The Development of the Asymptotic Viscous Dissipation Profile in a Vertical Free Convective Boundary Layer Flow in a Porous Medium

The effect of viscous dissipation on the development of the boundary layer flow from a cold vertical surface embedded in a Darcian porous medium is investigated. It is found that the flow evolves gradually from the classical Cheng–Minkowycz form to the recently discovered asymptotic dissipation profile which is a parallel flow.     

On the polarizability of a pair of cylinders in a transverse electric field

A sequential scheme for calculating the polarizability of a pair of parallel cylinders with an arbitrary (but fairly symmetric) form is suggested. An infinite set of algebraic equations is derived for coefficients involved in an expression for the potential. The numerical solution of this set makes it possible to find the polarizability with any degree of accuracy. This method is unrelated to the cylinder shape. The electrostatic properties of the cylinders are described in terms of the multipolar polarizability matrix.     

Crystal and Molecular Structure of <Emphasis Type="Italic">Bis</Emphasis>(2,3-pentamethylene-3,4-dihydro-4-oxoquinazolinium) Tetrachlorocuprate(II) Sesquihydrate

The structure of bis-(2,3-pentamethylene-3,4-dihydro-4-oxoquinazolinium) tetrachlorocuprate (II) sesquihydrate, (C₁₃H₁₅N₂O)₂[CuCl₄]·1.5H₂O, was determined by single crystal X-ray diffraction. In contrast to the previously studied analogs, the compound contains crystallization water molecules.Original Russian Text Copyright © 2004 by K. K. Turgunov, B. Tashkhodzhaev, L. V. Molchanov, and Kh. M. Shakhidoyatov__________Translated from Zhurnal Strukturnoi Khimii, Vol. 45, No. 5, pp. 955–959, September–October, 2004.     

Catalysis by ionic liquid: a simple, green and efficient procedure for the Michael addition of thiols and thiophosphate to conjugated alkenes in ionic liquid, [pmIm]Br

A room temperature ionic liquid, 1-pentyl-3-methylimidazolium bromide, [pmIm]Br efficiently catalyzes Michael addition of thiols and diethyl dithiophosphate to a variety of conjugated alkenes such as α,β-unsaturated carbonyl compounds, carboxylic esters, nitriles and chalcones without requiring any other organic solvent and catalyst. The ionic liquid can be recycled for subsequent reactions without any appreciable loss of efficiency.     

A numerical and experimental investigation of the interactions between a non‐uniform planar array of incompressible free jets

The interaction between multiple incompressible air jets has been studied numerically and experimentally. The numerical predictions have been first validated using experimental data for a single jet configuration. The spreading features of five unequal jets in the configuration of one larger central jet surrounded by four smaller equi‐distant jets, have been studied, for different lateral spacing ratios of 1.5, 2.0 and 2.5 and a central jet Reynolds number of 1.24×105 (corresponding to a Mach number of 0.16). Flow of five equal jets has also been simulated, for the sake of comparison. The jet interactions commence at an axial distance of about 3–4 diameters and complete by an axial distance of about 10 diameters for the lowest spacing ratio of 1.5. For larger spacing ratios, the length required for the start and completion of jet interaction increase. Peripheral jets bend more towards the central jet and merge at a smaller distance, when their sizes are smaller than that of the central jet. The entrainment ratio for multiple jets is higher than that for a single jet. Excellent agreement is observed between the experimental data and theoretical predictions for both mean flow field and turbulent quantities, at regions away from the jet inlet. The potential core length and initial jet development, however, are not predicted very accurately due to differences in the assumed and actual velocity profiles at the jet inlet. Copyright © 2004 John Wiley & Sons, Ltd.     

Assessment of two‐equation turbulence modelling for high Reynolds number hydrofoil flows

This paper presents an evaluation of the capability of turbulence models available in the commercial CFD code FLUENT 6.0 for their application to hydrofoil turbulent boundary layer separation flow at high Reynolds numbers. Four widely applied two‐equation RANS turbulence models were assessed through comparison with experimental data at Reynolds numbers of 8.284×106 and 1.657×107. They were the standard k–εmodel, the realizable k–εmodel, the standard k–ωmodel and the shear‐stress‐transport (SST) k–ωmodel. It has found that the realizable k–εturbulence model used with enhanced wall functions and near‐wall modelling techniques, consistently provides superior performance in predicting the flow characteristics around the hydrofoil. Copyright © 2004 John Wiley & Sons, Ltd.     

Robust handling of non‐linear constraints for GA optimization of aerodynamic shapes

A new approach to the robust handling of non‐linear constraints for GAs (genetic algorithms) optimization is proposed. A specific feature of the approach consists of the change in the conventional search strategy by employing search paths which pass through both feasible and infeasible points (contrary to the traditional approach where only feasible points may be included in a path). The method (driven by full Navier–Stokes computations) was applied to the problem of multiobjective optimization of aerodynamic shapes subject to various geometrical and aerodynamic constraints. The results demonstrated that the method retains high robustness of conventional GAs while keeping CFD computational volume to an acceptable level, which allowed the algorithm to be used in a demanding engineering environment. Copyright © 2004 John Wiley & Sons, Ltd.