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This paper designs and simulates a circular heatsink (HSK) with a novel geometry. A number of cylindrical pin-fins (PIFs) are placed on the HSK. The flow of alumina/water nanofluid (NF) enters from the middle of the HSK, passes through the PIFs, goes toward the outer curvature, and exits from the HSK. Constant thermal flux is applied at the bottom of the HSK. The variables include the length of PIFs changing from 5 to 20 mm, the distance between PIFs varying from 10 to 15 mm, and the diameter of PIFs changing from 1 to 4 mm. The effect of these variables on the maximum of the HSK, the average temperature (T-AV) of the HSK is examined. Finally, numerical optimization is done on the results using machine learning and artificial intelligence in terms of the minimum HSK temperature. The flow of NF is simulated using a two-phase model and the finite element method (FEM). An increment in the length of the PIFs from 5 to 20 reduces the T-AV by 11.42 K. An increment in the diameter of the PIFs from 1 to 4 reduces the T-AV of the HSK by 5.98 K. [ABSTRACT FROM AUTHOR]

• A novel algorithm is presented for repetitive transcranial magnetic stimulation. • Tetrahedral mesh used in mesh discretization facilitates the pre-processing. • Our algorithm possesses higher calculation accuracy and faster convergence rate. • The developed model can achieve superior computational efficiency. • The proposed method is suitable for both simple and complex human head models. This paper presents a series of smoothed finite element methods (SFEM) for repetitive transcranial magnetic stimulation (rTMS) based on the quasi-static electromagnetic equations. The problem domain is first discretized into a set of tetrahedral elements and linear shape functions are used to interpolate the field variables. Then the smoothing domains (SDs) are constructed based on the edges, nodes, and faces of the background mesh. The smoothed gradient of electric potential and smoothed magnetic flux density over each SD are obtained by using the gradient smoothing technique (GST). The generalized smoothed Galerkin weakform is utilized to derive the discretized system equations. Numerical examples, including both spherical and realistic shaped heads, illustrate that the SFEM has the following important characteristics: (1) easier pre-processing; (2) better accuracy; (3) faster convergence; (4) higher computational efficiency. [ABSTRACT FROM AUTHOR]

This paper describes the mathematical modeling of a parabolic trough collector where the heat transfer fluid has temperature dependent physical properties for which we have developed our own mathematical expressions. For a specific location and date, the direct solar radiation and other sun–earth parameters are computed on a Julian day basis. Also, we have used certain known and recent correlations for the heat transfer coefficients appearing in this model. The mathematical model is governed by three nonlinear partial differential equations of parabolic type with initial/boundary value conditions. We describe a numerical algorithm in order to obtain the approximate solution of this model. Then, we carry out some numerical simulations which yield valuable information for the performance and efficiency of a solar PTC plant at the specific location. [ABSTRACT FROM AUTHOR]

Abstract Based on mimetic Green element method (GEM), which synthesizes some typical advantages of boundary element method (BEM), finite element method (FEM) and mimetic finite difference method (mimetic FDM), This paper study the application of mimetic GEM in the system of partial differential equations (PDEs) of oil-water two-phase flow in porous media. It is the first time to apply GEM to solve numerically the system of PDEs, which is one of novelties in this paper. For numerical simulation of oil-water two-phase flow in porous media, this paper provides a novel numerical method based on mimetic GEM, which is the other novelty of this work. [ABSTRACT FROM AUTHOR]

Abstract Park models, also known as dq-models, are a simple and very efficient way to obtain a faithful image of the behaviour of a machine in transient and steady-state operating conditions to deal with control issues. Their precision is based on the use of saturated direct and quadrature reactances that truly represent the dynamics and the magnitude of the electrical signals at nominal operating point. However, these constant parameters are not sufficient to accurately take into account the saliency of the machine and, therefore, to precisely simulate the harmonic contents of these signals: the latter point can be very problematic for diagnostic purposes. This paper uses simulation results and experimental measurements on a Leroy-Somer 27kVA alternator to clearly show the lack of coherence between the simulated spectra from a dq-model and the experimental data retrieved from a real power alternator. For that reason, a new methodology of machine modelling consisting of a co-simulation process between Flux2D and Matlab software is presented. The use of finite elements enables a fine identification of the inductances of the system. These take into account the geometrical specificities of both the exciter and the main generator and are then used in an analytical model developed in the Matlab environment. Spectral comparisons with experimental data demonstrate the improved accuracy of this new modelling method compared to dq-models in terms of harmonic contents. [ABSTRACT FROM AUTHOR]

