In this study,the new method of the vortex core line based on Liutex definition,also known as Liutex core line,is applied to support the hypothesis that the vortex ring is not a part of theΛ-vortex and the formation ...In this study,the new method of the vortex core line based on Liutex definition,also known as Liutex core line,is applied to support the hypothesis that the vortex ring is not a part of theΛ-vortex and the formation of the ring-like vortex is formed separately from theΛ-vortex.The proper orthogonal decomposition(POD)is also applied to analyze the Kelvin-VHelmholtz(K-H)instability happening in hairpin ring areas of the flow transition on the flat plate to understand the mechanism of the ring-like vortex formation.The new vortex identification method named modified Liutex-Omega method is efficiently used to visualize and observe the shapes of vortex structures in 3-D.The streamwise vortex structure characteristics can be found in POD mode one as the mean flow.The other POD modes are in stremwise and spanwise structures and have the fluctuation motions,which are induced by K-H instability.Moreover,the result shows that POD modes are in pairs and share the same characteristics such as amplitudes,mode shapes,and time evolutions.The vortex core and POD results confirm that theΛ-vortex is not self-deformed to a hairpin vortex,but the hairpin vortex is formed by the K-H instability during the development of Lambda vortex to hairpin vortex in the boundary layer flow transition.展开更多
基于常规天气观测资料和美国FNL1°×1°逐6 h再分析资料,对2014年4月23—24日昌吉地区一次寒潮天气过程进行分析和总结,并利用WRF3.7(The Weather Research and Forecasting Model)中尺度数值模式对10 m风场和地形作用进...基于常规天气观测资料和美国FNL1°×1°逐6 h再分析资料,对2014年4月23—24日昌吉地区一次寒潮天气过程进行分析和总结,并利用WRF3.7(The Weather Research and Forecasting Model)中尺度数值模式对10 m风场和地形作用进行分析,结果表明:(1)这次寒潮天气过程出现在欧洲高压脊东南衰退、西西伯利亚低槽东南下进入新疆爆发的大尺度环流背景下。(2)这次强寒潮过程的高位涡强冷空气来自欧亚北部和北极地区的平流层下部和对流层上部。(3)低层强西北风急流向山脉辐合,造成暖湿气流在天山迎风坡强烈爬升,是暴雪发生的触发机制。通过地形敏感性试验表明天山地形的抬升作用减弱所引起的降水变小。展开更多
基金The authors thank the Department of Mathematics of University of Texas at Arlington and Royal Thai Government for the financial support.
文摘In this study,the new method of the vortex core line based on Liutex definition,also known as Liutex core line,is applied to support the hypothesis that the vortex ring is not a part of theΛ-vortex and the formation of the ring-like vortex is formed separately from theΛ-vortex.The proper orthogonal decomposition(POD)is also applied to analyze the Kelvin-VHelmholtz(K-H)instability happening in hairpin ring areas of the flow transition on the flat plate to understand the mechanism of the ring-like vortex formation.The new vortex identification method named modified Liutex-Omega method is efficiently used to visualize and observe the shapes of vortex structures in 3-D.The streamwise vortex structure characteristics can be found in POD mode one as the mean flow.The other POD modes are in stremwise and spanwise structures and have the fluctuation motions,which are induced by K-H instability.Moreover,the result shows that POD modes are in pairs and share the same characteristics such as amplitudes,mode shapes,and time evolutions.The vortex core and POD results confirm that theΛ-vortex is not self-deformed to a hairpin vortex,but the hairpin vortex is formed by the K-H instability during the development of Lambda vortex to hairpin vortex in the boundary layer flow transition.
文摘基于常规天气观测资料和美国FNL1°×1°逐6 h再分析资料,对2014年4月23—24日昌吉地区一次寒潮天气过程进行分析和总结,并利用WRF3.7(The Weather Research and Forecasting Model)中尺度数值模式对10 m风场和地形作用进行分析,结果表明:(1)这次寒潮天气过程出现在欧洲高压脊东南衰退、西西伯利亚低槽东南下进入新疆爆发的大尺度环流背景下。(2)这次强寒潮过程的高位涡强冷空气来自欧亚北部和北极地区的平流层下部和对流层上部。(3)低层强西北风急流向山脉辐合,造成暖湿气流在天山迎风坡强烈爬升,是暴雪发生的触发机制。通过地形敏感性试验表明天山地形的抬升作用减弱所引起的降水变小。
