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In this paper, we investigated a non-signalized T-shaped intersection using the cellular automata model under the open boundary condition. Two different priority rules at intersection are introduced (Rule 1, Rule 2) to eliminate the jam-packed state. Phase diagram and its variation with the ratios of right and/or left turning vehicles are investigated. The space-time and the density profiles are also studied. The simulation results indicate that the system does not show the same performance under different priority rules, where Rule 1 (resp. Rule 2) can be better than Rule 2 (resp. Rule 1) according to the ratios of turning vehicles. [ABSTRACT FROM AUTHOR]

Abstract: The Immersed Boundary (IB) method is a widely-used numerical methodology for the simulation of fluid–structure interaction problems. The IB method utilizes an Eulerian discretization for the fluid equations of motion while maintaining a Lagrangian representation of structural objects. Operators are defined for transmitting information (forces and velocities) between these two representations. Most IB simulations represent their structures with piecewise linear approximations and utilize Hookean spring models to approximate structural forces. Our specific motivation is the modeling of platelets in hemodynamic flows. In this paper, we study two alternative representations – radial basis functions (RBFs) and Fourier-based (trigonometric polynomials and spherical harmonics) representations – for the modeling of platelets in two and three dimensions within the IB framework, and compare our results with the traditional piecewise linear approximation methodology. For different representative shapes, we examine the geometric modeling errors (position and normal vectors), force computation errors, and computational cost and provide an engineering trade-off strategy for when and why one might select to employ these different representations. [Copyright &y& Elsevier]

Abstract: Size effects are observed within discontinuous fibre composites, such that the material properties change with the specimen volume. Representative volume elements (RVEs) are commonly used to simulate random fibre architectures for finite element analysis of discontinuous fibre composites. A series of simplified 2D RVE models have been created and studied in this paper, in order to determine the relationship between the critical RVE size and fibre length and volume fraction. All models are subjected to periodic boundary conditions, but average properties are extracted from an inner region offset from the model boundary by a distance equivalent to two fibre lengths. According to Saint–Venant’s principle, this offset removes the uncertainty associated with the approximate boundary conditions. A statistical stopping criterion has been adopted to determine the number of realisations required to achieve a representative set of elastic properties for each fibre architecture. The critical RVE side length is shown to be approximately four times the fibre length when considering convergence of the tensile and shear stiffnesses for the range of fibre lengths and volume fractions studied. [Copyright &y& Elsevier]

Abstract: Various macroscopic models to describe instability pattern formation are discussed in this paper. They are similar to the Ginzburg–Landau envelope equation, but they can remain valid away from the bifurcation and are based on the technique of Fourier series with slowly varying coefficients. We focus on two questions: the need to take phase changes into account and the boundary conditions to be associated with macroscopic models. The analysis is carried out on the basis of numerical simulations for the problem of a compressed beam on a nonlinear foundation that is quite similar to the well known Swift–Hohenberg equation. The first macroscopic model involves a real envelope so that the phase is assumed to be constant. The second model is also macroscopic and it is a sort of Ginzburg–Landau equation with a complex envelope. The third one follows from a multi-scaled approach with a numerical bridging between the full model near the boundary and a macroscopic model in the bulk. [Copyright &y& Elsevier]

Abstract: This paper investigates the numerical simulation of non-Fourier transient heat transfer in a two-dimensional sub-100nm metal-oxide-semiconductor field-effect transistor (MOSFET). The dual-phase-lag (DPL) model with a specific normalization procedure is introduced for the modeling of nanoscale heat transport. The boundary conditions are selected similar to what existed in a real MOSFET device, both uniform and non-uniform heat generations within the transistor are applied, and the end parts of the top boundary which are in contact with the metallic material are left open. A temperature-jump boundary condition is used on all boundaries in order to consider the boundary phonon scattering at micro and nanoscale. A three-level finite difference scheme has been employed to generate the numerical results which are illustrated for a silicon sub-100nm MOSFET corresponding to the Knudsen number of 10. The results are presented at real times less than 50ps to avoid the three-dimensional effects. It is concluded that the combination of the DPL model with mixed-type temperature boundary condition is able to predict the heat flux and temperature distribution obtained from the Boltzmann transport equation (BTE) more accurate than the ballistic-diffusive equations (BDE). After verification of our results, the thermal field and the hotspot temperature within the bulk silicon are presented and the effect of adding a layer of silicon-dioxide to the transistor on its thermal behavior has been investigated. [Copyright &y& Elsevier]