This paper presents a novel numerical procedure based on the meshless local natural neighbor interpolation (MLNNI) method for modeling two-dimensional magneto–electro-elastic solids. As a special case of the generalized meshless local Petrov–Galerkin (MLPG) method, the MLNNI method satisfies the weak form equations locally in polygonal sub-domains which surround each node. The natural neighbor interpolation is used to approximate the unknown fields in numerical simulations and thus only a set of scattered nodes are utilized to represent the problem domain. The usage of three-node triangular FEM shape functions as test functions results in the reduction of the order of integrands in domain integrals. As the constructed shape functions possess a point interpolation property, the essential boundary conditions can be imposed directly without the need of introducing special techniques. Numerical examples for magneto–electro-elastic problems are presented to demonstrate the solutions of the present MLNNI method with other available solutions. [ABSTRACT FROM AUTHOR]

The nonlinear interaction between a bubble and a nearby free surface is an important phenomenon, which becomes more complex when the bubble breaks and re-closes at the free surface. In this paper, an axisymmetric bubble dynamics model based on the Eulerian finite element method with the interface tracked by the volume of fluid (VOF) method is established to numerically investigated the breaking and re-closure of a bubble near a free surface. An experimental validation of the numerical model reveals its good accuracy. The motion, breaking, and re-closure of small and large bubbles at a free surface are simulated. Complex phenomena are observed in the simulation after the break of the bubble. Under the effects of inward gas flow and the pressure difference between its inside and outside, a broken bubble finally recloses. The convergence and impact of a spike wall generate an upward water spray higher than that from an intact bubble. Furthermore, the critical depth at which the bubble period reaches its peak has a negative relationship with the weight of the explosive charge used to generate the bubble. [ABSTRACT FROM AUTHOR]

This paper presents a systematic approach for designing 3D auxetic lattice materials, which exhibit constant negative Poisson’s ratios over large strain intervals. A unit cell model mimicking tensile tests is established and based on the proposed model, the secant Poisson’s ratio is defined as the negative ratio between the lateral and the longitudinal engineering strains. The optimization problem for designing a material unit cell with a target Poisson’s ratio is formulated to minimize the average lateral engineering stresses under the prescribed deformations. Numerical results demonstrate that 3D auxetic lattice materials with constant Poisson’s ratios can be achieved by the proposed optimization formulation and that two sets of material architectures are obtained by imposing different symmetry on the unit cell. Moreover, inspired by the topology-optimized material architecture, a subsequent shape optimization is proposed by parametrizing material architectures using super-ellipsoids. By designing two geometrical parameters, simple optimized material microstructures with different target Poisson’s ratios are obtained. By interpolating these two parameters as polynomial functions of Poisson’s ratios, material architectures for any Poisson’s ratio in the interval of ν ∈ [ − 0.78 , 0.00 ] are explicitly presented. Numerical evaluations show that interpolated auxetic lattice materials exhibit constant Poisson’s ratios in the target strain interval of [0.00, 0.20] and that 3D auxetic lattice material architectures with programmable Poisson’s ratio are achievable. [ABSTRACT FROM AUTHOR]

In this paper, the issues of finite-time extended dissipative analysis and non-fragile control are investigated for a class of uncertain discrete time switched linear systems. Based on average dwell-time approach, sufficient conditions for the finite-time boundedness and finite-time extended dissipative performance of the considered systems are proposed by solving some linear matrix inequalities, where using the concept of extended dissipative, we can solve the H ∞ , L 2 − L ∞ , Passivity and ( Q, S, R )-dissipativity performance in a unified framework. Furthermore, two form of non-fragile state feedback controllers are designed to guarantee that the closed-loop systems satisfy the finite-time extended dissipative performance. Finally, simulation example is given to show the efficiency of the proposed methods. [ABSTRACT FROM AUTHOR]

