Portable Wind Tunnel Research Articles

Investigating the impact factors of dust emission efficiency over gobi with portable wind tunnel field experiments

AbstractThe contribution of the gobi to dust emission in arid northwestern China is largely uncertain due to the lack of studies on the surface properties of gobi. The dust emission efficiency ( ) as a comprehensive characterization of surface properties is an essential parameter for quantifying dust emission. However, the main influencing factors of dust emission efficiency are still unclear, as it is a big challenge to do a comprehensive field experiment and get the long‐term continuous field data in gobi due to its harsh environment. Here, we are aiming at quantitively identifying the main factors of dust emission efficiency by using a portable wind tunnel for field experiments over the gobi surface in Dunhuang Mogao grottoes. Results showed that (1) the abundance of bombardment sand regulates the relationship between and friction wind velocity ( ). The decreases as a power function with increasing , and the correlation is weak (R2 = 0.41, P < 0.05) in the shortage of bombardment sand. In contrast, increases with following a power function, and the correlation is strong (R2 = 0.91, P < 0.05) when bombardment sand is enriched. (2) The surface dust content of the gobi dominates the , which increases exponentially with the increased dust content. Relative to , the surface dust content has a bigger contribution to . (3) The gobi in Northwest China could be an underestimated dust source, as it has an enriched dust content and a higher than sandy desert. Therefore, the quantitative monitoring and further research of dust emissions in the gobi should be strengthened.

Sandblasting promotes shrub encroachment in arid grasslands.

Shrub encroachment is a common ecological state transition in global drylands and has myriad adverse effects on grasslands and the services they provide. This physiognomic shift is often ascribed to changes in climate (e.g. precipitation) and disturbance regimes (e.g. grazing and fire), but this remains debated. Aeolian processes are known to impact resource distribution in drylands, but their potential role in grassland-to-shrubland state changes has received little attention. We quantified the effects of 'sandblasting' (abrasive damage by wind-blown soil) on the ecophysiology of dryland grass vs shrub functional types using a portable wind tunnel to test the hypothesis that grasses would be more susceptible to sandblasting than shrubs and, thus, reinforce transitions to shrub dominance in wind-erodible grasslands when climate- or disturbance-induced reductions in ground cover occur. Grasses and shrubs responded differently to sandblasting, wherein water-use efficiency declined substantially in grasses, but only slightly in shrubs, owing to grasses having greater increases in day/nighttime leaf conductance and transpiration. The differential ecophysiological response to sandblasting exhibited by grass and shrub functional types could consequently alter the vegetation dynamics in dryland grasslands in favour of the xerophytic shrubs. Sandblasting could thus be an overlooked driver of shrub encroachment in wind-erodible grasslands.

Assessment of wind erosion and physical and mechanical properties of bentonite clay mulch in an arid region

This study was conducted to assess the effect of bentonite-based mulch on wind erosion and soil physical and mechanical properties. The texture of majority of the soils in the study area was loam. Suspension of purified 20 μm calcium-saturated bentonite clay was applied at a rate of 240 kg ha−1. Wind erosion rate was measured in situ using a portable wind tunnel device (height and width of 0.3 m, and length of 2.5 m) at 20 points of mulched area and 12 points of unmulched area. The results showed that the wind erosion rate varied in the range 0.50–1.05 kg m−2 h−1 in the mulched area which was significantly reduced when compared with the control/unmulched area (i.e., 28.5 kg m−2 h−1). Clay mulch application resulted in larger particles/aggregates than the control parts, because the bentonite clay was effective in structure formation as characterized by greater mean weight diameter (MWD of 0.68 mm) and geometric mean diameter (GMD of 0.73 mm) compared to their corresponding values of 0.18 and 0.40 mm in unmulched area. Clay mulching significantly increased the shear strength and penetration resistance of surface crust (9.37 and 175.2 kPa) compared to unmulched area (3.1 and 59 kPa) and lowered soil erodibility. Wind erosion rate had inverse and non-linear relationships with MWD, GMD, percent of aggregates larger than 0.25 mm (DSA>0.25 mm), shear strength and penetration resistance. The DSA>0.25 mm and shear strength showed the greatest effect on the wind erosion in the studied area.

