京都大学 / 0048 / 新制・論文博士 / 博士(理学) / 乙第12913号 / 論理博第1549号 / 新制||理||1591(附属図書館) / 32123 / 名古屋大学大学院理学研究科 / (主査)准教授 林 泰一, 教授 石川 裕彦, 教授 余田 成男 / 学位規則第4条第2項該当 / Doctor of Science / Kyoto University / DGAM

The following work represents the research attempt of Dr. Frasier's group to develop a FMCW wind profiler for atmospheric boundary layer studies. The hardware development and integration are described in detail.

La modélisation par simulation des grandes échelles (Large-Eddy Simulation - LES) des processus physiques régissant la couche limite atmosphérique (CLA) demeure complexe de part la difficulté des modèles à capter l'évolution de la turbulence entre différentes conditions de stratification. De ce fait, l'étude LES du cycle diurne complet de la CLA comprenant des situations convectives la journée et des conditions stables la nuit est très peu documenté. La simulation de la couche limite stable où la turbulence est faible, intermittente et qui est caractérisée par des structures turbulentes de petite taille est tout particulièrement compliquée. En conséquence, la capacité de la LES à bien reproduire les conditions météorologiques de la CLA, notamment en situation stable, est étudiée à l'aide du code de mécanique des fluides développé par EDF R&D, Code_Saturne. Dans une première étude, le modèle LES est validé sur un cas de couche limite convective quasi stationnaire sur terrain homogène. L'influence des modèles sous-maille de Smagorinsky, Germano-Lilly, Wong-Lilly et WALE (Wall-Adapting Local Eddy-viscosity) ainsi que la sensibilité aux méthodes de paramétrisation sur les champs moyens, les flux et les variances est discutées. Dans une seconde étude le cycle diurne complet de la CLA pendant la campagne de mesure Wangara est modélisé. L'écart aux mesures étant faible le jour, ce travail se concentre sur les difficultés rencontrées la nuit à bien modéliser la couche limite stable. L'impact de différents modèles sous-maille ainsi que la sensibilité au coefficient de Smagorinsky ont été analysés. Par l'intermédiaire d'un couplage radiatif réalisé en LES, les répercussions du rayonnement infrarouge et solaire sur le jet de basse couche nocturne et le gradient thermique près de la surface sont exposées. De plus l'adaptation de la résolution du domaine à l'intensité de la turbulence et la forte stabilité atmosphérique durant l'expérience Wangara sont commentées. Enfin un examen des oscillations numériques inhérentes à Code_Saturne est réalisé afin d'en limiter les effets / Large-eddy simulation (LES) of the physical processes in the atmospheric boundary layer (ABL) remains a complex subject. LES models have difficulties to capture the evolution of the turbulence in different conditions of stratification. Consequently, LES of the whole diurnal cycle of the ABL including convetive situations in daytime and stable situations in the night time is seldom documented. The simulation of the stable atmospheric boundary layer which is characterized by small eddies and by weak and sporadic turbulence is espacialy difficult. Therefore The LES ability to well reproduce real meteorological conditions, particularly in stable situations, is studied with the CFD code developed by EDF R&D, Code_Saturne. The first study consist in validate LES on a quasi-steady state convective case with homogeneous terrain. The influence of the subgrid-scale models (Smagorinsky model, Germano-Lilly model, Wong-Lilly model and Wall-Adapting Local Eddy-viscosity model) and the sensitivity to the parametrization method on the mean fields, flux and variances are discussed.In a second study, the diurnal cycle of the ABL during Wangara experiment is simulated. The deviation from the measurement is weak during the day, so this work is focused on the difficulties met during the night to simulate the stable atmospheric boundary layer. The impact of the different subgrid-scale models and the sensitivity to the Smagorinsky constant are been analysed. By coupling radiative forcing with LES, the consequences of infra-red and solar radiation on the nocturnal low level jet and on thermal gradient, close to the surface, are exposed. More, enhancement of the domain resolution to the turbulence intensity and the strong atmospheric stability during the Wangara experiment are analysed. Finally, a study of the numerical oscillations inherent to Code_Saturne is realized in order to decrease their effects

Title: Flow and diffusion characteristics inside the urban area Author: Hana Chaloupecká Department: Department of meteorology and enviroment protection Supervisor: prof. RNDr. Zbyněk Jaňour, DrSc., IT AS CR, v. v. i. Supervisor's e - mail: janour@it.cas.cz Abstract: Uniqueness of different towns, consists of various shapes of buildings. The main topic of this work is to compare concentration diffusion within groups of buildings of various types. We pursued houses made of single blocks of two different lengths - they were placed parallel or in courtyards. For research of pollution diffusion within the housing estates a method of physical modelling has been used. For this purpose we summarized a theory of atmospheric boundary layer and physical modelling at first. Then we pursued experiments. Measuring took place in a model in scale 1 : 300 inside an aerodynamic wind tunnel of the Institute of Thermomechanics AS in Nový Knín. We checked out the requirements placed on similarity of the real boundary layer and boundary layer modelled in the tunnel. By the measuring of concentration in urban areas we weren't watching a plume from the pollution source but we were studying an inversion task. We measured concentrations in two fixed points from different point sources inside the defined areas. A sensitivity of...