Abstract: The possibility of modeling the Navier–Stokes equations and together with the conventional second order slip boundary condition at high Knudsen numbers is explored in this paper by incorporating the Knudsen diffusion phenomenon in rarefied gases. An effective mean free path (MFP) model is augmented to the governing equation and the slip boundary condition, as gas transport properties can be related to the MFP. This simple modification is shown to implicitly take care of the complexities associated in the transitional flow regime, without necessitating dependency of the slip coefficients on the Knudsen number. Unique analytical model with fixed values of slip coefficients is proposed and rigorous comparisons with the experimental and simulation data for pressure driven and thermally driven rarefied gas flows support this conjecture. First and second order slip coefficients have been proposed as 1.1466 and 0.9756 for rectangular channels and 1.1466 and 0.14 for the capillaries, from the continuum to the transition flow regime. The current work is significant from the numerical simulation point of view because simulation tools are better developed for Navier–Stokes equations. [Copyright &y& Elsevier]

Abstract: Earth heat exchangers are essential parts of the ground-source heat pumps and the accurate prediction of their performance is of fundamental importance. This paper presents the development and validation of a numerical model for the simulation of energy flows and temperature changes in and around a borehole heat exchanger when a fluid circulates through a U-tube. Based on the time-dependent convection–diffusion equation, the FlexPDE software package is employed to solve the resulting boundary value problem that model a heat exchanger. First, the mathematical model is validated through a comparison with data obtained from experiments with real borehole set-ups in Cyprus. Then the validated model is used to study the heat flow and the temperature variation in the heat-exchanger. Finally conclusions are extracted on how various parameters like the U-tube diameter, the variation of the ground thermal conductivity and specific heat and the borehole filling material affect the temperature of the inlet and outlet fluid. [Copyright &y& Elsevier]

Abstract: In this work, we have assessed the results of the local and nonlocal versions of Rousselier’s damage model, which have been used here for simulation of ductile crack growth. There are several issues regarding the accuracy of the results which has been addressed in this paper, e.g., accuracy in simulation of crack path, extent and width of the damaged region, fracture resistance behaviour in situations such as symmetric vs. non-symmetric boundary-value problems, mixed-mode loading vs. mode-I loading of the crack-tip, etc. It was also observed that the shape and orientation of the elements at the crack-tip, in addition to their size, influence the results of the local damage model. In this work, it was shown that the above issues can be resolved through the use of nonlocal damage models. The predictions of the nonlocal model are also consistent with the experimental observations unlike its local counterpart. Several examples were presented, where the results as obtained by both the local and nonlocal models were compared. From this experience, it is recommended that the local damage models should not be used blindly by the analysts for all kinds of mesh design, loading, boundary conditions, etc. [Copyright &y& Elsevier]

Abstract: This paper presents a new, physically-based model for transport processes in wood for conditions below the fiber saturation point. The macroscopic mathematical description of these processes involves three coupled differential equations: two mass balance laws for the bound water and the water vapor phase, and an energy balance equation. These governing equations and the corresponding boundary conditions are expressed in terms of the state variables bound water concentration, water vapor concentration, and temperature. Macroscopic material properties are estimated based on a multiscale approach in the framework of continuum micromechanics. The phase change between the two water phases and the thus resulting coupling between the differential equations cannot be suitably captured in a purely macroscopic description, therefore a microscale sub-model is presented. Numerical solutions of the model equations are derived by means of the Finite Element Method. Finally, the model is applied to prediction of moisture profiles in a wood sample under transient environmental conditions. Comparing these results with corresponding profiles obtained non-destructively by proton magnetic resonance imaging (MRI) validates the model and confirms suitability of the underlying physical assumptions. [Copyright &y& Elsevier]

Abstract: This paper describes the methodology followed to perform a co-simulation between 1D (OpenWAM) and 3D (FLUENT) CFD codes. The Method of Characteristics (MoC) has been chosen to transfer the information between the two domains by properly updating the boundary condition at the shared interface. A short explanation of the MoC is provided, including the modifications needed by the Riemann invariants when dealing with non-homentropic flow. The implementation of the coupling is explained, focusing on the particular approach required by FLUENT in order to obtain the Riemann invariants. Two validation tests have been performed. The Sod’s problem has been used to test the numerical accuracy of the coupling methodology. On the other hand, an impulse test rig configuration has been simulated to show the potential capability of a co-simulation in terms of reducing the computational cost. In both cases a good agreement in the solution is found. [Copyright &y& Elsevier]