Experimental study of mass transfer by volatilization inside a portable wind tunnel used to estimate emission rates for odorous compounds

Wastewater treatment plants are sources of hydrogen sulfide in urban environments. This compound, at certain concentrations, may be associated with compromising the health and well-being of populations living near such sources, characterized by diffuse emission, which makes it difficult to quantify. The portable wind tunnel is one of the devices used to measure this type of emission; however, this equipment is not capable of simulating all significant mass transport phenomena. Thus, this study investigated mass transfer at the liquid-gas interface of hydrogen sulfide by estimating the global mass transfer coefficient within the portable wind tunnel. The inlet flow rate into the system ranged from 600 to 1,800 , and the analysis of concentration decay in the liquid phase was performed using spectrophotometry. The observed exponential decay is consistent with the adopted hypotheses; however, no significant variation in the mass transfer coefficient was observed for different system operation flow rates. The average value found was 2.70×10 -5 ±2.99×10 -6 . In summary, this study contributed to understanding the mass transfer of hydrogen sulfide in wastewater treatment environments using a portable wind tunnel as an experimental tool.

A field study of the surface disturbance effects of animals and motor vehicles on aeolian sediment emission from a silty playa surface

Dry playa surfaces can be extremely vulnerable to disturbance which breaks their surface crusts resulting in increased aeolian sand and dust emissions. Trampling by livestock and motor vehicles is an important source of this disturbance. The Hamoun Lakes in the Sistan region of Iran are a major source area of dust storms which are causing damage to infrastructure and communities. This study performed portable wind tunnel tests of controlled surface disturbance by animals (cow, sheep) and motor vehicles (automobile, motorcycle) on a silty playa surface of Hamoun Saberi lake. The aim of this study was to assess the effect of different levels of trampling and disturbed surfaces by both vehicles and livestock on dust emission at wind speeds of 6 and 12 m s−1. A significant increase of sediment emission was found with increased number of passes of vehicles and livestock and the degree of surface disturbance, more so at the high wind speed (12 m s−1). No significant differences were observed between a 10–20% disturbance level and an undisturbed surface, but statistically significant differences became apparent when disturbances reached 50–60% to 90–100% compared to undisturbed surfaces. Greater emission rates were reached by disturbances provided by automobile and cow compared to motorcycle and sheep, indicating greater trampling effects of automobile and cow likely related to greater weight and larger footprint. The automobile was the most surface-destructive of the four anthropogenic disturbances, providing emission in a lower number of passes compared to the motorcycle, cow and sheep. Better management of vehicle and livestock allocation on playas subject to disturbance, such as the Hamoun Lakes, will be a useful strategy to reduce disturbance and the frequency and intensity of dust storms.

Determination of the threshold velocity of soil wind erosion using a wind tunnel and its prediction for calcareous soils of Iran

AbstractDetermination of the threshold velocity (TV) is a crucial step for wind erosion evaluation. Due to the difficulties of direct field measurements, pedotransfer functions (PTFs) and easily measurable soil properties could be used to save time and cost in predicting TV. Therefore, the present study was conducted to predict the TV using PTFs and to assess its influential parameters for calcareous soils of Fars Province, southern Iran. To this end, the TV was measured by a portable wind tunnel at 72 locations in different land uses and soil types across the study site. Various physicochemical and mechanical soil properties were used to develop six PTFs using multiple linear regression. Results showed that the TV varied from 3.0 m s−1 in poor rangelands to 12.83 m s−1 in saline lands. Soil surface shear strength (SS) with a correlation coefficient of 0.85 was the most influential parameter affecting the TV, followed by aggregate mean weight diameter (MWD). Results of the predictive models revealed that PTF 5, which was developed using SS and penetration resistance (PR;R2 = 0.86, RMSE = 0.85 m s−1), and PTF 6, which was developed using MWD and PR (R2 = 0.81, RMSE = 1.07 m s−1), had the highest performance for predicting the TV. PTF 5 was selected as the final model for predicting the TV since it only needed easily measurable soil properties without soil sample collection. We concluded that the use of PTFs could be an applicable alternative way to predict the TV, particularly at large scales.

