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  • 1
    Electronic Resource
    Electronic Resource
    SHELTERBELTS AND WINDBREAKS: Mathematical Modeling and Computer Simulations of Turbulent Flows (2001)
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Fluid Mechanics 33 (2001), S. 549-586 
    Details
    ISSN: 0066-4189
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Shelterbelts or windbreaks were used for centuries to reduce wind speed, to control heat and moisture transfer and pollutant diffusion, to improve climate and environment, and to increase crop yields; but only within the last few decades have systematic studies considered the aerodynamics and shelter mechanisms of shelterbelts and windbreaks. This review examines recent modeling and numerical simulation studies as well as the mechanisms that control flow and turbulence around shelterbelts and windbreaks. We compare numerical simulations with experimental data and explain the relationships between sheltering effects and the structure of shelterbelts and windbreaks. We discuss how and why the desired effects are achieved by using numerical analysis. This chapter begins with the derivation of a general equation set for porous shelterbelts and windbreaks; the numerical model and simulation procedure are developed; unseparated and separated flows are predicted and characterized; the momentum budget and shelter mechanisms are analyzed; the effects of wind direction, density, width, and three dimensionality of shelterbelt structure on flow and turbulence are systematically described. Recent modeling and simulation of heat flux and evapotranspiration are also summarized. Finally, we discuss the use of high-performance distributed and parallel computing as well as clusters of networked workstations to enhance performance of the model applied to simulations of shelterbelts and windbreaks.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1146/annurev.fluid.33.1.549
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  • 2
    Electronic Resource
    Electronic Resource
    Application of a quasi-nonhydrostatic parameterization for numerically modeling neutral flow over an isolated hill (1988)
    Springer
    Boundary layer meteorology 44 (1988), S. 285-304 
    Details
    ISSN: 1573-1472
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract A parameterization of the nonhydrostatic pressure was modified and adapted to a nonlinear numerical model of the neutral atmospheric boundary layer. A hydrostatic model and the quasinonhydrostatic version were used to simulate neutral flow over a symmetrical hill of uniform roughness. Mean-flow quantities and some turbulence characteristics of the flow from both models are presented. These results were compared with observations, analytic theory, and other numerical models. The quasi-nonhydrostatic method produced qualitative features commonly observed in such flows that the hydrostatic model could not simulate. For instance, the observed velocity reduction at the hill base and the speedup at the summit both were simulated by the quasi-nonhydrostatic model. However, computation of vertical velocities from the incompressible continuity equation is inadequate above regions of recirculation and presents a limitation to the method.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00116067
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  • 3
    Electronic Resource
    Electronic Resource
    On three-dimensionality of shelterbelt structure and its influences on shelter effects (1996)
    Springer
    Boundary layer meteorology 79 (1996), S. 83-105 
    Details
    ISSN: 1573-1472
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Natural shelterbelts, unlike planar barriers, have a certain width, within which interactions among wind speed, drag force and pressure perturbations create a net sheltering effect. The variations of flow, drag force, permeability, and pressure perturbation for shelterbelts of different widths and different horizontal structures are numerically studied, and their influences on shelter efficiency are discussed. Comparisons are made of fourteen medium-dense shelterbelts, with the same overall leaf-area, that differ only in width or horizontal distribution of leaf-area density. The simulated results are consistent with both field observations and wind-tunnel measurements. The simulations demonstrate that the total drag force of the entire shelterbelt varies little with changes in width and structure. The results also show that shelter distance and the overall average wind speed reduction decrease only by 15–18% as width increases by a factor of 100, and changes even less for different internal structure. However, width greatly affects the location of minimum wind speed, pressure perturbation, and the permeability of shelterbelts. Horizontal changes of wind speed inside the uniform shelterbelts have four different patterns, which depend on shelterbelt width and height. The absolute pressure perturbation significantly decreases with increasing width. A possible cause of the insensitivity of shelter efficiency to width and internal inhomogeneous structure is the compensation between the effects of permeability and pressure perturbation on shelter efficiency.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00120076
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  • 4
    Electronic Resource
    Electronic Resource
    A numerical study of the influence of an air temperature-inversion layer and a seawater density-jump layer on the structure of interacting boundary layers (1994)
    Springer
    Boundary layer meteorology 67 (1994), S. 327-343 
