Wind Flow Behaviour Research Articles

High-Resolution Simulation of the Near-Field Pollutant Dispersion in a Nuclear Power Plant Community with High-Performance Computing

This study aims to employ numerical simulations to understand the dynamics of wind fields and air pollutant dispersion in the proximity of a nuclear plant, situated within a specified urban environment. By leveraging computational fluid dynamics (CFD) combined with geographical information system (GIS) data, the research comprehensively models atmospheric interactions in terms of wind flow patterns, building-induced pressure variances, and pollutant trajectories. The computational domain extends over an area of 8.8km×8.4km\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$8.8\\,\ extrm{km} \ imes 8.4\\,\ extrm{km}$$\\end{document}, vertically stretching to 0.5 km. The wind and pollutant distribution equations are discretized using the finite volume method, providing detailed insights into fluid interactions with urban topographies. Key findings highlight the profound influences of terrain, urban structures, and wind flow behavior on the dispersion of radioactive aerosols, shedding light on potential risks and safety protocols for nuclear plant environments.

Numerical analysis of airfoils used in an omni-directional-guide vane structure of vertical axis wind turbine for high-rise buildings

This document introduces a novel concept involving an Omni-Directional Guided Vane (ODGV) encompassing a vertical axis wind turbine (VAWT) with the goal of improving its overall performance. Extensive three-dimensional computational analysis of the airfoils used in this novel ODGV structure is conducted to investigate the impact of various geometric parameters. Diverse geometric configurations of the ODGV are explored to analyze wind flow behavior across the turbine utilizing a well-validated computational fluid dynamics (CFD) model. The numerical investigations employ the Reynolds Averaged Navier–Stokes (RANS) modeling approach with the k-epsilon turbulence model. The steady state governing equations are solved using the validated CFD solver STAR CCM+. The study considers three distinct inlet velocities: 3, 6, and 9[Formula: see text]m/s, with the aim of improving flow behavior and velocity through the ODGV. Four different modifications of the ODGV are examined, and the accuracy of the CFD model is affirmed through comparison with NACA airfoil data. Integration of the ODGV results in an enhanced self-starting behavior of the VAWT, leading to a reduction in the cut-in speed. Validation results demonstrate a strong agreement with the data obtained from CFD simulations. These results suggest that most shape ratios, except for 0.3 and 0.4 at Tip Speed Ratio (TSR) of 1.3 and 3, contribute to enhancing power and torque coefficients. Furthermore, the findings indicate that with a Sharpe ratio of 0.56, both torque and power coefficients could be improved by up to 48% and 58%, respectively.

Validation and application of pressure-driven RANS approach for wind parameter predictions in mountainous terrain

Computational Wind Engineering has undergone numerous developments over the past few decades and has been applied to solve a variety of wind engineering issues, but it cannot substitute wind tunnel testing and field measurements for accurately replicating wind characteristics in naturally hilly terrain. This paper is aimed at detecting the validity of the approach on numerical simulations by estimating wind flow behaviour at a bridge site in a Y-shaped valley and comparing the results from wind tunnel testing. Further, the terrain-induced effects on wind flow are investigated and the spatial distributions of wind parameters along the bridge structures are characterized. It is concluded that three Reynolds-Averaged Navier-Stokes (RANS) turbulence models, namely k-ε, k-ω and SST, make significant differences in the leeward regions and wind velocity, speed-up, and pitch angle profiles, with the k-model producing superior predictions within 20% error when compared to experimental results. The simulation results show that non-homogeneity of wind characteristics occurs frequently along bridge structures. One is significant rotations of the wind velocity profile up the height of both bridge towers, and then a practical equation for predicting wind deflection is proposed. The other is spanwise nonuniformities in mean wind speeds and pitch angles along the main girder, which necessitates the use of a modified terrain coefficient when securely predicting wind speed. The discussion of a few national bridge design codes reveals that most of them fall short of characterizing the wind load at the bridge site in mountainous areas.