Design and implementation of a portable, large-scale wind tunnel for wildfire research

Connecting the results from laboratory wildland fire experiments with in-situ field experiments under natural conditions remains an important challenge in wildland fire science, particularly because of differences in flow and boundary-layer conditions in the local atmosphere. Thus, as part of a broader investigation involving laboratory and field experimentation, a large-scale, portable wind tunnel capable of use in both the laboratory and the field was designed and implemented to bridge the two experimental domains. Two axial fans generate flow speeds of up to 8 m/s within the test section. Thorough flow-field characterization revealed good uniformity and minimal spatial variability within the flow field. Uniquely, the wind tunnel is portable; due to its modular design, the entire wind tunnel can be broken down to fit onto two shipping pallets for transportation. This portability allows for future experiments to be conducted in the field under the same boundary conditions as in the laboratory. These same boundary conditions created a unique research environment to iteratively test the effects of boundary conditions to validate computational models in different domains. The results from some of the wildland fire spread experiments conducted in the wind tunnel are presented to demonstrate and validate its laboratory capabilities.

Microplastics in agricultural soils from a semi-arid region and their transport by wind erosion

Despite the importance of agricultural soils, little is known about the fate of microplastics (MPs) in this environment. In the present study, MPs have been determined in soils and wind-eroded sediments from two vegetable-growing fields in the Fars province of Iran, one using plastic mulch for water retention (Field 1) and the other using wastewater for irrigation (Field 2). MPs were heterogeneously distributed in the surface (0–5 cm) and subsurface (5–15 cm) soils of both fields, with a maximum concentration overall of about 1.1 MP g−1 and no significant differences in concentrations between either fields or depths. Fibres represented the principal shape of MPs, but spherules, presumably from wastewater, also made a significant (∼25%) contribution to MPs in Field 2. Analysis of selected samples by Raman spectroscopy and scanning electron microscopy revealed that polyethylene terephthalate (PET) and nylon were the most abundant polymers and that MPs exhibited varying degrees of weathering. Concentrations of MPs in this study are within the range reported previously for agricultural soils, although the absence of PET observed in earlier studies is attributed to the use of insufficiently dense solutions to isolate plastics. Deployment of a portable wind tunnel revealed threshold wind velocities for soil erosion of up to 7 and 12 m s−1 and MP erosion rates up to about 0.4 and 1.1 MP m−2 s−1 for Fields 1 and 2, respectively. Erosion rates are considerably greater than published depositional rates for MPs and suggest that agricultural soils act as both a temporary sink and dynamic secondary source of MPs that should be considered in risk assessments and global transport budgets.

Dynamic processes of dust emission from gobi: A portable wind tunnel study atop the Mogao Grottoes, Dunhuang, China

The dynamic process of dust emission from gobi is a largely un-solved scientific question while it is essential for minimizing the dust hazards. In this study, field wind tunnel experiments have been performed to reveal the processes of dust emission from gobi on the top of the Mogao Grottoes. We found that the dust content of gobi is the dominant factor that determines the intensity of dust emission. The vertical PM10 flux increased exponentially with the increase of dust content on the gobi surface at a given wind speed. The impact energy of saltating particles is another control factor of the dust emission flux. The vertical PM10 flux due to saltation bombardment of the external sand supply was 5–13 times larger than that without the bombardment of sand supply. This study indicates that gobi on the top of the Mogao Grottoes is one of the main dust sources as it has an abundance of sand supply from Mingsha Mountain as well as its richness in dust content. Hence, it is imperative to expand the existing sand control system on the top of the Mogao Grottoes in order to minimize the impact of dust hazards on the Mogao Grottoes.

Evaluation of off-site effects of wind-eroded sediments especially the content of pesticides

Wind-eroded sediment, as an environmental transport pathway of toxic elements and pesticids, can result in environmental and human exposure far beyond the agricultural areas where it has been applied. In our research we quantified the pesticide residues moving in the soil near Szeged (Hungary) on the original soil surface of agricultural areas with a portable wind tunnel. Before the experiments, a portion of the sample area was treated with chlorpyrifos and pendimethalin. A control area was also selected. In 2017-2019, a total of 42 wind event experiments were conducted by examining the topsoil samples. During the experiments, moving soil particles were trapped at various heights (5-10 cm, 20-25 cm and 50-55 cm) and the pesticide concentrates by GC-MS were measured. The enrichment ratios (ER) were calculated, and statistical analyzes were also carried out (SPSS). The measurements obtained that the pendimethalin ER is much higher in the rolled fraction (mean: 13.7) than chlorpyrifos (mean: 2.9). Our measurements showed that the enrichment of chlorpyrifos and pendimethalin can be detected in the rolling and suspended soil particles.