    Details
    ISSN: 1573-1472
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The effects of an air-temperature inversion in the atmosphere and a seawater density jump in the ocean on the structure of the atmospheric and oceanic boundary layers are studied by use of a coupled model. The numerical model consists of a closed system of equations for velocities, turbulent kinetic energy, turbulent exchange coefficient, local turbulent length scale, and stratification expressions for both air and sea boundary layers. The effects of the temperature inversion and the density jump are incorporated into the equations of turbulent kinetic energy of the atmosphere and ocean by a parameterization. A series of numerical experiments was conducted to determine the effects of various strengths of the inversion layer and surface heat fluxes in the atmosphere and of the density-jump layer in the ocean on the structure of the interacting boundary layers. The numerical results show that the temperature inversion in the atmosphere and density jump in the ocean have strong influences on turbulent structure [especially on the turbulent exchange coefficient (TEC) and turbulent kinetic energy (TKE)] and on air-sea interaction characteristics. Maxima of TKE and TEC strongly decrease with increasing strength of the inversion layer, and they disappear for strong inversions in the atmosphere. Certain strengths (density differences between the upper and the lower layers) of the density-jump layer in the ocean (Δρ2 ⩾0.1 g/cm3) produce double maxima in TEC-profiles and TKE-profiles in the ocean. The magnitudes of air-sea interaction characteristics such as geostrophic drag coefficient, and surface drift current increase with increasing strength of the density-jump layer in the ocean. The density-jump layer plays the role of a barrier that limits vertical mixing in the ocean. The numerical results agree well with available observed data and accepted quantitive understanding of the influences of a temperature inversion layer and a density-jump layer on the interacting atmospheric and oceanic boundary layers.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00705437
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  • 5
    Electronic Resource
    Electronic Resource
    Evaluation of an alternative method for numerically modeling nonhydrostatic flows over irregular terrain (1988)
    Springer
    Boundary layer meteorology 44 (1988), S. 181-206 
    Details
    ISSN: 1573-1472
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Modeling nonhydrostatic atmospheric flow requires the solution of the vertical equation of motion and a prognostic or diagnostic equation for pressure. If the nonhydrostatic components of the flow are relatively small, they can be approximated and incorporated into a purely hydrostatic model, which usually is conceptually simpler and computationally more efficient. A method to do this for a linear model of local thermally-induced circulations is further developed and adapted to a non-linear numerical model of the neutral atmospheric boundary layer. A hydrostatic model and the quasi-nonhydrostatic version were used to simulate neutral flow over simple terrain features. One set of observations taken over a simple change in roughness and another set taken over a change in both roughness and terrain were simulated by both models to assess the capabilities of the quasi-nonhydrostatic technique. It is found that (as expected) the pressure deviation from the hydrostatic state is negligible for the roughness change, but it is an important aspect of neutral flow over terrain. Thus, for flow encountering a simple roughness change, the hydrostatic approximation is good, even for small horizontal scales. However, the quasi-nonhydrostatic model qualitatively produces the features in the observations for flow over a terrain change that the hydrostatic model cannot produce.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00117298
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  • 6
    Electronic Resource
    Electronic Resource
    Interaction of the sea breeze with a river breeze in an area of complex coastal heating (1991)
    Springer
    Boundary layer meteorology 56 (1991), S. 101-139 
    Details
    ISSN: 1573-1472
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract A three-dimensional finite-element mesoscale model is used to study the interaction of two different but related mesoscale phenomena in an area having a complex pattern of surface heating. The model simulations have been compared with temperature and wind fields observed on a typical fall day during the Kennedy Space Center Atmospheric Boundary Layer Experiment on the east coast of Florida. Numerical results and observations both show that the meso-β scale flow field is significantly modified from the conventional coastal-flow patterns by the smaller meso-γ scale irregular geographic features in this area. A local river breeze is observed to develop around the Indian River almost the same time as the Atlantic sea breeze. A comparison of the sea and the river breezes shows a large difference in their horizontal circulations but only slight differences in their vertical scales. The sea breeze intensifies more rapidly than the river breeze, so that a lag of 1 to 1.5 h exists between their most developed stages. The river breeze is relatively stationary, whereas the sea breeze propagates inland, with an eventual merger of the two circulations occurring about 6–8 h after their onset. Different synoptic wind regimes create different flow structures. Well-defined sea- and river-breeze circulations become established under calm, weak offshore, and weak alongshore synoptic-wind conditions. Maximum vertical velocities occur in the sea-breeze front (river-breeze front) in the cases of calm (offshore winds). The sea breeze and the river breeze are weaker when the synoptic winds are stronger. Finally, the results from numerical experiments designed to isolate the rivers' effect indicate that the convergence in the sea-breeze front is suppressed when it passes over the cooler surface of the rivers.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00119964
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  • 7
    Electronic Resource
    Electronic Resource
    Boundary-layer flow and turbulence near porous obstacles (1995)
    Springer
    Boundary layer meteorology 74 (1995), S. 73-88 
    Details
    ISSN: 1573-1472
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract We derive a set of governing equations for flow through porous obstacles by employing a two-step averaging processes. The Navier-Stokes equations under the Boussinesq approximation that describe the air space of the porous obstacle are subjected to high-wavenumber a veraging, which leads to a set of high-frequency (wake) turbulence equations. We then use conventional Reynolds-averaging methods to obtain statistically steady mean and turbulence equations that include interactions between wake and shear turbulence. Our method provides a theoretical basis for the cascade of turbulent kinetic energy. We use this approach to analyze the constants and parameters of simpleK-theory and higher-order closure models. We also discuss qualitatively the theory of the turbulence energy generation process and the significance of interactions between different turbulent mechanisms.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00715711
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  • 8
    Electronic Resource
    Electronic Resource
    A numerical simulation of boundary-layer flows near shelterbelts (1995)
    Springer
    Boundary layer meteorology 75 (1995), S. 141-173 
    Details
    ISSN: 1573-1472
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract We have developed a shelterbelt boundary-layer numerical model to study the patterns and dynamic processes relating to flow interaction with shelterbelts. The model simulates characteristics of all three zones of airflow passing over and through shelterbelts: the windward windspeed-reduction zone, the overspeeding zone above the shelterbelt, and the leeward windspeed-reduction zone. Locations of the maximum windspeed reduction and recirculation zone, as well as the leeward windspeed-recovery rate are well simulated by the model. Where comparisons with field measurements and wind-tunnel experiments were possible, the model demonstrated good performance for flows over and through shelters ranging from almost completely open to almost solid. The dynamic pressure resulting from the convergence and divergence of the flow field alters the perturbation pressure field. The disturbed pressure controls not only the formation of the separated flow but also the location of maximum windspeed reduction, streamline curvature, speed-up over the shelterbelt, and leeward windspeed recovery rate. The interaction of pressure with the flow produces complex flow patterns, the characteristics of which are determined, to a great extent, by shelterbelt structure.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00721047
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  • 9
    Electronic Resource
    Electronic Resource
    Reply to Comments by J. D. Wilson and C. J. Mooney on ’a Numerical Simulation of Boundary-Layer Flows Near Shelterbelt'S (1997)
    Springer
    Boundary layer meteorology 85 (1997), S. 151-159 
    Details
    ISSN: 1573-1472
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1000496425393
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  • 10
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    100 Years of Progress in Mesoscale Planetary Boundary Layer Meteorological Research (2019)
    American Meteorological Society
    Details
    Publication Date: 2019-01-01
    Description: This chapter outlines the development of our understanding of several examples of mesoscale atmospheric circulations that are tied directly to surface forcings, starting from thermally driven variations over the ocean and progressing inland to man-made variations in temperature and roughness, and ending with forced boundary layer circulations. Examples include atmospheric responses to 1) overocean temperature variations, 2) coastlines (sea breezes), 3) mesoscale regions of inland water (lake-effect storms), and 4) variations in land-based surface usage (urban land cover). This chapter provides brief summaries of the historical evolution of, and tools for, understanding such mesoscale atmospheric circulations and their importance to the field, as well as physical processes responsible for initiating and determining their evolution. Some avenues of future research we see as critical are provided. The American Meteorological Society (AMS) has played a direct and important role in fostering the development of understanding mesoscale surface-forced circulations. The significance of AMS journal publications and conferences on this and interrelated atmospheric, oceanic, and hydrological fields, as well as those by sister scientific organizations, are demonstrated through extensive relevant citations.
    Print ISSN: 0065-9401
    Electronic ISSN: 1943-3646
    Topics: Geography , Geosciences , Physics
    Published by American Meteorological Society
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