Time-dependent variation of bed microtopography around an isolated, surface-mounted cylindrical roughness element and its impact on wind flow (2023)

An accurate description of the erosion and depositional characteristics around unique model plants of different shapes is important to assess the protective function of plants in wind erosion control. The temporal variation in bed topography was measured in a wind tunnel for two flexible models and two rigid tree models. The height of the bed surface near the plant decreases and a deep pit forms, while on the leeward side there is generally a depositional area, the shape of which depends on the plant species. The local wind erosion rate on both sides generally decreases over time, and the Lee depositional area with less than zero local erosion rate gradually moves downwind over time while disappearing for the formed plant model. Tree with a long trunk and a large crown. Among similar frontal areas of plants, both the areas of erosion and deposition around the short-stemmed, conical-crown tree plant and the flexible, large-top, small-bottom plant are generally larger than those visible. They are thin and thin flexible around the plant. Attachment. The rigid tree-like plant with a short trunk and a dense conical crown is better suited for erosion control due to the lower net erosion rate and area of ​​erosion similar to the depositional area, while the other plant models have a higher net erosion rate and a much larger area of ​​erosion. erosion area.

Accurately simulating the spread of contamination over rough terrain with intricate obstacles is a difficult but important scientific and technological problem. The input limit was important, and weather factors with only one limit (e.g., wind speed and direction) were commonly used for computational fluid dynamics (CFD) simulation. However, on rough terrain with complicated obstacles, boundary weather conditions can be very different. Entering a single limit can lead to large simulation uncertainty. Accordingly, the influence of different input boundary numbers and locations on the CFD simulation was investigated using a field experiment with low trace gas content, which was carried out in a chemical industrial park in a mountainous area. The experimental results suggested that the diffusion of the gas was influenced by a combination of meteorological conditions from the boundaries of several inputs. The simulation results confirmed and showed that the commonly used single-point limit entry can lead to large inaccuracies. The case where the entry limits are close to the emission sources and intersect with the crosswind plane agrees better with the measurements. The number of entry boundaries and locations has also been found to have a significant impact on velocity and turbulence. Finally, a guideline for setting entry limits was proposed. This study can improve understanding of CFD simulation and is useful for selecting input weather locations for accurate forecasts.

Aeolian Research, Volume 50, 2021, Item 100674

Sand dune hills stabilized by oil mulch and biological methods in south-west Iran. The aim of the present study is to determine the impact of these landscapes on airborne dust retention in five regions including hillside (UH), hillside (DH) and treetop positions at 54 years. These locations were at different distances from dust sources and prevailing winds. The results showed that the salinity in the study areas showed the following trend: canopy > UH > DH. Four times more mud particles were trapped in the corner than in the interior areas. In addition, the sludge deposition flux was 54 g⁻²Year⁻¹(the minimum) at the inner site (Al-Baji) at 207.4 g⁻²Year⁻¹(the maximum) at the corner location (SG). Unlike Schlick, clay flow was greatest at high altitudes in both the interior (124.4) and corners (123.4) due to the movement of fine materials. Total material deposition (silt+clay) was maximum (330.8 g) and minimum (155.6 g).⁻²Year⁻¹) in the corner and interior areas. The mineralogy of the clays indicated that these mounds contained two mineral groups. The primary minerals, i.e. carbonates and silicates, were inherited from the starting materials. Secondary minerals were identified in surface soil and subsurface peaks were very faint. Windblown sediments contributed these clays to the surfaces. The abundance of these clays showed the following trend: paligorskite > smectite > vermiculite. It was found that these areas do not disturb the atmosphere with dust and play an important role in air purification, since the roughness of the surface of these mounds has been promoted by artificially planted trees.

Aeolian Research, Volume 50, 2021, Item 100697

The dominance of wind processes in dry areas has created a harsh environment for soil and vegetation in these regions, where soil fertility, ecosystem productivity, air clarity and human health depend on wind activity and dust emission rate. Biological soil crusts (biocrusts) are communities of living organisms on the soil surface that play an important role in soil ecosystem services in arid regions. Lichens are organisms that can accumulate certain elements or substances in high concentrations in the atmosphere. The relationship between lichen species and soil geochemistry and dust uptake in the geomorphic zones of north-eastern Iran was investigated. Different lichen species and soil particles were analyzed using scanning electron microscopy (SEM-EDS). The results of the XRF and XRD analyzes showed that the lichen crusts affected the mineralization of the soil. By creating a microtopography, he indicated that the lichen trapped the dust. They also increased the amount of clay on the soil surface. The results showed the important role of lichens in soil ecosystem services in arid regions.