Simulações numéricas do escoamento atmosférico em microescala constituem o foco principal deste estudo. Estas simulações são abordadas tendo em vista aplicações para o setor eólico, em especial para avaliações de produção de energia em parques eólicos. Existem diversas categorias de incertezas associadas às estimativas de produção de energia para um projeto eólico, mas na maioria dos casos, a incerteza associada ao modelo de escoamento é a maior e mais relevante de todas. Dentro do setor eólico, o termo “modelo de escoamento” refere-se à ferramenta numérica utilizada para extrapolar o recurso eólico medido na posição das torres anemométricas (e sensores remotos) até as posições projetadas para os aerogeradores. Diversos autores sugerem através de estudos comparativos que os modelos tipo “CFD RANS k-ε” atualmente representam o “estado da arte” para aplicações em parques eólicos e são os mais utilizados comercialmente no setor. Contudo, o escoamento atmosférico livre é intrinsicamente turbulento, e a dinâmica dos escoamentos turbulentos é um campo científico que ainda não foi totalmente dominado pelo conhecimento humano. O presente estudo demonstra que a maioria dos “modelos de escoamento” atualmente disponíveis possuem pontos fracos, em especial quando aplicados em simulações do escoamento atmosférico livre sobre áreas com topografia e rugosidade complexas Uma das fraquezas presentes na maioria dos modelos de microescala para escoamento atmosférico é a “incapacidade” de simular com precisão o escoamento que ocorre durante períodos de “estabilidade atmosférica”. Diversos locais com elevado potencial eólico apresentam ciclos durante os quais as características do escoamento são afetadas pela ocorrência de estratificação térmica dentro da Camada Limite Atmosférica. Tendo como objetivo principal melhorar as simulações do escoamento nestas condições, propõe-se através deste estudo algumas modificações na modelagem “CFD RANS k-ε” tradicionalmente empregada. Dentre estas, destacam-se a inclusão de um perfil estratificado de temperatura potencial como condição de contorno, a inclusão dos efeitos das forças de empuxo no equacionamento “k-ε” e a solução simultânea das equações para balanço de energia e para o fluxo de temperatura potencial. Este modelo foi chamado de “RANS estável”. Para validação deste modelo foram utilizadas cinco torres anemométricas instaladas em um local com topografia complexa. Estas torres foram montadas e instrumentadas conforme as melhores práticas internacionais Os dados anemométricos registrados por essas torres demonstram a presença de ciclos diários de estabilidade atmosférica. Os erros de previsão cruzada foram calculados comparando-se as previsões de cada modelo com as medições reais registradas na posição das torres. O erro global médio de previsão cruzada entre torres anemométricas obtido com a composição dos modelos RANS “estável + neutro” foi de 3,8% enquanto o erro obtido apenas com o modelo RANS k-ε tradicional foi de 5,2%. Para o modelo linear WAsP, amplamente utilizado no setor eólico, o erro foi de 7,1%. Além dos erros de previsão cruzada entre torres, os perfis verticais de velocidade e os fatores de aceleração direcionais obtidos com a composição dos modelos RANS “estável + neutro” também sugerem que esta é uma alternativa versátil e promissora para capturar os ciclos de estabilidade atmosférica utilizando simulações numéricas em regime permanente. / Microscale numerical simulations of the atmospheric wind flow are the central focus of this study. These simulations are analysed from the wind energy perspective. Special attention is given to the usage and application of these simulations in energy production assessments for proposed wind farms. There are multiple uncertainty categories associated with energy production forecasts for future wind farms. However, in most cases the uncertainty factors related with wind flow modelling are the largest and most relevant of them all. The wording “flow model” refers to the numerical simulations (or “models”) that are used to extrapolate the anemometric data recorded at meteorological masts positions to the proposed wind turbine positions. Several authors have demonstrated through comparative studies that the “CFD RANS k-ε” models currently represent the “state of the art” when it comes to microscale wind flow simulations targeted at wind farms. Nonetheless, the atmospheric wind flow is turbulent by nature, and the dynamics of turbulent flows represent one of the scientific fields that have not yet been fully dominated by the human knowledge. The present study demonstrates that the majority of flow models currently available to mankind still lack in precision, even more so when it comes to modelling free atmospheric wind flow over complex terrain. One of the major weak