Weather radars are increasingly used for the study of clouds, understanding the precipitation systems and also for forecasting very short range weather (one hour to a few hours). Now, Doppler Weather Radar (DWR) data are available in India and it is possible to study cloud properties at fine temporal and spatial scales. Radar is a complex system and calibration of a radar is not an easy job. But derived cloud properties strongly depend on the absolute magnitude of the reflectivity. Therefore, there is a need to check how data from two or more radars compare if they measure a common volume. Chennai and SHAR radars are within 66 km from each other, and the data collected during their calibration and intercomparison experiment in 2006 enables the comparison of their reflectivity(Z) values. Individual reflectivity are compared after plotting SHAR versus Chennai in a scatter plot. Fitting a least square linear best fit line shows that the intercept has a value around 6 dBZ and the slope of the line is 1.06. Thus, there is a trend as well, and the difference between the two radars increase with Z, and for Z around 40 dBZ (for SHAR DWR), the difference between the two is around 8.5 dBZ. Visual intercomparison also validated the results. Data from the two radars are compared with Precipitation Radar (PR) data on board TRMM satellite. TRMM radar slightly overestimates compared to Chennai radar above the range of 30 dBZ. After standardized, SHAR data is used for understanding the evolution and propagation of cloud systems. The diurnal variation in convection is strong in the study region, with increase around local evening and morning and weakening around midnight except in December. Average liquid water content in the clouds is about 0.5 gm/m3. There is some seasonal dependence but no clear dependence on cloud size. Smaller systems of May have more liquid water content compared to larger ones. For nowcasting vertically projected maximum reflectivity is taken. A threshold of 30 dBZ is set to identify the cloud systems. Both center of gravity tracking (CG) and cross-correlation (CC) methods are used to track them. Frequent merging and splitting is common in the clouds which makes storm tracking difficult. Tracking by CC is giving better result than that by the CG method in the case of large systems (i.e., clusters). For smaller systems (individual cloud systems), CC method gives better result than CG method but not as good as cluster.

Aquesta tesi permet adquirir una millor comprensió de la dinàmica dels plomalls hidrotèrmics en l'estany de Banyoles i correlacionar la meteorologia amb els processos de fluïdització que s'hi produeixen. S'han trobat els patrons atmosfèrics que generen els esdeveniments de les fluïditzacions així com la seva freqüència. Això és crucial per a determinar la qualitat de l'aigua de l'estany. S'han trobat inhomogeneïtats espacials tant en el plomall crònic que es desenvolupa en la cubeta B1, com en el plomall episòdic de la cubeta B2. S'ha caracteritzat l'estructura del plomall generat a la cubeta B2 i s'ha comparat amb el desenvolupat a la cubeta B1. Finalment, s'han realitzat simulacions numèriques mitjançant un model numèric: MIT General Circulation Model, en el qual s'ha hagut de fer canvis en les condicions de contorn per a situar la font convectiva al fons de la columna d'aigua. Les simulacions s'han comparat amb els resultats experimentals trobats mitjançant campanyes. / The aim of this thesis is to acquire a better understanding of the dynamics of the hydrothermal plumes in the lake and to gain more insight into the interrelationship between meteorology and fluidization. They have been found the atmospheric patterns that generate the fluidization events, as well as their frequency. This is crucial to determining the water quality of Lake Banyoles. They have been found spatial inhomogeneities of the chronic thermal plume found in B1 and of the episodic thermal plume in B2. The structure of thermal plume in B2 has been characterized and compared to the plume developed in B1. Finally, it has been used a numerical model: MIT General Circulation Model. It has been necessary to modify the boundary conditions moving the buoyancy source from the top of the water surface to the bottom. Results have been compared to experimental data undertaken from the field campaigns.

No description available.

