Wind Fence Research Articles

Aerial dispersal of Venturia inaequalis ascospores with under-canopy sprinkler irrigation for apple scab management

AbstractSprinkler irrigation systems can release ascospores of Venturia inaequalis, the cause of apple scab, from infected leaves on the ground under conditions unsuitable for infection, and thus reducing the primary inoculum. Under-canopy irrigation was carried out for two hours in the middle of the day over overwintered apple leaves heavily infected with scab, either in a wind-protected enclosure or in a wind-exposed orchard. Ascospores were captured with rotating-arm spore traps at heights ranging from 0.3 m to 3.0 m above the ground. Ascospores dispersed above the irrigated layer and were detected at all heights above the sprinklers. Wind played a critical role in spore transport, evident from the set-up where wind interference was minimised by a wind fence, resulting in higher airborne spore numbers across all measured heights compared with the orchard exposed to unrestricted wind conditions. Furthermore, vertical temperature gradients significantly correlated with spore distributions, particularly where negative gradients at heights between 0.3 m and 0.05 m and positive gradients at heights between 1.0 m and 0.3 m led to spore retention within the irrigated zone. The findings highlight that ascospores, dispersed above the irrigated layers, could settle on susceptible tissues. It thus becomes imperative to ensure a rain-free period of at least 24 h post-irrigation and, if a rainfall shortly occurs after irrigation, the application of curative fungicides becomes essential following unexpected rain. Reliable weather forecasts are therefore crucial in determining the effectiveness of under-canopy irrigation to reduce apple scab incidence.

Richard Raspet's contributions to our understanding of low-frequency wind noise

Richard Raspet's research in wind noise spanned three decades and took the acoustics community from a rudimentary understanding of how low-frequency wind noise is generated in pressure sensors to a firm theoretical understanding derived from first principles in fluid dynamics. This talk will present a technical overview of his work starting with early quantitative studies, progressing through the development of the theoretical framework for wind noise studies, and finishing with a summary of research including wind noise at the ground surface, wind noise under tree canopies, wind fences, and wind induced seismic noise.

Effects of Wind-Induced Error on the Climatology and Trends of Observed Precipitation in China from 1960 to 2018

Abstract Since the 1950s, precipitation has been measured at national weather stations in China using national standard precipitation gauges. Gauges without a wind fence can significantly underestimate precipitation amounts, while this undercatch bias is closely related to surface wind speed and precipitation type. The observed surface wind speed across China has substantially declined during the past decades. Therefore, this study investigated the wind-induced error of the observed precipitation and its impact on regional and national mean trends in precipitation over China due to the reduction in surface wind speed. It was found that the wind-induced error for the mean annual precipitation nationwide was 29.28 mm yr−1, accounting for 3.92% of total precipitation amount. The variation of precipitation at the regional scale was large but the trends were both positive and negative, approximately cancelling at the national level and resulting in a small national mean trend. The raw observation data showed that the national mean precipitation increased at a rate of 1.85 mm yr−1 (10 a)−1 from 1960 to 2018, which was reduced to 0.33 mm yr−1 (10 a)−1 after correction, demonstrating that the correction of wind-induced error had an important impact on the trend of annual precipitation. Meanwhile, the reduction of surface wind speed was consistent at both the regional and national levels. On average, the wind-induced errors decreased at rates of −1.52, −1.34, and −0.14 mm yr−1 (10 a)−1 for total precipitation, rainfall, and snowfall, respectively. It illustrates that the decreases of the wind-induced error result in the increasing precipitation of raw observation.

Heavy-Vehicle Response to Crosswind: Evaluation of Driver Reactions Using a Dynamic Driving Simulator

Heavy vehicles exiting (or entering) a tunnel at high speed under a strong crosswind is a particularly critical condition since the aerodynamic load changes drastically, greatly affecting the lateral stability of the vehicle. Often, active control systems (active suspensions, active front steering, etc.) and infrastructure elements (e.g., wind fences) are proposed to reduce the induced risks. To help the design of these devices, the present paper investigates the response of the vehicle–driver system in the case of a high-sided lorry exiting a tunnel under crosswind, by using Driver-In-the-Loop simulations. The study was performed using the dynamic driving simulator of Politecnico di Milano and 28 test drivers. Vehicle and aerodynamic models have been developed to reproduce the phenomenon in a highly immersive environment. During the tests, several combinations of vehicle and wind speed were considered. The effect of vehicle loading condition (Empty and Laden) was also investigated. The performed tests allowed us to gain information about the sequence of the driver’s actions and associated delays, which may induce lane deviation or, in the worst case, rollover. It was found that lane invasion may happen for ratios of lateral aerodynamic force over vehicle weight force bigger than 0.1, while rollover could happen for ratios bigger than 0.3. Moreover, it was found that the driver’s response typically happens with a delay of ∼0.25 s with respect to the onset of the crosswind stimulus.

