Many operations that need to be performed in modern finiteelement codes can be described as an operation that needs to be done independently on every cell, followed by a reduction of these local results into a global...
详细信息
Many operations that need to be performed in modern finiteelement codes can be described as an operation that needs to be done independently on every cell, followed by a reduction of these local results into a global data structure. For example, matrix assembly, estimating discretization errors, or converting nodal values into data structures that can be output in visualization file formats all fall into this class of operations. Using this realization, we identify a software design pattern that we call WorkStream and that can be used to model such operations and enables the use of multicore shared memory parallel processing. We also describe in detail how this design pattern can be efficiently implemented, and we provide numerical scalability results from its use in the DEAL. II software library.
It is difficult to represent properties of agro-food and forest products in mathematical models to simulate heat and water transport processes. Geometry of such products is complex, material structure is non-homogeneo...
详细信息
ISBN:
(纸本)9788021323889
It is difficult to represent properties of agro-food and forest products in mathematical models to simulate heat and water transport processes. Geometry of such products is complex, material structure is non-homogeneous and anisotropic, and properties vary with temperature and moisture content. Heat and water transport processes affect the end-use quality of agro-food and forest products, so it is important to support design and management of advanced systems of processing and storage of such products with mathematical modelling and computer predictions. In the paper an integrated computer-aided approach to estimate geometric and physical properties of agro-food and forest products was developed. The method was effective and it resulted in more accurate predictions of heat and water transport processes in investigated products.
In this paper finiteelement approaches for fretting fatigue are proposed on the basis of a non-local model of continuum damage coupled to friction and wear. The model is formulated in the frame-work of a standard mat...
详细信息
In this paper finiteelement approaches for fretting fatigue are proposed on the basis of a non-local model of continuum damage coupled to friction and wear. The model is formulated in the frame-work of a standard material. In a previous paper this was done in the spirit of Maugin, where an extra entropy flux is introduced in the second law in order to include the gradient of the internal variable in a proper manner. In this paper we follow instead the ideas of Fremond and others, where this extra entropy flux is no longer needed, but instead new non-classical balance laws associated to damage, friction and wear, respectively, are derived from the principle of virtual power. The standard material is then defined as usual by state laws based on free energies and complementary laws based on dissipation potentials. In particular, we pick free energies and dissipation potentials that correspond to a non-local continuum damage model coupled to friction and wear. In addition, the boundary conditions at the contact interface creates a coupling between damage and wear. This is a key feature of our model, which makes it very useful in studies of fretting fatigue. By starting from a variational formulation of the governing equations, two different finite element algorithms are implemented. Both algorithms are based on a Newton method for semi-smooth equations. In the first algorithm the Newton method is applied to the entire system of equations, while in the second algorithm the system of equations is split into two different parts such that an elastic wear problem is solved for fixed damage followed by the solution of the damage evolution problem for the updated displacements and contact forces in an iterative process. The latter algorithm can be viewed as a Gauss-Seidel scheme. The numerical performance of the algorithms is investigated for three two-dimensional examples of increasing complexity. Based on the numerical solutions, the behavior of the model is also discussed.
The velocity-vorticity formulation is selected to develop a time-accurate CFD finiteelement algorithm for the incompressible Navier-Stokes equations in three dimensions. The finiteelement implementation uses equal o...
详细信息
The velocity-vorticity formulation is selected to develop a time-accurate CFD finiteelement algorithm for the incompressible Navier-Stokes equations in three dimensions. The finiteelement implementation uses equal order trilinear finiteelements on a non-staggered hexahedral mesh. A second order vorticity kinematic boundary condition is derived for the no slip wall boundary condition which also enforces the incompressibility constraint. A biconjugate gradient stabilized (BiCGSTAB) sparse iterative solver is utilized to solve the fully coupled system of equations as a Newton algorithm. The solver yields an efficient parallel solution algorithm on distributed-memory machines, such as the IBM SP2. Three dimensional laminar flow solutions for a square channel. a lid-driven cavity, and a thermal cavity are established and compared with available benchmark solutions. Copyright 0 2002 John Wiley Sons, Ltd.
A characteristic finiteelement (CFE) algorithm for modelling contaminant transport problems coupled with non-linear competitive adsorption is presented. An alternative algorithm, termed as the transport-equilibrium P...
详细信息
A characteristic finiteelement (CFE) algorithm for modelling contaminant transport problems coupled with non-linear competitive adsorption is presented. An alternative algorithm, termed as the transport-equilibrium Petrov-Galerkin (TEPG) methods in this paper, is also presented for comparison. Through analyses of a number of examples with Peclet number ranging from zero to infinity, it is shown that the CFE algorithm is very competitive with the middle-point TEPG method in terms of accuracy, stability and efficiency. The fully explicit and fully implicit TEPG methods are found to be less appropriate for transport problems coupled with non-linear equilibrium equations. Copyright (C) 2000 John Wiley & Sons, Ltd.
The disturbed state concept (DSC) provides a unified approach for constitutive modelling of engineering materials including such factors as elastic, plastic and creep strains, microcracking, damage and softening, and ...
详细信息
The disturbed state concept (DSC) provides a unified approach for constitutive modelling of engineering materials including such factors as elastic, plastic and creep strains, microcracking, damage and softening, and stiffening responses. The interacting mechanisms in the material mixture composed of the relative intact and fully adjusted states provide implicitly for various factors such as microcrack interaction and characteristic dimension. The DSC model can allow for well-posedness, reduction or elimination of spurious mesh dependence and localization. A number of problems are solved to illustrate convergence and uniqueness of the finiteelement procedures, localization, spurious mesh dependence, and validation with respect to observed behavior of simulated and practical problems. (C) 1997 by John Wiley & Sons, Ltd.
暂无评论