海岸黑松和紫穗槐对间歇强净风和风沙流吹袭的生理响应机制

以海岸防风固沙优势树种紫穗槐（Amorpha fruticosa Linn）和黑松（Pinus thunbergii Parl）为研究对象，利用野外便携式沙风洞用间歇风吹模拟自然阵风，通过分析间歇强净风（18m/s）和强风沙流（172.93g cm^-1 min^-1）吹袭过程中和风后恢复中，两树种叶片膜脂过氧化产物含量、抗氧化酶活力、渗透调节物含量的变化，以探讨其对自然阵风吹袭响应机制及自愈修复生理机制。结果表明，自然状况下，紫穗槐和黑松叶片相对含水量（RWC）相近，但抗氧化酶活力及种类和渗透调节物含量及种类上存在差异。紫穗槐叶片丙二醛含量（MDA）、脯氨酸含量及过氧化氢酶（CAT）和过氧化物酶（POD）活力分别较黑松高93.3%、78.6%、118.8%、6.5倍。而黑松可溶糖含量和超氧化物歧化酶（SOD）活力较紫穗槐高111.5%和28.2%。在间歇净风和风沙流处理中，随着风吹袭次数增多，黑松叶片RWC趋于小幅降低，可溶性糖含量及POD、SOD、CAT活力呈小幅波动式变化；紫穗槐叶片RWC大幅下降，伴随着脯氨酸含量，POD、CAT、SOD活力大幅增高和MDA含量下降。在风吹袭中，叶片抗氧化酶活力和渗透调节含量的变化与叶片含水量变化密切相关。在风吹袭处理后的恢复期，黑松叶片MDA、可溶性糖、脯氨酸含量和CAT活力下降，但叶片一直维持较高可溶性糖含量和SOD活力；而紫穗槐伴随叶片RWC回升，而MDA、可溶性糖、脯氨酸含量下降和POD、CAT、SOD活力的增高。研究表明，风吹袭引发叶片水分亏缺成为启动植物对缺水补偿机制的诱导因子（自愈修复）。在风吹袭中增高的渗透调节物通过提高细胞吸水力为自愈修复提供物质基础，而抗氧化酶通过抑制膜脂过氧化、维护膜的完整性和弹性为自愈修复提供生理保护。因此，渗透调节和抗氧化酶通过维护水分平衡和氧自由基代谢平衡而在抗风生长和自愈修复中起重要生理保护作用。;In this study, the coastal area wind and sand blowing resistant Amorpha fruticosa Linn and Pinus thunbergii Parl were used as materials to learn how they responded physiologically to intervals of strong wind and wind-drift blowing, and what mechanisms of physiological adaptation and self-repairing were involved in their resistance to wind-drift blowing and self-repairing after wind blowing. The plants were subjected to 18 m/s wind speed and wind-drift blowing (172.93g cm^-1 min^-1) for 20 min and allowed to repair for 24h after the blowing treatment (repair period); these treatments were repeated three times using an outdoor portable wind tunnel. Relative water content (RWC), malondialdehyde (MDA), proline, soluble sugar, and the activities of superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD) were measured in the leaves of the plants. The results showed that in the natural environment, there were no difference in RWC in the two species, but there were differences in the kinds of antioxidant enzyme and osmotic regulators between A. fruticosa and P. thunbergii, with the MDA content, proline content, and the activities of CAT and POD in leaves of A. fruticosa higher by 93.3%, 78.6%, 118.8%, and 650% than those in leaves of P. thunbergii. The soluble sugar content and SOD activity in leaves of P. thunbergii were higher by 111.5% and 28.2% than those in leaves of A. fruticosa. With increasing repetitions of blowing, RWC tended to decrease to a lower level, while the soluble sugar content and the activities of POD, SOD, CAT exhibited slight fluctuations in the leaves of P. thunbergii, but in A. fruticosa leaves, RWC dramatically dropped, and proline content and the activities of POD, CAT, and SOD significantly increased. Furthermore, during the repairing period, the contents of MDA, soluble sugar, and proline and CAT activity decreased in the leaves of P. thunbergii but the contents of MDA, soluble sugar, and proline decreased, and the activities of POD, CAT, and SOD increased, accompanied by an increase of RWC, in the leaves of A. fruticosa. These results indicate that water shortage induced by wind blowing was a direct factor causing physiological regulation and activating the compensation mechanism for water shortage (self-healing repair) in both trees. Although the two tree species belonged to different families and used different kinds of osmotic regulator and antioxidant enzymes in the physiological regulation of wind resistance, they both had the same strong ability to regulate physiological mechanisms during strong wind blows and post-wind repairing periods. It suggests that water shortage might activate the self-healing physiological mechanism. Under wind blowing, the increased content of soluble sugar and proline might provide materials for self-healing by improving cell water absorption, while antioxidases played an important physiological protective role in inhibition of membrane lipid peroxidation, thus maintaining membrane integrity and elasticity for self-healing. Therefore, self-healing is the key physiological adaptative mechanism for the two trees to adjust to the intervals of strong sea wind blowing on the coast.

