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The Selective Control Feature for Physically Accurate Solutions of All Variables and Application in First Order Linear Transient Hyperbolic Systems
Get PDFThe objective in this paper is to extend the previously developed twoparameter GS4-1 (Generalized Single System Single Solve for 1st order transient systems) computational framework from parabolic to hyperbolic type of applications pertaining to first order linear transient systems. In particular, attention is paid to the selective control feature inherit in the framework, which is the new feature that enables different amounts of high frequency damping for the primary variable and its time derivative, allowing for physically accurate solutions of all variables in the system. This is in contrast to having only limited, often indiscriminate, control of the high frequency damping on these variables which may not be sufficient to suppress the numerical oscillations in the time derivative variable
Dynamic Mesh Refining and Iterative Substructure Method for FilletWelding Thermo-Mechanical Analysis
Get PDFDynamic mesh refining method (DMRM) developed previously was extended to multi-level refinement, and employed to perform thermal-mechanical analysis of fillet welding. The DMRM has been successfully incorporated with another efficient technique, the iterative substructure method (ISM) to greatly enhance the computation speed of welding simulation. The basic concept, hierarchical modeling and computation flowchart are described for the proposed method. A flange-to-pipe welding problem has been solved with a commercial code and the novel method to demonstrate its high accuracy and efficiency. Furthermore, the numerical analysis was performed on a large scale stiffened welding structure, and comparison of welding deformation between simulation and measurement was shown
Differing Mapping using Ensemble of Metamodels for Global Variable-fidelity Metamodeling
Get PDFComputational simulation models with different fidelity have been widely used in complex systems design. However, running the most accurate simulation models tends to be very time-consuming and can therefore only be used sporadically, while incorporating less accurate, inexpensive models into the design process may result in inaccurate design alternatives. To make a trade-off between high accuracy and low expense, variable fidelity (VF) metamodeling approaches that aim to integrate information from both low fidelity (LF) and high-fidelity (HF) models have gained increasing popularity. In this paper, a Difference Mapping Framework using Ensemble of Metamodels (DMF-EM) for global VF metamodeling is proposed. In DMF-EM, a tuned model is created to bring the low fidelity model as close as possible to high fidelity model. Then, a VF metamodel is obtained by calibrating the tuned model using scaling function that is used to map the difference between the high fidelity model and the tuned model. Since the nature of the scaling function is not a priori, it is fitted using ensemble of metamodels to decrease the risk of adopting inappropriate metamodels. As a demonstration, the proposed approach is compared to existing methods using several numerical cases and two engineering examples. Results illustrate that the proposed DAD-VFM approach is more accurate and robust, that is needed in metamodel-based engineering design problems
Hybrid Adaptive Particle Swarm Optimized Particle Filter for Integrated Navigation System
Get PDFParticle swarm optimization algorithm based particle filter is trapping in local optimum easily, it is not able to satisfy the requirement of modern integrated navigation system. In order to solve the problem, A novel particle filter algorithm based on hybrid adaptive particle swarm optimization(HPSO-PF) is presented in this paper. This improved particle filter will conduce to finding the ideal solution domain by making use of the global convergence of artificial fish swarm and enhancement of fusion precision by guiding particles to move toward the high likelihood area through particle swarm optimization. Finally different models are used for simulation and the experiment results show that this new particle filter improves the precision of integrated navigation system
Fast Mold Filling Simulation Based on the Geodesic Distance Calculation Algorithm for Liquid Composite Molding Processes
Get PDFIn Liquid Composite Molding (LCM) processes, resin is introduced into a stationary fiber reinforcement placed in the mold, until the reinforcement gets fully saturated with resin and all volatiles are vented out of the part. Finite element based software packages have been developed to simulate the mold filling process and eliminate expensive and tedious trial and error practices to arrive at a successful mold filling without any voids. However, the non-homogeneity of the fiber reinforcement material and its placement and layup in the mold creates a large degree of variability of flow patterns during the resin impregnation process. Executing simulations for every possible permutation of flow scenarios, which is required to devise a robust process design is computationally expensive. Therefore, it is necessary to find faster approximate mold filling simulation methods so that all simulations can be performed within a reasonable time frame.
