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A Comparison Between A First Order Closure Model For Disturbed Urban Canopy Flows With Observations For Mean Wind And Turbulence
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Book Synopsis A Comparison Between a First-Order Closure Model for Disturbed Urban Canopy Flows with Observations for Mean Wind and Turbulence by :
Download or read book A Comparison Between a First-Order Closure Model for Disturbed Urban Canopy Flows with Observations for Mean Wind and Turbulence written by and published by . This book was released on 2001 with total page 79 pages. Available in PDF, EPUB and Kindle. Book excerpt: Two canopy windflow models (basic model and alternative model) are described and assessed against measurements of mean wind and turbulence in a wide range of canopies (both vegetative and urban). The windflow models are based on a first-order turbulence closure for the description of both the mean wind (U) and kinetic energy of turbulence (kappa), viz. Reynolds' equations are closed using eddy-viscosity K lambda kappa 1/2, where lambda is an algebraically specified turbulence length scale. The windflow models are compared with eleven different canopy flows (aeroelastic plant canopy; corn canopy; square and staggered arrays of cubical obstacles at three different frontal area densities 0.0625, 0.16, AND 0.44; square and staggered arrays of billboard-shaped obstacles at a frontal area density of 0.16; and, the Tombstone canopy). Comparisons of model predictions with these different canopies show that the alternative windflow model gives the best overall conformance with respect to both mean flow and turbulence profiles. The basic windflow model was found to underpredict the turbulence kinetic energy within the canopy, although this underprediction does not appear to affect its reasonably good predictions of the mean wind speed and the shear stress. However, both the basic and alternative windflow models underpredict severely the magnitude of the mean wind shear at the canopy top for 'urban' canopies at the highest frontal area density 0.44 investigated. It is suggested that the alternative windflow model can be used probably unmodified (viz., without resorting to tuning of any model constants) for the simulation of a wide range of canopy flows provided the frontal area densities of the 'urban' canopies are not so large as to provoke skimming flow.
Book Synopsis A One-dimensional Mean Wind and Turbulence Model for a Uniform Urban Canopy by :
Download or read book A One-dimensional Mean Wind and Turbulence Model for a Uniform Urban Canopy written by and published by . This book was released on 2000 with total page 44 pages. Available in PDF, EPUB and Kindle. Book excerpt: This report presents a fully analytical model for the prediction of the one-dimensional mean wind speed, kinematic shear stress, turbulence kinetic energy, and velocity variances in a horizontally homogeneous canopy. The model was developed originally for vegetative canopies such as forests, but is applied in the report to urban canopies. The report shows how to derive analytical expressions for the within-canopy velocity variances using two methods: equilibrium partitioning and algebraic stress model partitioning. Model predictions are compared with some measurements of mean flow & turbulence statistics obtained in two urban canopies. The results show the degree of success of the model in providing estimates of a number of important flow quantities. The model provides all the statistics of the wind field required as input to drive a physically-based model for the prediction of urban dispersion of contaminants.
Book Synopsis A One-Dimensional Mean Wind and Turbulence Model for a Uniform Urban Canopy by : Eugene C. Yee
Download or read book A One-Dimensional Mean Wind and Turbulence Model for a Uniform Urban Canopy written by Eugene C. Yee and published by . This book was released on 2000 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: This report presents a fully analytical model for the prediction of the one-dimensional mean wind speed, kinematic shear stress, turbulence kinetic energy, and velocity variances in a horizontally homogeneous canopy. The model was developed originally for vegetative canopies such as forests, but is applied in the report to urban canopies. The report shows how to derive analytical expressions for the within-canopy velocity variances using two methods: equilibrium partitioning and algebraic stress model partitioning. Model predictions are compared with some measurements of mean flow & turbulence statistics obtained in two urban canopies. The results show the degree of success of the model in providing estimates of a number of important flow quantities. The model provides all the statistics of the wind field required as input to drive a physically-based model for the prediction of urban dispersion of contaminants.
