The fluid-structure interaction (FSI) problem has received great attention in the last few years, mainly because it is present in many physical systems, industrial applications, and almost every biological system. In ...
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The fluid-structure interaction (FSI) problem has received great attention in the last few years, mainly because it is present in many physical systems, industrial applications, and almost every biological system. In the parallel computational field, outstanding advances have been achieved for the individual components of the problem, allowing, for instance, simulations around complex geometries at very high Reynolds numbers or simulations of the contraction of a beating heart. However, it is not an easy task to combine the advances of both fields, given that they have followed development paths in a rather independent way, and also because physical and numerical instabilities arise when dealing with two highly nonlinear partial differential equations. Nonetheless, in the last few years great advances in the coupled FSI field have been achieved, recognizing the most challenging problems to tackle and enabling a new generation of numerical simulations in aerodynamics, biological systems, and complex industrial devices. Keeping in mind that efficient parallel codes for the individual components already exist, this paper presents a framework to build a massively parallel FSI solver in a multicode coupling partitioned approach, with strong focus in the parallel implementation aspects and the parallel performance of the resulting application. The problem is casted in an algebraic form, and the main points of interest are the parallel environment needed to be able to transfer data among the codes, the location of the exchange surface, and the exchange of information among the parallel applications. The proposed framework has been implemented in the HPC multiphysics code Alya, and the multicode coupling is carried out running separated instances of this code. Two coupling algorithms with different acceleration schemes are revised, and three representative cases of different areas of interest showing the reach of the proposed framework are solved. Good agreement with litera
Purpose The purpose of this study is to model the dynamic characteristics of an opened supersonic disk-gap-band parachute. Design/methodology/approach A fluid-structure interaction (FSI) method with body-fitted mesh i...
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Purpose The purpose of this study is to model the dynamic characteristics of an opened supersonic disk-gap-band parachute. Design/methodology/approach A fluid-structure interaction (FSI) method with body-fitted mesh is used to simulate the supersonic parachute. The compressible flow is modeled using large-eddy simulation (LES). A contact algorithm based on the penalty function with a virtual contact domain is proposed to solve the negative volume problem of the body-fitted mesh. Automatic unstructured mesh generation and automatic mesh moving schemes are used to handle complex deformations of the canopy. Findings The opened disk-gap-band parachute is simulated using Mach 2.0, and the simulation results fit well with the wind tunnel test data. It is found that the LES model can successfully predict large-scale turbulent vortex in the flow. This study also demonstrates the capability of the present FSI method as a tool to predict shock oscillation and breathing phenomenon of the canopy. Originality/value The contact algorithm based on the penalty function with a virtual contact domain is proposed for the first time. This methodology can be used to solve the negative volume problem of the dynamic mesh in the flow field.
BACKGROUND: Circle of Willis (COW) is a network of cerebral artery which continually supplies the brain with blood. Any disturbance in this supply will result in trauma or even death. One of these damages is known as ...
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BACKGROUND: Circle of Willis (COW) is a network of cerebral artery which continually supplies the brain with blood. Any disturbance in this supply will result in trauma or even death. One of these damages is known as brain Aneurysm. Clinical methods for diagnosing aneurysm can only measure blood velocity;while, in order to understand the causes of these occurrences it is necessary to have information about the amount of pressure and wall shear stress, which is possible through computational models. OBJECTIVE: In this study purpose is achieving exact information of hemodynamic blood flow in COW with an aneurysm and investigation of effective factors on growth and rupture of aneurysm. METHODS: Here, realistic three-dimensional models have been produced from angiography images. Considering fluid-structure interaction have been simulated by the ANSYS. CFX software. RESULTS: Hemodynamic Studying of the COW and intra-aneurysm showed that the WSS and wall tension in the neck of aneurysms for case A are 129.5 Pa, and 12.2 kPa and for case B they are 53.3 Pa and 56.2 kPa, and more than their fundus, thus neck of aneurysm is prone to rupture. CONCLUSION: This study showed that the distribution of parameters was dependent on the geometry of the COW, and maximum values are seen in areas prone to aneurysm formation.