This paper aims to comprehensively understand a 3D model for simulating dam-break floods through three test cases. The advantages and characteristics of this model are evaluated from different perspectives. Firstly, vertical inertial is considered in the 3D model. In the existing 1D and 2D flooding models, vertical inertia is usually ignored, resulting in unreliable results in high vertical inertia situations. A circular dam break case was designed and widely used for testing 2D models. Here it has been adopted to test the 3D model. Evident difference has been observed when compared with 2D modelling results. In order to reduce the vertical inertial in this case, we scaled the vertical size by 1:100, while kept the original horizontal size, then amplified the results according to the Froude number scaling rule. The results of the scaled model is very close to 2D modelling results. Therefore, the difference between the 3D and 2D modelling results are mainly caused by the vertical inertia. Thus it can be seen that 3D modelling techniques are needed when vertical inertia is not negligible. Secondly, the use of unstructured mesh makes this model more powerful in operating with complex topography, which is very important in real-world application. Five similar cases with different topography demonstrated that the complexity of topography affects the numerical solution process directly. However, this 3D model has powerful ability in utilizing very complex terrain. Thirdly, sensitivity of the model to the thickness of the artificial thin layer in dry areas ( d 0 ) and mesh resolution ( Δx ) have been analysed with a realistic dike-break flooding case. Smaller d 0 produces more realistic results but costs more computational time. The model is more sensitive to mesh resolution when the terrain is more complex. Therefore, a multi-scale mesh with high-resolution in areas with complex terrain and low-resolution in flat regions is a good choice for this model. Also, trade-offs between modelling precision and efficiency should be considered when choosing a proper value of d 0 and mesh resolution. [ABSTRACT FROM AUTHOR]

This paper introduces a three-phases model based on the finite element method to simulate the generation and propagation of landslide-generated impulse waves, and this model can be employed to predict and prevent wave-induced hazards. The fluid-like landslide mass is treated as a non-Newtonian viscoplastic fluid. The motion of landslides, water and air is modelled by the incompressible Navier–Stokes equations and the interfaces between these three phases are captured with the n -phases improved conservative level set method which can preserve mass and provide precious interface parameters, including normals and curvatures. The conservative feature of this method is proven by the three-phases Zalesak slotted disk test case. This method is then adopted to simulate the impulse wave generated by the Lituya Bay landslide and the current outputs are compared with other existing results. Finally, this verified model is utilized to model the impulse waves generated by the Halaowo landslide near the Xiangjiaba Dam in the Jinsha River and the results could provide references for further protective activities. [ABSTRACT FROM AUTHOR]

In this paper, an enhanced octree polyhedral scaled boundary finite element method (SBFEM) is proposed in which arbitrary convex polygon (pentagon, hexagon, heptagon, octagon etc.) can be directly served as boundary face elements. The presented method overcomes the existing SBFEM's limitation that boundary face is strictly restricted to be a quadrangle or triangle. The conforming shape functions are constructed using a polygon mean-value interpolation scheme for polyhedral face. A highly efficient octree mesh generation technology is introduced to accelerate the progress of pre-treatment, wherein the mesh information can be directly used in the enhanced SBFEM. The accuracy of the proposed method is first verified using a beam under shear and torsion load. Another three more complicated geometries including a nuclear power plant structure, as well as two sculptures named Terra-Cotta Warriors and Sioux Falls Church are presented to demonstrate the application and robustness of the proposed method. The new method possesses appealing versatility and offers a swift adaptive capacity in mesh generation, which can provide a powerful technique for the simulation of complex geometries, rapid-design analysis and multi-scale problems. [ABSTRACT FROM AUTHOR]

The study of solid–solid interaction problems is of significant interest in many engineering areas, such as structural dynamics or soil–structure interaction problems. In many of these cases, a localized and well-defined structure is embedded or connected to an infinite or semi-infinite domain, and thus the best option is to use different numerical techniques to model each part of the problem. In this paper, the authors propose two iterative coupling strategies to tackle this type of problem, considering the structure to be modelled by the FEM and the soil by the BEM. In both approaches, optimized relaxation parameters are employed, improving the efficiency of the analyses. Within the proposed iterative coupling algorithms, adaptive refinement of the FEM mesh may also be performed, in order to increase the accuracy of the calculations. Numerical examples are presented in the end of the manuscript, illustrating the main features of the proposed methods, assessing their applicability and effectiveness. [ABSTRACT FROM AUTHOR]

