Experimental investigation of an axisymmetric, impinging turbulent jet. 2. Scalar field

In this, the second part of a two-part study of an impinging air jet, measurements of mean and rms concentrations and concentration probability density functions obtained using a Mie scattering technique are reported. Results in the wall jet are in good agreement with earlier data obtained using laser Raman spectroscopy, although differences in the spreading rate of the wall jet do occur, most likely due to buoyancy. The data demonstrate the influence of the recirculation zone, identified in the first part of the study, on the mixing field in causing low levels of jet fluid to persist to large distances from the surface. This finding has important consequences for many mass transfer applications of impinging jets.     

Turbulence enhancement of stagnation point heat transfer on a body of revolution

Enhancement, by free stream turbulence, of convective heat transfer to the stagnation region of a hemispherical-nosed cylinder has been studied. Increases in heat transfer were found to depend primarily on the Reynolds number and turbulence intensity of the free stream, experimental results being most successfully correlated on a NuRe^?0.5 versus TuRe^0.5 basis. Flow visualization studies have demonstrated the validity of a phenomenological model of the enhancement process, predictions of this theory showing good agreement with experimental results. The effect of free stream turbulence on the stagnation point velocity gradient has also been evaluated.     

Almost block diagonal linear systems: sequential and parallel solution techniques,and applications

Almost block diagonal (ABD) linear systems arise in a variety of contexts, specifically in numerical methods for two‐point boundary value problems for ordinary differential equations and in related partial differential equation problems. The stable, efficient sequential solution of ABDs has received much attention over the last fifteen years and the parallel solution more recently. We survey the fields of application with emphasis on how ABDs and bordered ABDs (BABDs) arise. We outline most known direct solution techniques, both sequential and parallel, and discuss the comparative efficiency of the parallel methods. Finally, we examine parallel iterative methods for solving BABD systems. Copyright © 2000 John Wiley & Sons, Ltd.     

Effect of Shape on Inertial Particle Dynamics in a Channel Flow

Particle dynamics in a channel flow are investigated using large eddy simulation and a Lagrangian particle tracking technique. Following validation of single-phase flow predictions against DNS results, fluid velocities are subsequently used to study the behaviour of particles of differing shape assuming one-way coupling between the fluid and the particles. The influence of shape- and orientation-dependent drag and lift forces on both the translational and rotational motion of the particles is accounted for to ensure accurate representation of the flow dynamics of non-spherical particles. The size of the particles studied was obtained based on an equivalent-volume sphere, and differing shapes were modelled using super-quadratic ellipsoid forms by varying their aspect ratio, with their orientation predicted using the incidence angle between the particle relative velocity and the particle principal axis. Results are presented for spherical, needle- and platelet-like particles at a number of different boundary layer locations along the wall-normal direction within the channel. The time evolution and probability density function of selected particle translational and rotational properties show a clear distinction between the behaviour of the various particles types, and indicate the significance of particle shape when modelling many practically relevant flows.     

Synthesis of the cyclic heptapeptide axinellin A

The first synthesis of the naturally occurring cyclic peptide axinellin A has been achieved. Cyclization and subsequent deprotection of linear precursors containing either a t-butyl protected Thr residue or a Thr(Ψ^Me,Mepro) derivative gave a cyclic peptide, identical in all respects to the naturally occurring material, with the exception that the synthetic peptide does not exhibit the cytotoxic activity reported for the natural product.     

The method of fundamental solutions for elliptic boundary value problems

The aim of this paper is to describe the development of the method of fundamental solutions (MFS) and related methods over the last three decades. Several applications of MFS-type methods are presented. Techniques by which such methods are extended to certain classes of non-trivial problems and adapted for the solution of inhomogeneous problems are also outlined. This revised version was published online in June 2006 with corrections to the Cover Date.     

漫谈有效数字和计算器

介绍了有效数字的概念及其计算规则,介绍了计算器的一般特性及使用技巧,并给出计算实例.     

Lattice approaches to packed column simulations

This work presents a review of the findings into the ability of a digitally based particle packing algorithm, called DigiPac, to predict bed structure in a variety of packed columns, for a range of generic pellet shapes frequently used in the chemical and process engineering industries. Resulting macroscopic properties are compared with experimental data derived from both invasive and non-destructive measurement techniques. Additionally, fluid velocity distributions, through samples of the resulting bed structures, are analysed using lattice Boltzmann method （LBM） simulations and are compared against experimental data from the literature.     

A matrix decomposition MFS algorithm for axisymmetric biharmonic problems

We consider the approximate solution of axisymmetric biharmonic problems using a boundary-type meshless method, the Method of Fundamental Solutions (MFS) with fixed singularities and boundary collocation. For such problems, the coefficient matrix of the linear system defining the approximate solution has a block circulant structure. This structure is exploited to formulate a matrix decomposition method employing fast Fourier transforms for the efficient solution of the system. The results of several numerical examples are presented. AMS subject classification 65N38, 65F30, 65T50, 65Y99