A two-dimensional model was developed to predict concentration profiles from passive, laminar mixing of concentration layers formed in a fractal-like merging channel network. Both flat and parabolic velocity profiles were used in the model. A physical experiment was used to confirm the results of the model. Concentration profiles were acquired in the channels using laser induced fluorescence. The degree of mixing was defined and used to quantify the mixing in the test section. Although the results of the experiment follow the trend predicted by the two-dimensional model, the model under predicts the results of the experiment. A three-dimensional CFD model of the flow field in the channel network was used to explain the discrepancies between the two-dimensional model and the experiment. For the channel network considered, the degree of mixing is a function of Peclet number. The effect of geometry on the degree of mixing is investigated using the two-dimensional model by varying the flow length, the width of the inlet channels, and the number of branching levels. A non-dimensional parameter is defined and used to predict an optimum number of branching levels to maximize mixing for a fixed inlet channel width, total length, and channel depth. / Graduation date: 2003

Described in this thesis is an investigation of the fully developed natural convection heat transfer in a vertical channel formed by two infinitely wide parallel plates maintained at a uniform wall temperature. Closed-form solutions for the velocity and temperature profiles are developed along with local and averaged Nusselt numbers. The local Nusselt number based on bulk temperature is found to be 3.77. This result is an analog corresponding to 7.60 for fully developed laminar forced convection in a parallel plate channel with uniform wall temperature boundary condition. The local Nusselt number based on the ambient temperature is deduced as a function of flowwise location. Results are compared with existing numerical and experimental data to find good agreement. / Graduation date: 1997

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In this thesis the critical parameters involved in the dislodgement and deformation of microbubbles in laminar channel flow, are determined and evaluated. Experimentally the effects of surface tension, viscosity, fluid flow rate, density, and bubble diameter on bubble dislodgement were evaluated. A theoretical scale analysis was performed which provided a general relationship between the parameters. Experimental results provided reasonable comparisons with values calculated from the scale analysis. Non-dimensional plots were generated of Weber number, at bubble dislodgement, versus Reynolds number and Weber number as a function of a non-dimensional bubble diameter. A calculated velocity detachment equation was also produced. This work is applicable to many areas of science and industry, particularly in the field of ink-jet printing. / Graduation date: 1992

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Emissions of oxides of nitrogen (NOx) from combustion devices is a topic of tremendous current importance. The bulk of the review of NOx emissions has been in the field of turbulent jet flames. However laminar jet flames have provided much insight into the relative importance of NOx reaction pathways in non premixed combustion for various flame conditions. The existing models include detailed chemistry kinetics for various species involved in the flame. These detailed models involve very complex integration of hundreds of chemical reactions of various species and their intermediates. Hence such models are highly time consuming and also normally involve heavy computational costs. This work proposes a numerical model to compute the total production of NOx in a non-premixed isolated circular laminar jet flame. The jet consists of the fuel rich inner region and the O2 rich outer region. The model estimates both thermal NOx and prompt NOx assuming single step kinetics for NOx formation and a thin flame model. Further the amount of air entrainment by jet depends upon the Sc number of fuel. The higher the Sc number, the higher is the air entrained which lowers the flame temperature and hence NOx formation. With increasing Sc number, flame volume increases which leads to an increase in the NOx formation. The effect of the Sc number variation on the net production of NOx and flame structure is also investigated. The effect of equilibrium chemistry for CO2 <-> CO + 1/2 O2 and H2O <-> H2 +1/2 O2 on total NOx emission is studied. Also the effect of both CO2 and H2O equilibrium is considered simultaneously and the net x NO formation for propane is 45 ppm. The split between pre-flame and post-flame regions is also investigated. For Propane, 96% of NO emissions occur in the pre-flame region and about 4% in the post-flame region. The model predictions are compared with experimental values of NOx missions reported elsewhere.

Darbe nagrinėtas skysčio tekėjimas laminariniame pasienio sluoksnyje. Skysčio tekėjimo greičio vektoriaus komponentės yra išreiškiamos tokiomis lygtimis v1 ir v2. Atsižvelgiant į hidrodinamikos dėsnius, prie šių lygčių yra pridedamos kraštinės sąlygos: v1=v2=0, kai x1≥0, x2=0, v1=U, kai x2→±∞. Gautas uždavinys buvo nagrinėtas matematiniu paketu MathCAD 13. Skaitiškai gauti rezultatai patvirtina teorines žinias apie skysčio tekėjimą laminariniame pasienio sluoksnyje. Iš darbe gautų grafikų galime daryti konkrečias išvadas apie sprendinio elgesį. / The laminar boundary layer flow of the incompressible liquid over semi – infinite flat plate is discussed. Components of the velocity vector are expressed in the form v1 and v2. In accordance with hydrodynamic laws the following boundary conditions are prescribed v1=v2=0, when x1≥0, x2=0, v1=U as x2→±∞. The problem was analyzed numerically using MathCAD 13. The obtained numerical results confirm the theoretical results about in laminar boundary layer flow of a viscous incompressible liquid. From the diagrams that are shown in the diploma work one can make certain specific conclusions about the behavior of the flow.

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