L’utilisation d’une méthode d’assimilation de données, associée à un modèle de convection anélastique, nous permet la reconstruction des structures physiques d’une partie de la zone convective située en dessous d’une région solaire active. Les résultats obtenus nous informent sur les processus d’émergence des tubes de champ magnétique au travers de la zone convective ainsi que sur les mécanismes de formation des régions actives. Les données solaires utilisées proviennent de l’instrument MDI à bord de l’observatoire spatial SOHO et concernent principalement la région active AR9077 lors de l’ ́évènement du “jour de la Bastille”, le 14 juillet 2000. Cet évènement a conduit à l’avènement d’une éruption solaire, suivie par une importante éjection de masse coronale. Les données assimilées (magnétogrammes, cartes de températures et de vitesses verticales) couvrent une surface de 175 méga-mètres de coté acquises au niveau photosphérique. La méthode d’assimilation de données employée est le “coup de coude direct et rétrograde”, une méthode de relaxation Newtonienne similaire à la méthode “quasi-linéaire inverse 3D”. Elle présente l’originalité de ne pas nécessiter le calcul des équations adjointes au modèle physique. Aussi, la simplicité de la méthode est un avantage numérique conséquent. Notre étude montre au travers d’un test simple l’applicabilité de cette méthode à un modèle de convection utilisé dans le cadre de l’approximation anélastique. Nous montrons ainsi l’efficacité de cette méthode et révélons son potentiel pour l’assimilation de données solaires. Afin d’assurer l’unicité mathématique de la solution obtenue nous imposons une régularisation dans tout le domaine simulé. Nous montrons enfin que l’intérêt de la méthode employée ne se limite pas à la reconstruction des structures convectives, mais qu’elle permet également l’interpolation optimale des magnétogrammes photosphériques, voir même la prédiction de leur évolution temporelle. / We use a data assimilation technique, together with an anelastic convection model, in order to reconstruct the convective patterns below a solar active region. Our results yield information about the magnetic field emergence through the convective zone and the mechanisms of active region formation. The solar data we used are taken from the instrument MDI on board the spatial observatory SOHO on July 2000 the 14th for the event called ”bastille day event”. This specific event leads to a solar flare followed by a coronal mass ejection. Assimilated data (magnetograms, temperature maps and vertical velocity maps) cover an area of 175 Mm × 175 Mm at photospheric level. The data assimilation technique we used, the ”Nudging Back and Forth”, is a Newtonian re- laxation technique similar to the ”quasi linear inverse 3D”. Such a technique does not require computation of the adjoint equations. Thus, simplicity of this method is a numerical advantage. Our study shows with a simple test case the applicability of this method to a convection model treated with the anelastic approximation. We show the efficiency of the NBF technique and we detail its potential for solar data assimi- lation. In addition, to ensure mathematical unicity of the obtained solution, a regularization has been imposed in the whole simulation domain. This is a new approach. Finally, we show that the interest of such a technique is not limited to the reconstruction of convective patterns but that it also allows optimal interpolation of photospheric magnetograms and predictions.

This study analyzes the available radar evidence in order to describe the morphology of channel networks around the north polar seas of Titan. Critical flow depths necessary to entrain water-ice grains, and denudation rates for a north polar channel network are discussed. The results indicate that channel networks on Titan have similar morphologies to channel networks cut by water on Earth. We also find that water-ice sediment should be readily entrained in the headwaters and downstream sections of the analyzed Titanian basin, given sufficient flow depths of liquid hydrocarbons. Also, the importance of slope and the elevated topography of the highlands surrounding the polar lakes are considered, as well as potential formation theories for the elevated highlands and low-lying maria that dominate the north polar region.

