An understanding of the dispersion of contaminants in turbulent flows is important in many fields ranging from air pollution to chemical engineering, and random walk models provide one approach to understanding and calculating aspects of dispersion. Two types of random walk model are investigated in this thesis. The first type, so-called "one-particle models", are capable of predicting only mean concentrations while the second type, "two-particle models", are able to give some information on the fluctuations in concentration as well. Many different one-particle random walk models have been proposed previously and several criteria have emerged to distinguish good models from bad. In this thesis, the relationships between the various criteria are examined and it is shown that most of the criteria are equivalent. It is also shown how a model can be designed to (i) satisfy the criteria exactly and (ii) be consistent with inertial subrange theory. Some examples of models which obey the criteria are described. The theory developed for one-particle models is then extended to the two-particle case and used to design a two-particle model suitable for modelling dispersion in high Reynolds number isotropic turbulence. The properties of this model are investigated in detail and compared with previous models. In contrast to most previous models, the new model is three-dimensional and leads to a prediction for the particle separation probability density function which is in agreement with inertial subrange theory. The values of concentration variance from the new model are compared with experimental data and show encouraging agreement.

Made available in DSpace on 2016-02-26T14:53:10Z (GMT). No. of bitstreams: 0 Previous issue date: 2007-03-30 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The Mutillidae wasps are parasitoids. The samplings had been carried through in seven distinct areas a long two portions to hymenopteras that can attack diverse orders of insects, being its hosts, in the majority other hymenopteras Mountain range of the Bodoquena, that presents about 300 length km and 20 to 50 width km, with altitudes that vary 450 to 650 m and in area bordering to National Park that enclose 76,481 ha divided in two fragments and the predominant vegetation are the Forest Estacional Decidual Submontana. Two quantitative methodologies of collection had been adopted (Pitfall and Covering area) and a qualitative one (manual collections). Has beem collected 44 individuals pertaining two subfamilies, four tribes, 13 sorts and distributed in 23 species. The sort that presented greater wealth was Traumatomutilla with 6 species (26,08%), followed Timulla (3 species, 13.04%) and Ephuta (3 species, 13.04%); the sort most abundant was raumatomutilla with 20 individuals (45,45%) and the species most abundant was lame Traumatomutilla with 9 captures individuals (20,45%), being the other species considered rare for region to presenting only 1 register. The register of few individuals must it geologic formation area, that is predominantly rocky. Analyzing the index of diversity from environments, we have the Antropizada area being most diverse (H'=3,585), followed for Decidual forest (H'=3,096), Ciliar forest (H'=2,419) and Closed (H'=2,252). The different formations had presented basses similarity indices and with these data we can suggest that it has one strong trend the mutillidae to be fit in specific functional groups for each environment. Different methodologies must be applied for fauna s inventory of mutillidae, being the collections qualitative the most indicated for study the wealth and diversity / As vespas Mutillidae são himenópteros parasitóides que podem atacar diversas ordens de insetos, sendo seus hospedeiros, na maioria outros himenópteros. As amostragens foram realizadas em sete áreas distintas ao longo das duas porções da Serra da Bodoquena, que apresenta cerca de 300 km de comprimento e de 20 a 50 km de largura, com altitudes que variam de 450 a 650 m e em área limítrofes ao Parque Nacional que abrange 76.481 ha divididos em dois fragmentos e a vegetação predominante é a Floresta Estacional Decidual Submontana. Foram adotadas duas metodologias de coleta quantitativas (Pitfall e Cobertura de área) e uma qualitativa (coletas manuais). Foram coletados 44 indivíduos pertencentes a duas subfamílias, quatro tribos, 13 gêneros e distribuídos em 23 espécies. O gênero que apresentou maior riqueza foi Traumatomutilla com 6 espécies (26,08%), seguido de Timulla (3 espécies, 13,04%) e Ephuta (3 espécies, 13,04%); o gênero mais abundante foi Traumatomutilla, com 20 indivíduos (45,45%) e a espécie mais abundante foi Traumatomutilla manca com 9 indivíduos capturados (20,45%), sendo as outras espécies consideradas raras para a região por apresentarem apenas 1 registro. O registro de poucos indivíduos deve-se a formação geológica da área, que é predominantemente rochosa. Analisando o índice de diversidade a partir dos ambientes, temos a área Antropizada sendo a mais diversa (H´=3,585), seguida pela Mata Decidual (H´=3,096), Mata Ciliar (H´=2,419) e Cerrado (H´=2,252). As diferentes formações apresentaram baixos índices de similaridade e com esses dados podemos sugerir que haja uma forte tendência de os mutilídeos serem enquadrados em grupos funcionais específicos para cada ambiente. Diferentes metodologias devem ser aplicadas para o inventário da fauna de Mutillidae, sendo as coletas qualitativa a mais indicada para o estudo da riqueza e diversidade