CoordenaÃÃo de AperfeiÃoamento de Pessoal de NÃvel Superior / Realizou-se o levantamento de curvas de eficiÃncia utilizando odelos numÃricos RANS de uma e duas equaÃÃes para um erogerador com 3m de diÃmetro, utilizando pÃs projetadas para operar em diferentes condiÃÃes de λ com perfis NACA 0012, 4412 e 6412. A parametrizaÃÃo da geometria da malha para a dimensÃo do rotor, juntamente com a parametrizaÃÃo do refinamento frente à capacidade dos modelos RANS obteve a independÃncia da malha à soluÃÃo. Posteriormente a anÃlise numÃrica realizou a comparaÃÃo do melhor resultado â pà projetada λ=6 com o perfil NACA 6412 â com dados experimentais. O aparato experimental foi capaz de coletar dados de rotaÃÃo e torque do rotor simultaneamente com a mediÃÃo da velocidade do vento, no qual foi obtido um valor mÃximo de eficiÃncia de aproximadamente 25% e uma faixa de operaÃÃo limitada a λ=6. Conclui-se que os modelos fornecem boa precisÃo em predizer a faixa operacional de λ, no entanto os valores de Cp foram subestimados. O modelo k-ω SST apresentou o melhor resultados dentre todos. / A survey was conducted, consisting of efficiency curves applying RANS turbulence numerical models of one and two equations for a wind turbine with a diameter of 3m, using blades designed to operate under different λ with NACA 0012, 4412 and 6412 profiles. The parameterization of the mesh geometry to the size of the rotor, together with the parameterization of the refinement level compared to the ability of RANS models reached independence from the grid to the solution. Later, a numerical analysis was performed to compare the best result â a blade designed to operate under λ = 6 with the NACA 6412 profile - against experimental data. The experimental apparatus was able to collect data rotation and torque of the rotor simultaneously with the measurement of wind velocity, which obtained a maximum efficiency of approximately 25% and an operating range limited to λ = 6. It can be concluded that the models provide good accuracy in predicting the operating range of λ, however the values of Cp were underestimated. The k-ω SST model showed the best results among all.

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In gas stirred steelmaking ladles, entrainment of slag into metal and vice versa takes place. The slag entrainment has been shown to abruptly increase the mass transfer rates of refining reactions through high temperature and water modeling studies of the past. However such an effect has not been correlated with the degree of entrainment, since the latter has not been quantified in terms of operating parameters like gas injection rate and fluid properties. Much of the past works are limited to finding the critical conditions for onset of entrainment. The difficulty lies in measuring the degree of entrainment in industrial ladles or even in a water model. Mathematical modeling is also challenging due to the complexity of the multiphase phenomena. So in this thesis, a modular mathematical modeling approach is presented wherein the phenomena of slag entrainment into metal is resolved into four aspects, models developed for each and finally integrated to study its role. The individual models are (1) multiphase large eddy simulations to simulate slag entrainment in a narrow domain that receives its boundary conditions from (2) single phase RANS simulation of a full ladle, (3) a Lagrangian particle tracking method to compute the residence times of slag droplets in metal phase and (4) a kinetic model that integrates the above three models to compute mass transfer rate as a function of degree of entrainment. Mass transfer rate predictions comparable to a literature correlation were obtained. This supports the modeling approach and also the assessment of role of various system parameters on entrainment characteristics. In essence, the present work shows a systematic approach to model and study the complex multiphase phenomena. / Thesis / Doctor of Philosophy (PhD) / The entrainment of liquid slag into liquid steel in gas stirred-steelmaking ladles is known to increase the rate of refining drastically. However, there is lack of correlation between degree of entrainment and ladle operating conditions, which this thesis addresses through mathematical modeling.