An original signal processing method called delayed Time Reversal-Nonlinear Elastic Wave Spectroscopy is introduced in the present paper. The method could be used to amplify signal in certain regions of the material under Non Destructive Testing. It allows to optimize and change the shape of the received focused wave in the material, either by making the focusing sharper by decreasing the side lobes or making it wider by modifying the actual focusing peak. It is also possible to use the focused signal as a delta-basis to construct a signal with arbitrary envelope or reduce the side lobes of the focused signal. These concepts are shown to work well in the simulations and the physical experiments. This signal processing method is particularly promising for nonlinear and solitary wave analysis, since it allows to create an interaction of sharp and solitary wave peaks just underneath the receiving transducer. Due to simple and accurate linear prediction of the received interaction signal, any differences of measurements and predictions could indicate the presence of nonlinearities. [ABSTRACT FROM AUTHOR]

Abstract: This paper investigates the stabilization of three dimensional chaotic systems in a finite time by extending our previous method for chaos stabilization. Based on the finite-time stability theory, a control law is proposed to realize finite-time stabilization of three dimensional chaotic systems. In comparison with the previous methods, the controller obtained by our method is simpler than those. Moreover, the method obtained in this paper is suitable for a class of three dimensional chaotic systems. The efficiency of the control scheme is revealed by some illustrative simulations. [Copyright &y& Elsevier]

Acoustic behavior of fluid saturated, heterogeneous, rigid porous media which consist of two micro-porous materials with high permeability contrast is studied using a two-scale model based on the homogenization theory. At the mesoscopic level, the fluid motion is governed by the generalized Darcy flow model. At the macroscopic scale, effective acoustic properties are described by a model which has recently been derived using the periodic unfolding method (Rohan, 2013).This paper presents a computational procedure for estimating the pressure and the velocity fields at both the mesoscale and the macroscale. The model is validated by comparing the multiscale solutions with those of the model with exact periodic mesostructural geometry. The numerical solutions are computed via the finite element method. The ranges of applicability of homogenized models with “high contrast” and “low contrast” permeabilities are also investigated. [ABSTRACT FROM AUTHOR]

In this paper we show the numerical stability of the Proper Orthogonal Decomposition (POD) reduced order method used in cardiac electrophysiology applications. The difficulty of proving the stability comes from the fact that we are interested in the bidomain model, which is a system of degenerate parabolic equations coupled to a system of ODEs representing the cell membrane electrical activity. The proof of the stability of this method is based on a priori estimates controlling the gap between the reduced order solution and the Galerkin finite element one. We present some numerical simulations confirming the theoretical results. We also combine the POD method with a time splitting scheme allowing a faster solving of the bidomain problem and show numerical results. Finally, we conduct numerical simulation in 2D illustrating the stability of the POD method in its sensitivity to the ionic model parameters. We also perform 3D simulation using a massively parallel code. We show the computational gain using the POD reduced order model. We also show that this method has a better scalability than the full finite element method. [ABSTRACT FROM AUTHOR]

This paper is devoted to the valuation of American multi-asset put options. It is well known that the American multi-asset put option satisfies a linear complementary problem (LCP) on an unbounded domain. We consider a penalty method in which the LCP could be reformulated into a nonlinear parabolic problem on an unbounded domain. For the unbounded computational domain, a perfectly matched layer (PML) technique is applied to truncate it. As to the resulting bounded domain problem related to the option, we use a semi-implicit finite element method (SIFEM) to solve it. The convergence of this method is analyzed in detail. Finally, we present some numerical simulations to show the validity and efficiency of the theoretical analysis. [ABSTRACT FROM AUTHOR]

