The fog occurs frequently over the Yellow Sea in spring（April–May）, a climatical period of Asian monsoon transition. A comprehensive survey of the characteristic weather pattern and the air-sea condition is provide...The fog occurs frequently over the Yellow Sea in spring（April–May）, a climatical period of Asian monsoon transition. A comprehensive survey of the characteristic weather pattern and the air-sea condition is provided associated with the fog for the period of 1960–2006. The sea fog is categorized by airflow pathways of backward trajectory cluster analysis with the surface observations derived from international comprehensive oceanatmosphere dataset（I_COADS） I_COADS datasets and contemporaneous wind fields from the National Centers for Environmental Prediction（NCEP）/National Center for Atmospheric Research（NCAR） reanalysis. On the basis of the airflow paths, the large-scale lower-tropospheric circulation patterns and the associated surface divergence,the distribution of a vertical humidity, the horizontal water vapor transportation and the air-sea temperature difference are investigated and the major findings are summarized as follows.（1） Four primary clusters of the airflow paths that lead to spring sea fog formation are identified. They are originated from the northwest, east,southeast and southwest of the Yellow Sea, respectively.（2） Springtime Yellow Sea fog occurs under two typical weather patterns： the Yellow Sea high（YSH） and cyclone and anticyclone couplet（CAC）. Each pattern appears by about equal chance in April but the YSH occurrence drops to around one third and the CAC rises to around two third of chance in May.（3） The common feature in the two types of synoptic conditions is that surface divergence center is located over the Yellow Sea.（4） For the YSH type of fog, water vapor comes mainly from local evaporation with a well-defined dry layer present in the lower atmosphere; for the CAC type of fog, however, water vapor comes mainly from areas outside the Yellow Sea with a thick surface layer of high humidity.（5） With the differences in weather patterns and its associated vertical distribution of the humidity and the transportation of water vapor, there are two types of sea fogs. Most fogs of the CAC types are ＂warm＂ fog, while fogs of YSH type have nearly equal chance to be ＂warm＂ and ＂cold＂ fog.展开更多
Knowledge of the airflow patterns and methane distributions at a continuous miner face under different ventilation conditions can minimize the risks of explosion and injury to miners by accurately forecasting potentia...Knowledge of the airflow patterns and methane distributions at a continuous miner face under different ventilation conditions can minimize the risks of explosion and injury to miners by accurately forecasting potentially hazardous face methane levels. This study focused on validating a series of computational fluid dynamics(CFD) models using full-scale ventilation gallery data that assessed how curtain setback distance impacted airflow patterns and methane distributions at an empty mining face(no continuous miner present). Three CFD models of face ventilation with 4.6, 7.6 and 10.7 m(15, 25, and 35 ft) blowing curtain setback distances were constructed and validated with experimental data collected in a full-scale ventilation test facility. Good agreement was obtained between the CFD simulation results and this data.Detailed airflow and methane distribution information are provided. Elevated methane zones at the working faces were identified with the three curtain setback distances. Visualization of the setback distance impact on the face methane distribution was performed by utilizing the post-processing capability of the CFD software.展开更多
从N av ier-S tokes方程出发,运用CFX软件对外界风向与屋脊平行和相夹45°两种情形下温室内气流场进行了稳态模拟研究。结果显示,对于前者,气流从山墙门和侧窗的上部进入,从侧窗的下部流出,气流在温室内沿中心纵截面分布的对称性较...从N av ier-S tokes方程出发,运用CFX软件对外界风向与屋脊平行和相夹45°两种情形下温室内气流场进行了稳态模拟研究。结果显示,对于前者,气流从山墙门和侧窗的上部进入,从侧窗的下部流出,气流在温室内沿中心纵截面分布的对称性较好,在温室的后半部气流逐渐扩散,紊流加强;对于后者,气流从山墙门和迎风侧窗处进入,两股气流相遇后受棚面形状及作物的影响而形成各种涡流,最后从背风侧窗处流出。气流在接触到栽培作物时流速迅速减小,作物冠层边界受到周围空间气流的影响,但在作物冠层内受周围空间气流影响不大。展开更多