Book Synopsis The Atmospheric Boundary Layer by : J. R. Garratt
Download or read book The Atmospheric Boundary Layer written by J. R. Garratt and published by Cambridge University Press. This book was released on 1994-04-21 with total page 340 pages. Available in PDF, EPUB and Kindle. Book excerpt: The book gives a comprehensive and lucid account of the science of the atmospheric boundary layer (ABL). There is an emphasis on the application of the ABL to numerical modelling of the climate. The book comprises nine chapters, several appendices (data tables, information sources, physical constants) and an extensive reference list. Chapter 1 serves as an introduction, with chapters 2 and 3 dealing with the development of mean and turbulence equations, and the many scaling laws and theories that are the cornerstone of any serious ABL treatment. Modelling of the ABL is crucially dependent for its realism on the surface boundary conditions, and chapters 4 and 5 deal with aerodynamic and energy considerations, with attention to both dry and wet land surfaces and sea. The structure of the clear-sky, thermally stratified ABL is treated in chapter 6, including the convective and stable cases over homogeneous land, the marine ABL and the internal boundary layer at the coastline. Chapter 7 then extends the discussion to the cloudy ABL. This is seen as particularly relevant, since the extensive stratocumulus regions over the subtropical oceans and stratus regions over the Arctic are now identified as key players in the climate system. Finally, chapters 8 and 9 bring much of the book's material together in a discussion of appropriate ABL and surface parameterization schemes in general circulation models of the atmosphere that are being used for climate simulation.
Book Synopsis A Study of Planetary Boundary Layer Forcing on the Turbulent Flow Characteristics of Tree Canopies Using Project Wind Data by :
Download or read book A Study of Planetary Boundary Layer Forcing on the Turbulent Flow Characteristics of Tree Canopies Using Project Wind Data written by and published by . This book was released on 1997 with total page 33 pages. Available in PDF, EPUB and Kindle. Book excerpt: A non-local closure numerical model based on the Transilient Turbulence Theory (TTT) has been developed and verified in and above a homogeneous tree canopy. The first order volumetrically averaged governing equations for momentum, heat and humidity were coupled dynamically with canopy processes such as evapotranspiration and radiation within the canopy. The simulated profiles of momentum, heat, and humidity, were compared to measurements in a homogeneous orchard during project WIND. The model provides evidence that non-local turbulence closure by TTT is a consistent and efficient technique to parameterize the turbulent transport near the ground in canopies as well as above and can be incorporated into numerical models. The spatial resolution in surface parameterizations for spatially distributed models was quantified using spatial autocorrelations. The resulting error prediction model was used to quantify the statistical errors due averaging different patch sizes and contrasts. Sensitivity of process models to these averaging errors in boundary conditions was quantified using probable error vectors. Overall these efforts have rigorously set the stage for future use of the non-local turbulent transport approach and as an efficient and accurate method to model spatially distributed canopy flow in three dimensions.
Book Synopsis Numerical Simulation of Canopy Flows by : Günter Groß
Download or read book Numerical Simulation of Canopy Flows written by Günter Groß and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 243 pages. Available in PDF, EPUB and Kindle. Book excerpt: Starting with the description of meteorological variables in forest canopies and its parameter variations, a numerical three-dimentional model is developed. Its applicability is demonstrated, first, by wind sheltering effects of hedges and, second, by the effects of deforestation on local climate in complex terrain. Scientists in ecology, agricultural botany and meteorology, but also urban and regional lanners will profit from this study finding the most effective solution for their specific problems.