spots of most microscale wind flow models is their inability to precisely simulate the wind flow that occurs during periods of atmospheric stability Numerous locations with large potential for wind energy production present cyclic periods of thermal stratification inside the atmospheric boundary layer. These cycles alter the dynamics and characteristics of the wind stream. With the purpose of improving wind flow simulations under stable atmospheric conditions, some modifications to the standard “RANS k-ε” model implementation are proposed. The most significant of these modifications are the usage of a potential temperature profile among the boundary conditions, the inclusion of the buoyancy forces in the “k-ε” equations and the simultaneous solution of the equations for energy balance and for potential temperature transport. This “modified” model was named “stable RANS”. It was validated using five well mounted meteorological masts installed in a location with complex topography. The anemometric data measured by these site masts suggest the existence of strong daily cycles of atmospheric stability. Cross prediction errors were calculated by comparing the forecasts (outputs) from each flow model against real wind data measured at each mast position The global average cross prediction error yielded by the RANS “stable +neutral” model was around 3,8%, whereas the error yielded by the traditional “RANS k-ε” implementation was near 5,2%. For the linear model WAsP the error was calculated to be 7,1%. In addition to cross prediction errors, the vertical wind speed profiles and speed-up factors calculated with the RANS “stable +neutral” model composition also suggest that it is a promising and versatile alternative for capturing the effects from atmospheric stability on wind flow using steady state numerical simulations.

This thesis deals with the estimation of plant-atmosphere trace gas exchange and isotopic discrimination from atmospheric concentration measurements. Two space scales were investigated: canopy and regional. The canopy-scale study combined a Lagrangian model of turbulent dispersal with ecophysiological principles to infer vertical profiles of fluxes of CO2, H2O and heat as well as carbon and oxygen isotope discrimination during CO2 assimilation, from concentration measurements within a forest. The regional-scale model used a convective boundary layer budget approach to infer average regional isotopic discrimination and fluxes of CO2 and sensible and latent heat from the evolution during the day of boundary layer height and mean concentrations of CO2 and H2O, temperature and carbon and oxygen isotope composition of CO2. For the canopy study, concentrations of five scalar quantities, CO2, 13CO2, C18O16O, H2O and temperature, were measured at up to nine heights within and above a mixed fir and spruce forest in central Siberia over several days just after snow melt in May 2000. Eddy covariance measurements of CO2, H2O and heat fluxes were made above the canopy over the same period, providing independent verification of the model flux estimates. Photosynthesis, transpiration, heat exchange and isotope discrimination during CO2 assimilation were modelled for sun and shade leaves throughout the canopy through a combination of inversion of the concentration data and principles of biochemistry, plant physiology and energy balance. In contrast to the more usual inverse modelling concept where fluxes are inferred directly from concentrations, in this study the inversion was used to predict unknown parameters within a process-based model of leaf gas and energy exchange. Parameters relating to photosynthetic capacity, stomatal conductance, radiation penetration and turbulence structure were optimised by the inversion to provide the best fit of modelled to measured concentration profiles of the five scalars. Model results showed that carbon isotope discrimination, stomatal conductance and intercellular CO2 concentration were depressed due to the low temperatures experienced during snow melt, oxygen isotope discrimination was positive and consistent with other estimates, radiation penetrated further than simple theoretical predictions because of leaf clumping and penumbra, the turbulence coherence was lower than expected and stability effects were important in the morning and evening. For the regional study, five flights were undertaken over two days in and above the convective boundary layer above a heterogeneous pine forest and bog region in central Siberia. Vertical profiles of CO2 and H2O concentrations, temperature and pressure were obtained during each flight. Air flask samples were taken at various heights for carbon and oxygen isotopic analysis of CO2. Two budget methods were used to estimate regional surface fluxes of CO2 and plant isotopic discrimination against 13CO2 and C18O16O, with the first method also used to infer regional sensible and latent heat fluxes. Flux estimates were compared to ground-based eddy covariance measurements. Model results showed that afternoon estimates for carbon and oxygen isotope discrimination were close to those expected from source water isotopic measurements and theory of isotope discrimination. Estimates for oxygen isotope discrimination for the morning period were considerably different and could be explained by contrasting influences of the two different ecosystem types and non-steady state evaporative enrichment of leaf water.

