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A New Constitutive Model for Ferromagnetic Shape Memory Alloy Particulate Composites
Get PDFFerromagnetic shape memory alloy particulate composites, which combine the advantages of large magnetic field induced deformation in ferromagnetic shape memory alloys (FSMAs) with high ductility in matrix, can be used for sensor and actuator applications. In this paper, a new constitutive model was proposed to predict the magneto-mechanical behaviors of FSMA particulate composites based on the description for FSMAs, incorporating Eshelby’s equivalent inclusion theory. The influencing factors, such as volume fraction of particles and elastic modulus, were analyzed. The magnetic field induced strain and other mechanical properties under different magnetic field intensity were also investigated
Three-dimensional Numerical Study of the Effect of Heating Sources Dimension on Natural Convection in a Cavity Submitted to Constant Heat Flux
Get PDFNatural convection in a cubical cavity, discretely heated is studied numerically using a three-dimensional finite volume formulation. Two heating square portions are placed on the vertical wall of the enclosure, while the rest of the considered wall is adiabatic. The opposite vertical wall is maintained at a cold uniform temperature and the other walls are adiabatic. Effects of the heating sections dimensions ε (0.15 ≤ ε ≤ 0.35) and the Rayleigh number Ra (103 ≤ Ra ≤ 107) on the fluid flow and the heat transfer within the cavity are studied. The obtained results show that the flow intensity and the heat transfer can be significantly improved by an optimal choice of the governing parameters. Streamlines, isotherms and variations of the average Nusselt number are shown for different sets of the considered parameters
A High-order Coupled Compact Integrated RBF Approximation Based Domain Decomposition Algorithm for Second-order Differential Problems
Get PDFThis paper presents a high-order coupled compact integrated RBF (CC IRBF) approximation based domain decomposition (DD) algorithm for the discretisation of second-order differential problems. Several Schwarz DD algorithms, including one-level additive/ multiplicative and two-level additive/ multiplicative/ hybrid, are employed. The CCIRBF based DD algorithms are analysed with different mesh sizes, numbers of subdomains and overlap sizes for Poisson problems. Our convergence analysis shows that the CCIRBF two-level multiplicative version is the most effective algorithm among various schemes employed here. Especially, the present CCIRBF two-level method converges quite rapidly even when the domain is divided into many subdomains, which shows great promise for either serial or parallel computing. For practical tests, we then incorporate the CCIRBF into serial and parallel two-level multiplicative Schwarz. Several numerical examples, including those governed by Poisson and Navier-Stokes equations are analysed to demonstrate the accuracy and efficiency of the serial and parallel algorithms implemented with the CCIRBF. Numerical results show: (i) the CCIRBF-Serial and -Parallel algorithms have the capability to reach almost the same solution accuracy level of the CCIRBF-Single domain, which is ideal in terms of computational calculations; (ii) the CCIRBF-Serial and -Parallel algorithms are highly accurate in comparison with standard finite difference, compact finite difference and some other schemes; (iii) the proposed CCIRBF-Serial and -Parallel algorithms may be used as alternatives to solve large-size problems which the CCIRBF-Single domain may not be able to deal with. The ability of producing stable and highly accurate results of the proposed serial and parallel schemes is believed to be the contribution of the coarse mesh of the two-level domain decomposition and the CCIRBF approximation. It is noted that the focus of this paper is on the derivation of highly accurate serial and parallel algorithms for second-order differential problems. The scope of this work does not cover a thorough analysis of computational time
Estimation of Isotropic Hyperelasticity Constitutive Models to Approximate the Atomistic Simulation Data for Aluminium and Tungsten Monocrystals
Get PDFIn this paper, the choice and parametrisation of finite deformation polyconvex isotropic hyperelastic models to describe the behaviour of a class of defect-free monocrystalline metal materials at the molecular level is examined. The article discusses some physical, mathematical and numerical demands which in our opinion should be fulfilled by elasticity models to be useful. A set of molecular numerical tests for aluminium and tungsten providing data for the fitting of a hyperelastic model was performed, and an algorithm for parametrisation is discussed. The proposed models with optimised parameters are superior to those used in non-linear mechanics of crystals
Finding the Generalized SolitaryWave Solutions within the (G'/G)-Expansion Method
Get PDFIn this study, the solitary wave solutions for third order equal-width wave-Burgers (EW-Burgers) equation, the second order Bratu and sinh-Bratu type equations will be discussed. The EW-Burgers equation models the propagation of nonlinear and dispersive waves with certain dissipative effects and furthermore the Bratu type problem appears a simplification of the solid fuel ignition model in thermal combustion theory. Our methodology, is investigated by using (G'/G)- expansion method. The obtained results can be extended to the other models
On the Numerical Study of Capillary-driven Flow in a 3-D Microchannel Model
Get PDFIn this article, we demonstrate a numerical 3-D chip, and studied the capillary dynamics inside the microchannel. We applied the level set method on the Navier-Stokes equation which incorporates the surface tension and two-phase flow characteristics. We analyzed the capillary dynamics near the junction of two microchannels. Such a highlighting point is important that it not only can provide the information of interface behavior when fluids are made into a head-on collision, but also emphasize the idea for the design of the chip. In addition, we study the pressure distribution of the fluids at the junction. It is shown that the model can produce nearly 2000 Pa pressure difference to help push the water through the microchannel against the air. The nonlinear interaction between capillary flows is recorded. Such a nonlinear phenomenon, to our knowledge, occurs due to the surface tension takes action with the wetted wall boundaries in the channel and the nonlinear governing equations for capillary flow
