Modelling Of Atmospheric Flow Fields
Modelling Of Atmospheric Flow Fields

Author: Demetri P Lalas

Publisher: World Scientific

Published: 1996-01-11

Total Pages: 768

ISBN-13: 9814602833

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This volume is a collection of lectures given at the two colloquia on atmospheric flows over complex terrain with applications to wind energy and air pollution, organized and sponsored by ICTP in Trieste, Italy. The colloquia were the result of the recognition of the importance of renewable energy sources, an important aspect which grows yearly as the environmental problems become more pronounced and their effects more direct and intense, while at the same time, the wise management of the Earth's evidently limited resources becomes imperative.It is divided into two main parts. The first, which comprises Chaps. 1 to 4, presents the structure of the atmospheric boundary layer with emphasis in the region adjacent to the ground. The second, Chaps. 5 to 10, discusses methods for the numerical computation of the wind field on an arbitrary terrain. The unique feature of this book is that it does not stop at the theoretical exposition of the analytical and numerical techniques but includes a number of codes, in a diskette, where the mechanisms and techniques presented in the main part are implemented and can be run by the reader. Some of the codes are of instructional value while others can be utilized for simple operational work.Some of the lecturers are: D N Asimakopoulos, C I Aspliden, V R Barros, A K Blackadar, G A Dalu, A de Baas, D Etling, G Furlan, D P Lalas, P J Mason, C F Ratto and F B Smith.

Numerical Simulation of Canopy Flows
Numerical Simulation of Canopy Flows

Author: Günter Groß

Publisher: Springer Science & Business Media

Published: 2012-12-06

Total Pages: 243

ISBN-13: 364275676X

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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.

Simulations of Neutral Atmospheric Boundary Layer Flow Over Complex Terrain with Comparisons to Field Measurements
Simulations of Neutral Atmospheric Boundary Layer Flow Over Complex Terrain with Comparisons to Field Measurements

Author: Yi Han

Publisher:

Published: 2019

Total Pages: 172

ISBN-13: 9781088395493

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The present work establishes a complete process to perform the micro-scale simulations of the neutral atmospheric boundary layer (ABL) flow over realistic terrain with multi-fidelity turbulence modeling approaches, and to validate the numerical predictions with the available on-site wind data. The complex terrain is located within the Chokecherry and Sierra Madre wind farm site which encompasses about 500 square kilometers of rugged and diverse terrain in south-central Wyoming. A robust conditional sampling procedure for the meteorological tower (met-tower) data to identify near-neutral ABL condition based on a criterion of the turbulence intensity is developed. The conditionally averaged wind data on fourteen met-towers is used for the model validation. The ABL flow simulations are conducted based on the OpenFOAM-based simulator for on/offshore wind farm applications (SOWFA) with both RANS and LES turbulence modeling approaches. The turbulent inflow is generated through a two-stage iterative approach using a precursor method. Appropriate boundary conditions are developed to adjust the real flow patterns over the complex terrain. In the RANS approach, a new formulation to calculate the production term in the transport equation for the turbulent kinetic energy (TKE) is developed to greatly reduce the commonly observed nonphysical near-surface TKE peak, and to improve the prediction of law-of-the-wall scaling in the near-surface region. In the LES approach, a low-dissipative, scale-selective discretization scheme is applied to the non-linear convection term of the filtered momentum equation. The aim is to reduce the numerical dissipation arising from the typically adopted upwind-biased schemes while maintaining second-order accuracy. The simulation results from both RANS and LES approaches are qualitatively compared with each other, and quantitatively compared to the conditional met-tower data in terms of the mean, standard deviation and direction of the wind at three about ground levels. The instantaneous flow field and turbulent structures are predicted by the LES approach. Overall, the wind statistic obtained by RANS and LES approaches show reasonable agreement compared to the met-tower data, except for some under-predictions at four met-tower located closer to the main ridge of the hill in a region of strong terrain variations.

Numerical Modelling of Atmospheric Flows Over Complex Sites with Special Regard to the Forest Canopy
Numerical Modelling of Atmospheric Flows Over Complex Sites with Special Regard to the Forest Canopy

Author: Asmae El Bahlouli-Öztürk

Publisher:

Published: 2021

Total Pages: 0

ISBN-13:

