In this paper, numerical analysis aiming at simulating biological organisms immersed in a fluid are carried out. The fluid domain is modeled through the lattice Boltzmann (LB) method, while the immersed boundary metho...
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In this paper, numerical analysis aiming at simulating biological organisms immersed in a fluid are carried out. The fluid domain is modeled through the lattice Boltzmann (LB) method, while the immersed boundary method is used to account for the position of the organisms idealized as rigid bodies. The time discontinuous Galerkin method is employed to compute body motion. An explicit coupling strategy to combine the adopted numerical methods is proposed. The vertical take-off of a couple of butteries is numerically simulated in different scenarios, showing the mutual interaction that a buttery exerts on the other one. Moreover, the effect of lateral wind is investigated. A critical threshold value of the lateral wind is defined, thus corresponding to an increasing arduous take-off.
In modern turbomachinery, accurate prediction of rotor blade shape for manufacture from its design shape is vital for performance, efficiency and aeroelastic stability. The manufacture “cold” blade shapes of a large...
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ISBN:
(纸本)9781510804159
In modern turbomachinery, accurate prediction of rotor blade shape for manufacture from its design shape is vital for performance, efficiency and aeroelastic stability. The manufacture “cold” blade shapes of a large-scale ratio transonic hollow fan and a NASA Rotor 67 fan were predicted from the design “hot” shapes utilised four kinds of numerical simulation methods, such as non-coupling, weak coupling, steady two-way coupling, and unsteady bidirectional coupling methods. The advantages and disadvantages of these methods were discussed by emphasizing on aerodynamic loading modes in the iterative procedure of blade unrunning design. The last numerical method employs a fluid-structure coupling scheme to determine blade deflections due to unsteady aerodynamic loads. The results show that there is a big difference between the “cold” blade shapes predicted using non-coupling method and the other three methods which conside aerodynamic coupling, this illustrates that the aerodynamic influence cannot be ignored. Comparison of the calculation “cold” shapes of the hollow swept and bowed fan with the conventional fan shows that improvements of the manufacture profile of the hollow fan blade can be made by including proper nonlinear aerodynamic effect on blade deflections in the numerical model. The results also illustrate that aerodynamic nonlinear effects should be included for a better blade unrunning design.
A detonation is a combustion wave that propagates in an inflammable medium at supersonic speeds. This phenomenon is important in the fields of supersonic propulsion and combustion safety. A shock wave or explosion wav...
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A detonation is a combustion wave that propagates in an inflammable medium at supersonic speeds. This phenomenon is important in the fields of supersonic propulsion and combustion safety. A shock wave or explosion wave shows complicated behavior when it interacts with a structure. Studying the behavior of a pressure wave loaded by a shock wave or detonation wave in a confined tube and its interaction with the tube wall is important. This type of coupling problem has gained even more importance after the Fukushima nuclear reactor accident in 2011 and has become the topic of many studies. One difficulty with the coupling problem is how a gas or liquid couples with a solid. A numerical solution to this problem has not yet been found. In the present study, we numerically examined the one-way coupling between a shock wave/a detonation wave and a tube. We used the open-source code Elmer to calculate the solid phase and our in-house code to calculate the shock wave. We compared our numerical results for the shock wave problem with experimental results from another research group for validation and simulated the detonation to observe the physics of the solid tube behavior. The results revealed an interesting behavior in the solid tube response.
Aiming at improving the credibility of the firing control of the underwater rocket fuze, which is based on the principle that the firing control system is triggered by the collision signal of the projectile, a finite ...
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Aiming at improving the credibility of the firing control of the underwater rocket fuze, which is based on the principle that the firing control system is triggered by the collision signal of the projectile, a finite element method to analyze the characteristics of the collision of a projectile striking a hard target in water is proposed. Considering the influence of the water environment and the projectile structure, a solid projectile model and a shell projectile model with housing in the head are established to impact a hard target respectively in air and in water by using the LS-DYNA module of the ANSYS software. The results truly reflect the collision course showing that the acceleration of projectile during the collision course in air is significantly larger than in water, while the shell projectile model nearly has the same acceleration with the solid projectile model during the collision course, and the error can be ignore. The conclusions provide the basis for the selection of firing control system.
In this article the UDF script file in the Fluent software was rewritten as the ＂connecting file＂ for the Fluent and the ANSYS/ABAQUS in order that the joined file can be used to do aero-elastic computations. In thi...
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In this article the UDF script file in the Fluent software was rewritten as the ＂connecting file＂ for the Fluent and the ANSYS/ABAQUS in order that the joined file can be used to do aero-elastic computations. In this way the fluid field is computed by solving the Navier-Stokes equations and the structure movement is integrated by the dynamics directly. An analysis of the computed results shows that this coupled method designed for simulating aero-elastic systems is workable and can be used for the other fluid-structure interaction problems.
Due to the flexibility of the envelope of large stratosphere airships, the aerodynamic solution of such airship is closely related to its shape and the external aerodynamic forces which lead to the structural deformat...
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Due to the flexibility of the envelope of large stratosphere airships, the aerodynamic solution of such airship is closely related to its shape and the external aerodynamic forces which lead to the structural deformation. It is essentially one of the fluid-structure interaction （FSI） problems. This article aims at the numerical investigation of nonlinear airship aeroelasticity in consideration of aerodynamics and structure coupling, using an iteration method. The three-dimensional flow around the airship was numerically studied by means of the SIMPLE method based on the finite volume method. Nonlinear finite element analysis was employed for geometrically nonlinear deformation of the airship shape. Comparison of aerodynamic parameters and the pressure distribution between rigid and aeroelastic models was conducted when an airship is in a trimmed flight state in specified flight conditions. The effect ofaeroelasticity on the airship aerodynamics was detailed.
