The interaction of U-shaped rings used for power transmission hardware with a wind-sand field is simulated numerically.A standard kturbulence model is used in synergy with an Eulerian-Lagrangian approach.The results...The interaction of U-shaped rings used for power transmission hardware with a wind-sand field is simulated numerically.A standard kturbulence model is used in synergy with an Eulerian-Lagrangian approach.The results show that the wind pressure on the windward side of the U-shaped ring is the highest,a negative pressure zone appears on both sides of the U-shaped ring,while a Kármán Vortex Street is created on its leeward side.There are three possible regimes of motion for the sand grains in the wind field.Sand grains with size below 0.125 mm can follow the airflow directly into the contact area of two U-shaped rings.When the sand size is about 0.1 mm,the number of sand grains that are blown into the contact area attains a maximum.Through the simulation of U-shaped rings in the wind-sand field,the dynamics of such processes are explained in detail,thereby providing relevant information for the subsequent protection and design of connecting hardware used for power transmission.展开更多
The structure of wind-sand flow under different total sand transport rates was measured with field vertical anemometer and sand trap on the crest of typical coastal transverse ridge in Changli Gold Coast of Hebei Prov...The structure of wind-sand flow under different total sand transport rates was measured with field vertical anemometer and sand trap on the crest of typical coastal transverse ridge in Changli Gold Coast of Hebei Province, which is one of the most typical coastal aeolian distribution regions in China and famous for the tall and typical coastal transverse ridges. The measurement results show that, on the conditions of approximate wind velocities and same surface materials and environments, some changes happen to the structure of wind-sand flow with the increase of total sand transport rate on the crest of coastal transverse ridge. First, the sand transport rates of layers at different heights in the wind-sand flow increase, with the maximum increase at the height layer of 4-8cm. Second, the ratios of sand trans-port rates of layers at different heights to total sand transport rate decrease at the low height layer (0-4cm), but increase at the high height layer (4-60cm). Third, the distribution of the sand transport rate in the wind-sand flow can be expressed by an exponential function at the height layer of 0-40cm, but it changes from power function model to ex-ponential function model in the whole height layer (0-60cm) and changes into polynomial function model at the height layer of 40-60cm with the increase of total sand transport rate. Those changes have a close relationship with the limit of sand grain size of wind flow transporting and composition of sand grain size in the wind-sand flow.展开更多
The influence of sand dust on discharge of external insulation has caused widespread concern.At present,the research results show wind-sand electricity has a remarkable effect on the discharge characteristics of insul...The influence of sand dust on discharge of external insulation has caused widespread concern.At present,the research results show wind-sand electricity has a remarkable effect on the discharge characteristics of insulator and has little influence on the discharge characteristics of air gap.The flashover of insulator strings occurs along the insulator surface and air gaps,and the sand dust deposited on the insulator surface may affect the flashover characteristics of insulator strings.This paper studies the flashover characteristics of flat plate model under DC voltage in wind-sand condition.The experimental results show that under positive polarity voltage,the flashover voltage of the flat plate model has a maximum value,while under negative polarity voltage,the flashover voltage of the flat plate model has a minimum value with a certain degree of sand dust deposition.The wind or sand in sand-dust weather has an important effect on the flashover characteristics of the flat plate model.In certain variation range of electric charge,electric charge of sand dust has little effect on the flashover voltage of flat plate model under DC voltage.The deposition of sand has significant influence on the flashover process of flat plate model,which is related to the deposition density and moisture content of sand particle.展开更多
Sand drift disasters are mainly manifested in the destruction by wind-sand currentto engineering installations, rapid aggravation of soil erosion, land desertification,etc. The reason for the damage lies in the fact t...Sand drift disasters are mainly manifested in the destruction by wind-sand currentto engineering installations, rapid aggravation of soil erosion, land desertification,etc. The reason for the damage lies in the fact that moving sand grains obtain largequantity of energy under the action of wind force. However, judgement of the intensi-ty of sand drift depends on the determination of energy accumluated by wind-sand cur-展开更多
风蚀监测可反映风沙运动规律,集沙仪是风蚀监测的必备仪器,而以往研究大多在沙漠或沙地开展,较少涉及黑土农田。本研究基于BSNE(Big Spring Number Eight)集沙仪,将采沙盒底部阻风结构中的18目孔径筛网改进为逆向百叶窗式的阻风挡板,采...风蚀监测可反映风沙运动规律,集沙仪是风蚀监测的必备仪器,而以往研究大多在沙漠或沙地开展,较少涉及黑土农田。本研究基于BSNE(Big Spring Number Eight)集沙仪,将采沙盒底部阻风结构中的18目孔径筛网改进为逆向百叶窗式的阻风挡板,采用模拟试验对比分析BSNE集沙仪和改进后rBSNE(Revised Spring Number Eight)集沙仪的保沙和集沙能力,并将其应用于野外黑土农田风蚀监测。研究结果表明:与BSNE集沙仪相比,rBSNE集沙仪降低了小粒级颗粒的损失率,当风速低于20 m·s^(-1)时,对<0.25 mm粒径的土壤颗粒的损失率显著降低74.3%~87.1%;当风速达到20 m·s^(-1)时,对所有试验粒径的土壤颗粒的损失率显著降低46.9%~74.3%。与BSNE集沙仪相比,rBSNE集沙仪有助于对小粒级颗粒的收集,当风速低于20 m·s^(-1)时,对粒径为<0.5 mm的集沙量显著增加了9.0%~44.0%;当风速达到20 m·s^(-1)时,对所有试验粒径的集沙量均显著增加7.3%~34.4%。野外监测结果显示风蚀输沙量随高度增加呈指数函数递减趋势,说明rBSNE集沙仪可应用于黑土农田风蚀的监测。展开更多
基金National Natural Science Foundation of China(51865055)Tianshan Talents Plan of Xinjiang Autonomous Region of China(201720025)。
文摘The interaction of U-shaped rings used for power transmission hardware with a wind-sand field is simulated numerically.A standard kturbulence model is used in synergy with an Eulerian-Lagrangian approach.The results show that the wind pressure on the windward side of the U-shaped ring is the highest,a negative pressure zone appears on both sides of the U-shaped ring,while a Kármán Vortex Street is created on its leeward side.There are three possible regimes of motion for the sand grains in the wind field.Sand grains with size below 0.125 mm can follow the airflow directly into the contact area of two U-shaped rings.When the sand size is about 0.1 mm,the number of sand grains that are blown into the contact area attains a maximum.Through the simulation of U-shaped rings in the wind-sand field,the dynamics of such processes are explained in detail,thereby providing relevant information for the subsequent protection and design of connecting hardware used for power transmission.