Predicting wind erosion rate using portable wind tunnel combined with machine learning algorithms in calcareous soils, southern Iran

Wind erosion is a critical factor in land degradation worldwide, particularly in arid and semi-arid regions of southern Iran, which have been severely exposed to wind erosion in the recent years due to climate change and land use changes. The main objective of the present study was to predict the wind erosion rate (WER) using easily measurable soil properties combined with some data mining approaches. For this purpose, the WER was measured at 100 locations with different land uses and soil types in the Fars Province, southern Iran using a portable wind tunnel. The WER was predicted by multiple linear regression (MLR), support vector regression (SVR) and decision tree (DT) algorithms using easily measurable soil properties. Results revealed that land use and soil type had significant effect on the WER. The highest mean WER was observed in Entisols with the lowest organic matter (OM), the lowest penetration resistance (PR) and the lowest aggregate mean weight diameter (MWD). Bare lands with the lowest OM and MWD showed the highest WER compared to other land uses. R2 and RMSE of the non-linear regression models developed based on the type of the relationship between the WER and easily measurable soil properties improved by 15% and 12%, respectively, compared to the linear regression model. In both train and test datasets, the SVR and DT models coupled to a genetic algorithm (GA) used for selecting the effective easily measurable soil properties had higher performance than the SVR and DT models using all easily measurable soil properties for predicting WER. With respect to statistical indices, the SVR model with R2 = 0.91 and RMSE = 0.68 g m−2 s−1 outperformed the MLR and DT for predicting the WER. We concluded that combining the SVR with GA could be an applicable and promising method for predicting WER.

Investigation of a Portable Wind Tunnel for Energy Harvesting

Current wind tunnels possess a large space volume and high manufacturing cost, which are not suitable for investigating micro energy harvesters. This paper aims to design and fabricate a small, portable and low-speed wind tunnel for energy harvesting. A wind tunnel structure was first designed, a finite element analyses is then utilized to obtain the airflow velocity and turbulence intensity at the testing section, and the influence of the structural parameters of the wind tunnel on the flow field performance is finally investigated to achieve better performance. An experimental prototype of the wind tunnel was fabricated to verify the simulation results. Results demonstrated that the distribution uniformity and average turbulence intensity at the test section decrease first and then increase with the increase of both the diffuser and contraction lengths. The rectifying and damping effect of the honeycomb increase with increasing porosity and thickness. When the diffuser and contraction lengths are 850 mm and 480 mm, respectively, a better distribution uniformity and a lower turbulence intensity can be achieved. Experimental results were in good agreement with the simulation values. The maximum airflow velocity can reach up to 24.74 m/s, and the minimum error was only 1.23%. The designed wind tunnel achieved low-speed, small, portable and stable functions. This work provides an important guidance for further investigating the piezoelectric energy harvesting.