基金The National Natural Science Foundation of China under contract No.41275025the Special Fund for Strategic Pilot Technology of Chinese Academy of Sciences under contract No.XDA11010403the National Key Basic Research Program(973 Progrom)of China under controut No.2014CB953903
文摘The fog occurs frequently over the Yellow Sea in spring（April–May）, a climatical period of Asian monsoon transition. A comprehensive survey of the characteristic weather pattern and the air-sea condition is provided associated with the fog for the period of 1960–2006. The sea fog is categorized by airflow pathways of backward trajectory cluster analysis with the surface observations derived from international comprehensive oceanatmosphere dataset（I_COADS） I_COADS datasets and contemporaneous wind fields from the National Centers for Environmental Prediction（NCEP）/National Center for Atmospheric Research（NCAR） reanalysis. On the basis of the airflow paths, the large-scale lower-tropospheric circulation patterns and the associated surface divergence,the distribution of a vertical humidity, the horizontal water vapor transportation and the air-sea temperature difference are investigated and the major findings are summarized as follows.（1） Four primary clusters of the airflow paths that lead to spring sea fog formation are identified. They are originated from the northwest, east,southeast and southwest of the Yellow Sea, respectively.（2） Springtime Yellow Sea fog occurs under two typical weather patterns： the Yellow Sea high（YSH） and cyclone and anticyclone couplet（CAC）. Each pattern appears by about equal chance in April but the YSH occurrence drops to around one third and the CAC rises to around two third of chance in May.（3） The common feature in the two types of synoptic conditions is that surface divergence center is located over the Yellow Sea.（4） For the YSH type of fog, water vapor comes mainly from local evaporation with a well-defined dry layer present in the lower atmosphere; for the CAC type of fog, however, water vapor comes mainly from areas outside the Yellow Sea with a thick surface layer of high humidity.（5） With the differences in weather patterns and its associated vertical distribution of the humidity and the transportation of water vapor, there are two types of sea fogs. Most fogs of the CAC types are ＂warm＂ fog, while fogs of YSH type have nearly equal chance to be ＂warm＂ and ＂cold＂ fog.
文摘Knowledge of the airflow patterns and methane distributions at a continuous miner face under different ventilation conditions can minimize the risks of explosion and injury to miners by accurately forecasting potentially hazardous face methane levels. This study focused on validating a series of computational fluid dynamics(CFD) models using full-scale ventilation gallery data that assessed how curtain setback distance impacted airflow patterns and methane distributions at an empty mining face(no continuous miner present). Three CFD models of face ventilation with 4.6, 7.6 and 10.7 m(15, 25, and 35 ft) blowing curtain setback distances were constructed and validated with experimental data collected in a full-scale ventilation test facility. Good agreement was obtained between the CFD simulation results and this data.Detailed airflow and methane distribution information are provided. Elevated methane zones at the working faces were identified with the three curtain setback distances. Visualization of the setback distance impact on the face methane distribution was performed by utilizing the post-processing capability of the CFD software.
文摘从N av ier-S tokes方程出发,运用CFX软件对外界风向与屋脊平行和相夹45°两种情形下温室内气流场进行了稳态模拟研究。结果显示,对于前者,气流从山墙门和侧窗的上部进入,从侧窗的下部流出,气流在温室内沿中心纵截面分布的对称性较好,在温室的后半部气流逐渐扩散,紊流加强;对于后者,气流从山墙门和迎风侧窗处进入,两股气流相遇后受棚面形状及作物的影响而形成各种涡流,最后从背风侧窗处流出。气流在接触到栽培作物时流速迅速减小,作物冠层边界受到周围空间气流的影响,但在作物冠层内受周围空间气流影响不大。
