For problems involving large deformations of thin structures, simulating fluid-structure interaction (FSI) remains a computationally expensive endeavour which continues to drive interest in the development of novel ap...
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For problems involving large deformations of thin structures, simulating fluid-structure interaction (FSI) remains a computationally expensive endeavour which continues to drive interest in the development of novel approaches. Overlapping domain techniques have been introduced as a way to combine the fluid-solid mesh conformity, seen in moving-mesh methods, without the need for mesh smoothing or re-meshing, which is a core characteristic of fixed mesh approaches. In this work, we introduce a novel overlapping domain method based on a partition of unity approach. Unified function spaces are defined as a weighted sum of fields given on two overlapping meshes. The method is shown to achieve optimal convergence rates and to be stable for steady-state Stokes, Navier-Stokes, and ALE Navier-Stokes problems. Finally, we present results for FSI in the case of 2D flow past an elastic beam simulation. These initial results point to the potential applicability of the method to a wide range of FSI applications, enabling boundary layer refinement and large deformations without the need for re-meshing or user-defined stabilization. (C) 2020 Elsevier B.V. All rights reserved.
We consider a fluid-structure interaction model for an incompressible fluid where the elastic response of the free boundary is given by a damped Kirchhoff plate model. Utilizing the Newton polygon approach, we first p...
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We consider a fluid-structure interaction model for an incompressible fluid where the elastic response of the free boundary is given by a damped Kirchhoff plate model. Utilizing the Newton polygon approach, we first prove maximal regularity in L-p-Sobolev spaces for a linearized version. Based on this, we show existence and uniqueness of the strong solution of the nonlinear system for small data.
With global warming, the ice-covered areas in the Arctic are being transformed into open water. This provides increased impetuses for extensive maritime activities and attracts research interests in sea ice modelling....
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With global warming, the ice-covered areas in the Arctic are being transformed into open water. This provides increased impetuses for extensive maritime activities and attracts research interests in sea ice modelling. In the polar region, ice sheets can be several kilometres long and subjected to the effects of ocean waves. As its thickness to length ratio is very small, the wave response of such a large ice sheet, known as its hydroelastic response, is dominated by an elastic deformation rather than rigid body motions. In the past 25 years, sea ice hydroelasticity has been widely studied by theoretical models;however, recent experiments indicate that the ideal assumptions used for these theoretical models can cause considerable inaccuracies. This work proposes a numerical approach based on OpenFOAM to simulate the hydroelastic wave-ice interaction, with the Navier-Stokes equations describing the fluid domain, the St. Venant Kirchhoff solid model governing the ice deformation and a coupling scheme to achieve the fluid-structure interaction. Following validation against experiments, the proposed model has been shown capable of capturing phenomena that have not been included in current theoretical models. In particular, the developed model shows the capability to predict overwash, which is a ubiquitous polar phenomenon reported to be a key gap. The present model has the potential to be used to study wave-ice behaviours and the coupled wave-ice effect on marine structures.
Shape optimization via the method of mappings is investigated for unsteady fluid-structure interaction (FSI) problems that couple the Navier-Stokes equations and the Lame system. Building on recent existence and regul...
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Shape optimization via the method of mappings is investigated for unsteady fluid-structure interaction (FSI) problems that couple the Navier-Stokes equations and the Lame system. Building on recent existence and regularity theory we prove Frechet differentiability results for the state with respect to domain variations. These results form an analytical foundation for optimization und inverse problems governed by FSI systems. Our analysis develops a general framework for deriving local-in-time continuity and differentiability results for parameter dependent nonlinear systems of partial differential equations. The main part of the paper is devoted to conducting this analysis for the FSI problem, transformed to a shape reference domain. The underlying shape transformation-actually we work with the corresponding shape displacement instead-represents the shape and the main result proves the Frechet differentiability of the solution of the FSI system with respect to the shape transformation.
This study investigates the dynamic vibration and static deformation of a long flexible underwater body suspended from the ocean surface. A numerical model is constructed by considering (i) the structural mechanics, (...
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This study investigates the dynamic vibration and static deformation of a long flexible underwater body suspended from the ocean surface. A numerical model is constructed by considering (i) the structural mechanics, (ii) hydrodynamic forces induced by vortex shedding, (iii) motion mechanics associated with the free bottom end of the suspended body, and (iv) the interactions among (i)-(iii). Numerical computations are performed by applying uniform vertical distributions of the ocean flow speed and a sheared distribution, and by varying the weight of the body at the free bottom end. Comparing the computed results of these cases elucidates the mechanics of the fluid-structure interaction of the suspended body. In particular, the sheared flow velocity profile allows the growth of multiple frequency components of vibrations in the flexible body. The frequency multiplicity at a point in the body arises from the vortex-induced vibrations excited at that point, and those that are excited in other regions then propagate to that point.
fluid-structure interaction (FSI) in pipes can significantly affect pressure fluctuations during water hammer event. In transmission pipelines, anchors with axial stops have an important role in the waterhammer-induce...
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fluid-structure interaction (FSI) in pipes can significantly affect pressure fluctuations during water hammer event. In transmission pipelines, anchors with axial stops have an important role in the waterhammer-induced FSI as they can suppress or allow the propagation of additional stress waves in the pipe wall. More specifically, a reduction in the number of axial stops and/or their stiffness causes significant oscillations in the observed pressure signal due to the enhancement of Poisson's coupling. To confirm these physical arguments, this research conducts experimental investigations and then processes the collected pressure signals. The laboratory tests were run on an anchored pipeline with multiple axial supports which some of them removed at some sections to emerge Poisson's coupling. The collected pressure signals are analyzed in the time and frequency domain in order to decipher fluctuations that stem from Poisson coupling and other anchors effects. The analysis of the laboratory data reveals that the pattern of the time signals of pressure is primarily affected by the stiffness and location of the supports. Likewise, the properties of structural boundaries characterize the frequency spectrum of the transient pressures, which is manifested by altering the amplitudes corresponding to dominant frequencies of the system. The study is of particular importance in practice of transient based defect detections and pipe system design. (C) 2019 Elsevier Ltd. All rights reserved.
