A microfluídica juntamente com a intensificação de processos são duas áreas de pesquisa interessadas no estudo e desenvolvimento de processos em escala micrométrica capazes de manipular diminutas quantidades de reagentes. Para tanto, estes devem contar com dispositivos de pequena escala de tamanho e ao mesmo tempo serem tão confiáveis e eficientes quanto os de escala industrial. Uma das operações unitárias envolvidas nesses processos é a agitação. Em função da ordem de grandeza dos equipamentos e dos materiais em que são fabricados, grandes diferenciais de pressão não podem ser aplicados nos mesmos e como conseqüência no interior dos micromisturadores, como são conhecidos tais equipamentos, o escoamento se dá em regime laminar, sob está condição o processo de mistura é controlado pela difusão entre os componentes. Uma maneira de superar esta dificuldade é gerar no interior do micromisturador o aparecimento de um escoamento caótico. Para tal, podem-se utilizar fontes de energia externa (micromisturadores ativos) ou a própria energia do escoamento (micromisturadores passivos) através da construção de geometrias especiais. O desenvolvimento em laboratório destes equipamentos demanda tempo e geralmente é oneroso. A principal alternativa para este trabalho é a dinâmica dos fluidos computacional (CFD), ferramenta aplicada no presente estudo para analisar três geometrias diferentes propostas e analisadas experimentalmente no trabalho de Cunha (2007). Para caracterizar o funcionamento dos mesmos foram testadas quatro vazões distintas, com as quais foi possível levantar os perfis de pressão, velocidade e fração mássica de dois componentes que eram misturados. Com o intuito de demonstrar a eficiência dos equipamentos dois parâmetros foram analisados: o avanço da qualidade da mistura e a perda de carga para as diferentes condições operacionais. Apesar da limitação da malha e de não ter-se obtido resultados independentes da malha, foi possível se fazer uma comparação entre as três geometrias e identificouse que os micromisturadores M2 e M3 são os que apresentam o melhor desempenho para a faixa de vazão simulada (120 < Re < 1200). / Microfluidics and process intensification are two research areas interested in the study and development of new micrometric-scale devices capable of manipulating and processing small quantities of reagents. These processes have to deal with small scale equipment and at the same time be as reliable and efficient as the large-scale one. Because of the scale of this equipment and the material it is made of, large pressure differential is not possible, as a consequence in the interior of the micromixers, as they are known; a laminar flow develops, under those circumstances the mixing process is controlled by the diffusion mechanism between the two components. One way to suppress this deficiency is to generate a chaotic flow on the micromixer, which can be done by using external energy (active micromixer) or its own flow energy (passive micromixer) through special geometry construction. The experimental development of such microdevices demands time and, generally, is very expensive. The main alternative for this activity is the use of computational fluid dynamics; this tool was employed on this work with the aim of studying three geometries proposed by Cunha (2007). To characterize their working process, four different volumetric flows were simulated and analyzed the pressure, velocity and mass fraction profiles. Two parameters were calculated in order to characterize their efficiency: the mixture quality along the micromixers cross sections and the pressure drop for different operational conditions. Although we have mesh size limitations and a mesh independent results were not obtained it was possible to compare the three micromixers geometries and it was found out that both M2 and M3 micromixers had the best performance under operational conditions tested (120 < Re < 1200).

A microfluídica juntamente com a intensificação de processos são duas áreas de pesquisa interessadas no estudo e desenvolvimento de processos em escala micrométrica capazes de manipular diminutas quantidades de reagentes. Para tanto, estes devem contar com dispositivos de pequena escala de tamanho e ao mesmo tempo serem tão confiáveis e eficientes quanto os de escala industrial. Uma das operações unitárias envolvidas nesses processos é a agitação. Em função da ordem de grandeza dos equipamentos e dos materiais em que são fabricados, grandes diferenciais de pressão não podem ser aplicados nos mesmos e como conseqüência no interior dos micromisturadores, como são conhecidos tais equipamentos, o escoamento se dá em regime laminar, sob está condição o processo de mistura é controlado pela difusão entre os componentes. Uma maneira de superar esta dificuldade é gerar no interior do micromisturador o aparecimento de um escoamento caótico. Para tal, podem-se utilizar fontes de energia externa (micromisturadores ativos) ou a própria energia do escoamento (micromisturadores passivos) através da construção de geometrias especiais. O desenvolvimento em laboratório destes equipamentos demanda tempo e geralmente é oneroso. A principal alternativa para este trabalho é a dinâmica dos fluidos computacional (CFD), ferramenta aplicada no presente estudo para analisar três geometrias diferentes propostas e analisadas experimentalmente no trabalho de Cunha (2007). Para caracterizar o funcionamento dos mesmos foram testadas quatro vazões distintas, com as quais foi possível levantar os perfis de pressão, velocidade e fração mássica de dois componentes que eram misturados. Com o intuito de demonstrar a eficiência dos equipamentos dois parâmetros foram analisados: o avanço da qualidade da mistura e a perda de carga para as diferentes condições operacionais. Apesar da limitação da malha e de não ter-se obtido resultados independentes da malha, foi possível se fazer uma comparação entre as três geometrias e identificouse que os micromisturadores M2 e M3 são os que apresentam o melhor desempenho para a faixa de vazão simulada (120 < Re < 1200). / Microfluidics and process intensification are two research areas interested in the study and development of new micrometric-scale devices capable of manipulating and processing small quantities of reagents. These processes have to deal with small scale equipment and at the same time be as reliable and efficient as the large-scale one. Because of the scale of this equipment and the material it is made of, large pressure differential is not possible, as a consequence in the interior of the micromixers, as they are known; a laminar flow develops, under those circumstances the mixing process is controlled by the diffusion mechanism between the two components. One way to suppress this deficiency is to generate a chaotic flow on the micromixer, which can be done by using external energy (active micromixer) or its own flow energy (passive micromixer) through special geometry construction. The experimental development of such microdevices demands time and, generally, is very expensive. The main alternative for this activity is the use of computational fluid dynamics; this tool was employed on this work with the aim of studying three geometries proposed by Cunha (2007). To characterize their working process, four different volumetric flows were simulated and analyzed the pressure, velocity and mass fraction profiles. Two parameters were calculated in order to characterize their efficiency: the mixture quality along the micromixers cross sections and the pressure drop for different operational conditions. Although we have mesh size limitations and a mesh independent results were not obtained it was possible to compare the three micromixers geometries and it was found out that both M2 and M3 micromixers had the best performance under operational conditions tested (120 < Re < 1200).

