. Appl. Math., 36 (1983), pp. 111-138] concerns unusual modes in bounded elastic bodies-time-harmonic displacements whose tractions and norma...
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The Jones eigenvalue problem first described in [D. S. Jones, Quart. T. Mech. Appl. Math., 36 (1983), pp. 111-138] concerns unusual modes in bounded elastic bodies-time-harmonic displacements whose tractions and normal components are both identically zero on the boundary. This problem is usually associated with a lack of unique solvability for certain models of fluidstructureinteraction. The boundary conditions in this problem appear, at first glance, to rule out any nontrivial modes unless the domain possesses significant geometric symmetries. Indeed, Jones modes were shown to not be possible in most C-infinity domains in [T. Harge, C. R. Acad. Sci. Paris Ser. I Math., 311 (1990), pp. 857-859]. However, in this paper we will see that while the existence of Jones modes sensitively depends on the domain geometry, such modes do exist in a broad class of domains. This paper presents the first detailed theoretical and computational investigation of this eigenvalue problem in Lipschitz domains. We also analytically demonstrate Jones modes on some simple geometries.
作者：
Cho, H.Lee, N.Shin, S-JLee, S.Seoul Natl Univ
BK21 Plus Transformat Training Program Creat Mech Inst Adv Machines & Design Seoul South Korea Hanwha Def Syst
R&D Strategy Team Vehicle & Launcher Syst R&D Div Gyeongsangnam Do South Korea Seoul Natl Univ
Inst Adv Aerosp Technol Dept Mech & Aerosp Engn Seoul South Korea Inha Univ
Dept Aerosp Engn Incheon South Korea
In this study, an improved fluid-structure interaction (FSI) analysis method is developed for a flapping wing. A co-rotational (CR) shell element is developed for its structural analysis. Further, a relevant non-linea...
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In this study, an improved fluid-structure interaction (FSI) analysis method is developed for a flapping wing. A co-rotational (CR) shell element is developed for its structural analysis. Further, a relevant non-linear dynamic formulation is developed based on the CR framework. Three-dimensional preconditioned Navier-Stokes equations are employed for its fluid analysis. An implicit coupling scheme is employed to combine the structural and fluid analyses. An explicit investigation of a 3D plunging wing is conducted using this FSI analysis method. A further investigation of this plunging wing is performed in relation to its operating condition. In addition, the relation between the wing's aerodynamic performance and plunging motion is investigated.
fluid-structure interaction has been largely utilized in wind turbine, but the related studies on building wind loading are relatively less frequent. In this study, a numerical study was carried out to investigate the...
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fluid-structure interaction has been largely utilized in wind turbine, but the related studies on building wind loading are relatively less frequent. In this study, a numerical study was carried out to investigate the wind load characteristics of a building based on two-way fluid-structure interaction, where synchronous interactions between wind and building were considered. Based on the comparison with experiments, it was indicated that a grid size of 0.4 m is adequate for a 6 m cube model and a computational zone with a domain of 25 m high and 50 m long is enough for the target problem in this study. It was also known that large eddy simulation provides the best fit with experiments, followed by detached eddy simulation, where the k-epsilon, k-omega and shear stress transport models give higher predictions. To provide reliable numerical results for building wind analysis, a computational domain with at least 4 times of the building height and 8 times of building length were suggested, while no strict requirement was shown for the domain width when it is longer than 20 m. The research outcomes can provide a technical guide on the applications of building wind analysis.
In this work, we present a monolithic finite-element-based strategy for problems involving the deformation of a hyperelastic solid, an incompressible fluid and electrostatics. We use a two-field hybrid Lagrangian form...
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In this work, we present a monolithic finite-element-based strategy for problems involving the deformation of a hyperelastic solid, an incompressible fluid and electrostatics. We use a two-field hybrid Lagrangian formulation for the structure, and a velocity-based ALE mixed formulation for the fluid with appropriately chosen interpolations for the various field variables to ensure stability of the resulting numerical procedure. The equations of electrostatics are solved on the reference configuration over both the solid and fluid domains, with voltage and electric displacement continuity imposed at the interface. Keeping in view that the thickness of typical MEMS structures is small, a stress-based hybrid formulation is used to prevent locking. The use of a monolithic strategy provides a robust and stable algorithm, and allows the user to take large time steps. The consistent linearization ensures a quadratic rate of convergence of the non-linear iterations at each time step. Detailed expressions for the tangent stiffness and associated matrices for the three-way coupled problem are provided. The robustness and accuracy of the proposed method are demonstrated by solving several benchmark problems from the literature.
An unsteady Reynolds-averaged Navier-Stokes (URANS) model coupled with an immersed-body method is used to model fluid-structure interaction (FSI) for moderate Reynolds number flows. Particular attention is paid to the...
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An unsteady Reynolds-averaged Navier-Stokes (URANS) model coupled with an immersed-body method is used to model fluid-structure interaction (FSI) for moderate Reynolds number flows. Particular attention is paid to the application of suitable flow boundary conditions with the immersed-body method. This model couples a combined finite-discrete element solid model and a finite element fluid model with the standard k - epsilon model. A thin shell mesh surrounding the solid surface is first used as a delta function to apply the interface boundary conditions for both the URANS model and the momentum equation. In order to reduce the computational cost, a log-law wall function is used within this thin shell to resolve the flow near the solid wall. To improve the accuracy of the wall function, a novel shell mesh external surface intersection approach is introduced to identify sharp solid-fluid interfaces. More importantly, an unstructured anisotropic mesh adaptivity is used to refine the mesh according to the interface and the velocity, which improves the accuracy of this immersed-body URANS model with use of a limited number of fluid cells. This immersed-body URANS method is validated by several test cases and results are in good agreement with both experimental and numerical data from the literature. (C) 2018 Elsevier Ltd. All rights reserved.
Slamming water impact occurs frequently on high-speed craft and restricts the operating envelope of a vessel. One approach to understanding the hydroelastic nature of this phenomenon is to study the vertical impact of...
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Slamming water impact occurs frequently on high-speed craft and restricts the operating envelope of a vessel. One approach to understanding the hydroelastic nature of this phenomenon is to study the vertical impact of a V-shaped wedge on calm water, which models a single slamming event after a vessel has become partially airborne. The dynamic structural response of the bottom plate of a wedge dropped vertically (drop height = 7.9 cm) is investigated both experimentally and computationally. The experiments were conducted with a flexible bottom model at Virginia Tech. Pressure on the wedge bottom, rigid body motion (vertical acceleration and vertical position), and fullfield out-of-plane deflection were measured. The out-of-plane deflection was measured using stereoscopic digital image correlation. Predictions on the hydrodynamic pressure field were made using Wagner's method, Vorus's method, and an unsteady Reynoldsaveraged Navier-Stokes solver, all assuming a rigid plate. In the present work, the reconstructed pressure distribution from the experiment was used as the loading condition in a dynamic, linear finite element plate model (one-way coupled approach). Both the predicted pressure and predicted deflection were compared with the experiment. It was found that in the experiment, there is a slight reduction in the measured hydrodynamic pressure compared with predictions. This reduction in pressure leads to a reduction in the reactions at the plate edges, which get transmitted to the frames of the vessel. This slight reduction at small loading cases has the potential to be more noticeable when more severe slamming loads are encountered.
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