Abstract: Theoretical models which approximate individual sand dunes as particles that move and interact via simple rules are currently the only viable method for examining whether large dune fields will evolve into a patterned structure. We find that these types of simulations are sensitive to the influx condition and interaction function, and are not necessarily robust under common assumptions. In this paper, we review continuum dune models and how they connect to models of dune fields that approximate dunes as interacting particles with collision and coalescence dynamics. This type of simple dune field model is examined under different boundary and initial conditions. We identify different long-term behaviors depending on model parameters as well as the way in which dunes are initialized and collide. A “rule” for predicting the end state of a modelled dune field is derived, based on the statistics of a uniform influx dune size distribution and the interaction function. Possible future adjustments to the multiscale model, such as the use of a Gaussian influx dune size distribution, and their effect on the prediction rule are also discussed. [Copyright &y& Elsevier]

Abstract: This paper focuses on the investigation of the 3D mathematical model to simulate the coupled heat and liquid moisture transfer in hygroscopic porous fibrous media. The flow of the liquid moisture, the water vapor sorption/desorption by fibers and the diffusion of the water vapor are taken into account in this 3D model. Prediction-corrector method is used to solve the 3D governing equations. A series of computational results of the coupled heat and moisture transfer are obtained with the specific initial conditions and boundary conditions. The distribution of the water vapor concentration in the void spaces, the volume fraction of the liquid water in the void spaces, the distribution of the water content in fibers and the changes of the temperature in porous fibrous media are computed. It is shown that the effects of the gravity and capillary actions are significant in hygroscopic porous fibrous media. The comparison with the experimental measurements shows the reasonable agreement between the two. The results illustrate that the 3D model of the coupled heat and liquid moisture transfer in hygroscopic porous fibrous media is satisfactory. [Copyright &y& Elsevier]

Abstract: A three dimensional coupled ocean (HYCOM) and sea ice model (CICE) is applied to a regional setup of the Lincoln Sea, the Nares Strait, and the Baffin Bay. As the sea ice model is originally developed for global simulations, boundary conditions have been implemented for the regional setup. The model results are compared with satellite images and with the large scale simulation that is specified for the boundary conditions. The main focus in this paper is on the simulated variations in the modeled sea ice flux and oceanic volume flux through the Nares Strait in the period September 2005–August 2008. The total sea ice area flux in 2006 is 14×103 km2/year and in 2007 it is 69×103 km2/year. The reason for this difference is mainly the blocking of the ice flow in the Nares Strait in spring 2006. The corresponding volume fluxes are 20km3/year and 120km3/year. The average annual oceanic volume flux varies from 0.6Sv to 1.3Sv from 2006 to 2008. The freshwater flux with a reference salinity of 34.8 varies in the same period from 12mSv to 29mSv. The opening and closing of the North Water, which is one of the largest polynyas in the world, are investigated. A February storm event with opening and refreezing of the North Water is well reproduced. The model results show that the net heat flux in the polynya area at the surface is positive into the ocean from May until the end of July, and hence while the wind is responsible for opening the polynya, the main mechanism for maintaining the polynya in late spring and early summer is the surface heat flux. [ABSTRACT FROM AUTHOR]

Abstract: A self-developed simulation platform of natural gas internal reforming solid oxide fuel cell (IRSOFC)–gas turbine (GT) hybrid generation system was described in this paper. It fully reflected the concept of multi-level and hierarchical modeling. For SOFC, there are the general electrochemical model including both H2 and CO oxidation, the advanced electrochemical model considering surface diffusion and competition absorption, the mechanistic transport model and its approximate analytical solution. With a set of uniform governing equations for both planar and tubular SOFCs, description of flow and heat transfer in cell-level models provides the boundary conditions for the different types of electrode-level models. And the models with different complexity of other balancing components were also developed for different system requirements. Via the interface configuration and graphic specification in the commercial environment of gPROMS, it fully realized the flexible configuration and modular design for the different cases. By comparison with the experimental data of the Siemens–Westinghouse 220kW demonstration SOFC–GT hybrid generation system, our model library was validated with better performance than the advanced power system analysis tool (APSAT). And the simulation platform can be further used for the performance prediction, system optimization and controller design. [Copyright &y& Elsevier]