In this paper we apply the artificial compressibility method (ACM) in strongly coupled fluid-structure interaction (FSI) computation of blood flow in an elastic artery. Previously published and here referred to as the...
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In this paper we apply the artificial compressibility method (ACM) in strongly coupled fluid-structure interaction (FSI) computation of blood flow in an elastic artery. Previously published and here referred to as the ACM/FSI method uses the idea of artificial compressibility by Chorin 1967, except the term of pressure time derivative in the continuity equation is used to mimic the response of the walls, thereby stabilizing the iterative coupling. To reach the aim, we present a new way, the test load method, to improve ACM/FSI computations. In the test load method, the compressibility parameter is computed locally and is based on the mesh deformation of the fluid domain. The functionality of the ACM/FSI coupling with the test load method is demonstrated in an arterial flow simulation, and the combination is shown to provide a robust convergence. In order to get the test cases to correspond better to human physiology, one-dimensional FSI models are combined with the higher dimensional test models. (C) 2007 IPEM. Published by Elsevier Ltd. All rights reserved.
Flight dynamics of flapping insects is still an open area of research, though it is well known that they can provide superior flight abilities such as hovering motion. The numerical analysis of flapping wing requires ...
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Flight dynamics of flapping insects is still an open area of research, though it is well known that they can provide superior flight abilities such as hovering motion. The numerical analysis of flapping wing requires fluid-structure interaction (FSI) analysis to evaluate the effect of deformable wing on flight ability. Such FSI analysis is quite challenging because not only the tight coupling approach to predict flight ability accurately, but also the robust mesh control to trace the large motion of the wing with elastic deformation are required. A new iterative partitioned coupling algorithm for the FSI problems is proposed in this paper. In the proposed approach, non-linearity of the FSI problems is mainly treated on the interface using the line search method, which minimizes non-equilibrated displacements on the interface in each fixed point iteration. This approach is introduced to improve the robustness and efficiency of computation. A two-dimensional FSI analysis of a flapping wing shows that elastic deformation of the wing results in passive feathering motion and generates lift force effectively.
Elasto-plastic earthquake response of arch dams including fluid-structure interaction by the Lagrangian approach is mainly investigated in this study. To this aim, three-dimensional eight-noded version of Lagrangian f...
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Elasto-plastic earthquake response of arch dams including fluid-structure interaction by the Lagrangian approach is mainly investigated in this study. To this aim, three-dimensional eight-noded version of Lagrangian fluid finite element including the effects of compressible wave propagation and surface sloshing motion, and three-dimensional version of Drucker-Prager model based on associated flow rule assumption were programmed in FORTRAN language by authors and incorporated into the program NONSAP. Two new components added into the NONSAP were tested on a simple fluid tank and a simple fluid-structure system and obtained very reasonable results. Elasto-plastic earthquake analysis of an arch dam including fluid-structure interaction by the Lagrangian approach was performed using Wilson-theta method. The El Centro N-S component of Imperial Valley earthquake in 1940 was chosen as a ground motion. The component considered was applied in upstream-downstream direction. Displacements at various nodes on dam body, hydrodynamic pressures at three fluid elements near the dam-reservoir interface and yield functions at two elements predicted cracks in dam body were obtained. The elasto-plastic response of the arch dam was also compared to its linear response. It is seen that Drucker-Prager model in the representing elasto-plastic behaviour of arch dams and in estimating location of cracks in dam body is a fast tool. (C) 2007 Elsevier Inc. All rights reserved.
Constant coefficient one-dimensional linear hyperbolic systems of partial differential equations (PDEs) are often used for description of fluid-structure interaction (FSI) phenomena during transient conditions in pipi...
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Constant coefficient one-dimensional linear hyperbolic systems of partial differential equations (PDEs) are often used for description of fluid-structure interaction (FSI) phenomena during transient conditions in piping systems. In the past, these systems of equations have been numerically solved with method of characteristics (MOCs). The MOC method is actually the most efficient and accurate method for description of the single-phase transient in the cold liquid where the constant coefficient mathematical model describes phenomenon with sufficient accuracy. In energy production systems where hot pressurized liquid is used for heat transfer between the heat source and the steam generator, more complex and nonlinear mathematical models are needed to describe transient flow and these models cannot be solved with MOC method because the models are not constant. In addition, the MOC method can be used for pipes having discontinuities like elbows, geometrical changes, material properties changes, etc., but only with some extra numerical modeling. An interesting alternative is explicit characteristic upwind numerical method, known as Godunov's method that is frequently used for nonlinear systems or systems where properties change with position. In the present study, applicability of the Godunov's method for the FSI analyses is tested with eight first order PDEs mathematical model. The conventional linear mathematical model is improved with convective term that makes the system nonlinear and additional terms that enable simulations of the FSI in arbitrarily shaped piping systems located in a plane. Two PDEs describe pressure waves in the single-phase fluid and six PDEs describe axial, lateral, and rotational stress waves in the pipe. The applied system of equations has stiff source terms. This numerical problem is solved introducing implicit iterations. The proposed model is verified with a rod impact experiment that is carried out on single-elbow pipe hanging on wires. God
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