Wind responses on twin box girder bridge deck using a fluid–structure interaction approach

Wind responses on a twin box girder bridge can be observed by a wind tunnel experiment or by having a full-scale setup if possible. Another possible approach is to go through a numerical approach, which is the CFD simulation of the atmospheric boundary layer surrounding the twin box girder bridge deck. A virtual wind tunnel CFD modelling simulation was carried out on the bridge deck using the Ansys Fluent FSI technique to find out the displacement of the bridge deck. The steady-state simulations were computed. The turbulence model was used to calculate the mean force coefficients as K-ω SST. It has been seen that steady simulation is needed to get the static aerodynamic coefficients right when modelling. Ansys ICEM CFD is used for meshing the bridge deck. In this study, the wind flow behaviour around the structure is analysed at different wind incident angles of − 10°, − 5°, 0°, 5°, and 10°. The pressure variations at different wind directions are mapped in the present work. Responses across and along the wind are also depicted. It was found that the drag coefficient was higher at low angles of attack, whereas the moment and the lift coefficients showed fewer values at large angles.

Effects of Interference of Hill on Wind Flow around Tall Buildings Situated in Hilly Region Using CFD

Abstract: The location of tall building in complex region, wind is the powerful factor exerted on tall buildings. This pressure has a direct affected on the drag force. The drag force has a significant impact on the building's surface. All the faces of a tall building's drag force or maximum pressure coefficient have generally been measured through wind tunnel experiments. It's difficult and costly, but it's the best option. Computational Fluid Dynamics (CFD) has been used in this study to determine the external pressure coefficient on the front and back sides of a tall building in the presence of hill interference in complex region. In addition, the current research investigates the behaviour of wind flow around tall buildings at different location of hill first scenario the top of a hill, second scenario the front and third scenario back zones of a hill, and the interactions between tall buildings and the hill itself

Investigations of Exterior Wind Flow and Aerodynamic Coefficient around Y-Plan Shape Tall Building

In recent years, the construction of skyscrapers is emerging in many countries and the study on the behaviour of wind around the building receives an additional interest among structural engineers and architects. Mostly, tall skyscrapers are planned in the shape of ‘Y’ in order to have a maximum exterior view and to support the central core of the structure. In the current scenario, it is important to study the actual wind load for irregular plan shape building. This paper presents the numerical wind flow simulation around ‘Y’ plan shape tall building using ANSYS Fluent software and validation is done using wind tunnel testing. The building model and wind velocity are scaled to the ratio 1:300 and 1:5 respectively. A wind velocity of 10 m/s is applied both for wind tunnel testing and for the numerical simulation. Error analysis is carried out in order to check the accuracy of the results obtained between wind tunnel and CFD. From the test results the mean Cp is investigated for various faces of the building for the wind angle 0˚, 45˚ and 90˚ from both using CFD and wind tunnel. The investigation of drag and lift coefficient is made on Y-plan shape building and it is observed that the maximum drag occurs at 45˚ wind angle, because of the less projected area when compared with the other wind angles 0˚ and 90˚ respectively. Further, this paper continues with the physics of wind flow behaviour around Y-plan shape building and flow character such as vortex formation, streamlines and identification of wake region for different wind angles.

The impact of dynamic wind flow behavior on forest fire spread using cellular automata: Application to the watershed BOUKHALEF (Morocco)

Modeling the forest fire phenomena represents one of the most challenging and difficult problems, which need further investigations. Many research works have tackled this issue by developing simulation models in order to investigate the impact of climate change on fire spread behavior. In our previous work, a forest fire spread model has been introduced. The developed model takes into account some parameters that affect this phenomenon, such as topography, land use, nature and density of vegetation, humidity and wind by only considering uniform wind direction and speed. The work presented in this paper provides an improvement of this model for being integrated in real-sitting scenarios. In fact, a model of wind flow has been proposed. It is able to determine accurately the wind direction and speed according to the topography and land use. The proposed model was evaluated using dataset from a region in the north of Morocco, and results are reported to show the impact of the dynamic behavior of the wind on fire propagation.

