Particle Image Velocimetry(PIV)techniques were developed to measure the convec- tive N_2-air flow under gradient magnetic fields.The velocity fields were calculated by the Minimum Quadratic Difference(MQD)algorithm an...Particle Image Velocimetry(PIV)techniques were developed to measure the convec- tive N_2-air flow under gradient magnetic fields.The velocity fields were calculated by the Minimum Quadratic Difference(MQD)algorithm and spurious vectors were eliminated by Delaunay Tessellation. The N_2-air flow was measured as the magnetic flux density varying from 0～1.5 T.A strengthened vortex flow of air was observed under the condition that the magnetic field was applied,and the ve- locity of N_2 jet rose with the increase of the magnetic density.The experimental results show that the magnetic force will induce a vortex flow and cause a convection flow of the air mixture when both gradients of the O_2 concentration and the magnetic field intensity exist.展开更多
For the purpose of enhancing air convection and controlling solar radiation, a new crushed-rock slope embankment design combined with a sun-shade measure is proposed. A newly designed embankment was constructed in the...For the purpose of enhancing air convection and controlling solar radiation, a new crushed-rock slope embankment design combined with a sun-shade measure is proposed. A newly designed embankment was constructed in the Tuotuohe section of the Qinghai-Tibet Railway and a field-testing experiment was carried out to determine its convection and temperature characteristics. The results show that distinct air convection occurred in the crushed-rock layer of the new embankment, especially in cold seasons, which was enhanced when it flowed upwards along the slope. This preliminarily indicated that the new design of the embankment slope was good for reinforcing air convection in the crushed-rock layer. The frequent fluctuations of the convection speed and the environmental wind speed were in good agreement, suggesting that the convection in the crushed rock primarily came from the ambient wind. It was also preliminarily determined that the new embankment had a better cooling effect and sun-shade effect for decreasing the temperature of the embankment slope compared with a traditional crushed-rock slope embankment, and the mean temperature difference between them was up to 1.7 °C. The mean annual temperature at the bottom boundary of the crushed-rock layer was obviously lower than that at the top boundary, and heat flux calculation showed that the shallow soil beneath the embankment slope was weakly releasing heat, all of which indicated that the new embankment slope design was beneficial to the thermal stability of the embankment. This study is helpful in providing some references for improved engineering design and maintenance of roadbeds in permafrost regions.展开更多
基金The project supported by the National Natural Science Foundation of China(50206019)Zhejiang Provincial Natural Science Foundation of China(502046)SRF for ROCS,SEM
文摘Particle Image Velocimetry(PIV)techniques were developed to measure the convec- tive N_2-air flow under gradient magnetic fields.The velocity fields were calculated by the Minimum Quadratic Difference(MQD)algorithm and spurious vectors were eliminated by Delaunay Tessellation. The N_2-air flow was measured as the magnetic flux density varying from 0～1.5 T.A strengthened vortex flow of air was observed under the condition that the magnetic field was applied,and the ve- locity of N_2 jet rose with the increase of the magnetic density.The experimental results show that the magnetic force will induce a vortex flow and cause a convection flow of the air mixture when both gradients of the O_2 concentration and the magnetic field intensity exist.
基金supported by the Western Project Program of the Chinese Academy of Sciences (No. KZCX2-XB3-19)the National Key Basic Research Program of China, 973 Program (No. 2012CB026101)
文摘For the purpose of enhancing air convection and controlling solar radiation, a new crushed-rock slope embankment design combined with a sun-shade measure is proposed. A newly designed embankment was constructed in the Tuotuohe section of the Qinghai-Tibet Railway and a field-testing experiment was carried out to determine its convection and temperature characteristics. The results show that distinct air convection occurred in the crushed-rock layer of the new embankment, especially in cold seasons, which was enhanced when it flowed upwards along the slope. This preliminarily indicated that the new design of the embankment slope was good for reinforcing air convection in the crushed-rock layer. The frequent fluctuations of the convection speed and the environmental wind speed were in good agreement, suggesting that the convection in the crushed rock primarily came from the ambient wind. It was also preliminarily determined that the new embankment had a better cooling effect and sun-shade effect for decreasing the temperature of the embankment slope compared with a traditional crushed-rock slope embankment, and the mean temperature difference between them was up to 1.7 °C. The mean annual temperature at the bottom boundary of the crushed-rock layer was obviously lower than that at the top boundary, and heat flux calculation showed that the shallow soil beneath the embankment slope was weakly releasing heat, all of which indicated that the new embankment slope design was beneficial to the thermal stability of the embankment. This study is helpful in providing some references for improved engineering design and maintenance of roadbeds in permafrost regions.