Snow surface energy balance was studied along an elevational gradient and under varying forest cover types during the ablation season of 2007 in the Coldstream Basin, Okanagan, British Columbia, Canada. During the snowmelt period, 1-4% of the peak annual snow-water equivalent (SWE) was lost to sublimation in open sites – averaging 0.4 mm d-1. Melt and sublimation rates increased significantly with elevation, and were higher and more variable in the open sites than under forest canopies. Melt rates were driven almost entirely by sensible heat fluxes and exceeded 30 mm d-1 during large-scale advection events. The melt and sublimation processes observed at the snow surface were significantly linked to conditions in the atmospheric boundary layer. From these linkages, a proxy record of historical ablation season energy fluxes for the period 1972-2007 was created. Significant trends towards earlier dates of snowmelt and freshet onset were detected, as was a trend towards increasing ablation-season temperatures at the 850 mb height. Significant correlations between estimated historical ablation-season melt and sublimation and the regionally dominant teleconnection indices were also found. This study significantly advances the understanding of ablation season snow-surface energy exchanges, and the links to the driving atmospheric conditions in the Okanagan Basin.

[pt] A questão da poluição ambiental está recebendo cada vez mais importância. Por esse motivo, os estudos relacionados a processos de dispersão de poluentes estão ganhando cada vez mais destaques. Como estudos em campo são mais custosos, os estudos realizados em laboratório, com modelos reduzidos, estão sendo mais aplicáveis, uma vez que permitem análises de problemas específicos. Este trabalho tem como objetivo realizar um estudo exploratório em um túnel de vento do comportamento de uma pluma emitida por uma chaminé, que permita modificações nas condições de velocidade e temperatura da pluma. Para isso, foi realizada a reprodução da camada limite atmosférica, através do Método de Irwin, simulando um ambiente suburbano, em que o perfil de velocidades média foi medido com a técnica de Anemometria de Fio Quente. Foram realizados ensaios para três condições do escoamento principal e levantados os perfis de velocidade e intensidade turbulenta à jusante da chaminé. Foi realizado um estudo da inclinação da pluma, tanto pela influência da velocidade, quanto pela diferença de temperatura da pluma em relação à do escoamento principal, que foi variada em 10 e 20 graus Celsius. As análises de concentração foram possíveis através das imagens obtidas com a técnica de Velocimetria por Imagem de Partículas. Foram feitas análises do perfil de concentração a diferentes posições a sotavento da chaminé e o coeficiente de dispersão vertical obtido foi comparado com diversas literaturas conhecidas. / [en] Environmental pollution issue is becoming increasingly important. For this reason, studies related to processes of atmospheric dispersion of pollutants are gaining prominence. Since studies in situ are expensive, laboratory studies with reduced models are useful, since specific problem can be investigated. The present work performs an experimental study, in a wind tunnel, evaluating the behavior of a plume generated by a chimney. For this, the reproduction of the atmospheric boundary layer was made, using the Irwin method, simulating a suburban environment, in which the mean velocity profile was measured with the Hot Wire Anemometry technique. Tests were performed for three main flow conditions and the profiles of velocity and turbulent intensity were made upstream of the stack. A study of the bent of the plume was made, both by the influence of the velocity, and by the temperature difference between the plume and the main flow, that was varied at 10 and 20 degrees Celsius. The concentration analyzes were possible through the images obtained with the Particle Image Velocimetry technique. Concentration profile analyzes were performed at different leeward positions of the chimney and the vertical dispersion coefficient obtained was compared with several known literatures.