The main purpose of this paper is the multi-physics modeling of magnetically sensitive porous materials. We develop for this a magneto-poromechanics formulation suitable for the description of such a coupling. More specifically, we show how the current state of the art in the mathematical modeling of magneto-mechanics can easily be integrated within the unified framework of continuum thermodynamics of open media, which is crucial in setting the convenient forms of the state laws to fully characterize the behavior of porous materials. Moreover, due to the soft nature of these materials in general, the formulation is directly developed within the finite strain range. In a next step, a modeling example is proposed and detailed for the particular case of magneto-active foams with reversible deformations. In particular, due to their potentially high change in porosity, a nonlinear porosity law recently proposed is used to correctly describe the fluid flow through the interconnected pores when the solid skeleton is finitely strained causing fluid release or reabsorption. From the numerical point of view, the variational formulation together with an algorithmic design is described for an easy implementation within the context of the finite element method. Finally, a set of numerical simulations is presented to illustrate the effectiveness of the proposed framework. [ABSTRACT FROM AUTHOR]

An efficient method for modelling the wave propagation in semi-infinite domain is proposed. It is applicable to soil–structure interaction problems for complex inclined soil field. The scaled boundary finite element method is modified through the original scaling center substituting by a scaling line. Based on this scaling line, the dynamic stiffness equation is derived. Then, an accurate and efficient continued fraction method is firstly introduced for solving equation for the model with rigid bedrock. By using the continued fraction solution and introducing auxiliary variables, the equation of motion of unbounded domain is built. Coupling the far field modelling by modified scaled boundary finite element method with the near field modelling by the finite element method, the global time-domain equation is obtained, which is a standard equation of motion for the whole domain. As a key point, the precise time-integration method is firstly employed to solve global equation of motion. The advantages of this integration method are that the integral interval is divided into quite small piece. It makes sure the precision achieve to computer precision. Owning to adopting five terms Taylor expansion for each small integral interval, the computational precision is increased greatly. Applying precise time-integration method in this paper, it greatly improves the accuracy and computing speed of proposed method. By using the sub-structure method, the inclined soil field is modelled. Numerical examples demonstrate accuracy and high efficiency of the new method, especially for complex dip mediums. [ABSTRACT FROM AUTHOR]

This paper considers the issues of both state estimation and unknown information reconstruction for a class of uncertain complex dynamical networks subject to unknown inputs. First, a robust adaptive sliding mode observer which can be used to estimate the states of complex networks through available measurement outputs is developed by employing both adaptive technique and sliding mode control approach. Second, a high-gain second-order sliding mode observer is considered to exactly estimate the derivatives of the output vectors in a finite time. Third, by using the estimates of the states and output derivatives, a kind of algebraic unknown input reconstruction method is proposed. Finally, some numerical simulation examples are given to illustrate the effectiveness of the proposed methods. [ABSTRACT FROM AUTHOR]

In this paper, the flow-induced vibrations of an elastically mounted circular cylinder subjected to the planar shear flow with the 1-DOF (only transverse direction) and 2-DOF (in-line and cross-flow directions) movements are studied numerically in the laminar flow (Re = 150). Based on a characteristic-based-split (CBS) finite element method, the numerical simulation is conducted, and is verified through the benchmark problem of the uniform flow past an elastically mounted circular cylinder. The computation is carried out for lower reduced mass of M r = 2.0 and the structural damping ratio is set to zero to maximize the vortex-induced response of the cylinder. The effects of some key parameters, such as shear rate ( k = 0.0–0.1), reduced velocity ( U r = 3.0–12.0) and natural frequency ratio ( r = 1.0–2.0), on the characteristics of vortex-induced vibration (VIV) responses are studied. The results show that, in the 1-DOF system, the frequency synchronization region extends with the increasing of k . The shear rate greatly affects the phase portraits, which shift from the double-valued type to the single-valued one. On the other hand, in the 2-DOF system, the increasing of k causes the extension of the single-resonant region and dual-resonant one at the lower natural frequency ratios. While at the higher natural frequency ratios, the change of k only expands the single-resonant region in the transverse direction. The predominant vortex shedding patterns are 2S and P + S modes. Finally, the interaction between vortex and cylinder as well as the mechanism of flow-induced vibration in planar shear flow are revealed. The phase between the force and its corresponding displacement changes from out-of-phase to in-phase and the higher harmonic forces appear with the increasing of shear rate, resulting in the energy transferring from the fluid to the structure and then the dynamic response of the cylinder intensifying. [ABSTRACT FROM AUTHOR]