Wind Load Effect Study on Large-Aperture Parabolic Trough Collector Mirror Fields

Abstract Large-aperture parabolic trough collectors (LPTCs) are recognized as one of the most promising next-generation linear-focus concentrating solar power (CSP) technologies. However, large apertures inevitably introduce higher wind loads and stronger inter-row interactions. In the present study, a multi-physics-coupled model is established to study the wind load effect on multiple rows of LPTCs. First, it is found that wind load fluctuates significantly in the first four rows and then decreases gradually. The first and second rows suffer the most and least damage, respectively. Because wind load effect is highly dependent on the row number, it is recommended to build wind fences and reinforce the strength of collectors according to their positions in the solar field. Second, the wind load reduction effectiveness of the varied focal length design, incorporated in the LPTC, is numerically validated so that the stress and optical efficiency loss can be reduced by 29.1% and 58.9%, respectively. Finally, the optical efficiency loss is first introduced to evaluate the wind load reduction performance of different mirror gap sizes. The optimal mirror gap size is found to be dependent on the weight coefficient between the wind load reduction and the optical efficiency, which should be determined by the actual scenario. For weight coefficients of 1:1, 1:2, and 2:1, optimal mirror gap sizes of 90 mm, 30 mm, and 120 mm, respectively, are recommended for reference.

Optimal design for wind fence based on 3D numerical simulation

Vegetative windbreaks and wind barriers are the two most important types of wind fences for controlling soil erosion by wind and are often used in combination. However, optimal configurations of wind fences have rarely been investigated, especially wind fences combining vegetative windbreaks and wind barriers. This study systematically explored the optimal configuration of the combined wind fence based on morphological observation data of wild Artemisa arenaria, Salix psammophila, and artificially planted Caragana korshinskii using three-dimensional computational fluid dynamics (CFD) technology. Furthermore, the airflow fields around wind fences were simulated using the shear stress transport(SST)k−ω Reynolds Average Navier Stokes (RANS) turbulence model in OpenFOAM. The effectiveness of different wind fences was compared in terms of the multiple barrier effectiveness index “mBEI” and a proposed index, downwind speed percentage “DSP”. The main findings are as follows: (1) The combined wind fence showed much higher shelter efficiency than either pure wind barriers or pure wild vegetative windbreaks. The shelter efficiency of the artificially planted Caragana windbreak was higher than that of naturally growing vegetative windbreaks irrespective of double-row or triple-row planting, and even exceeded that of the combined wind fence at higher wind speeds. (2) Regarding symbiotic wind fences with high-low shrubs, wind fences with a row of artificially planted shrubs showed higher shelter efficiency than those with pure wild shrubs. The shelter efficiency of wind fences was mainly determined by the morphological traits of plants and wind barriers. The results of this study can provide direct reference for practical sand control engineering.

Spatial composition and building techniques of farmhouses prone to windstorms:a case study in Arakawa Village, Shiga Prefecture, Japan

ABSTRACT In Arakawa Village, the strong Hira downslope windstorm blowing from the Hira Mountains toward Lake Biwa, poses a great challenge for timber housing structures, which are prone to deformation. To understand the countermeasures applied in local farmhouses to mitigate the effect of wind attacks, features of historical housing and land lot layouts from the Meiji Era (1868–1912) were studied and interviews with local villagers and craftsmen were conducted. It was found that a significant majority of houses were built along the wind direction, with a closed front façade. Contrariwise, subsidiary structures, such as storage buildings and retirement houses, were placed perpendicularly to the wind direction, forming wind fences to protect the front yards, which served as agricultural workspaces. The features of spatial composition have been explained by local craftsmen as technical countermeasures; according to them, farmhouses were built on an incline of about 3–5 cm into the wind direction to mitigate deformation of timber structure. The study suggests that spatial composition of vernacular farmhouses and building techniques could offer effective strategies for sustainable rural planning and be employed to enhance the wind resistance of modern timber constructions, especially for regions prone to powerful prevailing winds worldwide.