海岸抗风植物黑松对净风和风沙流的生理响应

PDF HTML阅读 XML下载 导出引用 引用提醒 海岸抗风植物黑松对净风和风沙流的生理响应 DOI: 10.5846/stxb201912202754 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金项目（31770762） Physiologial response of Pinus thunbergii Parl in wind resistant to coastal wind blowing and win-drift blowing Author: Affiliation: Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:利用野外便携式风洞仪对盆栽黑松（Pinus thunbergii Parl）幼株在不同风速（6、9、12、15、18 m/s）、不同风沙流强度（0、1.00、28.30、63.28、111.82、172.93 g cm-1 min-1）、不同时间（10、20、30、40、50 min）进行了净风和风沙流吹袭，通过测定其叶片相对含水量（Relative water content，RWC）、丙二醛（Malondialdehyde，MDA）、可溶性糖、脯氨酸含量，及超氧化物歧化酶（superoxide dismutase，SOD）、过氧化氢酶（Catalase，CAT）、过氧化物酶（Peroxidase，POD）活力等变化规律以揭示黑松抗风沙流生长的生理适应机制。结果表明，在净风吹袭下，随着风速提高至15 m/s，黑松叶片RWC相对稳定，MDA含量和细胞膜透性小幅增加且较低，而脯氨酸含量下降17.5%。同时叶片SOD、CAT、POD活力也小幅增加。在风沙流吹袭下，随着风沙流风速提高至15 m/s，黑松在短时低风速吹袭时叶片RWC就开始下降（4.4%），叶片平均MDA含量、细胞膜透性分别较对照增加61.3%、25.6%，脯氨酸含量增加8.9%，叶片SOD、CAT、POD活力分别较对照增加21.5%、30.4%、13.9%。同风速吹袭下，风沙流处理组叶片抗逆生理指标均高于净风处理。如15 m/s风速下，风沙流处理组叶片平均MDA、脯氨酸、可溶性糖含量分别较净风处理组高4.7%、36.6%、22.1%，SOD和CAT活力较净风处理组高21.5%、36.5%。在高风速（18 m/s）净风和风沙流吹袭中，随着风吹时间延长（50 min），叶片MDA、脯氨酸、可溶性糖含量和SOD、CAT、POD活力均下降。研究表明，风吹袭中黑松叶片较高抗脱水力与其抗风性相关。风沙流引发的叶片失水可能是黑松抗逆生理变化的诱因。风吹袭下叶片失水能快速促使脯氨酸的积累和维持可溶性糖含量，以维护细胞中水分平衡。同时，叶片失水又快速激活抗氧化保护酶系统来防御和清除氧自由基、抑制膜脂过氧化维护细胞膜的完整性使黑松在风沙流吹袭中生存。黑松较强的渗透调节能力和抗氧化防御系统在其适应风沙流吹袭中起重要的生理调控作用。 Abstract:The experiment was designed that there were different wind speed (6, 9, 12, 15 and 18m/s), different wind-drift blowing (0.00, 1.00, 28.30, 63.28, 111.82 and 172.93 g cm-1 min-1), and five wind blowing times (10, 20, 30, 40 and 50 min) in spring, 2018 in Yantai, Shandong Province by using outdoor portable wind tunnel to understand the how physiological responses of Pinus thunbergii Parl seedlings to wind blowing and wind-drift blowing. The relative water content (RWC), malondialdehyde (MDA) contents, membrane permeability, osmotic regulators (soluble sugar, proline), and antioxidant enzyme activities (superoxide dismutase (SOD), catalase(CAT), peroxidase(POD)) were tested in the leaves of seedlings of Pinus thunbergii Parl under the previous treatments. The results showed that under treatment of wind blowing, with increasing of wind speed to 15m/s, the RWC was not changed, MDA content and membrane permeability increased slightly, while the proline content decreased, and the activities of SOD, CAT, and POD were slightly enhanced in the leaves of Pinus thunbergii Parl.. Under treatment of wind-drift blowing, with increasing of wind speed to 15 m/s, the RWC decrease, the membrane permeability and the contents of MDA and proline increased, and the activities of SOD, CAT, POD enhanced. At same wind speed, the value of each resistant physiological index under treatment of wind-drift blowing was higher than those under treatment of wind blowing in the leaves of Pinus thunbergii Parl. However, under wind blowing and wind-drift blowing at 18 m/s, the contents of MDA, proline, soluble sugar, and the activities of SOD, CAT, POD decreased with time extension to 50 min in the leaves of Pinus thunbergii Parl. It indicated that leaves of Pinus thunbergii Parl had stronger capacity of resistant dehydration, which was correlated with its ability of resistance to wind blowing. But cell dehydration induced by wind-drift blowing would be a main factor, which could not only promote the accumulation of proline and keeping on soluble sugar content to maintain water balance, but also activate antioxidant defense system to scavenge oxygen free radicals, and inhibit membrane lipid peroxidation to preserve the integrity of cell membranes. It suggested that Pinus thunbwould beergii had stronger capacity of osmotic adjustment and antioxidant defense system could be an important physiological adaptation mechanism for it to resistance to wind-drift blowing. 参考文献 相似文献 引证文献