Download or read book Urban Climates written by T. R. Oke and published by Cambridge University Press. This book was released on 2017-09-14 with total page 549 pages. Available in PDF, EPUB and Kindle. Book excerpt: Urban Climates is the first full synthesis of modern scientific and applied research on urban climates. The book begins with an outline of what constitutes an urban ecosystem. It develops a comprehensive terminology for the subject using scale and surface classification as key constructs. It explains the physical principles governing the creation of distinct urban climates, such as airflow around buildings, the heat island, precipitation modification and air pollution, and it then illustrates how this knowledge can be applied to moderate the undesirable consequences of urban development and help create more sustainable and resilient cities. With urban climate science now a fully-fledged field, this timely book fulfills the need to bring together the disparate parts of climate research on cities into a coherent framework. It is an ideal resource for students and researchers in fields such as climatology, urban hydrology, air quality, environmental engineering and urban design.
Book Synopsis Characterization and Modeling of Atmospheric Flow Within and Above Plant Canopies by : Livia Souza Freire Grion
Download or read book Characterization and Modeling of Atmospheric Flow Within and Above Plant Canopies written by Livia Souza Freire Grion and published by . This book was released on 2017 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The turbulent flow within and above plant canopies is responsible for the exchange of momentum, heat, gases and particles between vegetation and the atmosphere. Turbulence is also responsible for the mixing of air inside the canopy, playing an important role in chemical and biophysical processes occurring in the plants environment. In the last fifty years, research has significantly advanced the un- derstanding of and ability to model the flow field within and above the canopy, but important issues remain unsolved. In this work, we focus on (i) the estimation of turbulent mixing timescales within the canopy from field data; and (ii) the development of new computationally efficient modeling approaches for the coupled canopy-atmosphere flow field.The turbulent mixing timescale represents how quickly turbulence creates a well- mixed environment within the canopy. When the mixing timescale is much smaller than the timescale of other relevant processes (e.g. chemical reactions, deposition), the system can be assumed to be well-mixed and detailed modeling of turbulence is not critical to predict the system evolution. Conversely, if the mixing timescale is comparable or larger than the other timescales, turbulence becomes a controlling factor for the concentration of the variables involved; hence, turbulence needs to be taken into account when studying and modeling such processes. In this work, we used a combination of ozone concentration and high-frequency velocity data measured within and above the canopy in the Amazon rainforest to characterize turbulent mixing. The eddy diffusivity parameter (used as a proxy for mixing efficiency) was applied in a simple theoretical model of one-dimensional diffusion, providing an estimate of turbulent mixing timescales as a function of height within the canopy and time-of-day. Results showed that, during the day, the Amazon rainforest is characterized by well-mixed conditions with mixing timescales smaller than thirty minutes in the upper-half of the canopy, and partially mixed conditions in the lower half of the canopy. During the night, most of the canopy (except for the upper 20%) is either partially or poorly mixed, resulting in mixing timescales of up to several hours. For the specific case of ozone, the mixing timescales observed during the day are much lower than the chemical and deposition timescales, whereas chemical processes and turbulence have comparable timescales during the night. In addition, the high day-to-day variability in mixing conditions and the fast increase in mixing during the morning transition period indicate that turbulence within the canopy needs to be properly investigated and modeled in many studies involving plant-atmosphere interactions.Motivated by the findings described above, this work proposes and tests a new approach for modeling canopy flows. Typically, vertical profiles of flow statistics are needed to represent canopy-atmosphere exchanges in chemical and biophysical processes happening within the canopy. Current single-column models provide only steady-state (equilibrium) profiles, and rely on closure assumptions that do not represent the dominant non-local turbulent fluxes present in canopy flows. We overcome these issues by adapting the one-dimensional turbulent (ODT) model to represent atmospheric flows from the ground up to the top of the atmospheric boundary layer (ABL). The ODT model numerically resolves the one-dimensional diffusion equation along a vertical line (representing a horizontally homogeneous ABL column), and the