The paper discusses the application of a hybrid Finite Element–Boundary Element technique to the electromagnetic dosimetric analysis of voxel based human models, with particular attention to the Magnetic Resonance Imaging appliances. A rational organization of the large amount of data involved by the voxel anatomy is presented to reduce the computational burden. The most suitable choice of the unknowns and the possible simplifying assumptions are also investigated. A hybrid Finite Element–Boundary Element approach is derived from the previous considerations, underlining the procedure for the system solution adopted when the whole algebraic matrix exceeds the RAM capabilities. The work is completed with some examples of applications. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, the three-dimensional transient heat conduction problems in functionally graded materials (FGMs) have been solved using the method of fundamental solutions (MFS). To be more specific, we consider the FGMs with thermal conductivity and specific heat vary exponentially in z-direction. In the numerical simulation, we coupled the fundamental solution of diffusion equation with the method of time–space unification which provides a simple and direct approach for solving time-dependent problems. The parameter transformation technique is also utilized to obtain the fundamental solutions which contain the thermal conductivity and the specific heat conditions. The MFS is very attractive in handling problems with irregular domain due to the simplicity of the method. The numerical results are in good agreement comparing with analytical solution and results obtained from the finite element method. [Copyright &y& Elsevier]

Abstract: The evaluation of macroscopic material parameters such as fracture toughness as functions of microstructural attributes is a fundamental issue in material science. The task requires the quantification of both microstructure and material response. Currently, no systematic approach other than experiments exists for establishing microstructure–fracture toughness relations for materials. In this paper, we present a multi-scale computational framework based on the cohesive finite element method (CFEM) for predicting fracture toughness of materials as a function of microstructure. This framework provides a means for evaluating fracture toughness through explicit simulation of fracture processes in microstructures. The approach uses the J-integral, allowing fracture toughness to be calculated for microstructures with random heterogeneous phase distributions and fracture processes with arbitrary crack paths or micro-crack patterns. Calculations carried out concern two-phase Al2O3/TiB2 ceramic composites and focus on the effects of constitute behavior, phase morphology, phase distribution, phase size scale, and interphase bonding on fracture toughness. Results show that microstructure and constituent properties can significantly influence fracture behavior and combine to determine the overall fracture toughness through the activation of different fracture mechanisms. In particular, a combination of fine microstructure size scale, rounded reinforcement morphology, appropriately balanced interphase bonding strength and compliance can best promote desirable crack–reinforcement interactions and lead to enhanced fracture toughness. [Copyright &y& Elsevier]

Abstract: This paper presents applications of a recently proposed immersed boundary method to the solution of fluid–solid interaction. Solid objects immersed into the fluid are considered rigid and their movement is determined from the interaction forces with the fluid. The use of body-conformal meshes to solve such problems may involve extensive mesh adaptation work that has to be repeated each time a change in the shape of the domain or in the position of immersed solids is needed. Mesh generation and solution interpolation between successive grids may be costly and introduce errors if the geometry changes significantly during the course of the computation. These drawbacks are avoided when the solution algorithm can tackle grids that do not fit the shape of immersed objects. We present here an extension of our recently developed immersed boundary (IB) finite element method to the computation of interaction forces between the fluid and immersed solid bodies. A fixed mesh is used covering both the fluid and solid regions, and the boundary of immersed objects is defined using a time dependent level-set function. Boundary conditions on the immersed solid surfaces are imposed accurately by using a Body Conformal Enrichment (BCE) method. In this approach, the finite element discretization of interface elements is enriched by including additional degrees of freedom which are latter eliminated at element level. The forces acting on the solid surfaces are computed from the enriched finite element solution and the solid movement is determined from the rigid solid momentum equations. Solutions are shown for various fluid–solid interaction problems and the accuracy of the present approach is measured with respect to solutions on body-conformal meshes. [Copyright &y& Elsevier]