Submitted by Emanuel Varela Cardoso (emanuel.varela@ufcg.edu.br) on 2018-06-13T20:31:59Z No. of bitstreams: 1 FABRÍCIO BATISTA BORGES – TESE (PPGEP) 2016.pdf: 4027586 bytes, checksum: c02ca04ae0983633d70b155cc190bf48 (MD5) / Made available in DSpace on 2018-06-13T20:31:59Z (GMT). No. of bitstreams: 1 FABRÍCIO BATISTA BORGES – TESE (PPGEP) 2016.pdf: 4027586 bytes, checksum: c02ca04ae0983633d70b155cc190bf48 (MD5) Previous issue date: 2016-09-23 / Objetiva-se com este trabalho realizar estudos usando as soluções analítica e numérica da equação de difusão para descrever a secagem em camada fina de grãos de milho nas temperaturas de 45, 55, 65 e 75 ºC, os quais têm uma forma que pode ser aproximada a de um paralelepípedo. Foram utilizadas ferramentas numéricas e analíticas para o estudo dos fenômenos difusivos envolvendo as três dimensões geométricas dos grãos mencionados. Para a solução numérica proposta, a equação de difusão tridimensional foi discretizada utilizando os métodos dos volumes finitos, com uma formulação totalmente implícita, fazendo uso das coordenadas cartesianas. Com a finalidade de estabelecer a correta condição de contorno na descrição da cinética de secagem dos grãos de milho, foram utilizados três softwares para a determinação dos parâmetros de processo a partir dos dados experimentais via otimização. O primeiro software usado para simular a cinética de secagem do milho foi “Prescribed Adsorption – Desorption” V.2.2, que utiliza a solução analítica da equação de difusão empregando a condição de contorno do primeiro tipo. O segundo software utilizado foi o “Convective Adsorption – Desorption” V. 2.4. Este simula a cinética de secagem de produtos usando a solução analítica da equação de difusão empregando a condição de contorno do terceiro tipo. Já o terceiro software usado na otimização foi o “LS Optimizer” V.2.1, que determina os parâmetros de uma equação diferencial usando o método dos mínimos quadrados na solução numérica da equação de difusão com a condição de contorno do terceiro tipo. Esses dois últimos geraram resultados coerentes e consistentes em todas as etapas efetuadas durante os testes. Pode-se concluir que o segundo e o terceiro modelos propostos para analisar os dados da pesquisa foram coerentes e equivalentes, e os resultados obtidos foram satisfatórios. Assim, a condição de contorno do terceiro tipo foi usada para a solução numérica tridimensional da equação de difusão em coordenadas cartesianas. Testes de validação indicaram que a solução numérica desenvolvida apresenta resultados coerentes com aqueles esperados. / The objective with this essay is to carry out studies using analytical and numerical solutions of the diffusion equation to describe the drying of thin layer of corn grains at temperatures of 45, 55, 65 and 75 ° C, which have a shape that can be approximated for a parallelepiped. Numerical and analytical tools were used for the study of the diffusive phenomena involving the three geometric dimensions of the mentioned grains. For the numerical solution proposed, the three dimensional diffusion equation was discretized using the finite volume method with a fully implicit formulation using the cartesian coordinates. In order to establish the right boundary condition in the description of the corn grain drying kinetics, three software were used for the determination of the process parameters from the experimental data using optimization. The first software used to simulate corn drying kinetics was "Prescribed Adsorption - Desorption" V.2.2, which uses the analytical solution of the diffusion equation using the boundary condition of the first type. The second software used was "Convective Adsorption - Desorption" V. 2.4. This one simulates the kinetics of drying products using the analytical solution of the diffusion equation using the boundary condition of the third kind. The third software used in the optimization was the "LS Optimizer" V.2.1 which determines the parameters of a differential equation using the method of least squares in the numerical solution of the diffusion equation using the boundary condition of the third kind.The latter two have generated coherent and consistent results in all steps performed during testing. It can be concluded that the second and third proposed models to analyze the survey data were consistent and equivalent and the results were satisfactory. Thus, the boundary condition of the third kind was used for three -dimensional numerical solution of the diffusion equation in cartesian coordinates. Validation tests indicated that the developed numerical solution provides coherent results with t hose expected.

No description available.