This study presents numerical simulations of a unidirectional ceramic matrix composite (CMC) plate under different loads considering the effect of fluid-structure interaction (FSI). The two-scale method was used in th...
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This study presents numerical simulations of a unidirectional ceramic matrix composite (CMC) plate under different loads considering the effect of fluid-structure interaction (FSI). The two-scale method was used in the dynamic simulation of CMC plate. The shear-lag model considering the damage modes of CMCs was used to simulate the constitutive behavior in the micro-scale. The explicit dynamic finite element method was used to simulate the dynamic response in the macro-scale. The dynamic responses of CMC plate under impulse and harmonic load were simulated. The incompressible Navier-Stokes equations were employed in the simulation of fluid. The dynamic response of CMC plate with FSI was solved based on the staggered method. The effect of fluid on the dynamic response of CMC plate was discussed.
Purpose Bicuspid aortic valve (BAV) is a congenital heart malformation with phenotypic heterogeneity. There is no prior computational study that assesses the haemodynamic and valve mechanics associated with BAV type 2...
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Purpose Bicuspid aortic valve (BAV) is a congenital heart malformation with phenotypic heterogeneity. There is no prior computational study that assesses the haemodynamic and valve mechanics associated with BAV type 2 against a healthy tricuspid aortic valve (TAV) and other BAV categories. Methods A proof-of-concept study incorporating three-dimensional fluid-structure interaction (FSI) models with idealised geometries (one TAV and six BAVs, namely type 0 with lateral and anterior-posterior orientations, type 1 with R-L, N-R and N-L leaflet fusion and type 2) has been developed. Transient physiological boundary conditions have been applied and simulations were run using an Arbitrary Lagrangian-Eulerian formulation. Results Our results showed the presence of abnormal haemodynamics in the aorta and abnormal valve mechanics: type 0 BAVs yielded the best haemodynamical and mechanical outcomes, but cusp stress distribution varied with valve orifice orientation, which can be linked to different cusp calcification location onset;type 1 BAVs gave rise to similar haemodynamics and valve mechanics, regardless of raphe position, but this position altered the location of abnormal haemodynamic features;finally, type 2 BAV constricted the majority of blood flow, exhibiting the most damaging haemodynamic and mechanical repercussions when compared to other BAV phenotypes. Conclusion The findings of this proof-of-concept work suggest that there are specific differences across haemodynamics and valve mechanics associated with BAV phenotypes, which may be critical to subsequent processes associated with their pathophysiology processes.
fluid-structure interaction (FSI) and wave propagation in engineering structures can cause severe damage to piping systems or fluid machines, inducing serious accidents. In these phenomena, the mechanism of structural...
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fluid-structure interaction (FSI) and wave propagation in engineering structures can cause severe damage to piping systems or fluid machines, inducing serious accidents. In these phenomena, the mechanism of structural damage depends on the wave propagation across the fluid-solid interface. Previous studies reported that disagreements between the induced pressure value on the solid-fluid movable interface and the value predicted by the classical one-dimensional theory arose from the effects of two-dimensional wave propagation. To address this problem, in this study, a two-dimensional axisymmetric simulation of wave propagation across the solid-fluid interface with FSI was conducted. The simulation was performed using ANSYS Autodyn with a Lagrangian solver for solids and Eulerian solver for water. The results showed that radial wave propagation caused by the dynamic effect of the tube and water's inertia affected the peak pressure on the solid-fluid interface. The peak pressure was attenuated near the tube wall because of the inertial effect of the tube and fluid expansion. By calculating the mean pressure and axial stress to compare the simulated peak pressure with that from one-dimensional acoustic theory, it was indicated that the transition region for transmitted pressure was located immediately after the solid-fluid interface. In this region, the transmitted peak pressure may exceed the value predicted by one-dimensional acoustic theory. The transition region was oriented in the axial direction from the interface. In addition, prediction of the transmitted peak pressure with one-dimensional acoustic theory was suggested via normal wave speed in the unconfined fluid from a safety engineering perspective, although the circumferential stress generated in the tube enclosing fluid can be sufficiently accurately predicted using the same theory with the Korteweg speed.
In this article, an accurate and robust numerical formulation is presented for the simulation of the fluid-structure interaction in incompressible fluid flow. The incompressible Navier-Stokes equation is discretized w...
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In this article, an accurate and robust numerical formulation is presented for the simulation of the fluid-structure interaction in incompressible fluid flow. The incompressible Navier-Stokes equation is discretized with a stabilized finite element framework on the fixed Eulerian grid. Both symmetric and non-symmetric Nitsche's methods are accessed and employed to weakly impose Dirichlet boundary condition along the interface embedded in the element together with the ghost penalty method stabilizing the solution jump across the element edges. An easy-to-implement and robust numerical integration scheme based on a projection approach is proposed. To the author's knowledge, so far, there is no application of a projection-based approach in the field of numerical integration to deal with discontinuities. Therefore, the results presented in this article is considered as a pioneered and novel projection-based approach in the field of numerical integration to deal with embedded discontinuous function. A second-order staggered-partitioned scheme is employed to weakly couple the fluid and structure solvers. A second-order accurate and unconditionally stable time integration scheme is implemented for simulations. Accurate numerical results are obtained in the numerical examples and validation cases, including vortex-induced vibration (VIV), rotation, freely fall and rigid-body contact. (C) 2020 Elsevier Inc. All rights reserved.
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