Wettability determination by contact angle measurements: hvbB coal-water system with injection of synthetic flue gas and CO2.
ABSTRACT Geological sequestration of pure carbon dioxide (CO(2)) in coal is one of the methods to sequester CO(2). In addition, injection of CO(2) or flue gas into coal enhances coal bed methane production (ECBM). The success of this combined process depends strongly on the wetting behavior of the coal, which is function of coal rank, ash content, heterogeneity of the coal surface, pressure, temperature and composition of the gas. The wetting behavior can be evaluated from the contact angle of a gas bubble, CO(2) or flue gas, on a coal surface. In this study, contact angles of a synthetic flue gas, i.e. a 80/20 (mol%) N(2)/CO(2) mixture, and pure CO(2) on a Warndt Luisenthal (WL) coal have been determined using a modified pendant drop cell in a pressure range from atmospheric to 16 MPa and a constant temperature of 318 K. It was found that the contact angles of flue gas on WL coal were generally smaller than those of CO(2). The contact angle of CO(2) changes from water-wet to gas-wet by increasing pressure above 8.5 MPa while the one for the flue gas changes from water-wet to intermediate-wet by increasing pressure above 10 MPa.
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ABSTRACT: Element Free Galerkin (EFG) methods are methods for solving partial differential equations with the help of shape functions coming from Moving Least Squares Approximation. The EFG-method is more flexible than the Finite Element (FE) method, since it requires only nodal data and no element connectivity is needed. Because the EFG-method is computationally expensive, combinations of the EFG-method and the FE-method are considered. Implementations based on several weak forms of the problem description are studied. Numerical examples in elastostatics and fracture mechanics show that the implementations are able to compute both displacement and stress fields accurately.Computer Methods in Applied Mechanics and Engineering 01/1996; · 2.62 Impact Factor
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ABSTRACT: . Inner products of wavelets and their derivatives are presently known as connection coefficients. The numerical calculation of inner products of periodized Daubechies wavelets and their derivatives is reviewed, with the aim at providing potential users of the publicly-available numerical scheme, details of its operation. The numerical scheme for the calculation of connection coefficients is evaluated in the context of approximating differential operators, information which is useful in the solution of partial differential equations using wavelet-Galerkin techniques. Specific details of the periodization of inner products in the solution differential equations are included in the presentation. . Introduction Wavelets have found a well-deserved niche in such areas of applied mathematics and engineering as approximation theory, signal analysis, and projection techniques for the solution of differential equations. While wavelets are not conceptually new   , the past fifteen...International Journal for Numerical Methods in Engineering 06/2000; · 2.06 Impact Factor
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ABSTRACT: This paper develops a class of finite elements for compactly supported, shift-invariant functions that satisfy a dyadic refinement equation. Commonly referred to as wavelets, these basis functions have been shown to be remarkably well-suited for integral operator compression, but somewhat more difficult to employ for the representation of arbitrary boundary conditions in the solution of partial differential equations. The current paper extends recent results for treating periodized partial differential equations on unbounded domains in R n, and enables the solution of Neumann and Dirichlet variational boundary value problems on a class of bounded domains. Tensor product, wavelet-based finite elements are constructed. The construction of the wavelet-based finite elements is achieved by employing the solution of an algebraic eigenvalue problem derived from the dyadic refinement equation characterizing the wavelet, from normalization conditions arising from moment equations satisfied by the wavelet, and from dyadic refinement relations satisfied by the elemental domain. The resulting finite elements can be viewed as generalizations of the connection coefficients employed in the wavelet expansion of periodic differential operators. While the construction carried out in this paper considers only the orthonormal wavelet system derived by Daubechies, the technique is equally applicable for the generation of tensor product elements derived from Coifman wavelets, or any other orthonormal compactly supported wavelet system with polynomial reproducing properties.Computational Mechanics 06/1995; 16(4):235-244. · 2.43 Impact Factor