Made available in DSpace on 2014-12-17T15:01:29Z (GMT). No. of bitstreams: 1 ErlyMMAN_DISSERT.pdf: 2763165 bytes, checksum: 02d0a064f93f95db42ddc7fc2c52410e (MD5) Previous issue date: 2012-03-30 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / Brazil, one of the largest agricultural producers in the world, has managed in recent years to significantly improve its production. However, in response to this advance in the agro-industrial sector, the generation of agro-industrial residues has also increased. New technological alternatives have to be implemented in order to bring economic and rational use of this material and drying is one of the possible choices. Considering the great importance that bioactive compounds present for food science and technology, this research aims to evaluate the air-drying process of acerola residue in a tray convective drier under controlled temperature (60, 70 e 80?C), air velocity (4.0, 5.0 e 6.0 m/s) and material width (0.5, 0.62 e 0.75 cm) by applying an experimental planning 23 + 3. Based on that, the impact on physical-chemical characteristics, color, bioactive compounds concentration and antioxidant activity of dried acerola waste was evaluated, having the in natura and freeze dried waste as control groups. Dried acerola residue presented natural pigments, mainly carotenoids (143.68 - 68.29 mg/g) and anthocyanins (290.92 - 90.11 mg/100 g), which explain the red and yellow instrumental color parameters observed. The acerola residue powder is also rich in phenolic compounds (3261.11 -2692.60 mgGAEeq/100g), proanthocyanidins (61.33-58.46 eq/100g), ascorbic acid (389.44 739.29 mg/100 g) and DPPH antioxidant activity (20.91 24.72 ?g Trolox eq/g). Results show decreased concentration of phenolic compounds, anthocyanins, carotenoids, proanthocyanidins and ascorbic acid caused by the air-drying process. However, even after the observed drying losses, the acerola residue powder can be considered a high value food ingredient, considering the high bioactive compounds concentration found in the final product, as well as the colorimetric characterization and microbiological stability of the dried powder / O Brasil, um dos maiores produtores agr?colas atuais, tem conseguido aumentar sua produ??o agroindustrial nos ?ltimos anos. Em conseq??ncia a isso a gera??o de res?duos tamb?m aumentou. Dessa forma, torna-se relevante a pesquisa de alternativas de uso racional e econ?mico para esse tipo de mat?ria prima, incluindo opera??es unit?rias de transforma??o como a secagem. Diante da import?ncia que os compostos bioativos apresentam para a ?rea de ci?ncia e tecnologia de alimentos, esta pesquisa objetivou avaliar a secagem do res?duo agroindustrial da acerola em secador convectivo de bandejas sob condi??es controladas de temperatura de trabalho (60; 70 e 80?C), velocidade do ar (4,0; 5,0 e 6,0 m/s) e espessura do material (0,5; 0,62 e 0,75 cm), mediante aplica??o de planejamento experimental do tipo fatorial 23 + 3 pontos centrais. A partir disso, o impacto da secagem sobre as caracter?sticas f?sico-qu?micas, cor, concentra??o de compostos bioativos selecionados e atividade antioxidante do res?duo da acerola s?o abordados, tomando os res?duos in natura e liofilizado como grupos-controle. Os p?s do res?duo desidratado de acerola apresentaram presen?a de pigmentos naturais, com colora??o vermelha e amarela, sobretudo caroten?ides (143,68 a 68,29 mg/g), antocianinas (290,92 a 90,11 mg/100 g), al?m de elevado teor de compostos fen?licos (3261,11 a 2692,60 mg GAE eq/100 g amostra), proantocianidinas (61,33 a 58,46 eq/100 g amostra) e ?cido asc?rbico (389,44 a 739,29 mg/100 g), bem como expressiva atividade antioxidante obtida pelo m?todo DPPH (20,91 a 24,72 ?g Trolox eq/g amostra). Os dados experimentais mostraram diminui??o da concentra??o de compostos fen?licos, antocianinas, caroten?ides, proantocianidinas e ?cido asc?rbico ocasionada pela secagem nas condi??es estudadas. No entanto, a concentra??o final desses compostos detectada no produto desidratado, bem como a caracteriza??o colorim?trica e a estabilidade microbiol?gica alcan?ada, caracteriza o p? do res?duo de acerola como ingrediente com elevado potencial bioativo

Nesta tese é apresentado um esquema novo de alta resolução upwind (denominado TDPUS-C3) para reconstrução de fluxos numéricos para leis de conservação não lineares e problemas relacionados em DFC. O esquema é baseado nos critérios de estabilidade CBC e TVD e desenvolvido utilizando condições de diferenciabilidade \'C POT. 3\'. Além disso, é realiozada a implementação da associação do esquema TDPLUS-C3 com a modelagem de turbulência RNG \'\\kappa - \\epsilon\'. O propósito é obter soluções numéricas de sistemas hiperbólicos de leis de conservação para dinâmica dos gases e equações de Navier-Stokes para escoamento incompreensível de fluidos newtonianos e não newtonianos (viscoelásticos). Fazendo o uso do esquema TDPUS-C3, a precisão global dos métodos numéricos é verificada acessando o erro em problemas teste (benchmark) 1D e 2D. Um estudo comparativo entre os resultados do esquema TDPUS-C3 e os esquemas upwind convencionais para leis de conservação hiperbólicas complexas é também realizado. A Associação das modelagens numéricas (upwinding mais RNG \'\\kappa - \\epsilon\') é , então, examinada na simulação de escoamentos turbulentos de fluidos newtonianos envolvendo superfícies livres móveis, usando a metodologia URANS. No geral, em termos do comportamento global, concordância satisfatória é observada / In this thesis, a new high-resolution upwind scheme (named TDPUS-C3) for reconstruction of numerical fluxes for nonlinear conservation laws and related CFD problems in presented. The scheme is based on CBC and TVD stability criteria and developed by employing differentiability condictions (\'C POT. 3\'). In additon, the implementation of an association of the TDPUS-C3 scheme with the RNG \'\\kappa - \\epsilon\' turbulence modelling is also performed. The purpose is to obtain numerical solutions of systems of hyperbolic conservation laws for gas dynamics and Navier-Stokes equations for incompressible flow of Newtonian and non-Newtonian (viscoelstic) fluids. By using the TDPUS-C3 scheme, the global accuracy of the numerical methods is verified by assessing the error on 1D and 2D benchmark test cases. A comparative study between the TDPUS-C3 scheme and convectional upwind schemes to solve standard and complex hyperbolic conservation laws is also accomplished. The association of the numerical modelling (upwinding plus RNG \'\\kappa - epsilon\') is then examined in the simulation of turbulent Newtonian fluid flows involving moving free surfaces, by using URANS methodology. Overall, satisfactory agreement is found in terms of the overall behaviour