Arctic observations and numerical simulations of surface wind effects on Multi-Angle Snowflake Camera measurements

Abstract. Ground-based measurements of frozen precipitation are heavily influenced by interactions of surface winds with gauge-shield geometry. The Multi-Angle Snowflake Camera (MASC), which photographs hydrometeors in free-fall from three different angles while simultaneously measuring their fall speed, has been used in the field at multiple midlatitude and polar locations both with and without wind shielding. Here, we present an analysis of Arctic field observations – with and without a Belfort double Alter shield – and compare the results to computational fluid dynamics (CFD) simulations of the airflow and corresponding particle trajectories around the unshielded MASC. MASC-measured fall speeds compare well with Ka-band Atmospheric Radiation Measurement (ARM) Zenith Radar (KAZR) mean Doppler velocities only when winds are light (≤5ms-1) and the MASC is shielded. MASC-measured fall speeds that do not match KAZR-measured velocities tend to fall below a threshold value that increases approximately linearly with wind speed but is generally <0.5ms-1. For those events with wind speeds ≤1.5ms-1, hydrometeors fall with an orientation angle mode of 12∘ from the horizontal plane, and large, low-density aggregates are as much as 5 times more likely to be observed. Simulations in the absence of a wind shield show a separation of flow at the upstream side of the instrument, with an upward velocity component just above the aperture, which decreases the mean particle fall speed by 55 % (74 %) for a wind speed of 5 m s−1 (10 m s−1). We conclude that accurate MASC observations of the microphysical, orientation, and fall speed characteristics of snow particles require shielding by a double wind fence and restriction of analysis to events where winds are light (≤5ms-1). Hydrometeors do not generally fall in still air, so adjustments to these properties' distributions within natural turbulence remain to be determined.

Large-eddy simulationによる遮風フェンスを考慮した貯炭場内風速分布の予測

Large-eddy simulationによる遮風フェンスを考慮した貯炭場内風速分布の予測

Geomorphologic characteristics and evolution of managed dunes on the South West Coast of France

The calibrated foredunes of the Aquitaine coast (SW France) constitute an example of secular extensive application of nature-based solution. Being one of the longest and largest dune systems in Europe, this iconic landscape offers considerable services to coastal societies. Since the mid-half of the 18th century, human work on sediment flows has resulted in the emergence of large sets of foredunes, currently constituting an almost 230 km-long managed barrier against inland sand invasion, coastline erosion, coastal flooding and also a major reserve of biodiversity. Last massive mechanic shaping of the foredunes following a so-called “ideal profile” date back to the 1970s–80s and aimed to limit erosion dynamics and sediment mobility. Since, they have been facing multiples disruptions over the years which have considerably modified their morphology, especially during the last decades. Calibrated foredunes are currently exhibiting impressive dimensions with a mean dune height of about 16.6 m (peaking at >30 m in some locations) and a dune width mean along the coast of 187 m. Today, 55.5% of them meet the “ideal profile” shape standards or surpass the in terms of dimensions whereas 21,5% of the calibrated foredunes are considered “narrowed” and need specific attention. This regional analysis, based on extensive airborne LiDAR datasets from 2011 to 2018, includes (i) a dune morphology classification based on several basic geomorphological indicators (dune width, height, crest position, back dune elevation) compared to a calibrated “idealised” shaped profile, (ii) a quantification of marine beach-dune and aeolian sediments flows (in m/year and m/m2/year) and forms on dunes (scarps, blowouts, depositional lobes), as an indicator of the recent dynamics affecting dune morphology and (iii) a study of management control of calibrated foredunes (4613 interventions) including actions taken after the outstanding winter of 2013–2014. As expected, intensive dune management are mainly focused where assets are directly threatened. The study highlights the importance and the efficiency of human management on dune evolutions (long term dune form stability, control of gullies and incipient frontal blowout after marine erosion, protection of human issues). However, today management actions (wind fence, branch cover, planting and reshaping) are not conditioned by foredune morphology or last decade's beach-dune dynamic (sediment availability, chronic coastline erosion). Considering long-term erosion projections and expected impact of climate change, the analysis shows the need of more global and extensive strategies in order to preserve the protection role of foredunes in the coming decades.