In this paper, a discretized one-dimensional flow model is developed to predict the fill time based on the distance resin travels. Combined with Dijkstra’s algorithm, this model is then implemented on spatial surface meshes to calculate fill time for each node and generate flow development pattern. The computational model developed can predict the mold filling pattern for complex parts even with variable permeability or thickness of the fiber preform, and can capture the disturbed flow behavior along any difficult geometric features at a fraction of the computational cost. Case studies are presented to demonstrate the efficiency and accuracy of the distance-based model
Dynamic Response Analysis of the Fractional-Order System of MEMS Viscometer
Get PDFThis paper presented dynamic response analysis for an MEMS viscometer. The responses are governed by a set of differential equations containing fractional derivatives. The memory-free Yuan-Agrawal’s approach was extended to solve fractional differential equations containing arbitrary fractional order derivative and then a simple yet efficient numerical scheme was constructed. Numerical examples show that the proposed method can provide very accurate results and computational efforts can be significantly saved. Moreover, the numerical scheme was extended to solve problems with a nonlinear spring. The influences of the nonlinear parameters on the dynamic responses were also efficiently analyzed. The dependence of the angular frequency on damping parameters was also revealed. The presented method can provide us a new perspective to measure the fluid viscosity
Meshless LocalWeak form Method Based on a Combined Basis Function for Numerical Investigation of Brusselator Model and Spike Dynamics in the Gierer-Meinhardt System
Get PDFIn this paper, at first, a new combined shape function is proposed. Then, based on this shape function, the meshless local weak form method is applied to find the numerical solution of time-dependent non-linear Brusselator and Gierer- Meinhardt systems. The combined shape function inherits the properties of radial point interpolation (RPI), moving least squares (MLS) and moving Kriging (MK) shape functions and is controlled by control parameters, which take different values in the domain [0;1]. The combined shape function provides synchronic use of different shape functions and this leads to more flexibility in the used method. The main aim of this paper is to show that the combined basis function can be used as a shape function in meshless local weak form methods and leads to better results in solving the system of non-linear partial differential equations especially Brusselator and Gierer-Meinhardt systems. The numerical results confirm the good efficiency of the proposed method for solving non-linear Brusselator and Gierer-Meinhardt systems
A Note on Solving the Generalized Dirichlet to Neumann Map on Irregular Polygons using Generic Factored Approximate Sparse Inverses
Get PDFA new transform method for solving boundary value problems in two dimensions was proposed by A.S. Fokas, namely the unified transform. This approach seeks a solution to the unknown boundary values by solving a global relation, using the known boundary data. This relation can be used to characterize the Dirichlet to Neumann map. For the numerical solution of the global relation, a collocation-type method was recently introduced. Hence, the considered method is used for solving the 2D Laplace equation in several irregular convex polygons. The linear system, resulting from the collocation-type method, was solved by the Explicit Preconditioned Generalized Minimum Residual restarted method in conjunction with the Modified Generic Factored Approximate Sparse Inverse matrix. Numerical results indicating the applicability of the proposed preconditioning scheme are provided, along with discussions on the implementation details of the method
Design of Orthopedic Plates and Its Modification Based on Feature
Get PDFTo quickly construct the orthopedic plates and to conveniently edit it, a novel method for designing the plates is put forward based on feature idea and parameterization. Firstly, attached to the existing or repaired bone model, the region of interest (ROI) is selected as the abutted surface of orthopedic plate, and the ROI is reconstructed to form a CAD surface. Secondly, the CAD surface is to be defined as a surface feature (SF) and then some semantic parameters are configured for it. Lastly, the plate body is constructed through thickening, and some higher parameters are defined for it so as to produce a volumetric feature (VF). In the above process, there exist two main problems: one is parameterization of the abutted surface, and the other is construction of the outer surface. Besides, the mapping relationship has to be built between surface feature parameters and volumetric feature parameters. This method supports the modification of high-level parameters, consequently promoting the quality and efficiency of orthopedic plate design
Theoretical Study of Solvation Effect on Diffusion Coefficient of Li Ion in Propylene Carbonate
No full textPropylene carbonate (PC) and ethylene carbonate are known as good candidates of organic solvents to be used in Li-ion rechargeable batteries, since Li+ ions exhibit preferable charge-discharge characteristics with such solvents. On the other hand, polar solvents usually form solvation shells with solute ions, and cause a drastic reduction of ionic conductivity. Along these lines, there has been a curious question why the diffusion coefficient DLi of Li+ strongly depends on the salt concentration. In the present study, a theoretical model is developed on the basis of the Langevin equation in which the interactions between ions and solvent molecules are explicitly taken into account. Interesting phenomena, which were found in experiments but had not yet been theoretically clarified, are discussed in detail. Molecular dynamics (MD) simulations are also performed to elucidate the relationship between the solvation shell of Li+ and DLi. Analyzing the radial distribution function of PC molecules around Li+ ions, the existence of first and second solvation shells (consisting of locally and highly concentrated PC molecules) is numerically clarified. In particular, overlapped regions of the second solvation shells are clearly observed, with the shell volume apparently increasing with an increase in the concentration of Li+ . This result indicates that the solvation structures can attractively interact with each other via overlaps of the second shells. The theoretical model and MD simulations are in excellent agreement with experimental data