This study investigates the capability of the dynamic downscaling method （DDM） in an East Asian climate study for June 1998 using the fifth-generation Pennsylvania State University-National Center for Atmospheric Re...This study investigates the capability of the dynamic downscaling method （DDM） in an East Asian climate study for June 1998 using the fifth-generation Pennsylvania State University-National Center for Atmospheric Research non-hydrostatic Mesoscale Model （MM5）.Sensitivity experiments show that MM5 results at upper atmospheric levels cannot match reanalyses data,but the results show consistent improvement in simulating moisture transport at low levels.The downscaling ability for precipitation is regionally dependent.During the monsoon season over the Yangtze River basin and the pre-monsoon season over North China,the DDM cannot match observed precipitation.Over Northwest China and the Tibetan Plateau （TP）,where there is high topography,the DDM shows better performance than reanalyses.Simulated monsoon evolution processes over East Asia,however,are much closer to observational data than reanalyses.The convection scheme has a substantial impact on extreme rainfall over the Yangtze River basin and the pre-monsoon over North China,but only a marginal contribution for Northwest China and the TP.Land surface parameterizations affect the locations and pattern of rainfall bands.The 10-day re-initialization in this study shows some improvement in simulated precipitation over some sub-regions but with no obvious improvement in circulation.The setting of the location of lateral boundaries （LLB） westward improves performance of the DDM.Including the entire TP in the western model domain improves the DDM performance in simulating precipitation in most sub-regions.In addition,a seasonal simulation demonstrates that the DDM can also obtain consistent results,as in the June case,even when another two months consist of no strong climate/weather events.展开更多
Precise estimation of the location and magnitude of boundary layer transition is essential for the exact computation of aero-thermodynamics and the performance of hypersonic vehicles.Compared with resource-intensive m...Precise estimation of the location and magnitude of boundary layer transition is essential for the exact computation of aero-thermodynamics and the performance of hypersonic vehicles.Compared with resource-intensive methods such as large eddy simulation,direct numerical simulation,and experimental approaches,Reynolds-averaged Navier-Stokes(RANS)-based models offer an efficient and cost-effective solution for engineering applications.Therefore,this review focuses on the capabilities of various RANS-based models for prediction of boundary layer transition in hypersonic flows.The formulation and underlying assumptions of these models are described and their predictive performance in terms of transition initiation and length in hypersonic regimes is examined.Critical gaps and limitations of existing models are outlined and a framework is established for future development of RANS-based transition models,with the aim of developing more robust,reliable,and cost-effective techniques for prediction of hypersonic boundary layer transition that are suitable for use in current state-of-the-art computational codes.展开更多
基金supported by the funding of the Key Program of the Chinese Academy of Sciences (Grant No.KZCX2-YW-328)the National Key Basic Research Program (2005CB422003)+1 种基金National Science Foundation Center of China (NSFC) (40871001)the US JPL Grant No. 1278492,NOAA Grant Nos NA07OAR4310226 and NA08OAR4310591
文摘This study investigates the capability of the dynamic downscaling method （DDM） in an East Asian climate study for June 1998 using the fifth-generation Pennsylvania State University-National Center for Atmospheric Research non-hydrostatic Mesoscale Model （MM5）.Sensitivity experiments show that MM5 results at upper atmospheric levels cannot match reanalyses data,but the results show consistent improvement in simulating moisture transport at low levels.The downscaling ability for precipitation is regionally dependent.During the monsoon season over the Yangtze River basin and the pre-monsoon season over North China,the DDM cannot match observed precipitation.Over Northwest China and the Tibetan Plateau （TP）,where there is high topography,the DDM shows better performance than reanalyses.Simulated monsoon evolution processes over East Asia,however,are much closer to observational data than reanalyses.The convection scheme has a substantial impact on extreme rainfall over the Yangtze River basin and the pre-monsoon over North China,but only a marginal contribution for Northwest China and the TP.Land surface parameterizations affect the locations and pattern of rainfall bands.The 10-day re-initialization in this study shows some improvement in simulated precipitation over some sub-regions but with no obvious improvement in circulation.The setting of the location of lateral boundaries （LLB） westward improves performance of the DDM.Including the entire TP in the western model domain improves the DDM performance in simulating precipitation in most sub-regions.In addition,a seasonal simulation demonstrates that the DDM can also obtain consistent results,as in the June case,even when another two months consist of no strong climate/weather events.
基金supported by a National Research Foundation of Korea(NRF)grant funded by the Korean Government-(No.RS-2025-00557769).
文摘Precise estimation of the location and magnitude of boundary layer transition is essential for the exact computation of aero-thermodynamics and the performance of hypersonic vehicles.Compared with resource-intensive methods such as large eddy simulation,direct numerical simulation,and experimental approaches,Reynolds-averaged Navier-Stokes(RANS)-based models offer an efficient and cost-effective solution for engineering applications.Therefore,this review focuses on the capabilities of various RANS-based models for prediction of boundary layer transition in hypersonic flows.The formulation and underlying assumptions of these models are described and their predictive performance in terms of transition initiation and length in hypersonic regimes is examined.Critical gaps and limitations of existing models are outlined and a framework is established for future development of RANS-based transition models,with the aim of developing more robust,reliable,and cost-effective techniques for prediction of hypersonic boundary layer transition that are suitable for use in current state-of-the-art computational codes.
