A coupled total Lagrangian (TL) and weakly compressible (WC) smoothed particle hydrodynamics (SPH) method is presented to model three-dimensional fluid-structure interactions (FSI) with deformable structures. In the c...
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A coupled total Lagrangian (TL) and weakly compressible (WC) smoothed particle hydrodynamics (SPH) method is presented to model three-dimensional fluid-structure interactions (FSI) with deformable structures. In the coupled TL-WC SPH, the fluid phase is simulated using WCSPH, while the structure solver is based on TLSPH. The three main deficiencies of solid simulation using conventional SPH, i.e. inconsistency, tensile instability and hourglass mode are circumvented in the stabilized TLSPH by means of corrected kernel gradient, Lagrangian kernel function and hourglass control technique, respectively. The resulted stabilized TLSPH is stable, accurate and has almost quadratic convergence rate in solid modeling. To increase the accuracy in FSI modeling, the delta-SPH technique is employed to improve the pressure results in the fluid phase. Based on the Adami boundary condition (Adami et al., 2012), a unified framework for modeling solid boundaries and the fluidstructure interfaces is presented. Furthermore, the GPU parallelization is employed to accelerate the proposed TL-WC SPH method for higher efficiency. The coupled method is employed to simulate problems of pure fluid flow, elastic solids with large deformation and fluid-structure interaction with deformable structures. The numerical results are compared with analytical solutions and results from literature. The GPU efficiency and speed-up compared with CPU implementations are analyzed. The novelty of this work consists: (1) three-dimensional SPH modeling of FSI problems with deformable structures, (2) stabilized structure simulation free of hourglass mode, (3) a unified framework for FSI problems taking advantages of delta-SPH, TLSPH, hourglass control, and GPU acceleration. Importantly, with the hourglass control technique proposed by Ganzenmuller (2015), stresses can be captured accurately in the TL-WC SPH-based FSI simulations. (C) 2019 Elsevier Ltd. All rights reserved.
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.
Background and objective: Cerebral aneurysm, which is defined as one of the weakened area in the wall of an artery in the brain, ruptures when wall tension exceeds its mechanical strength. Traumatic brain injury (TBI)...
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Background and objective: Cerebral aneurysm, which is defined as one of the weakened area in the wall of an artery in the brain, ruptures when wall tension exceeds its mechanical strength. Traumatic brain injury (TBI) by exerting a sudden impact load to the brain can lead to mechanical failure of the cerebral blood vessels followed by an alteration in not only the structure but also the function of the cerebrovascular. TBI also alters the hemodynamics of the blood flow in the cerebrovascular, while it has been shown that hemodynamics has a key asset in the progression and rupture of the cerebral aneurysms. So far, there is a lack of knowledge on the risk of rupture of the cerebral aneurysm in relation to TBI. Therefore, this study aimed to calculate the mechanical stresses and deformations in the arterial wall as well as the pressure and velocity of the blood using a fluid-structure interaction (FSI) model of the cerebral aneurysm located in the anterior circulation region of the circle of Willis. Method: A patient-specific FSI model of the human skull, brain, and cerebral aneurysm, was established using human computed tomography (CT)/magnetic resonance imaging (MRI) data and subjected to a frontal TBI. Results: The results revealed considerable increasing of similar to 8 kPa (60 mmHg) and 0.40 m/s in the pressure and velocity of the blood in the intraluminal of the cerebral artery after TBI. The von Mises stress, shear stress, and deformation of the cerebral aneurysm wall also showed the increasing of 56.03 kPa, 15.66 Pa, and 0.072 mm after TBI, respectively. Conclusions: Although the injury to the aneurysm wall after TBI is lower than that of the aneurysm wall mechanical strength, it still can alter the stress pattern in the wall and disrupt the hemodynamics of the blood. These results have implications in understanding the rupture risk of the cerebral aneurysm due to TBI, which may contribute in establishing preventive and/or treatment methods. (C) 2019 Elsevier
This study was aimed at assessing the robustness of a fixed-grid fluid-structure interaction method (Multi-Material Arbitrary Lagrangian-Eulerian) to modelling the two-dimensional native aortic valve dynamics and comp...