A presente tese trata da análise experimental do efeito da geometria da seção transversal do canal e do desempenho de refrigerantes de reduzido GWP (Global Warming Potential) durante a ebulição convectiva em canais de reduzidas dimensões. A tese inclui ainda um estudo extenso e crítico da literatura sobre métodos de previsão da perda de pressão e do coeficiente de transferência de calor, e sobre estudos experimentais em canais não-circulares e de refrigerantes com reduzido GWP na ebulição convectiva em canais de dimensões reduzidas. Resultados para o coeficiente de transferência de calor e perda de pressão durante a ebulição convectiva foram obtidos para canais com geometrias de seção circular, quadrada e triangular para o refrigerante R134a. Nos testes utilizou-se canais com perímetros internos similares obtidos a partir da conformação de um tubo com diâmetro interno igual a 1,1 mm. No caso do canal circular, dados foram também levantados para os HFOs R1234ze(E) e R1234yf e o hidrocarboneto R600a, fluidos com reduzido GWP. Ensaios foram executados para amplas faixas de fluxos de calor e velocidades mássicas, temperaturas de saturação de 31 e 41°C e títulos de vapor entre 0 e 0,95. Aspectos relacionados aos efeitos da geometria e do fluido refrigerante foram minuciosamente investigados através da análise paramétrica dos resultados. Com base na comparação do banco de dados coletado com os métodos de previsão disponíveis na literatura, constatou-se que estes proporcionam previsões satisfatórias apenas para condições experimentais especificas. Portanto, novos métodos de previsão da perda de pressão e do coeficiente de transferência de calor foram desenvolvidos com base nos dados levantados no presente estudo. Os métodos propostos preveem satisfatoriamente o banco de dados do presente estudo e resultados independentes disponíveis na literatura. Adicionalmente, com base nos resultados levantados, verificou-se que dissipadores de calor baseados em multi-microcanais com canais de seção triangular apresentam desempenho superior comparados a dissipadores com canais quadrados e circulares. / The present thesis concerns an experimental study on the effects of cross-sectional geometry and low GWP refrigerants on the thermal-hydraulic performance for convective boiling inside micro-scale channels. Experimental results for heat transfer coefficient and pressure drop gradient during convective boiling were obtained for circular, square and triangular channels for the fluid R134a. The evaluated channels present the same external perimeter and equivalent diameters of 1.1, 0.977 and 0.835 mm, respectively. In the case of the circular geometry, experimental results were also acquired for the HFOs R1234ze(E) and R1234yf and the hydrocarbon R600a (isobutane), which are fluids with low GWP and null ODP. Experiments were performed for a wide range of heat fluxes and mass velocities, saturation temperatures of 31 and 41°C and vapor qualities up to 0.95. The experimental data were carefully analyzed and discussed based on a parametrical analysis focusing on the effect of the cross-sectional geometry and the working fluid. Subsequently, the experimental data were compared against the most quoted predictive methods from literature. In general, it was verified that none of the predictive methods were able to accurately capture the experimental trends of the overall database. So, new predictive methods for the pressure drop and heat transfer coefficient were developed based on the broad database obtained in the present study. The proposed methods provided satisfactory results not only for the experimental database used for its development, but also for independent databases collected in the literature. Additionally, based on the data obtained in the present study and a performance analysis taken into account pressure drop, heat transfer coefficient and the channel packing factor, triangular cross sectional geometry is recommended for heat sinks.