Laminar flow of a reacting gaseous mixture through a vertical duct with catalytic walls

Numerical analysis has been performed for predicting the onset and establishment of a steady state flow of a reactive hydrogen/air/vapour mixture through a two-dimensional vertical duct of finite length with its side walls coated by catalytic material. The flow is initiated by the exothermic reaction of hydrogen with air oxygen on the catalytic wall, that causes the hot gases to flow upwards through the vertical duct and by continuity sucks fresh mixture through the lower end of the duct. The flow is always laminar and the two-dimensional governing transport differential equations are solved by means of the numerical finite volume method, using a collocated variable arrangement. Comparisons between calculated and experimental data are presented, showing good agreement between them. The method is employed for various initial mixture compositions and duct geometries.     

Numerical simulation of the three-dimensional micro-scale dispersion of air-pollutants in regions with complex topography

 A computational method for predicting the dispersion of gaseous emissions in regions with complex topography is presented. Different meteorological conditions, source data, and gas compositions and specific weights are taken into consideration. The three-dimensional governing equations of fluid- and thermodynamics are numerically solved by means of the finite volume method. The kɛ turbulence model is utilized to account for the turbulent nature of the flow. The numerical results obtained by the proposed method show satisfactory agreement with both results obtained by other numerical methods and experimental and/or measured data. The presented method is applied to four test cases, including steady and unsteady problems, in order to illustrate its usefulness. Received on 1 March 2001     

Measuring the Student Group Capacity for Obtaining Geometric Information in the van Hiele Developmental Thought Process：A Fuzzy Approach

1　 IntroductionThe van Hiele level theory of geometric reasoning[1,5,9] describes the ways of studentreasoning inEuclidean geometry.The ontogeny of thiscognitive activity of mental developmentis characterised byfive hierarchical and qualitatively differe…