基金Under the auspices of National Natural Science Foundation of China (No 40571019)
文摘The structure of wind-sand flow under different total sand transport rates was measured with field vertical anemometer and sand trap on the crest of typical coastal transverse ridge in Changli Gold Coast of Hebei Province, which is one of the most typical coastal aeolian distribution regions in China and famous for the tall and typical coastal transverse ridges. The measurement results show that, on the conditions of approximate wind velocities and same surface materials and environments, some changes happen to the structure of wind-sand flow with the increase of total sand transport rate on the crest of coastal transverse ridge. First, the sand transport rates of layers at different heights in the wind-sand flow increase, with the maximum increase at the height layer of 4-8cm. Second, the ratios of sand trans-port rates of layers at different heights to total sand transport rate decrease at the low height layer (0-4cm), but increase at the high height layer (4-60cm). Third, the distribution of the sand transport rate in the wind-sand flow can be expressed by an exponential function at the height layer of 0-40cm, but it changes from power function model to ex-ponential function model in the whole height layer (0-60cm) and changes into polynomial function model at the height layer of 40-60cm with the increase of total sand transport rate. Those changes have a close relationship with the limit of sand grain size of wind flow transporting and composition of sand grain size in the wind-sand flow.
基金Project Supported by National Natural Science Foundation of China（90510014 ）.
文摘The influence of sand dust on discharge of external insulation has caused widespread concern.At present,the research results show wind-sand electricity has a remarkable effect on the discharge characteristics of insulator and has little influence on the discharge characteristics of air gap.The flashover of insulator strings occurs along the insulator surface and air gaps,and the sand dust deposited on the insulator surface may affect the flashover characteristics of insulator strings.This paper studies the flashover characteristics of flat plate model under DC voltage in wind-sand condition.The experimental results show that under positive polarity voltage,the flashover voltage of the flat plate model has a maximum value,while under negative polarity voltage,the flashover voltage of the flat plate model has a minimum value with a certain degree of sand dust deposition.The wind or sand in sand-dust weather has an important effect on the flashover characteristics of the flat plate model.In certain variation range of electric charge,electric charge of sand dust has little effect on the flashover voltage of flat plate model under DC voltage.The deposition of sand has significant influence on the flashover process of flat plate model,which is related to the deposition density and moisture content of sand particle.
文摘Sand drift disasters are mainly manifested in the destruction by wind-sand currentto engineering installations, rapid aggravation of soil erosion, land desertification,etc. The reason for the damage lies in the fact that moving sand grains obtain largequantity of energy under the action of wind force. However, judgement of the intensi-ty of sand drift depends on the determination of energy accumluated by wind-sand cur-
文摘风蚀监测可反映风沙运动规律,集沙仪是风蚀监测的必备仪器,而以往研究大多在沙漠或沙地开展,较少涉及黑土农田。本研究基于BSNE(Big Spring Number Eight)集沙仪,将采沙盒底部阻风结构中的18目孔径筛网改进为逆向百叶窗式的阻风挡板,采用模拟试验对比分析BSNE集沙仪和改进后rBSNE(Revised Spring Number Eight)集沙仪的保沙和集沙能力,并将其应用于野外黑土农田风蚀监测。研究结果表明:与BSNE集沙仪相比,rBSNE集沙仪降低了小粒级颗粒的损失率,当风速低于20 m·s^(-1)时,对<0.25 mm粒径的土壤颗粒的损失率显著降低74.3%~87.1%;当风速达到20 m·s^(-1)时,对所有试验粒径的土壤颗粒的损失率显著降低46.9%~74.3%。与BSNE集沙仪相比,rBSNE集沙仪有助于对小粒级颗粒的收集,当风速低于20 m·s^(-1)时,对粒径为<0.5 mm的集沙量显著增加了9.0%~44.0%;当风速达到20 m·s^(-1)时,对所有试验粒径的集沙量均显著增加7.3%~34.4%。野外监测结果显示风蚀输沙量随高度增加呈指数函数递减趋势,说明rBSNE集沙仪可应用于黑土农田风蚀的监测。