High-Resolution Analysis of Wind Flow Behavior on Ship Stacks Configuration: A Portuguese Case Study

Atmospheric emissions related to harbor-related activities can significantly contribute to air pollution of coastal urban areas and so, could have implications to the citizens’ health that live in those areas. Of great concern is the local impact of the emissions that are generated while ships are at berth, since not all types of ships switch off the main engines. This paper intends to investigate the influence of the stack configuration for generic cargo ships on the exhaust smoke dispersion, using the Port of Leixões as a case study and a series of wind tunnel experiments with support of Particle Image Velocimetry (PIV) technique. For that, different configurations of the stack of a cargo ship (in terms of height, geometry and diameter) were simulated under the typical wind conditions of the study area. The PIV results indicate negligible differences between the medium and long stack height, with the short stack height presenting a strong impact on the flow field around the stack. For the short stack height, the flow field is not only disturbed by the stack, but also by the cargo ship bridge, with both obstacles promoting disturbances on the flow field and creating a large wake turbulence effect, which is important for the downwash phenomena. Regarding the effects linked with two distinct geometries (straight or curved), the results show that the straight chimney led to higher perturbation of wind field when compared with the curved geometry. The curved stack presents an increase of vorticity, indicating the generation of more turbulent structures. The PIV results also confirmed that higher wind velocity at the inlet conducts to higher vorticity levels, as well as a higher number of Kelvin–Helmholtz structures. For distinct wind conditions the PIV measurements point out different patterns, indicating the northern wind direction as the most favorable condition for the exposure of dock workers to pollutants. Overall, the results showed that a ship stack with a curved end, medium length and smaller diameter has the capability to promote the behaviors in the flow that are coherent with increased pollutant dispersion.

Numerical investigation of scale resolved turbulence models (LES, ELES and DDES) in the assessment of wind effects on supertall structures

Scale resolved turbulence models, such as large eddy simulation (LES), have been increasingly utilised in applications of computational wind engineering (CWE) for tall buildings, due to their proven numerical accuracy. The demand for computational time and resources in LES is still a concern in practical applications of CWE, where it is necessary to explore alternative modelling techniques. The main objective of this study is to critically investigate the possibility of using a computationally efficient hybrid RANS/LES approach, specifically embedded-LES (ELES), to predict wind effects on a supertall 406 m slender tower of non-standard geometry. Numerical predictions of LES and ELES are compared and critically analysed with experimental results obtained by performing boundary layer wind tunnel (BLWT) tests. It was shown that the choice of sub-grid scale (SGS) modelling in LES has an impact on the wind effects predicted on the structure. Out of the five SGS models tested, the wall adapting local eddy viscosity (WALE) model was the most suitable due to its treatment of the near wall region. An optimum domain configuration based on a parametric study was proposed for the application of ELES. The importance of overall mesh quality and its impact on fluctuating pressures and dynamic properties of wind is presented. Wind flow behaviour on the structure, such as Von-Karman vortex shedding and its dynamic implications, is also discussed. Finally, using the proposed modelling techniques, ELES can generate similar numerical accuracy to that of an LES model at a lower computational cost.

Experimental and computational investigation of outdoor wind flow around a setback building

In recent days, the behaviour of wind flow around the buildings receives more interest among urban planners, architects, researchers and wind engineers. Hence, these wind flow patterns are assessed extensively using CFD (Computational Fluid Dynamics) simulations, as it re-creates the atmospheric and wind tunnel environment following the turbulence parameters. This paper presents a logical assessment using IDDES (Improved Delayed Detached Eddy Simulation) turbulence model in CFD for predicting wind pressure coefficients and flow features on and around a 300:1 scaled setback tall building model at 0° and 90° AOI (Angle of Incidence) under open terrain condition. The computation is based on gird sensitivity study and validation with Boundary Layer Wind Tunnel (BLWT) experiment measurements. The evaluation shows that the downdraught and downwind effects are suppressed by the increasing wind pressure distribution along the height. The results demonstrate that IDDES can reproduce wind pressure coefficients and aerodynamic coefficients of the setback building accurately. The maximum deviation of the wind pressure coefficients (Cp rms) is found to be 12% in CFD when compared with wind tunnel measurements. Besides, the CFD simulation demonstrates the wind flow distribution patterns, size of re-circulation, wake separation zones and velocity profiles in a three-dimensional plane which are quantified concerning the width of the building.