Abstract: The subject of the paper is the numerical simulation of the interaction of two-dimensional incompressible viscous flow and a vibrating airfoil with large amplitudes. A solid airfoil with three degrees of freedom performs rotation around an elastic axis, oscillations in the vertical direction and rotation of a flap. The numerical simulation consists of the finite element solution of the Navier–Stokes equations coupled with a system of nonlinear ordinary differential equations describing the airfoil motion. The time-dependent computational domain and a moving grid are treated by the arbitrary Lagrangian–Eulerian (ALE) formulation of the Navier–Stokes equations. High Reynolds numbers require the application of a suitable stabilization of the finite element discretization. With the aid of numerical experiments we analyze the convergence of the method, if the computational mesh is refined and the time step is successively decreased. Also the effect of the loose (weak) and strong coupling of the flow and structure problems is tested. The applicability of the method is demonstrated by the comparison with NASTRAN computations and the solution of the coupled fluid–structure problem with increasing far-field velocity up to and behind the flutter instability. The developed method can be used in theoretical prediction of dynamic behaviour of aeroelastic systems especially when the system stability has been lost. [Copyright &y& Elsevier]

Abstract: In the numerical simulation of three dimensional fluid dynamical equations, the huge computational quantity is a main challenge. In this paper, the discontinuous Galerkin (DG) finite element method combined with the adaptive mesh refinement (AMR) is studied to solve the three dimensional Euler equations based on conforming unstructured tetrahedron meshes, that is according the equation solution variation to refine and coarsen grids so as to decrease total mesh number. The four space adaptive strategies are given and analyzed their advantages and disadvantages. The numerical examples show the validity of our methods. [Copyright &y& Elsevier]

Abstract: The traditional scaled boundary finite-element method (SBFEM) is a rather efficient semi-analytical technique widely applied in engineering, which is however valid mostly for linear differential equations. In this paper, the traditional SBFEM is combined with the homotopy analysis method (HAM), an analytic technique for strongly nonlinear problems: a nonlinear equation is first transformed into a series of linear equations by means of the HAM, and then solved by the traditional SBFEM. In this way, the traditional SBFEM is extended to nonlinear differential equations. A nonlinear heat transfer problem is used as an example to show the validity and computational efficiency of this new SBFEM. [ABSTRACT FROM AUTHOR]

Abstract: The lattice Boltzmann method (LBM) is the simple numerical simulator for fluids because it consists of linear equations. Excluding the higher differential term, the LBM for a temperature field is also achieved as an easy numerical simulation method. However, the LBM is hardly applied to body fitted coordinates for its formulation. It is then difficult to calculate complex lattices using the LBM. In this paper, the finite element discrete Boltzmann equation (FEDBE) is introduced to deal with this weakness of the LBM. The finite element method is applied to the discrete Boltzmann equation (DBE) of the basic equation of the LBM. For FEDBE, the simulation using complex lattices is achieved, and it will be applicable for the development in engineering fields. The natural convection in a square cavity and the Rayleigh–Bernard convection are chosen as the test problem. Each simulation model is accurate enough for the flow patterns, the temperature distribution and the Nusselt number. This method is now considered good for the flow and temperature field, and is expected to be introduced for complex lattices using the DBE. [ABSTRACT FROM AUTHOR]

Abstract: The objective of this paper is to develop a realistic model for ice–structure interaction. To this end, the experiments made by Bridges et al. [Bridges FG, Hatzes A, Liu DNC. Structure, stability and evolution of Saturn’s rings. Nature 1984;309:333–5] in order to measure the coefficient of restitution for ice particles are thoroughly analyzed. One particularly troublesome aspect of the aforementioned experiments is fracture of the ice particles during a collision. In the present effort, the collisional properties of the ice particles are investigated using a Finite Element approach. It is found that a major challenge in modeling collision of the ice balls is the prediction of the onset of fracture and crack propagation in them. In simulations of a block of ice collision to a structure, it is crucial that fracture is determined correctly, as it will influence the collisional properties of the ice particles. The results of the simulation, considering fracture criterion implemented into the Finite Element Model [Zamankhan P, Bordbar M-H. Complex flow dynamics in dense granular flows. Part I: experimentation. J Appl Mech (T-ASME) 2006;73:648–57; Zamankhan P, Huang J. Complex flow dynamics in dense granular flows. Part II: simulations. J Appl Mech (T-ASME) 2007;74:691–702] together with a material model for the ice, imply that most of the kinetic energy dissipation occurs as a result of fracturing at the contact surface of the ice particles. The results obtained in the present study suggest that constitutive models such as those proposed by Brilliantov et al. [Brilliantov NV, Spahn F, Hertzsch JM, Poschel T. Model for collisions in granular gases. Phys Rev E;1996;53:5382–92] for collisions of ice particles are highly questionable. [Copyright &y& Elsevier]