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The present thesis describes the work carried out using the OpenFOAM solver with a Reynolds-Averaged Navier Stokes (RANS) approach to investigate the wind flow at complex sites for wind-energy exploitation. Toward this objective, several physical effects such as buoyancy, forest canopies, Coriolis forces, stratification as well as humidity have been implemented in the model to improve wind-field predictions. First, the wind flow in an urban environment and, more precisely, a university campus is investigated. A stationary logarithmic profile for the wind velocity at the inlet is prescribed. Despite the assumption of a flat terrain, which is a drastic simplification of the real ground, the study shows how a simple canopy model improves the prediction of the flow at the site. The simulation is validated with long term measurements from a network of six stations. Secondly, results from a rural case in the Swabian Alb in Southern Germany, characterized by a forested escarpment, are presented. The model is adapted to atmospheric boundary layer (ABL) flows and a computational domain with a ground conforming to the site orography is built. To get more realistic boundary conditions and to avoid the assumption of logarithmic profiles, the solver is coupled with a numerical weather prediction (NWP) model. The coupling is performed using a one-way approach, i.e the coarse weather model provides input to the OpenFOAM solver through the lateral boundary conditions of the computational domain. Simulations with and without forest are compared. The results with a canopy model clearly show at the lower levels a flow deceleration and an increase in turbulence intensities by a factor of four, when compared to results without forest. The study reveals again the important impact of the forest on the wind-field, especially at turbine-relevant heights. Finally, the transient approach (unsteady RANS) is tested by using time-dependent boundary conditions. The accuracy of the coupling is evaluated by validating the simulation results against measurements from a tall meteorological tower as well as an unmanned aircraft system. Adopting a transient approach leads to an excellent agreement of the model. The thesis shows that an unsteady RANS based solver, which accounts for first-order relevant physics, can be valuable for a wind resource assessment at low computational cost compared to detached-eddy (DES) or large-eddy (LES) simulations.

The Atmospheric Boundary Layer
The Atmospheric Boundary Layer

Author: J. R. Garratt

Publisher: Cambridge University Press

Published: 1994-04-21

Total Pages: 340

ISBN-13: 9780521467452

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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.

Boundary Layer Structure
Boundary Layer Structure

Author: Hadassah Kaplan

Publisher: Springer Science & Business Media

Published: 2012-12-06

Total Pages: 480

ISBN-13: 9400965141

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In this volume, we present the lectures given during the 1984 OHOLO Conference, held in Zichron Yaacov, Israel. The Conference was organized by the Israel Institute for Biological Research, Department of Mathematics, which is involved in Environmental Risk Evaluation, and in Projects Estimating the Potential of Wind Energy. The lectures cover a broad spectrum of mathematical models, ranging from those that deal with the solution of atmospheric conservation equations, and to those models that yield empirical estimates based on real time measure ments and thus are unique to the locale where measured. The goal of the Conference was to allow scientists from various countries to meet and discuss topics of mutual interest, including the following: 1. Structure of the boundary layer - primarily models dealing in the understanding of the various processes of atmospheric energy transfer, and their influence on the size and composition of the boundary 1 ayer. 2. Advanced mathematical techniques for describing flow and diffusion - lectures on approximations and techniques for solving the diffu sion and transport equations. 3. Flow over complex terrain - research into various aspects of the problem - mathematical models, physical models, experimental results. 4. Models of pollution transport and deposition.

Large-eddy Simulations of Atmospheric Flows Over Idealized and Realistic Double-hill Terrain in the WRF Model
Large-eddy Simulations of Atmospheric Flows Over Idealized and Realistic Double-hill Terrain in the WRF Model

Author: Yayun Qiao

Publisher:

Published: 2020

Total Pages:

ISBN-13:

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Airflow over complex terrain throughout the atmospheric boundary layer (ABL) governs the transport and mixing of mass, momentum, and heat. Topography causes obstruction of the airflow and generates airflow distortion and turbulence. Perturbations in land-atmosphere interactions cause various weather phenomena like cold-air pools (CAPs) leading to changes in many aspects of weather and climate that impact the optimal position of wind-turbine, forest-fire behavior, and forecasting, as well as trace-gas and pollutant dispersion. This thesis investigates the flow over complex terrain, specifically double-hill terrain, with new numerical model approaches. The first study utilizes the Weather Research and Forecasting (WRF) model with large eddy simulations (LES) and the immersed-boundary method (IBM) to improve the simulations of the flow and recirculation regions over steep double-hill terrain. The gap distance controls the flow distribution behind both hills. The upwind hill has a significant influence on the second hill. When the gap distance is too small, the flow after the upwind hill cannot regain its momentum. The second study examines the flow distribution over a forested double-hill and the impact of the gap distance between two hills on scalar transport (CO2 and H2O). This study uses the WRF-LES model coupled with a new multiple-layer canopy module (MCANOPY module). We find that flow recirculation is the primary factor dominating scalar transport. Scalars are transported and trapped in both recirculation regions and accumulated on the lee sides of both hills. Our simulation shows the occurrence of two vortices on the lee side of the upstream hill enhances the accumulation of scalars in the valleys. In the end, we extend our work from the first study to understand flow patterns over a realistic double-hill topography. Results show that the valley gap distance is so small that the recirculation region in the valley between two hills cannot fully develop. Additionally, the WRF-IBM captures the structure of microscale flows that other models have not captured in the previous studies.