Design and Flow Simulation of Concentrator Augmented Wind Turbine

In order for wind technology to compete with conventional sources of energy in terms of energy production costs, researchers are working on different ways to increase the energy density in wind and therefore augment wind turbine power output. Concentrator augmented wind turbines (CAWTs) have been thought to be one of the ways to augment wind turbine power output and hence improve the cost effectiveness of wind energy. This concept involves enclosing the wind turbine rotor with a duct that reduces in cross-sectional area downstream of the blade-plane and hence increasing mass flow rate through the turbine. No efforts have been done to commercialize this concept because little is known about the wind flow behaviour in the CAWT, its influence on turbine power output and the optimum concentrator design parameters. The main objective of this research is to propose a new design for CAWT and optimize the concentrator design parameters. Furthermore, the effect of wind velocity and air pressure on the proposed design concepts are also investigated. Four different CAWT design concepts were designed and simulated using Solidworks and Computational Fluid Dynamics (CFD) tool Ansys Fluent, respectively. The wind velocity and air pressure vs. the position of convergent nozzle were plotted. Results showed an outstanding improvement in wind speed, which is 16.1 m/s (5.4 times increment), over the 3 m/s inlet wind velocity in the design concept 3 (CAWT 3.0) with the nozzle angle 20°.

A field‐based parameterization of wind flow recovery in the lee of dryland plants

AbstractWind erosion is a key component of land degradation in vulnerable dryland regions. Despite a wealth of studies investigating the impact of vegetation and windbreaks on windflow in controlled wind‐tunnel and modelling environments, there is still a paucity of empirical field data for accurately parameterizing the effect of vegetation in wind and sediment transport models. The aim of this study is to present a general parameterization of wind flow recovery in the lee of typical dryland vegetation elements (grass clumps and shrubs), based on their height (h) and optical porosity (θ). Spatial variations in mean wind velocity around eight isolated vegetation elements in Namibia (three grass clumps and five shrubs) were recorded at 0.30 m height, using a combination of sonic and cup anemometry sampled at a temporal frequency of 10 seconds. Wind flow recovery in the lee of the elements was parameterized in an exponential form, . The best‐fit parameters derived from the field data were u0 = uref(0.0146θ − 0.4076) and b = 0.0105θ + 0.1627. By comparing this parameterization to existing models, it is shown that wind recovery curves derived from two‐dimensional wind fence experiments may not be suitable analogues for describing airflow around more complex, three‐dimensional forms. Field‐derived parameterizations such as the one presented here are a crucial step for connecting plant‐scale windflow behaviour to dryland bedform development at landscape scales. © 2016 The Authors. Earth Surface Processes and Landforms published by John Wiley & Sons Ltd.

La sinergia entre el diseño estructural y la dinámica de fluidos: el caso particular del velódromo de Medellín, en Colombia

This paper presents the advantages that the performance determination of wind actions from methods based in computational fluid dynamics has in the structural design of buildings with tapered or complex geometry. The analysis of the wind flow behaviour in lighter and more ethereal architectural and structural designs by means of advanced simulation tools, that use a wide theoretical ground based in fluid dynamics and continuum, has made possible to minimise the impact of wind loads in the size of the main structural elements. This paper shows the work methodologies that have allowed to optimize the main structure of the new Cycle track of Medellin, in Colombia.

Measurement of Wind Flow Behavior at the Leeward Side of Porous Fences Using Ultrasonic Anemometer Device

Efficiency of wind fences is evaluated by the reduction of wind velocity and the effective shelter area behind the fence. Fence porosity is the most influential structural parameters in the porous fence design, and has significant impact on the structure of wind velocity and turbulence leeward. In this work, three fences with porosity of 23%, 35% and 45% have been tested under 10m/s inlet velocity in an environmental wind tunnel. An ultrasonic anemometer was used to measure three dimensional velocity vectors and the fluctuations of velocity vectors with a designed spatial resolution. The obtained data were used to calculate velocity magnitudes, turbulence intensities and turbulent kinetic energies in the test domain. Porosity influencing the structure of turbulence intensity and effective fence zone were discussed in this paper. Neither the distribution of wind velocities nor the structure of turbulence alone can provide sufficient information to assess the performance of porous fences. Consideration of the targeted reduction rate of wind velocity needs to be taken for optimal fence design.