Field-based measurements of volcanic ash resuspension by wind

The resuspension of volcanic ash by wind is a significant source of hazard during and after volcanic eruptions. Parameterizing and modeling ash resuspension requires direct measurement of the minimum wind shear stress required to move particles, usually expressed as the threshold friction velocity U⁎th, a parameter that, for volcanic ash, has been measured only scarcely and always in the laboratory. Here, we report the first field measurements of U⁎th for volcanic ash, with a portable wind tunnel specifically developed, calibrated, and tested. Field measurements, performed on natural reworked ash deposits from Sakurajima (Japan) and Cordón Caulle (Chile) volcanoes, agree well with our laboratory determinations on ash from the same deposits, with values of U⁎th ranging from 0.13 to 0.38 m/s. Our results show that the median grain size of the deposit and particle shape have a stronger control on U⁎th than the local substratum nature and deposit texture.

Design of a continuous portable indraft supersonic wind tunnel

Programs in mechanical and aeronautical engineering commonly include courses in compressible fluid flow. As such, learning can be greatly enhanced if theory is taught in conjunction with hands on experimentation. While supersonic wind tunnels are not uncommon at many universities, such facilities are generally of the blow down configuration. Consequently, run time is very short and ear protection is required during operation, potentially hindering instruction. Furthermore, blow down configurations are typically expensive and large. This article presents the design and manufacture of a continuous, indraft, miniature supersonic wind tunnel. The tunnel was designed for a nominal test section Mach number of 2; validation indicated a Mach number of 1.96 was achieved. Vacuum was provided by a regenerative blower. The facility is portable and quiet; measurements indicated that the sound level around the tunnel when operational was less than 81 dB (compared to 119dB generated by the department’s blow down supersonic wind tunnel).

Spectral behavior of Persian oak under compound stress of water deficit and dust storm

Persian oak (Quercus Brantii Lindl.) which is the most widely distributed tree in the Zagros Mountain forests is affected by western dust storms, mostly originating in Iraq, and harsh water stress as well. The objective of this research is to analyze the spectral behavior of Persian oak under water and dust stress scenarios, aiming to pave the way for modeling the stresses of drought and dust storms on oak trees using remote sensing images. Experiments were carried out on 54 two-year old oak tree seedlings, using a portable wind tunnel in greenhouse conditions. Water stress was induced on seedlings by means of changes in irrigation practices, i.e. well-watered (100 % field capacity), medium water deficit condition (40 % field capacity), and severe water deficit condition (20 % field capacity) treatments. Dust stress is also investigated by using three different dust particle concentrations, i.e. 350, 750 and 1500 (μg/m³). The spectrometry experiments were carried out at leaf and canopy levels in dark room by Fieldspec-3-ASD spectrometer. Spectral analysis was conducted using four procedures: (i) narrow-band spectral indices analysis, (ii) geometric indicators extraction from absorption features, (iii) Partial Least Squares Regression (PLSR), and SVM classifier. Results show that water stress could be modeled much better using PLSR statistic (R2 = 0.87, RMSE = 0.12), narrow-band indices analysis (R2cv = 0.75, RMSEcv = 0.17), and continuum removal (R2 = 0.71, RMSE = 0.20), respectively. For dust stress, PLSR (R2 = 0.83, RMSE = 0.14) and narrow-band indices (R2cv = 0.7, RMSE cv = 0.30) showed the best results, respectively. SVM could successfully separate stressed and not-stressed samples and also the stress types at both leaf and canopy levels, but it could not distinguish the different levels of stresses.

