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Effects of the method of identification of the diffusion coefficient on accuracy of modeling bound water transfer in wood 总被引:2,自引:0,他引:2
An alternative approach to determining the bound water diffusion coefficient is proposed. It comprises a method for solving
the inverse diffusion problem, an improved algorithm for the bound-constrained optimization as well as an alternative submodel
for the diffusion coefficient’s dependency on the bound water content. Identification of the diffusion coefficient for Scots
pine wood (Pinus sylvestris L.) using the proposed inverse approach is presented. The accuracy of predicting the diffusion process with the use of the
coefficient values determined by traditional sorption methods as well as by the inverse modeling approach is quantified. The
similarity approach is used and the local and global relative errors are calculated. The results show that the inverse method
provides valuable data on the bound water diffusion coefficient as well as on the boundary condition. The results of the identification
can significantly improve the accuracy of mass transfer modeling as studied for drying processes in wood. 相似文献
3.
The flow of non-Newtonian fluids through two-dimensional porous media is analyzed at the pore scale using the smoothed particle
hydrodynamics (SPH) method. A fully explicit projection method is used to simulate incompressible flow. This study focuses
on a shear-thinning power-law model (n < 1), though the method is sufficiently general to include other stress-shear rate relationships. The capabilities of the
proposed method are demonstrated by analyzing a Poiseuille problem at low Reynolds numbers. Two test cases are also solved
to evaluate validity of Darcy’s law for power-law fluids and to investigate the effect of anisotropy at the pore scale. Results
show that the proposed algorithm can accurately simulate non-Newtonian fluid flows in porous media. 相似文献
4.
In this chapter of the special issue of the journal “Transport in Porous Media,” on the topic “Flow and transport above permeable
domains,” we present modeling of flow and transport above permeable domains using the homogenization method. Our goal is to
develop a heuristic approach which can be used by the engineering community for treating this type of problems and which has
a solid mathematical background. The rigorous mathematical justification of the presented results is given in the corresponding
articles of the authors. The plan is as follows: We start with the section “Introduction” where we give an overview and comparison
with interface conditions obtained using other approaches. In Sect. 2, we give a very short derivation of the Darcy law by
homogenization, using the two-scale expansion in the typical pore size parameter ε. It gives us the definition of various auxiliary functions and typical effective properties as permeability. In Sect. 3,
we introduce our approach to the effective interface laws on a simple 1D example. The approximation is obtained heuristically
using the two steps strategy. For the 1D problem we calculate the approximation and the effective interface law explicitly
and show that it is valid at order O(ε
2). Next, in Sect. 4 we give a derivation of the Beavers–Joseph–Saffman interface condition and of the pressure jump condition,
using homogenization. We construct the corresponding boundary layer and present a heuristic calculation, leading to the interface
law and being based on the rigorous mathematical result. In addition, we show the invariance of the law with respect to the
small variations in the choice of the interface position. Finally, there is a short concluding section.
The research of A.M. was partially supported by the GDR MOMAS (Modélisation Mathématique et Simulations numériques liées aux
problèmes de gestion des déchets nucléaires) (PACEN/CNRS, ANDRA, BRGM, CEA, EDF, IRSN). 相似文献
5.
The paper investigates transverse vibration of a thin annular plate clamped at its inner edge to a rigid shaft, while its
outer edge is clamped to a rigid cylinder. The shaft and the outer edge of the plate are loaded by torques of the same intensity,
but of opposite directions. The whole structure rotates at a constant angular speed. The solution has been determined using
Galerkin’s method. The obtained results illustrate the impact of the torque, angular speed and inner and outer radia ratio
to transverse asymmetric vibration frequency of the plate. Stability of the plate has been examined and critical values of
angular speed and torque leading to the loss of stability of the plate have been determined. Some mode shapes have been drawn
and the influence of torque and angular speed on nodal lines has been shown. 相似文献
6.
In Part I Moyne and Murad [Transport in Porous Media 62, (2006), 333–380] a two-scale model of coupled electro-chemo-mechanical phenomena in swelling porous media was derived by
a formal asymptotic homogenization analysis. The microscopic portrait of the model consists of a two-phase system composed
of an electrolyte solution and colloidal clay particles. The movement of the liquid at the microscale is ruled by the modified
Stokes problem; the advection, diffusion and electro-migration of monovalent ions Na+ and Cl− are governed by the Nernst–Planck equations and the local electric potential distribution is dictated by the Poisson problem.
The microscopic governing equations in the fluid domain are coupled with the elasticity problem for the clay particles through
boundary conditions on the solid–fluid interface. The up-scaling procedure led to a macroscopic model based on Onsager’s reciprocity
relations coupled with a modified form of Terzaghi’s effective stress principle including an additional swelling stress component.
A notable consequence of the two-scale framework are the new closure problems derived for the macroscopic electro-chemo-mechanical
parameters. Such local representation bridge the gap between the macroscopic Thermodynamics of Irreversible Processes and
microscopic Electro-Hydrodynamics by establishing a direct correlation between the magnitude of the effective properties and
the electrical double layer potential, whose local distribution is governed by a microscale Poisson–Boltzmann equation. The
purpose of this paper is to validate computationally the two-scale model and to introduce new concepts inherent to the problem
considering a particular form of microstructure wherein the clay fabric is composed of parallel particles of face-to-face
contact. By discretizing the local Poisson–Boltzmann equation and solving numerically the closure problems, the constitutive
behavior of the diffusion coefficients of cations and anions, chemico-osmotic and electro-osmotic conductivities in Darcy’s
law, Onsager’s parameters, swelling pressure, electro-chemical compressibility, surface tension, primary/secondary electroviscous
effects and the reflection coefficient are computed for a range particle distances and sat concentrations. 相似文献