Sand Weather Research Articles

基于 CFD 数值模拟的联合沙障间距优化与风沙流特征研究

Strong wind and sand activities will seriously damage the ecological restoration and agricultural safety production on the edge of desert areas, resulting in irreversible economic losses. In order to prevent and protect the agro-ecological environment in the wind-blown sand area, this paper constructs a combination of double-row vertical nylon net sand barrier and grass grid sand barrier. Through numerical simulation and wind tunnel experiment, the protection benefits of double-row vertical nylon net sand barrier and grass grid under different spacing conditions are analyzed, and the layout conditions with optimal spacing are obtained. The results show that when the spacing between double-row vertical sand barrier and grass grid is 5H-10H, the airflow velocity behind the double-row vertical sand barrier cannot be fully developed, the increase of airflow velocity is small, and the average wind prevention efficiency is above 85%. The effective protection distance com-pletely covers the entire combined sand barrier area, and a large number of sand particles near the surface are fixed to the grass grid, so the sand resistance rate is over 77%. The combined sand barrier has a good cooperative protection effect and achieves efficient wind prevention and sand fixation. The wind tunnel experiment verifies the reliability of the results. It also realizes efficient wind prevention and sand fixation under extreme wind and sand weather, and avoids sand burial on farmland and ecological restoration areas caused by extreme wind and sand weather.

Corona Onset Characteristics of the 750-kV Bundle Conductor in Sand and Dust Weather in High-Altitude Area

In high-altitude areas of Northwest China, sand and dust weather is frequent, which may have an influence on the corona onset characteristics of the bundle conductors of the 750-kV power transmission lines. So the corona resistive currents of the used conductors of the 750-kV power transmission lines were measured based on the movable corona cage in fine and simulated sand and dust weather in Xining City, Northwest China, and the altitude of the test spot is 2200 m. The corona onset electric-field strength was gained according to the IEEE definition. The test result shows that compared with the no sand weather, the corona onset electric-field strength decreases in the sand and dust weather. When the sand concentration and sand particle size increase, the corona onset electric-field strength decreases accordingly. With further analysis, the roughness factor m decreases with the increase of the sand concentration and sand particle size.

Root proliferation in recent and weathered sandy soils from Veracruz, Mexico

ABSTRACTField observations and laboratory experiments on unweathered and weathered dune sand beneath a tropical deciduous forest in Veracruz, Mexico were used to test the hypothesis that temporary nutrient adsorption by more weathered soil facilitates more effective nutrient recycling through the stimulation of a superficial fine root system. An analysis of soil solution composition in the field indicated that K, P andwere being more effectively retained in weathered sand topsoil than in recent sand but, in a leaching experiment, onlywas more effectively adsorbed by this soil. Fine roots in weathered sand were more concentrated superficially than in recent sand, and a bioassay with seedlings ofCedrela odoratashowed more fine root proliferation in this medium than in recent sand. In combination, these data suggest that weathering of sand in this area promotes an increased nitrate adsorption capacity which may stimulate greater root proliferation in topsoils and lead to the entrainment of other nutrients in a more concentrated topsoil-vegetation cycle. If these results can be applied to the larger domain of tropical soils generally, they suggest that nitrate adsorption may play an important role in stimulating effective nutrient recycling by forests occupying weathered soils.

Clay Mineral Genesis of Some New York Spodosols

AbstractSome Spodosols in northern New York previously shown to have well crystallized montmorillonite in the albic horizon but only amorphous clay sized material in the spodic horizon were studied to determine the source or genesis of the montmorillonite. The soils used to test several hypotheses of the clay mineral genesis represented Orthods, Humods, and Aquods. These soils were also shown to be deficient in mica and chlorite in the sand, silt, and clay fractions. This allowed a test of the hypothesis that montmorillonite in albic horizons weathers from mica, a process which previously has been reported to be active. The presence of only traces of mica and chlorite in the sand and silt fractions would indicate that weathering of sand and silt sized minerals directly to clay sized minerals should not be important. However, the small amount (generally less than 3%) of clay sized materials in the pedons makes this assumption inconclusive.Soil solution studies, coupled with equilibrium diagrams, provide evidence that clay mineral synthesis from ions does not occur in these soils.The well crystallized clay sized minerals detected in the upper solum of the pedons studied may have (i) weathered directly from sand and silt sized minerals, (ii) been added as dust, or (iii) weathered from minerals added as dust. There is recent evidence that appreciable amounts of montmorillonite, illite, vermiculite, and kaolinite are deposited as dust throughout the northern United States. If projected figures are valid, dust could account for most of the montmorillonite in the albic horizons studied. Concomitant additions of chlorite and mica are not detected. Chlorite and mica added as dust, as well as any traces of these minerals present as sand or silt, must be weathered to some other species in the clay fraction, because they are not detected in the clays.It is proposed that in the Spodosols studied (i) any chlorite in the albic horizon is weathered to amorphous aluminosilicates and translocated to the spodic horizon, and (ii) mica is weathered to montmorillonite in the albic horizon, to vermiculite in the Bh horizon, and to “chloritized” vermiculite in the Bir horizon.