Abstract: Electrical capacitance tomography (ECT) is a new measurement technology, which is often used to identify two-phase/multi-phase flow regime and investigate the solid distribution in circulating fluidized bed. It is composed of forward problem and inverse problem. Usually, forward problem is solved using finite element method (FEM). Element-free Galerkin method (EFGM) is one of the meshless methods developed recently. In order to obtain the numerical solution using EFGM, a shape function is constructed by moving least-squares (MLS) approximation, a variational equation weak form of the studied problem is used to deduce the discrete equation, and Lagrange multipliers are used to satisfy essential boundary conditions. In EFGM, only nodal data are necessary compared with FEM. In this paper, EFGM was used to solve forward problem and simulation results showed EFGM has high accuracy and its post-processing is easy. [Copyright &y& Elsevier]

Abstract: This paper analyses the fragmentation of kidney stones by direct impact with Swiss Lithoclast Master®. Based on a previous work, the impact of the probe of the Lithoclast is modeled with a displacement control of the nodes inside the impacted area. Different computations are carried out focusing the efforts on new tentative designs of the cross section of the probe, as well as the influence of multiple impacts. The results show that a hollowed probe could improve the results obtained with the existing massive probe. Likewise, it is shown that there is an optimal internal radius of the hollowed probe for which the damage caused to the kidney stone is maximized. Finally the results demonstrate the existence of a synergetic effect of the application of multiple impacts at a high frequency. [Copyright &y& Elsevier]

Abstract: This paper presents a finite element (FE) computation model for estimating the equivalent mechanics parameters of a composite material with randomly distributed multi-scale grains. The model is based on statistical multi-scale analysis (SMSA). First, some definitions of the probability space and statistical two-scale analysis (STSA) of the mechanics parameters for a composite material with randomly distributed grains are briefly reviewed. Next, a computer simulation algorithm for composite materials with random grains is presented. Then an FE procedure based on STSA is proposed and some properties of the equivalent mechanics parameters are outlined. Finally, the FE procedure for a composite material with randomly distributed grains is described and two numerical examples are demonstrated. The numerical results show that the FE procedure based on SMSA is a valid and feasible method for predicting the mechanics parameters of a composite material with randomly distributed grains. [Copyright &y& Elsevier]

Abstract: Simulation of shape casting processes involves the simultaneous capture of the rapidly developing metal–air free surface and the liquid–solid moving boundary in the metal phase. Although a wide range of techniques have been developed to address this problem, there are occasions where existing techniques are limited, especially in very complex geometries where the mesh quality may inevitably be relatively poor at some key locations. Cell-centred finite volume methods, typical of most commercial CFD tools, are computationally efficient, but can lead to convergence problems on meshes that feature cells with highly non-orthogonal shapes. The control volume–finite element method uses a vertex-based approach and handles distorted meshes with relative ease, but is computationally expensive. A combined vertex-based–cell-centre technique, described in this paper, solves the flow field at the cell or element vertex, and all other variables are solved at the cell centre (as in conventional CFD tools). This flow solver strategy is much more tolerant of meshes with poor quality elements, allowing solutions on distorted meshes where purely cell-centred solutions procedures fail. The combined method enables the solution of simultaneous free surface flows coupled with solidification in very complex meshes, thus enabling the capture of such behavior in arbitrarily complex geometrical structures. It is relatively straightforward to embed within generic CC based CFD tools allowing it to be employed in a wide variety of processing applications. [Copyright &y& Elsevier]