Numerical modelling of shelter effect of porous wind fences

The wind blowing at high velocity in an open storage yard leads to wind erosion and loss of material. Fence structures can be constructed around the periphery of the storage yard to reduce the erosion. The fence will cause turbulence and recirculation behind it which can be utilized to reduce the wind erosion and loss of material. A properly designed fence system will produce lesser turbulence and longer shelter effect. This paper aims to show the applicability of Support Vector Machine (SVM) to predict the recirculation length. A SVM model was built, trained and tested using the experimental data gathered from the literature. The newly developed model is compared with numerical turbulence model, in particular, modified k-e model along with the experimental results. From the results, it was observed that the SVM model has a better capability in predicting the recirculation length. The SVM model was able to predict the recirculation length at a lesser time as compared to modified k-e model. All the results are analyzed in terms of statistical measures, such as root mean square error, correlation coefficient, and scatter index. These examinations demonstrate that SVM has a strong potential as a feasible tool for predicting recirculation length.

Numerical simulation and optimization study of surface pressure and flow field around a triangular prism behind a porous fence

The flow structure around upright porous fences and a triangular prism was numerically investigated by using the RNG k-e turbulence model. The numerical method was validated by comparing the simulations with the experimental data, and then the effects of porosity and height of the wind fence on the flow field around the prism model and surface pressures were studied. The aim of this paper is to achieve the best shelter effect of a porous fence on the triangular prism located behind the fence with the height of 0.5h and 1.0h respectively, where h is the height of the prism. The gradient algorithm was adopted as the optimization algorithm to determine the optimum porosity of the wind fence. Three objective functions were considered to minimize (1) the sum of the absolute values of the mean pressure coefficients on the prism surface; (2) the total turbulence kinetic energy around the prism model, and (3) the total values of the peak velocity ratios involving velocity and turbulence. The numerical results showed that a porous fence with the height of about 0.5h–1.0h seems to be most effective in reducing the absolute value of the mean pressure coefficient on the model surface. Additionally, all three objective functions were capable of finding an optimal shelter performance of porous fences on the prism with surface pressure or flow characteristics considerations.

Numerical simulation and optimization study of the wind flow through a porous fence

Three turbulence closure models (RNG k-e, SST k-ω and RSM) were used to investigate the flow characteristics around a two-dimensional isolated porous fence. The comparison between the numerical results and the experimental measurements indicated that RSM model shows a better performance than the other two models. The aim of this paper is to accurately and efficiently determine the optimum porosity that attain the best shelter effect of the wind fence in the near wake region (0–4hb) and in the far wake region (4hb–10hb) respectively, where hb is the height of the fence. The gradient algorithm was adopted as the optimization algorithm and the RSM model was used to model turbulent features of the flow. The shelter effect was parameterized by the peak velocity ratio involving velocity and turbulence. The objective was to reduce the peak velocity ratio in the near or far wake region by changing the design variable porosity (ϕ) of the fence, which ranged between 2 and 60%. The results revealed that a porosity of 10.2% was found as the optimum value giving rise to the best shelter effect in the near wake region, and ϕ = 22.1% was determined in the case of the far wake region. In addition, based on the proposed optimization method, it is found that the recirculating bubble behind the fence can only be detected when ϕ < 29.9%.

A Study on the Effects of Wind Fence on the Dispersion of the Particles Emitted from the Construction Site Using GIS and a CFD Model

A Study on the Effects of Wind Fence on the Dispersion of the Particles Emitted from the Construction Site Using GIS and a CFD Model

Effects of wind fences on the wind environment around Jang Bogo Antarctic Research Station

This study investigated the flow characteristics altered by Jang Bogo Antarctic Research Station using computational fluid dynamics (CFD) modeling. The topography and buildings around Jang Bogo Station were constructed with computer-aided-design data in the CFD model domain. We simulated 16 cases with different inflow directions, and compared the flow characteristics with and without Jang Bogo Station for each inflow direction. The wind data recorded by the site’s automatic weather station (AWS) were used for comparison. Wind rose analysis showed that the wind speed and direction after the construction of Jang Bogo Station were quite different from those before construction. We also investigated how virtual wind fences would modify the flow patterns, changing the distance of the fence from the station as well as the porosity of the fence. For westerly inflows, when the AWS was downwind of Jang Bogo Station, the decrease in wind speed was maximized (−81% for west-northwesterly). The wind speed reduction was also greater as the distance of the fence was closer to Jang Bogo Station. With the same distance, the fence with medium porosity (25%–33%) maximized the wind speed reduction. These results suggest that the location and material of the wind fence should be selected carefully, or AWS data should be interpreted cautiously, for particular prevailing wind directions.