A New Efficient Matrix Algorithm for a 3D Component Mode Synthesis (CMS) Model Used on Sound Transmission Problems
Get PDFThe main goal of this study is to present an alternative and more efficient algorithm for a three-dimensional Component Mode Synthesis model to be used on sound transmission problems. The influence of fluid-structure interaction on airborne sound transmission problems is analysed using this model, which is based on simple volume geometries. In principle, the same procedure can also be applied when the component modes are obtained from alternative numerical techniques. The modal behaviour of acoustic volumes and a partition is implemented in two steps. The novelty of this alternative model is that the structural modes are incorporated on the acoustic CMS components. In other words, each acoustic volume considers not only the acoustic modes of the volumes but also the structural modes of the partition. Comparison is made with predictions based on a modal model of which particle velocity continuity was not incorporated in the formulation
Efficient Load-balancing Scheme for Multi-agent Simulation Systems
Get PDFThis paper describes a scheme to improve efficiency of multi-agent simulation system (MAS) on single computer that has multiple processor cores. Simulation technology is applied for broad usage in the world, and MAS gathers attention from the fields that treat complicated and non-numeric issues such as traffic analysis, analyzing evacuation from a building, and defense training. Since the requirements of simulation scale and fidelity are growing, the importance of their performance is also increasing. However, CPU clock speedup is slowing, and improvement of computer performance has come to depend on the number of processors, cores, and graphics processing units. Consequently, load distribution and balancing are the keys to deriving better performance, and we consider there is a brilliant move to improve efficiency by utilizing MAS's peculiar attributes. We have developed a multi-agent system framework called Furuichi-lab Unified Simulation Environment (FUSE) that enables easy building of MAS systems and can control thousands of agents with human-like artificial intelligence in real time on standard personal computers. Since agents are heterogeneous and their cluster size can vary, including in our MAS application, we have based our load-balancing method on estimating each agent's workload. Load-balancing must be the basic function of the framework, and the load-balancing method must be available implicitly without any intention on the part of simulation developers. Therefore, the workload estimation process must be independent of the application. We propose an efficient load-balancing scheme for MAS that utilizes the history of agents' workload records. In this paper, we describe the algorithm of our proposed scheme, show an overview of preliminary experiments using a prototype core system, and then explain the results and discuss the effectiveness of this scheme by applying it to a practical simulation program
Assessment of Cell-centered and Cell-vertex Finite Volume Approaches for Computation of 2D Structural Dynamics on Arbitrary Quadrilateral Grids
Get PDFIn this study, cell-centered (CC) and cell-vertex (CV) finite volume (FV) approaches are applied and assessed for the simulation of two-dimensional structural dynamics on arbitrary quadrilateral grids. For the calculation of boundary nodes’ displacement in the CC FV approach, three methods are employed. The first method is a simple linear regression of displacement of boundary nodes from the displacement of interior cell centers. In the second method, an extrapolation technique is applied for this purpose and, in the third method; the line boundary cell technique is incorporated into the solution algorithm in an explicit manner. To study the effects of grid irregularity on the results of CC and CV FV approaches, different grid types are used ranging from regular square grids to irregular ones, including random perturbations of the grid nodes. A comparison between the CC and CV FV approaches is made in terms of accuracy and performance by simulating some benchmark test cases in structural dynamics on different grid types. The present study demonstrates the suitability of using CC FV approach for the simulation of structural dynamics problems and that the results obtained by careful implementation of the CC FV can be comparable with those of the CV FV. On irregular grids, the CC FV approach employing the extrapolation technique fails to obtain accurate results in the most cases studied, however, two other techniques, namely the linear regression and boundary cell methods provide reasonable results. It is indicated that the CV and CC approaches are equivalent in terms of accuracy and convergence rate on regular grids, though, the CV approach is more efficient in term of computational costs. The results obtained by these two approaches for the problems considered here are in good agreement with the analytical solutions
Real-Time Moving Targets Detection in Dynamic Scenes
Get PDFThe shift of the camera leads to unsteadiness of backgrounds in video sequences. The motion of camera will results in mixture of backgrounds and foregrounds motion. So it is a challenge for targets detection in dynamic scenes. A realtime moving target detection algorithm with low complexity in dynamic scenes is proposed in this paper. Sub-block based image registration is applied to remove the global motion of the video frame. Considering the blocks in one frame have different motion vectors, the global motion of each block is separately estimated. Then, a neighbor-based background modeling is applied to extract the moving objects. Moreover, combination of image registration and neighbor-based background modeling can precisely divided foregrounds from backgrounds. At last, a method, based on feature point motions, is adopted to track the foregrounds in time. The experimental results demonstrate that our method can process videos in real-time, without the effect of time delay. What is more, comparative results by quantitative evaluations manifest that the proposed approach can achieve the best classification accuracy