<p>The thesis is dealing with mixing processes havingapplication to ground improvement by deep mixing. The mainobjectives of the thesis is to make a contribution to knowledgeof the basic mechanisms in mixing binding agents into soil andimprove the knowledge concerning factors that influence theuniformity of stabilised soil.</p><p>A great part of the work consists of a literature surveywith particular emphasis on literature on the processindustries. This review forms a basis for a profounddescription and discussion of the mixing process and factorsaffecting the process in connection with deep mixingmethods.</p><p>The thesis presents a method for a simple field test for thestudy of influential factors in the mixing process. A number offactors in the installation process of lime-cement columns havebeen studied in two field tests using statistical multifactorexperiment design. The effects of retrieval rate, number ofmixing blades, rotation speed, air pressure in the storagetank, and diameter of the binder outlet on the stabilisationeffect and the coefficient of variation determined byhand-operated penetrometer tests for excavated lime-cementcolumns, were studied.</p><p>The literature review, the description of the mixingprocess, and the results from the field tests provide a morebalanced picture of the mixing process and are expected to beuseful in connection to ground improvement projects and thedevelopment of mixing equipments.</p><p>The concept of sufficient mixture quality, i.e. theinteraction between the mixing process and the mechanicalsystem, is discussed in the last section. By means ofgeostatistical methods, the analysis considers thevolume-variability relationship with reference to strengthproperties. According to the analysis, the design values forstrength properties depends on the mechanical system, the scaleof scrutiny, the spatial correlation structure, and the conceptof safety, i.e. the concept of sufficient mixture quality isproblem specific.</p><p><b>Key words:</b>Deep Mixing, Lime cement columns, Mixingmechanisms, Mixture quality, Field test, ANOVA, Variancereduction.</p>

The thesis is dealing with mixing processes havingapplication to ground improvement by deep mixing. The mainobjectives of the thesis is to make a contribution to knowledgeof the basic mechanisms in mixing binding agents into soil andimprove the knowledge concerning factors that influence theuniformity of stabilised soil. A great part of the work consists of a literature surveywith particular emphasis on literature on the processindustries. This review forms a basis for a profounddescription and discussion of the mixing process and factorsaffecting the process in connection with deep mixingmethods. The thesis presents a method for a simple field test for thestudy of influential factors in the mixing process. A number offactors in the installation process of lime-cement columns havebeen studied in two field tests using statistical multifactorexperiment design. The effects of retrieval rate, number ofmixing blades, rotation speed, air pressure in the storagetank, and diameter of the binder outlet on the stabilisationeffect and the coefficient of variation determined byhand-operated penetrometer tests for excavated lime-cementcolumns, were studied. The literature review, the description of the mixingprocess, and the results from the field tests provide a morebalanced picture of the mixing process and are expected to beuseful in connection to ground improvement projects and thedevelopment of mixing equipments. The concept of sufficient mixture quality, i.e. theinteraction between the mixing process and the mechanicalsystem, is discussed in the last section. By means ofgeostatistical methods, the analysis considers thevolume-variability relationship with reference to strengthproperties. According to the analysis, the design values forstrength properties depends on the mechanical system, the scaleof scrutiny, the spatial correlation structure, and the conceptof safety, i.e. the concept of sufficient mixture quality isproblem specific. Key words:Deep Mixing, Lime cement columns, Mixingmechanisms, Mixture quality, Field test, ANOVA, Variancereduction.