Aeolian Research, Volume 50, 2021, Item 100681

There is a trend to use high frequency piezoelectric, acoustic and optical sensors to measure wind sand transport rates in the wind community. However, most of these sensors are particle counters with inconsistent sensitivities or low saturation limits. Here we present a commercial Laser Sheet Sensor (LASS) that can be used streamwise to measure local salt flow or perpendicularly to capture the voluminous character of sand flows. The results of our laboratory and field experiments show that LASS sensors respond linearly to sand flows in the range from 0 to 20 kgm.⁻²S⁻¹, covering most of the wild jumping events. LASS are extremely consistent. They maintain functionality even with minor lens contamination or laser misalignment during use. LASS should not be used in environments with wet or poorly sorted sand or uneven winds.

Aeolian Research, Volume 50, 2021, Item 100683

Tracing the origin of wind sands in the Mu Us Desert is crucial for understanding surface processes in arid and semi-arid regions of China. However, the material source of the wind sands in the Mu Us desert is still up for debate. The origin of modern wind sands in different areas and with different particle sizes in the Mu Us Desert remains unclear, as does the relationship between the sources of different sediment types. Here, using a hierarchical cluster analysis, the Mu Us desert is divided into two sub-zones to the east and west. Based on the properties of trace elements and rare earths, we investigated the origin of eolian sands in different areas and with different particle sizes and analyzed the origin relationships between eolian sands, sandstones, fluvio-lacustrine sediments, loess sediments and floodplain sediments. in the desert. We report the following results: (1) The sources of coarse-grained eolian sands in the east and west of the Mu Us desert are different. The Aeolian sands in the eastern part are mainly derived from local sandstones and coarse-grained fluvio-lacustrine sediments from the east, while those in the western part are mainly from the Qilian orogenous belt on the northeastern Tibetan Plateau. (2) Fine-grained eolian sands throughout the desert show apparent homogeneity and have geochemical properties similar to fine-grained fluviolacustrine, loess and floodplain sediments, suggesting that these fine-grained fractions are fully mixed after a long time. long-distance transport. (3) Transport and deposition of wind sands are influenced by wind processes and river activity.

Aeolian Research, Volume 50, 2021, Item 100685

Star dunes, found on Mars and Titan and also found in the Earth's stratigraphic record, are widespread in the world's arid regions and 25 provinces have been identified and characterized from an analysis of Google images. Earth. They are found in East Asia, West Asia, America, southern Africa and North Africa. Star dunes are absent from the inland sand seas of Australia, the Kalahari and Indian Oceans, and southern Sahara. Morphometric measurements at a variety of sites show a density of stellar dunes ranging from 7 to 81 per 100 km.²(average 30 per km²), dune widths from 125 to 3071 m (mean 895 m) and heights from 4 to 291 m (mean 75 m). Star dunes exhibit a wide variety of shapes, including simple pyramids, complex structures, checkerboard patterns, symmetric and asymmetric shapes, stars along linear dunes, and stars along transverse dunes. In some areas, star dunes are associated with megadomes. In this work they are grouped into 10 types, although it is clear that some dunes may have characteristics of more than one type. Star dunes form in areas of low rainfall, changing wind directions, and in conjunction with topographical barriers. They are a more widespread and diverse phenomenon than previously thought.

Aeolian Research, Volume 50, 2021, Item 100646

To study the effects of cultivation on soil texture at local and regional scales during oasis expansion, a field study combined with remote sensing monitoring was conducted in the arid desert regions of Xinjiang, northwest China. We assess possible changes by comparing cultivated and uncultivated land in 2019 with matching reference land from China's second national soil survey. The results showed that the clay and silt content in the cultivated land increased with the years of cultivation (p<0.05), while the sand content decreased. A comparison of clay and silt content between 2019 and the late 1970s showed the accumulation of fine particles in the center of the oases and the removal of fine particles at their edges. Our results also show that sand content increased in reclaimed land, vacant land bordering oases, and sandy land. A comparison of 15 paired reference samples revealed that in most plots the clay and silt content on arable land is higher than on adjacent uncultivated land, although some plots showed a decreasing trend, suggesting that the dose of agricultural cultivation is not always at one Increase in fine particles leads. We conclude that the initial difference in soil texture before reclamation and reclamation history result in differences in soil texture between cultivated and adjacent uncultivated land. During oasis expansion, reclamation of sandy soil can reduce wind erosion, suggesting that appropriate agricultural conservation and reclamation measures can mitigate the adverse effects of soil texture changes.