Modelling the Flow of Carbon Dioxide Through Beds of Cereal Grains

The insect population in grain stores can be kept under control by maintaining a high concentration of CO₂ gas (greater than 35%) throughout the grain bed. In this paper the initial phase of this process is considered, where the gas is introduced into the bed. The flow of CO₂ through the grain bulk is modelled as fluid flow in a porous medium and the effect of advection, dispersion, sorption and curvilinear isobars and streamlines are considered. An analytic solution to this problem is developed using perturbation expansions and the analysis is restricted to the dominant term in each expansion. In curvilinear flow, a useful variable is the traverse time; the time taken for the gas to travel from the inlet duct. It is shown that lines of constant traverse time are also lines of constant CO₂ concentration throughout the grain bed except in the narrow region called the front, where the concentration gradient is large. For most grain stores the isobars have a negative curvature and in these situations the front moves more slowly than in uniform flow and the width of the front increases more rapidly as it travels through the grain bed. It is shown that sorption has an effect on the CO₂ concentration in the air for some grains such as canola but not for others such as wheat.     

Evaluation of linear and nonlinear convection schemes on multidimensional non‐orthogonal grids with applications to KVLCC2 tanker

Almost all evaluations of convection schemes reported in the literature are conducted using simple problems on uniform orthogonal grids; thus, having limited contribution when solving industrial computational fluid dynamics (CFD), where the grids are usually non‐orthogonal with distortions. Herein, several convection schemes are assessed in uniform and distorted non‐orthogonal grids with emphasis on industrial applications. Linear and nonlinear (TVD) convection schemes are assessed on analytical benchmarks in both uniform and distorted grids. To evaluate the performance of the schemes, four error metrics are used: dissipation, phase and L₁ errors, and the schemes' effective order of accuracy. Qualitative and quantitative deterioration of these error metrics as a function of the grid distortion metrics are investigated, and rigorous verifications are performed. Recommendations for effective use of the convection schemes based on the range of grid aspect ratio (AR), expansion ratio (ER) and skewness (Q) are included. A ship hydrodynamics case is studied, involving a Reynolds averaged Navier–Stokes simulation of a bare‐hull KVLCC2 tanker using linear and nonlinear convection schemes coupled with isotropic and anisotropic Reynolds‐stress (ARS) turbulence models using CFDShip‐Iowa v4. Predictions of local velocities and turbulent quantities from the midships to the nominal wake plane are compared with experimental fluid dynamics (EFD), and rigorous verification and validation analyses for integral forces and moments are performed for 0° and 12° drift angles. Best predictions are observed when coupling a second‐order TVD scheme with the anisotropic turbulence model. Further improvements are observed in terms of prediction of the vortical structures for 30° drift when using TVD2S‐ARS coupled with DES. Copyright © 2009 John Wiley & Sons, Ltd.     

一种可用于分析任意介电常数张量的各向异性波导导模的二维时域有限差分模型

为分析具有任意介电常数张量的各向异性波导的导模，本文通过把简化的二维时域有限差分（２－ＤＦＤＴＤ）法扩展至任意各向异性介质，提出了一种以Ｄ、Ｅ和Ｈ场为基础的统一的简化２－ＤＦＤＴＤ模型．利用该模型，研究了简化的复数２－ＤＦＤＴＤ方法与实变数２－ＤＦＤＴＤ方法之间的关系．文中还讨论了复变数方法和实变数方法的激励技术．     

Extrapolation of the bilinear element approximation for the Poisson equation on anisotropic meshes

The bilinear finite element approximation for the Poisson equation has an asymptotic error expansion on the anisotropic rectangular meshes. Extrapolation can be obtained based on this expansion and the postprocessing interpolation. © 2007 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq 2007     

二阶问题Adini元的误差估计(英文)

The main aim of this paper is to have an accurate analysis on the famous Adini's element for the second order problems under to the anisotropic meshes.We firstly show that the interpolation of Adini's element satisfy the anisotropic property.Then the optimal error estimate is obtained without the regularity assumption on the meshes.     

FURTHER STUDIES ON STROH-TYPE FORMALISMS FOR ANISOTROPIC PLATES WITH BENDING-EXTENSION COUPLING

Stroh-type formalisms for anisotropic thin plates in literature are reviewed and dis- cussed,and two kinds of hybrid Stroh-type formalisms are compared.It is seen that the two Stroh- type formalisms are essentially equivalent.With simple transfer relations,they can be expressed each other.In addition,with properly defined notation systems,the two Stroh-type formalisms can also be written in unified forms,which will be convenient in applications.     

Directions of Coaxiality between Pure Strain and Stress in Linear Elasticity

For a linear anisotropic hyperelastic body subjected to a state of pure strain it is shown that there are at least three directions such that the stress and strain tensors are coaxial.     

Boundary Mobility and Energy Anisotropy Effects on Microstructural Evolution During Grain Growth

We have performed mesoscopic simulations of microstructural evolution during curvature driven grain growth in two-dimensions using anisotropic grain boundary properties obtained from atomistic simulations. Molecular dynamics simulations were employed to determine the energies and mobilities of grain boundaries as a function of boundary misorientation. The mesoscopic simulations were performed both with the Monte Carlo Potts model and the phase field model. The Monte Carlo Potts model and phase field model simulation predictions are in excellent agreement. While the atomistic simulations demonstrate strong anisotropies in both the boundary energy and mobility, both types of microstructural evolution simulations demonstrate that anisotropy in boundary mobility plays little role in the stochastic evolution of the microstructure (other than perhaps setting the overall rate of the evolution. On the other hand, anisotropy in the grain boundary energy strongly modifies both the topology of the polycrystalline microstructure the kinetic law that describes the temporal evolution of the mean grain size. The underlying reasons behind the strongly differing effects of the two types of anisotropy considered here can be understood based largely on geometric and topological arguments.