We develop a numerical method for simulating coupled interactions of complex floating structures with large-scale ocean waves and atmospheric turbulence. We employ an efficient large-scale model to develop offshore wi...
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We develop a numerical method for simulating coupled interactions of complex floating structures with large-scale ocean waves and atmospheric turbulence. We employ an efficient large-scale model to develop offshore wind and wave environmental conditions, which are then incorporated into a high resolution two-phase flow solver with fluid-structure interaction (FSI). The large-scale wind-wave interaction model is based on a two-fluid dynamically-coupled approach that employs a high-order spectral method for simulating the water motion and a viscous solver with undulatory boundaries for the air motion. The two-phase flow FSI solver is based on the level set method and is capable of simulating the coupled dynamic interaction of arbitrarily complex bodies with airflow and waves. The large-scale wave field solver is coupled with the near-field FSI solver with a one-way coupling approach by feeding into the latter waves via a pressure-forcing method combined with the level set method. We validate the model for both simple wave trains and three-dimensional directional waves and compare the results with experimental and theoretical solutions. Finally, we demonstrate the capabilities of the new computational framework by carrying out large-eddy simulation of a floating offshore wind turbine interacting with realistic ocean wind and waves. (c) 2017 Elsevier Inc. All rights reserved.
Purpose A numerical model of an unsteady laminar free convection flow and heat transfer is studied in a cavity that comprises a vertical flexible thin partition. Design/methodology/approach The left and right vertical...
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Purpose A numerical model of an unsteady laminar free convection flow and heat transfer is studied in a cavity that comprises a vertical flexible thin partition. Design/methodology/approach The left and right vertical boundaries are isothermal, while the horizontal boundaries are insulated. Moreover, the thin partition, placed in the geometric centerline of the enclosure, is considered to be hyper elastic and diathermal. Galerkin finite-element methods, the system of partial differential equations along with the appropriate boundary conditions are transformed to a weak form through the fluid-structure interaction and solved numerically. Findings The heat transfer characteristics of the enclosure with rigid and flexible partitions are compared. The effect of Rayleigh number and Young's modulus on the maximum nondimensional stress and final deformed shape of the membrane is addressed. Originality/value Incorporation of vertical thin flexible membrane in middle of a cavity has numerous industrial applications, and it could noticeably affect the heat and mass transfer in the enclosure.
The complex fluid-structure interaction problem associated with the flow of blood through a heart valve with flexible leaflets is investigated both experimentally and numerically. In the experimental test rig, a pulse...
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The complex fluid-structure interaction problem associated with the flow of blood through a heart valve with flexible leaflets is investigated both experimentally and numerically. In the experimental test rig, a pulse duplicator generates a pulsatile flow through a biomimetic rigid aortic root where a model of aortic valve with polymer flexible leaflets is implanted. High-speed recordings of the leaflets motion and particle image velocimetry measurements were performed together to investigate the valve kinematics and the dynamics of the flow. Large eddy simulations of the same configuration, based on a variant of the immersed boundary method, are also presented. A massively parallel unstructured finite-volume flow solver is coupled with a finite-element solid mechanics solver to predict the fluid-structure interaction between the unsteady flow and the valve. Detailed analysis of the dynamics of opening and closure of the valve are conducted, showing a good quantitative agreement between the experiment and the simulation regarding the global behavior, in spite of some differences regarding the individual dynamics of the valve leaflets. A multicycle analysis (over more than 20 cycles) enables to characterize the generation of turbulence downstream of the valve, showing similar flow features between the experiment and the simulation. The flow transitions to turbulence after peak systole, when the flow starts to decelerate. Fluctuations are observed in the wake of the valve, with maximum amplitude observed at the commissure side of the aorta. Overall, a very promising experiment-vs-simulation comparison is shown, demonstrating the potential of the numerical method.