Abstract: In the present paper the finite element method for the solution of the eigenvalue problems for piezoelectric bodies with voids is considered. The porosity change properties are taken into account according to Cowin–Nunziato model. The vector–matrix formulations of the modal piezoelectric problems for media with voids are given. The finite element approximations of the continual equations are carried out and the finite dimensional eigenvalue problems are obtained in the expanded and in the various reduced forms. Algorithmic features of the boundary conditions account for electrode surfaces and the surfaces contacting with rigid stamps are discussed. The finite element eigenvalue problems for practically important electric resonance and antiresonance frequencies are obtained. As a numerical example the focusing spherical ultrasonic piezoelectric emitter fulfilled from porous piezoceramics is considered. With the use of Cowin–Nunziato model the effective moduli of the porous piezoceramic material are defined precisely. The results, which we obtain, show a good optimal agreement with the experimental data. The resonant frequency behavior modelling for free and loaded on acoustic media piezoelectric transducer is realized. [Copyright &y& Elsevier]

Abstract: A novel technique has been developed to fabricate uranium-ceramic nuclear fuel using the depleted uranium (DU), U3O8 powder, and allylhydridopolycarbosilane (AHPCS) polymer precursor. This process involves a continuous change of the composition, porosity, and material properties. To fabricate nuclear fuel with a uniform structure/volume ratio, it is important to understand the transport phenomena during high temperature processing and at different length scales. In our prior work, a system-level model based on the reactive porous medium theory was developed to account for pyrolysis process during the uranium-ceramic fuel fabrication. In this paper, a mesoscopic model based on the smoothed particle hydrodynamics (SPH) is developed to simulate the synthesis of filler U3O8 particles and SiC matrix. The system-level model provides the necessary thermal boundary conditions for the mesoscopic simulation. The evolution of the particle concentration and the structure as well as the composition of the composite produced is investigated. Since the process heat flux plays an important role in the material quality and uniformity, the effect of the heating rate, filler particle size and distribution on the uniformity and the structure of the final product are investigated. The uncertainty issue is also discussed. [Copyright &y& Elsevier]

Abstract: A diffused pneumatic silencer had been widely used in the pneumatic fields due to its small dimensions and high level of performance in noise reduction. A numerical simulation of its interior and exterior flow field was important for studying the gas flow in the silencer and the flow structure outside the silencer, as well as for understanding the mechanism of the silencer’s noise reduction. A porous media model and the Darcy–Forchheimer principle were used as the basic theoretical models in this paper. The unified governing equations were used here to describe the compressible flow in and out of the silencer. A robust numerical scheme was used to discritize the equations, and the TDBC (Time-dependent boundary conditions) was used to treat the non-reflecting boundaries. The detailed structures of the inner and outer flow fields of the diffused pneumatic silencer were obtained. The simulation results displayed the characteristics of the flow in the silencer. The nature of the flow outside the silencer, comparable with the experimental data, was also obtained. [Copyright &y& Elsevier]

Abstract: In this paper, we consider the multipoint boundary value problem for one-dimensional -Laplacian subject to the boundary conditions: where . Applying the fixed point theorem due to Avery and Peterson, we study the existence of at least three symmetric positive solutions to the above boundary value problem. The interesting point is that the nonlinear term contains the first-order derivative explicitly and the boundary condition is of Sturm–Liouville type. [Copyright &y& Elsevier]

Abstract: In this paper, two different 1D mechanistic models for the solidification of a pure substance are presented. The first model is based on the two-domain approach, resulting in 2 partial differential equations (PDEs) and one ordinary differential equation (ODE) with 2 boundary conditions, 2 interface conditions, and one initial condition: the Stefan problem. In the second model, the metal column is considered as one-domain, and one PDE is valid for the whole domain. The result is one PDE with two boundary conditions. The models are implemented in MATLAB, and the ODE solver ode23s is used for solving the systems of equations. The models are developed in order to simulate and control the dynamic response of the solidification rate. The control scheme is based on a linear PI controller. [Copyright &y& Elsevier]

Abstract: In the present paper, static and dynamical problems for linearly elastic shells in curvilinear coordinates are considered. Hierarchies of two-dimensional models for corresponding boundary and initial boundary value problems are constructed within the variational settings. The existence and uniqueness of solutions of the reduced problems are investigated in suitable spaces. Under the conditions of solvability of the original static or dynamical problem, convergence of the sequence of vector functions of three variables restored from the solutions of the constructed two-dimensional problems to the solution of the three-dimensional problem is proved and approximation error is estimated. [Copyright &y& Elsevier]