Simulações numéricas do escoamento atmosférico em microescala constituem o foco principal deste estudo. Estas simulações são abordadas tendo em vista aplicações para o setor eólico, em especial para avaliações de produção de energia em parques eólicos. Existem diversas categorias de incertezas associadas às estimativas de produção de energia para um projeto eólico, mas na maioria dos casos, a incerteza associada ao modelo de escoamento é a maior e mais relevante de todas. Dentro do setor eólico, o termo “modelo de escoamento” refere-se à ferramenta numérica utilizada para extrapolar o recurso eólico medido na posição das torres anemométricas (e sensores remotos) até as posições projetadas para os aerogeradores. Diversos autores sugerem através de estudos comparativos que os modelos tipo “CFD RANS k-ε” atualmente representam o “estado da arte” para aplicações em parques eólicos e são os mais utilizados comercialmente no setor. Contudo, o escoamento atmosférico livre é intrinsicamente turbulento, e a dinâmica dos escoamentos turbulentos é um campo científico que ainda não foi totalmente dominado pelo conhecimento humano. O presente estudo demonstra que a maioria dos “modelos de escoamento” atualmente disponíveis possuem pontos fracos, em especial quando aplicados em simulações do escoamento atmosférico livre sobre áreas com topografia e rugosidade complexas Uma das fraquezas presentes na maioria dos modelos de microescala para escoamento atmosférico é a “incapacidade” de simular com precisão o escoamento que ocorre durante períodos de “estabilidade atmosférica”. Diversos locais com elevado potencial eólico apresentam ciclos durante os quais as características do escoamento são afetadas pela ocorrência de estratificação térmica dentro da Camada Limite Atmosférica. Tendo como objetivo principal melhorar as simulações do escoamento nestas condições, propõe-se através deste estudo algumas modificações na modelagem “CFD RANS k-ε” tradicionalmente empregada. Dentre estas, destacam-se a inclusão de um perfil estratificado de temperatura potencial como condição de contorno, a inclusão dos efeitos das forças de empuxo no equacionamento “k-ε” e a solução simultânea das equações para balanço de energia e para o fluxo de temperatura potencial. Este modelo foi chamado de “RANS estável”. Para validação deste modelo foram utilizadas cinco torres anemométricas instaladas em um local com topografia complexa. Estas torres foram montadas e instrumentadas conforme as melhores práticas internacionais Os dados anemométricos registrados por essas torres demonstram a presença de ciclos diários de estabilidade atmosférica. Os erros de previsão cruzada foram calculados comparando-se as previsões de cada modelo com as medições reais registradas na posição das torres. O erro global médio de previsão cruzada entre torres anemométricas obtido com a composição dos modelos RANS “estável + neutro” foi de 3,8% enquanto o erro obtido apenas com o modelo RANS k-ε tradicional foi de 5,2%. Para o modelo linear WAsP, amplamente utilizado no setor eólico, o erro foi de 7,1%. Além dos erros de previsão cruzada entre torres, os perfis verticais de velocidade e os fatores de aceleração direcionais obtidos com a composição dos modelos RANS “estável + neutro” também sugerem que esta é uma alternativa versátil e promissora para capturar os ciclos de estabilidade atmosférica utilizando simulações numéricas em regime permanente. / Microscale numerical simulations of the atmospheric wind flow are the central focus of this study. These simulations are analysed from the wind energy perspective. Special attention is given to the usage and application of these simulations in energy production assessments for proposed wind farms. There are multiple uncertainty categories associated with energy production forecasts for future wind farms. However, in most cases the uncertainty factors related with wind flow modelling are the largest and most relevant of them all. The wording “flow model” refers to the numerical simulations (or “models”) that are used to extrapolate the anemometric data recorded at meteorological masts positions to the proposed wind turbine positions. Several authors have demonstrated through