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This study was aimed at assessing the robustness of a fixed-grid fluid-structure interaction method (Multi-Material Arbitrary Lagrangian-Eulerian) to modelling the two-dimensional native aortic valve dynamics and comparing it to the Arbitrary Lagrangian-Eulerian method. For the fixed-grid method, the explicit finite element solver LS-DYNA was utilized, where two independent meshes for the fluid and structure were generated and the penalty method was used to handle the coupling between the fluid and structure domains. For the Arbitrary Lagrangian-Eulerian method, the implicit finite element solver ADINA was used where two separate conforming meshes were used for the valve structure and the fluid domains. The comparison demonstrated that both fluid-structure interaction methods predicted accurately the valve dynamics, fluid flow, and stress distribution, implying that fixed-grid methods can be used in situations where the Arbitrary Lagrangian-Eulerian method fails.
The behavior of blood cells and vessel compliance significantly influence hemodynamic parameters, which are closely related to the development of aortic dissection. Here the two-phase non-Newtonian model and the fluid...
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The behavior of blood cells and vessel compliance significantly influence hemodynamic parameters, which are closely related to the development of aortic dissection. Here the two-phase non-Newtonian model and the fluid-structure interaction (FSI) method are coupled to simulate blood flow in a patient-specific dissected aorta. Moreover, three-element Windkessel model is applied to reproduce physiological pressure waves. Important hemodynamic indicators, such as the spatial distribution of red blood cells (RBCs) and vessel wall displacement, which greatly influence the hemodynamic characteristics are analyzed. Results show that the proximal false lumen near the entry tear appears to be a vortex zone with a relatively lower volume fraction of RBCs, a low time-averaged wall shear stress (TAWSS) and a high oscillatory shear index (OSI), providing a suitable physical environment for the formation of atherosclerosis. The highest TAWSS is located in the narrow area of the distal true lumen which might cause further dilation. TAWSS distributions in the FSI model and the rigid wall model show similar trend, while there is a significant difference for the OSI distributions. We suggest that an integrated model is essential to simulate blood flow in a more realistic physiological environment with the ultimate aim of guiding clinical treatment.
In this study, flow analyses were conducted inside pumping tube based on fluid-structure interaction analyses. First, a Computer Aided Engineering (CAE) model was constructed for fluid-structure interaction analyses. ...
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In this study, flow analyses were conducted inside pumping tube based on fluid-structure interaction analyses. First, a Computer Aided Engineering (CAE) model was constructed for fluid-structure interaction analyses. The interaction analyses of the three types of pumping tubes proposed herein were conducted under the same conditions, and their efficiencies were compared. Eccentricity analyses were carried out to determine the degree of eccentricity that can be tolerated in the process by selecting the most efficient tube. Subsequently, tests were conducted using negative pressure measurement equipment and simulation modeling was compared and verified under the same conditions. In order to verify the performance of the self-inflating tire developed on this basis, durability and air pressure restoration tests were carried out.
Flapping wing micro-air vehicles are biologically inspired by nature flyers, specifically insects and birds. Specifically, insect wings generally consist of veins and membrane components. In this study, a structural a...
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Flapping wing micro-air vehicles are biologically inspired by nature flyers, specifically insects and birds. Specifically, insect wings generally consist of veins and membrane components. In this study, a structural analysis considering the vein/membrane components of an insect-like flapping wing is presented. Co-rotational (CR) finite elements are adopted in order to consider the complex wing configuration including both vein and membrane. The CR beam elements with warping degrees of freedom are employed for veins and CR shell elements for the wing membrane. The present structural analysis is verified against the analytical results obtained by an existing software, and it is validated by comparison to existing results from the literature. A fluid-structure interaction analysis is then performed. In the procedure, an aerodynamic analysis based on three-dimensional preconditioned Navier-Stokes equations is employed. Finally, a comparative study with respect to the structural characteristics is conducted. As a result, an efficiency of the present structural analysis is confirmed by comparing with the existing software. It is found that the present FSI results are in good agreement with the existing experimental and numerical results. Moreover, the passive wing twist may have a significant influence on the hover performance.
