Eddies are frequently observed in the northeastern South China Sea （SCS）. However, there have been few studies on vertical structure and temporal-spatial evolution of these eddies. We analyzed the seasonal Luzon War...Eddies are frequently observed in the northeastern South China Sea （SCS）. However, there have been few studies on vertical structure and temporal-spatial evolution of these eddies. We analyzed the seasonal Luzon Warm Eddy （LWE） based on Argo float data and the merged data products of satellite altimeters of Topex/Poseidon, Jason-1 and European Research Satellites. The analysis shows that the LWE extends vertically to more than 500 m water depth, with a higher temperature anomaly of 5℃ and lower salinity anomaly of 0.5 near the thermocline. The current speeds of the LWE are stronger in its uppermost 200 m, with a maximum speed of 0.6 m/s. Sometimes the LWE incorporates mixed waters from the Kuroshio Current and the SCS, and thus has higher thermohaline characteristics than local marine waters. Time series of eddy kinematic parameters show that the radii and shape of the LWE vary during propagation, and its eddy kinetic energy follows a normal distribution. In addition, we used the empirical orthogonal function （EOF） here to analyze seasonal characteristics of the LWE. The results suggest that the LWE generally forms in July, intensifies in August and September, separates from the coast of Luzon in October and propagates westward, and weakens in December and disappears in February. The LWE＇s westward migration is approximately along 19°N latitude from northwest of Luzon to southeast of Hainan, with a mean speed of 6.6 cm/s.展开更多
Directional solidified(DS) turbine blades are widely used in advanced gas turbine engine. The size and orientation of columnar grains have great influence on the high temperature property and performance of the turbin...Directional solidified(DS) turbine blades are widely used in advanced gas turbine engine. The size and orientation of columnar grains have great influence on the high temperature property and performance of the turbine blade. Numerical simulation of the directional solidification process is an effective way to investigate the grain's growth and morphology,and hence to optimize the process. In this paper,a mathematical model was presented to study the directional solidified microstructures at different withdrawal rates. Ray-tracing method was applied to calculate the temperature variation of the blade. By using a Modified Cellular Automation(MCA) method and a simple linear interpolation method,the mushy zone and the microstructure evolution were studied in detail. Experimental validations were carried out at different withdrawal rates. The calculated cooling curves and microstructure agreed well with those experimental. It is indicated that the withdrawal rate affects the temperature distribution and growth rate of the grain directly,which determines the final size and morphology of the columnar grain. A moderate withdrawal rate can lead to high quality DS turbine blades for industrial application.展开更多
The nonlinear evolution process of new vortex structures at the late-stage of the transition, including the 3-D spatial structure of barrel-shaped vortex and "dark spots" structure observed by experiment res...The nonlinear evolution process of new vortex structures at the late-stage of the transition, including the 3-D spatial structure of barrel-shaped vortex and "dark spots" structure observed by experiment research, has been confirmed by our computational results. The formation mechanisms of these structures have been explored. It is revealed that the new vortex structures, the ring-like vortex chain and induced disturbance velocities play a dominant role in the generation of turbulent spots.展开更多
基金Supported by the Knowledge Innovation Program of the Chinese Academy of Sciences (Nos.KZCX1-YW-12 and KZCX2-YW-201)the National Natural Science Foundation of China (No. 90411013)the National High Technology Research and Development Program of China (863 Program) (No.2007AA092201)
文摘Eddies are frequently observed in the northeastern South China Sea （SCS）. However, there have been few studies on vertical structure and temporal-spatial evolution of these eddies. We analyzed the seasonal Luzon Warm Eddy （LWE） based on Argo float data and the merged data products of satellite altimeters of Topex/Poseidon, Jason-1 and European Research Satellites. The analysis shows that the LWE extends vertically to more than 500 m water depth, with a higher temperature anomaly of 5℃ and lower salinity anomaly of 0.5 near the thermocline. The current speeds of the LWE are stronger in its uppermost 200 m, with a maximum speed of 0.6 m/s. Sometimes the LWE incorporates mixed waters from the Kuroshio Current and the SCS, and thus has higher thermohaline characteristics than local marine waters. Time series of eddy kinematic parameters show that the radii and shape of the LWE vary during propagation, and its eddy kinetic energy follows a normal distribution. In addition, we used the empirical orthogonal function （EOF） here to analyze seasonal characteristics of the LWE. The results suggest that the LWE generally forms in July, intensifies in August and September, separates from the coast of Luzon in October and propagates westward, and weakens in December and disappears in February. The LWE＇s westward migration is approximately along 19°N latitude from northwest of Luzon to southeast of Hainan, with a mean speed of 6.6 cm/s.
基金supported by the National Basic Research Program of China (Grant Nos. 2005CB724105, 2011CB706801)National Natural Science Foundation of China (Grant No. 10477010)+1 种基金National High Technology Research and Development Program of China (Grant No. 2007AA04Z141)Important National Science & Technology Specific Projects (Grant Nos. 2009ZX04006-041, 2011ZX04014-052)
文摘Directional solidified(DS) turbine blades are widely used in advanced gas turbine engine. The size and orientation of columnar grains have great influence on the high temperature property and performance of the turbine blade. Numerical simulation of the directional solidification process is an effective way to investigate the grain's growth and morphology,and hence to optimize the process. In this paper,a mathematical model was presented to study the directional solidified microstructures at different withdrawal rates. Ray-tracing method was applied to calculate the temperature variation of the blade. By using a Modified Cellular Automation(MCA) method and a simple linear interpolation method,the mushy zone and the microstructure evolution were studied in detail. Experimental validations were carried out at different withdrawal rates. The calculated cooling curves and microstructure agreed well with those experimental. It is indicated that the withdrawal rate affects the temperature distribution and growth rate of the grain directly,which determines the final size and morphology of the columnar grain. A moderate withdrawal rate can lead to high quality DS turbine blades for industrial application.
基金supported by the National Natural Science Foundation of China (Grant No. 10772082)the Doctoral Foundation of Ministry of Education of China (Grant No. 20070287005)AFOSR (Grant No. FA9550-08-1-0201)
文摘The nonlinear evolution process of new vortex structures at the late-stage of the transition, including the 3-D spatial structure of barrel-shaped vortex and "dark spots" structure observed by experiment research, has been confirmed by our computational results. The formation mechanisms of these structures have been explored. It is revealed that the new vortex structures, the ring-like vortex chain and induced disturbance velocities play a dominant role in the generation of turbulent spots.