comparative studies that the “CFD RANS k-ε” models currently represent the “state of the art” when it comes to microscale wind flow simulations targeted at wind farms. Nonetheless, the atmospheric wind flow is turbulent by nature, and the dynamics of turbulent flows represent one of the scientific fields that have not yet been fully dominated by the human knowledge. The present study demonstrates that the majority of flow models currently available to mankind still lack in precision, even more so when it comes to modelling free atmospheric wind flow over complex terrain. One of the major weak spots of most microscale wind flow models is their inability to precisely simulate the wind flow that occurs during periods of atmospheric stability Numerous locations with large potential for wind energy production present cyclic periods of thermal stratification inside the atmospheric boundary layer. These cycles alter the dynamics and characteristics of the wind stream. With the purpose of improving wind flow simulations under stable atmospheric conditions, some modifications to the standard “RANS k-ε” model implementation are proposed. The most significant of these modifications are the usage of a potential temperature profile among the boundary conditions, the inclusion of the buoyancy forces in the “k-ε” equations and the simultaneous solution of the equations for energy balance and for potential temperature transport. This “modified” model was named “stable RANS”. It was validated using five well mounted meteorological masts installed in a location with complex topography. The anemometric data measured by these site masts suggest the existence of strong daily cycles of atmospheric stability. Cross prediction errors were calculated by comparing the forecasts (outputs) from each flow model against real wind data measured at each mast position The global average cross prediction error yielded by the RANS “stable +neutral” model was around 3,8%, whereas the error yielded by the traditional “RANS k-ε” implementation was near 5,2%. For the linear model WAsP the error was calculated to be 7,1%. In addition to cross prediction errors, the vertical wind speed profiles and speed-up factors calculated with the RANS “stable +neutral” model composition also suggest that it is a promising and versatile alternative for capturing the effects from atmospheric stability on wind flow using steady state numerical simulations.

abstract: Rapid urban expansion and the associated landscape modifications have led to significant changes of surface processes in built environments. These changes further interact with the overlying atmospheric boundary layer and strongly modulate urban microclimate. To capture the impacts of urban land surface processes on urban boundary layer dynamics, a coupled urban land-atmospheric modeling framework has been developed. The urban land surface is parameterized by an advanced single-layer urban canopy model (SLUCM) with realistic representations of urban green infrastructures such as lawn, tree, and green roof, etc. The urban atmospheric boundary layer is simulated by a single column model (SCM) with both convective and stable schemes. This coupled SLUCM-SCM framework can simulate the time evolution and vertical profile of different meteorological variables such as virtual potential temperature, specific humidity and carbon dioxide concentration. The coupled framework has been calibrated and validated in the metropolitan Phoenix area, Arizona. To quantify the model sensitivity, an advanced stochastic approach based on Markov-Chain Monte Carlo procedure has been applied. It is found that the development of urban boundary layer is highly sensitive to surface characteristics of built terrains, including urban land use, geometry, roughness of momentum, and vegetation fraction. In particular, different types of urban vegetation (mesic/xeric) affect the boundary layer dynamics through different mechanisms. Furthermore, this framework can be implanted into large-scale models such as Weather Research and Forecasting model to assess the impact of urbanization on regional climate. / Dissertation/Thesis / Doctoral Dissertation Civil and Environmental Engineering 2016