presence of three-dimensional turbulence is added through the effect of stochastic eddies. Simulations of ABL without canopy were performed for different atmospheric stabilities and a diurnal cycle, to test the capabilities of this modeling approach in representing unsteady flows with strong non-local transport. In addition, four different types of canopies were simulated, one of them including the transport of scalar with a point source located inside the canopy. The comparison of all simulations with theory and field data provided satisfactory results. The main advantages of using ODT compared to typical 1D canopy-flow models are the ability to represent the coupled canopy-ABL flow with one single modeling approach, the presence of non-local turbulent fluxes, the ability to simulate transient conditions, the straightforward representation of multiple scalar fields, and the presence of only one adjustable parameter (as opposed to the several adjustable constants and boundary conditions needed for other modeling approaches).The results obtained with ODT as a stand-alone model motivated its use as a surface parameterization for Large-Eddy Simulation (LES). In this two-way coupling between LES and ODT, the former is used to simulate the ABL in a case where a canopy is present but cannot be resolved by the LES (i.e., the LES first vertical grid point is above the canopy). ODT is used to represent the flow field between the ground and the first LES grid point, including the region within and just above the canopy. In this work, we tested the ODT-LES model for three different types of canopies and obtained promising results. Although more work is needed in order to improve first and second-order statistics within the canopy (i.e. in the ODT domain), the results obtained for the flow statistics in the LES domain and for the third order statistics in the ODT domain demonstrate that the ODT-LES model is capable of capturing some important features of the canopy-atmosphere interaction. This new surface superparameterization approach using ODT provides a new alternative for simulations that require complex interactions between the flow field and near-surface processes (e.g. sand and snow drift, waves over water surfaces) and can potentially be extended to other large-scale models, such as mesoscale and global circulation models.
Book Synopsis Turbulence in the Atmosphere by : John C. Wyngaard
Download or read book Turbulence in the Atmosphere written by John C. Wyngaard and published by Cambridge University Press. This book was released on 2010-01-28 with total page 407 pages. Available in PDF, EPUB and Kindle. Book excerpt: Based on his over forty years of research and teaching, John C. Wyngaard's textbook is an excellent up-to-date introduction to turbulence in the atmosphere and in engineering flows for advanced students, and a reference work for researchers in the atmospheric sciences. Part I introduces the concepts and equations of turbulence. It includes a rigorous introduction to the principal types of numerical modeling of turbulent flows. Part II describes turbulence in the atmospheric boundary layer. Part III covers the foundations of the statistical representation of turbulence and includes illustrative examples of stochastic problems that can be solved analytically. The book treats atmospheric and engineering turbulence in a unified way, gives clear explanation of the fundamental concepts of modeling turbulence, and has an up-to-date treatment of turbulence in the atmospheric boundary layer. Student exercises are included at the ends of chapters, and worked solutions are available online for use by course instructors.
Book Synopsis Climate Change and Terrestrial Ecosystem Modeling by : Gordon Bonan
Download or read book Climate Change and Terrestrial Ecosystem Modeling written by Gordon Bonan and published by Cambridge University Press. This book was released on 2019-02-21 with total page 459 pages. Available in PDF, EPUB and Kindle. Book excerpt: Provides an essential introduction to modeling terrestrial ecosystems in Earth system models for graduate students and researchers.
Book Synopsis Second-order Closure Models for Rotating Turbulent Flows by : Charles G. Speziale
Download or read book Second-order Closure Models for Rotating Turbulent Flows written by Charles G. Speziale and published by . This book was released on 1985 with total page 32 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Boise National Forest (N.F.), Prince John Timber Sale, Valley County by :
Download or read book Boise National Forest (N.F.), Prince John Timber Sale, Valley County written by and published by . This book was released on 1997 with total page 276 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Principles of Environmental Physics by : John Monteith
Download or read book Principles of Environmental Physics written by John Monteith and published by Butterworth-Heinemann. This book was released on 1990-02-15 with total page 308 pages. Available in PDF, EPUB and Kindle. Book excerpt: Thoroughly revised and up-dated edition of a highly successful textbook.
