摘要:

Coupled transport of multicomponent solutes in globally continuous systems is considered in the framework of the Generalized Taylor dispersion theory. Coupling between transports of n different species at the local (or micro-) scale, is considered to result from first-order irreversible surface reactions occurring on the local space boundaries, or from the off-diagonal terms of the solute diffusivity matrices.

ISSN:0098-6445    

DOI:10.1080/00986449608936515

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

This article discusses the mechanisms of a photolytic reaction, the formation of formaldehyde in the earth's prebiotic atmosphere, and the synthesis of methanol by processing the stoichiometric matrices of their sets of elementary mechanistic steps by a computer program. For methanol synthesis, we will distinguish between unidirectional and reversible elementary mechanistic steps. These problems will be discussed in conjunction with a description of the structure of a program, CatKin, written in FORTRAN, that we have developed to compute reaction mechanisms and King-Altman-Hill's steady-state fluxes of reaction paths.

ISSN:0098-6445    

DOI:10.1080/00986449608936516

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

A previously presented analytical method for determining the Stokes drag on a disk sedimenting in the presence of fixed boundaries (Davis, 1990) is adapted to the case of a disk translating broadside in a rotating fluid, possibly with relative rotation. By carefully simplifying the potentially lengthy algebra, concise formulations are again developed for the cases of two disks translating together with opposite relative rotations, a disk translating towards a rigid plane that rotates with the fluid and a disk translating within a similarly rotating concentric circular container. Flows that are asymmetric allow the possibility of adjusting the relative rotation so that the disk is torque free. Values of the Taylor number, based on the disk radius, up to 50 are considered.

ISSN:0098-6445    

DOI:10.1080/00986449608936517

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

An integral identity developed by Brenner (1964) is used in the “reversed” context to derive a fixed point iterative scheme for the surface tractions on a rigid particle of arbitrary shape submerged in Stokes flows. The iterative approach facilitates the solution of very large systems of equations and thus the employment of high resolution discretization schemes. The utility of the approach is demonstrated by illustrative computations of the tractions on regular polyhedra, with special emphasis on the results near the edges and corners where (integrable) singular behavior is expected to provide a stringent test for the numerical method. Excellent agreement between our numerical estimates for the exponent of these singularities with the analytical result (local 2-D analysis) were obtained. The emphasis in this work is on validation of the approach, but references to applications, such as fluidic self-assembly of semiconductor microstructures, are provided.

ISSN:0098-6445    

DOI:10.1080/00986449608936518

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

The flow of a quasi Newtonian model fluid, which allows shear thinning as well as extension thickening, through a sudden planar 4:1 contraction is studied numerically. Comparing with numerical results for a purely shear thinning fluid differences show up which follow the trend of experimental data.

ISSN:0098-6445    

DOI:10.1080/00986449608936519

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

It is shown how very general multi-phase models with a single, well-mixed reactive phase can be reduced to the simple model of a stirred tank.

ISSN:0098-6445    

DOI:10.1080/00986449608936520

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

General solutions to the Stokes equations for a sphere held fixed in a general quadratic flow are used to develop the hydrodynamic effects of a thin layer of material at the surface which has different rheological properties than the solution. These surface-layer effects are developed as an expansion toO(λ2) where λ is the ratio of the length scale of the surface layer (δ) to the particle radius (R). The formalism is developed such that the force, couple and stresslet on the coated sphere are calculated directly by substituting a rheological model for the surface layer into an analysis based on unidirectional flow; thus, the hydrodynamic effects toO(λ2) can be determined without solving the Stokes equations outside the layer. TheO(λ2) effect is independent of the type of flow (translation, rotation, extension) in the sense that a single parameter A, which depends only on the properties of the surface layer, applies to all flow types. However, theO(λ2) effects depend both on the properties of the surface layer and the type of flow about the particle. Examples are presented as models for particles in solutions of nonadsorbing and adsorbing polymers. In the case of an adsorbing polymer whose layer is modeled by the Brinkman equation, theO(λ2) effects can be computed from the lowest order description of velocity field, that is, viscous flow past a flat surface. The hydrodynamic interactions between two particles and between a particle and a solid boundary are developed by a method of reflections accounting for the presence of the surface layers on the particles.

ISSN:0098-6445    

DOI:10.1080/00986449608936521

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

Using empirical data for the effective migration velocity, the Deutsch-Anderson equation has been widely used for calculation of the total collection efficiency and design of electrostatic precipitators (ESPs). Based on a normal particle size distribution, the present paper develops a semi-empirical equation for the total collection efficiency of ESPs. The equation is then simplified and extended to other particle size distributions. The simplified equation shows that the total collection efficiency increases with increasing mass median diameter of particles and with increasing electrical field strengths. The effective migration velocity is found to be directly proportional to the mass median diameter and to the electrical field strengths for particle charging and collection. Moreover, an example is given to illustrate how to use the present simplified model in the design of ESPs.

ISSN:0098-6445    

DOI:10.1080/00986449608936522

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

A concise analytic method is developed to investigate the arbitrary motion of a circular disk through an unbounded fluid satisfying Stokes equation. Four elementary motions are considered within the same mathematical framework: broadside translation, edgewise translation, in-plane rotation and out-of-plane rotation of a disk. Stokes equations are reduced to a set of dual integral expressions relating the velocity and traction in the plane of the disk. The dual integral equations are solved exactly for each motion and lead, in turn, to closed-form analytical expressions for the velocity and pressure fields. Although many of these results have been previously reported, the approach described here unifies the analysis of the four different motions and presents a straightforward solution technique.

ISSN:0098-6445    

DOI:10.1080/00986449608936523

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

The application of boundary integral techniques to the study of mixing of viscous fluids is presented. Single Layer and Double Layer Representations for Stokes flows in bounded domains are formulated and numerical examples of mixing in selected geometrically-challenging two and three-dimensional problems are illustrated. Emphasis is given to the analysis of errors encountered in the point evaluation of the velocity field and the calculation of subsequent trajectories in time-perodic flows. It is shown that even though individual particle paths are sensitive to the accumulation of discretization errors, mixing templates can be calculated with reasonable accuracy. A simple error control formula is used that enables a systematic application of boundary integral methods to compute mixing patterns in time-periodic (chaotic) Stokes flows.

ISSN:0098-6445    

DOI:10.1080/00986449608936524

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor