Numerical Modelling of Airflow Within and Above Forests and Forest Clearing Using Computational Fluid Dynamics PDF Download
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Author: Timothy James Phaneuf
Publisher:
ISBN:
Category : Clearcutting
Languages : en
Pages : 0
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Book Description
The computational fluid dynamics program, FLUENT, was first tested to validate windtunnel measurements of a scaled 10 ha forest clearing in a two dimensional domain. A variety of domain and canopy configurations were examined along with processor settings. Validation of the CFD program produced excellent results for horizontal wind velocity. Conifer shaped tree elements for the forest stands performed well and similar to the more traditional way of representing forest canopies. Turbulent kinetic energy (TKE) values output by the program seem to over predict the values calculated by using wind tunnel statistics. Various sizes of forest clearings were simulated to determine the stress that would be experienced by a forest edge immediately downwind of a clearing. Shorter gaps (15 tree heights) seem to experience high values of TKE over the downwind forest, compared to the stand upwind of the clearing; and lower stress values along the downwind forest edge. Large gaps (60 tree heights) saw higher stress values but TKE values no larger than those reported upwind of the clearing. From the stress values calculated from various input velocities and gap sizes, a new tool was produced which takes into account a sites endemic wind speed and canopy density to predict stress on forest edges downwind of clearings.
Author: Timothy James Phaneuf
Publisher:
ISBN:
Category : Clearcutting
Languages : en
Pages : 0
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Book Description
The computational fluid dynamics program, FLUENT, was first tested to validate windtunnel measurements of a scaled 10 ha forest clearing in a two dimensional domain. A variety of domain and canopy configurations were examined along with processor settings. Validation of the CFD program produced excellent results for horizontal wind velocity. Conifer shaped tree elements for the forest stands performed well and similar to the more traditional way of representing forest canopies. Turbulent kinetic energy (TKE) values output by the program seem to over predict the values calculated by using wind tunnel statistics. Various sizes of forest clearings were simulated to determine the stress that would be experienced by a forest edge immediately downwind of a clearing. Shorter gaps (15 tree heights) seem to experience high values of TKE over the downwind forest, compared to the stand upwind of the clearing; and lower stress values along the downwind forest edge. Large gaps (60 tree heights) saw higher stress values but TKE values no larger than those reported upwind of the clearing. From the stress values calculated from various input velocities and gap sizes, a new tool was produced which takes into account a sites endemic wind speed and canopy density to predict stress on forest edges downwind of clearings.
Author: Timothy James Phaneuf
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
The computational fluid dynamics program, FLUENT, was first tested to validate windtunnel measurements of a scaled 10 ha forest clearing in a two dimensional domain. A variety of domain and canopy configurations were examined along with processor settings. Validation of the CFD program produced excellent results for horizontal wind velocity. Conifer shaped tree elements for the forest stands performed well and similar to the more traditional way of representing forest canopies. Turbulent kinetic energy (TKE) values output by the program seem to over predict the values calculated by using wind tunnel statistics. Various sizes of forest clearings were simulated to determine the stress that would be experienced by a forest edge immediately downwind of a clearing. Shorter gaps (15 tree heights) seem to experience high values of TKE over the downwind forest, compared to the stand upwind of the clearing and lower stress values along the downwind forest edge. Large gaps (60 tree heights) saw higher stress values but TKE values no larger than those reported upwind of the clearing. From the stress values calculated from various input velocities and gap sizes, a new tool was produced which takes into account a sites endemic wind speed and canopy density to predict stress on forest edges downwind of clearings.
Author: Zhen-jia Li
Publisher:
ISBN:
Category : Air flow
Languages : en
Pages : 96
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Book Description
Author: Günter Groß
Publisher: Springer Science & Business Media
ISBN: 364275676X
Category : Science
Languages : en
Pages : 243
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Book Description
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.
Author: Joseph H. Shinn
Publisher:
ISBN:
Category : Atmospheric circulation
Languages : en
Pages : 218
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Book Description
New semi-empirical models are obtained of the mean momentum transport processes in and above forests for two contrasting micrometeorological problems: (1) the equilibrium air flow in forests far upwind of any inhomogeneity in the fetch, and (2) the nonequilibrium air flow in the transition region of the surface layer flow disturbed by the entrance into a forest. The study is confined to neutral stability conditions. Experimental data are from studies in eight forests and a wind tunnel simulation. The equilibrium mean velocity profiles in forest canopies are shown to be two-dimensional. A lateral component of flow increases downward from the top of the canopy. A semi-empirical model of mean velocity components is derived and verified for the upper 90% of the forest canopy depth. In the nonequilibrium flow in the transition region downwind of a forest wall: (a) The logarithmic velocity profile is found to be an empirical approximation for the lower part of the boundary layer, assuming that only the friction velocity varies with downstream distance. An empirical relation for the horizontal variation of the friction velocity is obtained. (b) The mean velocity profiles in a mixing zone located at midcanopy level are shown to have a low-level velocity maximum and horizontal similarity. (Author).
Author: Asmae El Bahlouli-Öztürk
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Book Description
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.
Author: D. R. Miller
Publisher:
ISBN:
Category : Forest canopies
Languages : en
Pages : 4
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Book Description
Author: John Lawrence Hayes
Publisher:
ISBN:
Category : Numerical weather forecasting
Languages : en
Pages : 63
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Book Description
The nature of the interaction of atmospheric flow with a mountain range of finite length is investigated. An inviscid, adiabatic primitive equation model is used to simulate steady, vertically-unsheared flow past a mountain range; various cases of mountain height and width are analyzed. A similar model for two-dimensional Boussinesq flow past a mountain on an f-plane is solved analytically following Merkine (1975) for comparison to the numerical solution. Results indicate that the atmospheric response is quite similar to that observed in the Boussinesq model. Ridging over the mountains and responses which damp in the vertical are observed in both models. Differences are noted in the magnitude of the response in the vicinity of the mountains and in the position of the downstream trough. In addition, the effect of finite difference model grid resolution is investigated by comparing simulations based on differing horizontal and vertical resolution. Results indicate that for larger scale mountains, the effect of poorer horizontal resolution is significant; vertical resolution, however, is relatively unimportant. As the horizontal scale of the mountains is reduced, vertical resolution becomes increasingly more important so that the effects of both horizontal and vertical resolution are significant. (Author).
Author: W. Z. Sadeh
Publisher:
ISBN:
Category :
Languages : en
Pages : 71
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Book Description
The velocity and longitudinal turbulence intensity distributions inside and above a forest canopy along its center line were investigated. For this purpose a model forest canopy was used in a meteorological wind tunnel. The results indicate that the flow may be divided into an entrance and fully developed region followed by a short adjustment distance close to canopy end. The entrance region has a decisive effect on the flow characteristics through the canopy. The velocity and turbulence inside the canopy are strongly affected by its structure. A similar qualitative variation for both velocity and turbulence was found in and above the canopy. Its influence stretches over more than 4 roughness heights above it. Generally, the results are in relatively reasonable agreement with field measurements. Investigation of the modified logarithmic law for describing the velocity profile above the canopy revealed that both flow parameters, i.e., friction velocity and roughness length, are not local constants. On the contrary, they vary drastically with height. It is suspected that this is due to the fact the assumption of constant shear stress throughout the boundary layer or significant portions of it is not satisfied. (Author).
Author: Luis A. Cisternas
Publisher: MDPI
ISBN: 3039284002
Category : Technology & Engineering
Languages : en
Pages : 232
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Book Description
Mineral processing deals with complex particle systems with two-, three- and more phases. The modeling and understanding of these systems are a challenge for research groups and a need for the industrial sector. This Special Issue aims to present new advances, methodologies, applications, and case studies of computer-aided analysis applied to multiphase systems in mineral processing. This includes aspects such as modeling, design, operation, optimization, uncertainty analysis, among other topics. The special issue contains a review article and eleven articles that cover different methodologies of modeling, design, optimization, and analysis in problems of adsorption, leaching, flotation, and magnetic separation, among others. Consequently, the topics covered are of interest to readers from academia and industry.