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.
Object: Mitral regurgitation (MR) is a condition in which the mitral valve does not prevent the reversal of blood flow from the left ventricle into the left atrium. This study aimed at numerically developing a model t...
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Object: Mitral regurgitation (MR) is a condition in which the mitral valve does not prevent the reversal of blood flow from the left ventricle into the left atrium. This study aimed at numerically developing a model to mimic MR and poor leaflet coaptation and also comparing the performance of a normal mitral valve to that of the MR conditions at different gap junctions of 1, 3 and 5 mm between the anterior and posterior leaflets. Results: The results revealed no blood flow to the left ventricle when a gap between the leaflets was 0 mm. However, MR increased this blood flow, with increases in the velocity and pressure within the atrium. However, the pressure within the aorta did not vary meaningfully (ranging from 22 kPa for a 'healthy' model to 25 kPa for severe MR). Conclusions: The findings from this study have implications not only for understanding the changes in pressure and velocity as a result of MR in the ventricle, atrium or aorta, but also for the development of a computational model suitable for clinical translation when diagnosing and determining treatment for MR.
We present a novel formulation based on an immersed coupling of Isogeometric Analysis (IGA) and Peridynamics (PD) for the simulation of fluid-structure interaction (FSI) phenomena for air blast. We aim to develop a pr...
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We present a novel formulation based on an immersed coupling of Isogeometric Analysis (IGA) and Peridynamics (PD) for the simulation of fluid-structure interaction (FSI) phenomena for air blast. We aim to develop a practical computational framework that is capable of capturing the mechanics of air blast coupled to solids and structures that undergo large, inelastic deformations with extreme damage and fragmentation. An immersed technique is used, which involves an a priori monolithic FSI formulation with the implicit detection of the fluid-structure interface and without limitations on the solid domain motion. The coupled weak forms of the fluid and structural mechanics equations are solved on the background mesh. Correspondence-based PD is used to model the meshfree solid in the foreground domain. We employ the Non-Uniform Rational B-Splines (NURBS) IGA functions in the background and the Reproducing Kernel Particle Method (RKPM) functions for the PD solid in the foreground. We feel that the combination of these numerical tools is particularly attractive for the problem class of interest due to the higher-order accuracy and smoothness of IGA and RKPM, the benefits of using immersed methodology in handling the fluid-structure coupling, and the capabilities of PD in simulating fracture and fragmentation scenarios. Numerical examples are provided to illustrate the performance of the proposed air-blast FSI framework.
A ship in waves may experience a water impact event known as a slam. In this paper, slam-induced bending of wave-piercing catamarans in head seas is predicted by way of fluid-structure interaction simulations. The flo...
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A ship in waves may experience a water impact event known as a slam. In this paper, slam-induced bending of wave-piercing catamarans in head seas is predicted by way of fluid-structure interaction simulations. The flow field during slamming of a wave-piercing catamaran is highly non-linear and cannot be accurately captured using potential flow methods as a result of the interactions between the flow fields produced by water entry of the separate demihulls and centre bow. Thus, the Reynolds-Averaged Navier-Stokes (RANS) equations are solved for rigid body motion of a vessel at model-scale. Verification and validation is conducted using model-scale data from a Hydroelastic Segmented Model (HSM). One-way and two-way interactions are computed considering vibration of the hull girder. In the case of one-way interactions, the computed fluid loads affect the structure, but the structural response does not affect the fluid domain solution whereas for the two-way interactions the structural response affects the fluid solution. A new method for capturing the non-linear time variation in added mass is developed and deemed necessary when computing one-way interactions, primarily as a result of the large changes in forward wetted area present for a wave-piercing catamaran. It is shown that two-way interaction simulation is not needed for predicting the slam induced hull girder loads. One-way interaction simulation can therefore be used allowing reduced computational effort. (C) 2018 Elsevier Ltd. All rights reserved.
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