Experimental investigation of wake flow field and wind comfort characteristics of fractal wind fences

Wind fences are frequently utilized in many areas from agriculture to traffic safety in order to provide a sheltered region behind. The conventional geometry of wind fences are usually porous with circular or rectangular holes. Recent studies on fractal/multiscale grid geometries, i.e. a geometry that consists of smaller scales that are copies of the whole, show interesting results, indicating a potential towards using these types of grids as wind fences. Thus, the main purpose of this study is to investigate the performance of fractal grids as wind fences. For this purpose, four different types of wind fences, three of which have fractal grids, all having the same porosity ratio of 40%, are tested in a wind tunnel. Results of the two-dimensional PIV measurements downstream of each fence are presented. Comparisons of the details of the wake flow structure as well as quantitative comparisons of wind comfort and shelter characteristics up to 10H downstream of fences, where H is the fence height, are also presented. Results show that the jet-wake-wall interactions within the near wake of the fences have a major impact on wind comfort characteristics further downstream. These interactions can potentially be manipulated by custom designing fractal grid fences based on given wind comfort requirements in order to obtain required mean flow and sheltering characteristics.

Performance analysis of wind fence models when used for truck protection under crosswind through numerical modeling

This paper is focused on truck aerodynamic analysis under crosswind conditions by means of numerical modeling. The truck was located on the crest of an embankment during the study. In order to analyze the performance of three wind fence models, the truck's aerodynamic coefficients were obtained and compared in two different situations either with or without the wind fences installed. In addition, the effect of both height and porosity of wind fence models on the aerodynamic coefficients acting on truck with respect to separation distance between the truck and the wind fence, was analyzed. A finite volume (or computational fluid dynamic) code was used to carry out the numerical modeling. The Reynolds-averaged Navier–Stokes (RANS) equations along with the k−ω SST turbulence model were used to predict the behavior of turbulent flow. With respect to the results, the influence of the distance on the rollover coefficient is soft for all height values studied except for the lowest value (1 m of fence height), where the maximum value of rollover coefficient was obtained for the truck position closer to the fence. Regarding fence porosity, its effect on rollover coefficient is stronger for truck positions on road closer to the wind fence model.

Protection of Greenhouses against Wind Damage

The paper presents a case study of a greenhouse building affected by wind loads. The building is a lightweight steel structure with a height of 7.1meters, 12.8 meters wide and 171m long. The roof of the building is a lattice cupola. The main purpose of the authors was to find solutions in order to reduce wind loads on the building envelope, using some wind protection barriers. In order to identify the optimal solution, different types of wind barriers were analyzed. Using Ansys CFX, the authors carried out numerical simulation for each type of wind barrier, in order to find out which reduces the most the wind pressures on the walls and on the roof of the analyzed building. The results provided by numerical simulation of wind action on the building were used to make a comparative study between different patterns of wind fences. The comparison between pressures developed on the walls and roof for each type of fence, has allowed the choice of an optimal solution that can be applied also to other similar buildings.

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 &amp; Sons Ltd.

Cut-off frequency criterion for wind noise contributions for wind noise reduction enclosures

A cut-off frequency criterion for contributions for the wind noise generated from the undisturbed and surface regions for a wind noise reduction device, such as wind fence enclosures and semi-porous fabric domes, is given. The calculations of the measured wind noise inside an enclosure assume that contributions from the undisturbed region and the surface region dominate and are physically restricted to turbulence wavelengths that are larger than the enclosure and the same size or smaller than the enclosure, respectively. The cut-off frequency criterion defines the wavelength where the dominant source of wind noise transitions from interactions in the undisturbed region to the surface region. The transition point is determined by considering when a volume enclosed by a wavelength, Vλ, is equal to 100 times the volume enclosed by the reduction device, VE. Wind noise calculations following this criterion are presented for a set of semi-porous fabric domes that are 4 m wide and 2.1 m tall, and three cylindrical wind fences that are 5 m wide and 2.9 m tall, 5 m wide and 5.8 m tall, and 10 m wide and 2.9 m tall.