Papers by Keyword: Numerical Simulation

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Authors: Atsushi Osao, Gulbahar Wahap, Yoko Takakura, Norio Arai, Yoshifumi Konishi, Kazuaki Fukasaku, Nobumasa Kikuchi
Abstract: The purpose of this study is to accumulate data to predict the ruptures of aneurysms on the bifurcation of the middle cerebral arteries at the base of the brain. Particular stress is laid on understanding the elemental nature of branch flows with/without an aneurysm. Therefore, “flow patterns” and “wall shear stress”, which are important factors for the causes of ruptures, are investigated by the three-dimensional experiments in vitro and the two-dimensional numerical simulations with simplified models. In the branch arteries without an aneurysm, there is a possibility of growing aneurysms at the location slightly away from a stagnation point. If an aneurysm forms into a centrosymmetric shape for the inlet axis, it is considered that they tend to grow further in a symmetrical plane. From the viewpoint of the risk of ruptures, recirculation flows become problematic with the lower Reynolds number, while the influence of wall shear stress becomes larger with the higher Reynolds number.
Authors: Yi Hao, Lu Feng, Jing Wang
Abstract: Studies of strain gradient plasticity theory have achieved considerable achievements in recent years. However, the combination of the mechanisms of the pressure-sensitive yielding and the size dependence of plastic deformation still remains an open challenge, especially in the relevant numerical simulation. In this paper, the finite-element formulation based on the flow theory of MSG plasticity for pressure-sensitive materials is set up. The elastic indentation response of the single crystal copper is computed using a user-defined eight-node isoparametric element through the USER-ELEMENT interface supported by the commercial software ABAQUS. The results of the numerical simulation show that the indenter load and the hardness have been slightly enhanced when the strain gradient is taken into account, compared to the results obtained from the CAX8R element.
Authors: Xiao Ling Lei, Ji Wan, Kun Ping Chen, Bo Tao, Xiao Tao Fang
Abstract: The 2-D and 3-D numerical model have been developed to predict flow state and outlet velocity distribution by FLUENT based on the high-sludge setting tank in a large scale water treatment plant in Chongqing, and physical model has been built to verify the rationality and accuracy of the models. With the comparison of the two models, the following results can be found: 3-D model is lower in computing efficiency; both of the flow state are in substantial, but the stream lines of 3-D model are more complex; The velocities of 2-D model are slightly higher, both of the velocity distributions and tendency are approximately identical in 5 to 6 meters and 14 to18 meters, but not the same in 6 to 14 meters. 3-D model is more reasonable and accurate compared with 2-D model.
Authors: Y.L. Liu, B. Lv, P. Zhang, W.L. Wei
Abstract: In this paper, we use 3D time-averaged equations and the 3D k-ε turbulence model to numerically simulate the flow in a horizontal sedimentation tank. The PISO algorithm is used to couple velocity and pressure. The results show that the model can provide a reference in designing sedimentation tanks.
Authors: Hong Xian Liu, Bin Xia Li
Abstract: By using the computational fluid dynamics software Fluent and the choice of the reasonable mathematical model, the flow, heat transfer and combustion are simulated in a 300 MW tangential firing boiler furnace. In the process of numerical simulation in the furnace, the gas phase turbulent flow usesRealizable model for both sides and solves the governing equations using SIMPLEC algorithm. Calculation results show that the highest temperature in the furnace is in the burner area,the whole furnace space rotates flow field, residual rotation still exists in the exit of the furnace, and the smoke temperature deviation causes in the residual rotation of furnace exit.
Authors: Wei Ji, Peter M. Lofgren, Christer Hallin, Chun-Yuan Gu
Authors: B. Michel, Thomas Helfer, I. Ramière, C. Esnoul
Abstract: This paper focuses on the numerical simulation of crack initiation and growth in ceramic materials. This work is devoted to nuclear fuel modelling under irradiation and more precisely to fuel pellet fragmentation assessment at macroscopic and microscopic scales. Simulation tools are developed in the framework of a cooperative program between the CEA, EDF and AREVA devoted to a unified fuel performance software environment called PLEIADES. A smeared crack model is proposed to have a continuous description of crack nucleation and growth at macroscopic scale. This unified description is based on crack extension process from the microscopic scale up to the macroscopic scale. In order to deal with unstable crack extension a specific algorithm is proposed to solve the quasi static nonlinear mechanical problem. A 3D application is presented to illustrate performances and robustness of the smeared crack approach to simulate crack extension in nuclear fuel ceramics. In this application with an internal pressure loading a new methodology is proposed in order to avoid convergence problem due to the indetermination of the quasi static formulation of a softening material equilibrium under Neumann boundary condition.
Authors: Xia Jin, Shi Hong Lu
Abstract: Bending of the aluminum alloy is one of the processes frequently applied during manufacture of aircraft sheet metal. The bending operation involves springback, which is defined as elastic recovery of the part during unloading. In manufacturing industry, it is still a practical and difficult problem to predict the final geometry of the part after springback and to design appropriate tools in order to compensate for springback. In this study, 3D commercially available finite element analysis (FEA) software-MARC is used to analyse bending and springback of different aluminium materials (LY12CZ) with different thickness. The amount of springback, total equivalent plastic strains and equivalent von mises stresses are obtained. Moreover, the relation between bent angle and springback angle, R/t ratio and springback angle are presented and discussed in detail.The comparison results of FEA result and experiment data indicate that the FEM (finite element analysis method) simulation is a power tool for the highly accurate prediction of springback behavior in sheet metal bending.
Authors: Cheng Xiang Zhu, Chun Ling Zhu, Bin Fu
Abstract: Ice accretion on 3D complex configuration is studied by numerical methods. The flow field is obtained by using Fluent 6.0 with a S-A turbulence model. Droplet trajectories and impingement characteristics are obtained by using the Eulerian approach. Ice shape is calculated based on the improved Messinger model with a new runback distribution scheme. By applying the method presented in this paper, ice accretion on NACA0012 is computed and the results are in good agreement with the available experiment data. It preliminarily shows that the improved method in this paper is feasible, Meanwhile, ice accretion on a four-element wing is studied. According to the analysis of the calculated result, the method presented in the paper can correctly simulate the ice accretion on 3D complex configuration.
Authors: Zheng Zhao Liang, Chun An Tang, De Shen Zhao, Yong Bin Zhang, Tao Xu, Hou Quan Zhang
Abstract: A newly developed numerical code MFPA3D is applied to simulate the progressive damage and failure process of laminated cylindrical composite shell. Heterogeneities in meso-scale are taken into account by randomly distributing the material properties throughout the model by following a Weibull statistical distribution. The cylindrical composite shell is discretized into 3-D block elements with the fixed size and is subjected to a lateral compressive loading, applied with a constant displacement control manner. The numerical simulation results show that not only the process of crack initiation, propagation and coalescence but also the failure process can be numerically obtained in three dimensional. The MFPA3D modeling demonstrates that the code can simulate non-linear behavior of brittle materials with a simple mesoscopic constitutive law with a strength and elastic modulus reduction of the weaken elements.
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