Tidal energy is now considered as a renewable power source worldwide that can be used to reduce global warming. In order to harvest the tidal current power, horizontal and vertical axis tidal turbines (VATTs) have rec...
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Tidal energy is now considered as a renewable power source worldwide that can be used to reduce global warming. In order to harvest the tidal current power, horizontal and vertical axis tidal turbines (VATTs) have recently received increasing interests. To implement the detailed design process, the power outputs of 2D and 3D VATTs are simulated by a novel fidelity fluid-structure turbulence model in this work. This model is capable of simulating the fluid dynamics of the turbulent flow, as well as the stress, vibration, deformation, and motion of structures. Most importantly, flow-induced vibration for 3D VATTs is modelled by this model. In order to improve the computational efficiency, a large aspect ratio anisotropic mesh adaptivity is used to speed up simulations. The simulation results of these complex practical test cases are all in good agreement with experimental and numerical data in the literature. The model can be used to accurately predict the power output of VATTs, which can help to choose design configurations with high power output efficiency. More importantly, this model can be used to predict the flow-induced vibration of 3D VATTs, which can help to design VATTs with low vibration. Finally, the comparison between flexible and rigid VATTs shows the advantages of this model which demonstrates its capabilities when analysing the elasticities for realistic VATTs.
Air conditioners consist of heat exchangers, fans, motors and compressors as major components. From the viewpoint of noise, the compressor occupies a very large portion. In this study, rotary compressor which is mainl...
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Air conditioners consist of heat exchangers, fans, motors and compressors as major components. From the viewpoint of noise, the compressor occupies a very large portion. In this study, rotary compressor which is mainly used in domestic air conditioner was discussed. The noise generated from the rotary compressor can be classified into pressure pulsation of the refrigerant and structural vibration. During the operation of the compressor, the behavior of the refrigerant and the internal structure of the compressor strongly interact with each other. Therefore, an integrated interpretation is required when analyzing from the viewpoint of refrigerant. In this study, the rotary compressor behavior is implemented using the FSI technique and the noise and valve behavior with and without discharge muffler are analyzed.
Flow-driven piezoelectric energy harvesting is a strongly coupled multiphysics phenomenon that involves complex three-way interaction between the fluid flow, the electromechanical effect of the piezoelectric material ...
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Flow-driven piezoelectric energy harvesting is a strongly coupled multiphysics phenomenon that involves complex three-way interaction between the fluid flow, the electromechanical effect of the piezoelectric material mounted on a deformable substrate structure and the controlling electrical circuit. High fidelity computational solution approaches are essential for the analysis of flow-driven energy harvesters in order to capture the main physical aspects of the coupled problem and to accurately predict the power output of a harvester. While there are some phenomenological and numerical models for flow-driven harvesters reported in the literature, a fully three-dimensional strongly coupled model has not yet been developed, especially in the context of flow-driven energy harvesting. The weighted residuals method is applied to establish a mixed integral equation describing the incompressible Newtonian flow, elastic substrate structure, piezoelectric patch, equipotential electrode and attached electric circuit that form the multiphysics fluid-structure interaction problem. A monolithic numerical solution method is derived that provides consistent and simultaneous solution to all physical fields as well as to fluid mesh deformation. The approximate solution is based on a mixed space-time finite element discretization with static condensation of the auxiliary fields. The discontinuous Galerkin method is utilized for integrating the monolithic model in time. The proposed solution scheme is illustrated in the example of a lid driven cavity with a flexible piezoelectric bottom wall, demonstrating quantification of the amount of electrical energy extractable from fluid flow by means of a piezoelectric harvester device. The results indicate that in order to make reliable predictions on the power output under varying operational states, the realization of strong multiphysics coupling is required for the mathematical model as well as the numerical solution scheme to capture the
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