Book Synopsis Coastal Meteorology by : National Research Council
Download or read book Coastal Meteorology written by National Research Council and published by National Academies Press. This book was released on 1992-02-01 with total page 112 pages. Available in PDF, EPUB and Kindle. Book excerpt: Almost half the U.S. population lives along the coast. In another 20 years this population is expected to more than double in size. The unique weather and climate of the coastal zone, circulating pollutants, altering storms, changing temperature, and moving coastal currents affect air pollution and disaster preparedness, ocean pollution, and safeguarding near-shore ecosystems. Activities in commerce, industry, transportation, freshwater supply, safety, recreation, and national defense also are affected. The research community engaged in studies of coastal meteorology in recent years has made significant advancements in describing and predicting atmospheric properties along coasts. Coastal Meteorology reviews this progress and recommends research that would increase the value and application of what is known today.
Book Synopsis Computational Fluid Dynamics by : Adela Ionescu
Download or read book Computational Fluid Dynamics written by Adela Ionescu and published by BoD – Books on Demand. This book was released on 2018-02-14 with total page 412 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book is the result of a careful selection of contributors in the field of CFD. It is divided into three sections according to the purpose and approaches used in the development of the contributions. The first section describes the "high-performance computing" (HPC) tools and their impact on CFD modeling. The second section is dedicated to "CFD models for local and large-scale industrial phenomena." Two types of approaches are basically contained here: one concerns the adaptation from global to local scale, - e.g., the applications of CFD to study the climate changes and the adaptations to local scale. The second approach, very challenging, is the multiscale analysis. The third section is devoted to "CFD in numerical modeling approach for experimental cases." Its chapters emphasize on the numerical approach of the mathematical models associated to few experimental (industrial) cases. Here, the impact and the importance of the mathematical modeling in CFD are focused on. It is expected that the collection of these chapters will enrich the state of the art in the CFD domain and its applications in a lot of fields. This collection proves that CFD is a highly interdisciplinary research area, which lies at the interface of physics, engineering, applied mathematics, and computer science.
Book Synopsis Atmospheric Boundary Layer Flows by : J. C. Kaimal
Download or read book Atmospheric Boundary Layer Flows written by J. C. Kaimal and published by Oxford University Press, USA. This book was released on 1994 with total page 304 pages. Available in PDF, EPUB and Kindle. Book excerpt: This text gives a simple view of the structure of the boundary layer, the instruments available for measuring its mean and turbulent properties, how best to make the measurements, and ways to process and analyze the data.
Author :Task Committee on Outdoor Human Comfort Publisher :ASCE Publications ISBN 13 :9780784475379 Total Pages :76 pages Book Rating :4.4/5 (753 download)
Book Synopsis Outdoor Human Comfort and Its Assessment by : Task Committee on Outdoor Human Comfort
Download or read book Outdoor Human Comfort and Its Assessment written by Task Committee on Outdoor Human Comfort and published by ASCE Publications. This book was released on 2004-01-01 with total page 76 pages. Available in PDF, EPUB and Kindle. Book excerpt: Prepared by the Task Committee on Outdoor Human Comfort of the Aerodynamics Committee of the Aerospace Division of ASCE This report describes state-of-the-art methods for assessing and improving outdoor human comfort. Factors affecting outdoor comfort are wind, air temperature, humidity, sun, and precipitation. Wind, in particular, is greatly affected by large buildings, and many modern developments are wind-tunnel tested to examine how wind flows around new buildings will affect pedestrians. This report discusses testing methods and criteria for assessing comfort and safety. Criteria are expressed in terms of both threshold wind speeds for discomfort and also the percentage of time that conditions should be below those thresholds. Historically, wind and its mechanical effects?such as picking up dust, impairing balance, or blowing people over?were the factors receiving the most attention. More recently, however, methods have been developed to address other factors, such as solar radiation, air temperature, and humidity. Topics include: elements of the microclimate; methods of determining wind conditions; wind criteria and control measures; and assessing thermal comfort.