Wind Speed Measurements in the Vicinity of a Tubular Mast: Influence of Data Selection Methods on Wind Speed Average Determination

Wind measurements form an intrinsic part of the site selection process leading up to wind project development. Anemometers mounted on wind monitoring structures are expected to capture information on the free wind stream. However, the impacts of the structure and other hardware required to secure the sensors may have a marked influence on the data being compiled. This paper examines wind flow behaviour in the vicinity of an 80 metre tubular wind mast located at Ahrax Point on the Mediterranean Island of Malta. Mast and ancillary equipment effects are identified and quantified for two intermediate monitoring heights where dual and opposite anemometers were installed. A number of wind speed filtering methodologies are analysed in order to assess the methods' capabilities in reducing mast structure interference while enabling a conservative assessment of a site's wind potential.

Three dimensional airflow patterns within a coastal trough–bowl blowout during fresh breeze to hurricane force winds

Abstract Wind flow within blowouts is extremely complex as streamline compression, expansion and reversal may occur over and around a single landform. As a result high resolution temporal and spatial measurements are required during a range of incident wind conditions to resolve near surface airflow patterns and turbulent structures. This study examined three-dimensional airflow within a coastal dune trough–bowl blowout using 15 ultrasonic anemometers (UAs) and a high resolution computational fluid dynamics model. Measured total wind speed and vertical wind speed behaved consistently through 5 Beaufort wind scales ranging from ‘fresh breeze’ to ‘strong gale’, increasing relative to incident wind speed, whilst wind direction at each UA did not alter. Due to the agreement of modelled and measured data, ‘hurricane’ (37 m s −1 ) incident winds were also simulated and were consistent with modelled and measured wind direction at lower wind speeds. Modelled wind turbulence data was not compared with measured as only average conditions were simulated. However, the standard deviation of measured wind direction remained constant at each anemometer throughout the range of incident wind speeds, whilst the standard deviation of wind speed and turbulent kinetic energy increased relative to incident wind speed. This paper demonstrates that wind flow behaviour within blowouts throughout this range of wind speeds is governed by topography and is relative to, but does not change structurally with incident wind speed. As a result the extent of streamline compression, expansion, steering and reversal remain constant.

Modelling and analysis of a novel wind turbine structure

This study introduces a novel wind turbine structure for an urban environment. A computational modelling has been conducted to investigate the effect of the new structure on the flow behaviour of entrance wind through the structure and the feasibility of the new wind turbine working at different wind speeds in an urban area. The wind flow behaviour through a chamber of the wind turbine structure has resulted in an increase of 1.3 times of the wind velocity at the outlet of the wind turbine. This is equivalent to 2.5 times increase of wind energy. The wind tunnel tests were carried out to validate the simulation results. There is a good correlation between the experimental and computational results. It is evident that the presented computational method can predict and evaluate the performance of this new type of shroud structure in an urban environment.

Investigation of three‐dimensional wind flow behaviour over coastal dune morphology under offshore winds using computational fluid dynamics (CFD) and ultrasonic anemometry