Prediction of soil wind erodibility using a hybrid Genetic algorithm – Artificial neural network method

Understanding and consequent modeling of soil wind erodibility is hampered by the complex nature of the eroding processes and limited empirical data. It is often necessary to resort to robust approaches capable of finding correlated patterns among soil erodibility magnitudes and their drivers. To signify soil erodibility to wind, we used a portable wind tunnel to measure wind erosion rate (g m−2 s−1) at a total of 118 sites in Kerman Province, southeast Iran. At each sampling site, 17 different factors affecting soil erodibility were measured. Gravel coverage, surface crust, very fine and very coarse sands, aggregate stability, and calcium carbonate equivalent (CCE) were introduced as the more important parameters affecting soil erodibility by hybrid Genetic Algorithm-Artificial Neural Network (GA-ANN). A Multi-Layer Perception (MLP) neural network was developed to predict erodibility changes in response to spatial variation of the selected features. The developed MLP-model provided a strong basis for the prediction of soil erodibility, where the coefficient of determination (R2) values of 0.89 and 0.87 were obtained by comparing the measured and predicted wind erosion rates for the training and testing data, respectively. The acceptable levels of the statistical validation criteria were also an indication of the proper performance of the model. Furthermore, the soil erodibility was sensitive respectively to surface crust, very fine sand, and very coarse sand parameters.

The fractionation of soil aggregates associated with primary particles influencing wind erosion rates in arid to semiarid environments

Soil particle size distribution (PSD) plays an important role in wind erosion studies and sediment transport modeling. Few studies have been done focusing on the susceptibility of different soil fractions to wind erosion under natural conditions. This study was performed to measure in-situ wind erosion rates using a portable wind tunnel facility on 60 undisturbed soils of arid to semiarid regions. The effects of primary (i.e. clay, silt, and sand particles) and 16 secondary (aggregate) size classes were attributed to wind erosion rates. Moreover, the boundaries between major fractions of the soils (i.e. micro-aggregates, meso-aggregates and macro-aggregates) were determined. The result showed that clay and silt particles and also surface rock fragment were inversely proportional to wind erosion rates as power functions, whereas sand content showed a positive exponential relationship. The size ranges of <53 μm, 53–300 μm and >300 μm were distinguished for the micro-aggregates, meso-aggregates, and macro-aggregates, respectively. The meso-aggregate fraction was proportional and the micro-aggregate and macro-aggregate fractions were inversely proportional to wind erosion rates. Furthermore, a narrower size range of 75–150 μm was detected as the most erodible soil fraction. The distribution of the primary particles in the major aggregate fractions was different, so that in the meso-aggregates, sand particles and in the micro-aggregates and macro-aggregates, silt and especially clay particles predominated. It is concluded that the presence of macro-aggregates (>300 μm) associated with fine primary particles (clay) can significantly reduce wind erosion rate rather than the sandy soils containing weaker aggregates.

Optimal feature selection for prediction of wind erosion threshold friction velocity using a modified evolution algorithm

Threshold friction velocity (u⁎t) is a very important parameter, which represents wind erosion potential. Because of the difficulty of measuring u⁎t, it would be advantageous if u⁎t could be estimated indirectly from its effecting factors that can be easily measured. The main purpose of this research was to quantify relationships between u⁎t and various topsoil features using inexpensive approaches. To prepare a reliable dataset, we used a portable wind tunnel for measuring u⁎t at a total of 118 observation points in Kerman province, southeast Iran. We developed a non-dominated sorting genetic algorithm II (NSGA-II), specifically designed to operate with artificial neural network (ANN) to select the most determinant properties that influence u⁎t. A permutation of nine input features including surface crust (SC), gravel coverage (GC), very fine sand (VFS), fine sand (FS), very coarse sand (VCS), electrical conductivity (EC), sodium adsorption ratio (SAR), calcium carbonate equivalent (CCE), and mean weight diameter (MWD), was introduced as explanatory variables. We also examined the potential power of using a Multi-Layer Perception (MLP) neural network for prediction of u⁎t changes in response to spatial variation of the selected features. The results of constructed MLP model revealed the ability of the model for u⁎t prediction and showed that the coefficient of determination (R2) values were 0.91 and 0.89 for training and testing data, respectively. Furthermore, acceptable level of the statistical validation criteria verified reliable performance of the MLP model. This research provided a powerful basis for prediction of u⁎t from topsoil features and surface roughness in arid and semi-arid areas of Iran; however, its generic framework could be used to other arid and semi-arid regions with similar challenges.