ABSTRACTThe behaviour of offshore‐directed winds over coastal dune and beach morphology was examined using a combination of modelling (3‐D computational fluid dynamics (CFD)) and field measurement. Both model simulations and field measurements showed reversal of offshore flows at the back beach and creation of an onshore sediment transport potential. The influence of flow reversals on the beach‐dune transport system and foredune growth patterns has previously received little attention. Detailed wind flow measurements were made using an extensive array of mast‐mounted, 3‐D ultrasonic anemometers (50 Hz), arranged parallel to the dominant incident wind direction. Large eddy simulation (LES) of the offshore wind flow over the dune was conducted using the open‐source CFD tool openFOAM. The computational domain included a terrain model obtained by airborne LiDAR and detailed ground DGPS measurements. The computational grid (~22 million cells) included localized mesh refinement near the complex foredune terrain to capture finer details of the dune morphology that might affect wind flows on the adjacent beach.Measured and simulated wind flow are presented and discussed. The CFD simulations offer new insights into the flow mechanics associated with offshore winds and how the terrain steering of wind flow impacts on the geomorphological behaviour of the dune system. Simulation of 3‐D wind flows over complex terrain such as dune systems, presents a valuable new tool for geomorphological research, as it enables new insights into the relationship between the wind field and the underlying topography. The results show that offshore and obliquely offshore winds result in flow reversal and onshore directed winds at distances of up to 20 m from the embryo dune toe. The potential geomorphological significance of the findings are discussed and simple calculations show that incoming offshore and obliquely offshore winds with mean velocities over 13 m s−1 and 7 m s−1, respectively, have the potential to create onshore‐directed winds at the back beach with mean velocities above 3.3 m s−1. These are above the threshold of movement for dry sand and support previous conclusions about the significance of offshore winds in dune and beach budget calculations. Copyright © 2011 John Wiley & Sons, Ltd.

CFD wind tunnel test: Field velocity patterns of wind on a building with a refuge floor

This paper reports a CFD wind tunnel study of wind patterns on a square-plan building with a refuge floor at its mid-height level. In this study, a technique of using calibrated power law equations of velocity and turbulent intensity applied as the boundary conditions in CFD wind tunnel test is being evaluated by the physical wind tunnel data obtained by the Principal Author with wind blowing perpendicularly on the building without a refuge floor. From the evaluated results, an optimised domain of flow required to produce qualitative agreement between the wind tunnel data and simulated results is proposed in this paper. Simulated results with the evaluated technique are validated by the wind tunnel data obtained by the Principal Author. The results contribute to an understanding of the fundamental behaviour of wind flow in a refuge floor when wind is blowing perpendicularly on the building. Moreover, the results reveal that the designed natural ventilation of a refuge floor may not perform desirably when the wind speed on the level is low. Under this situation, the refuge floor may become unsafe if smoke was dispersed in the leeward side of the building at a level immediately below the refuge floor.

A turbulent flow over a curved hill Part 1. Growth of an internal boundary layer

Two experiments were performed to study the response of turbulent boundary layers to sudden changes in surface curvature and pressure gradient. In the first experiment, the behaviour of a boundary layer negotiating a two-dimensional curved hill was examined. Prior to separating on the leeward side of the hill, the layer experienced a short region of concave surface curvature, followed by a prolonged region of convex surface curvature. The corresponding pressure gradient changed from adverse to favourable, and back to adverse. In the second experiment, the flow over a symmetrical wing was studied. This wing had the same profile as the hill with a very similar pressure distribution. The obvious difference between the two experiments was the use of leading and trailing edge plates in the hill flow. The results show that an internal layer forms in the flow over the curved hill, and that this internal layer displays many similarities to the boundary layer observed on the free wing. The internal layer grows as an independent boundary layer beneath a turbulent free-shear layer, and as it develops it establishes its own wall (inner) and wake (outer) regions. The perturbation responsible for initiating the growth of the internal boundary layer seems to be an abrupt change in surface curvature. Once formed, the internal boundary layer dictates the skin-friction distribution and the process of separation over the hill. The effect of the perturbation in wall curvature appears to be different from that due to prolonged convex curvature in that the former affects the flow in the vicinity of the wall instantly, while the latter affects the flow far away from the wall only after the flow turns through some angle. Physical explanations are offered for the qualitative difference between the effects of mild and strong convex curvature, and for the saturated behaviour observed in strongly curved flows. Finally, the results are compared with the behaviour of wind flow over terrestrial hills. In both cases, the internal layer dominates the flow behaviour, even though the scaling laws for the flows over actual hills are not obeyed in the present case. A qualitative comparison reveals that the present internal layer is thicker than that reported in meteorological flows. This appears to be due to the effect of curvature, which perturbs the wake region of the internal layer in the present hill flow, while in meteorological studies the effect of curvature is generally small enough to be neglected.