An Eulerian-Eulerian two-fluid model was developed to study the vortex flow inside a slab continuous casting mold with argon gas injection. Interracial momentum transfer that accommodated various interracial forces in...An Eulerian-Eulerian two-fluid model was developed to study the vortex flow inside a slab continuous casting mold with argon gas injection. Interracial momentum transfer that accommodated various interracial forces including drag force, lift force, virtual mass force, and turbulent dispersion force was considered. Predicted results agree well vaith experimental measurements of the water model in two-phase flow pattern and vortex flow structures. Three typical flow patterns with different argon steel ratios （ASRs） have been obtained： ＂double roll＂, ＂three roll＂, and ＂single roll＂. The flow pattern inside the mold alternates among the three types or it may attain some intermedi ate condition. With increasing ASR, the positions of vortices move from the submerged entry nozzle to the narrow face of the mold, and the sizes of vortices are reduced gradually. The rotating directions of vortices are all from high velocity area to low velocity area. Two mechanisms of vortex formation on the top surface have been suggested, i. e. , congruous shear flow and incongruous shear flow.展开更多
基于AREM模式对发生在华南地区的3次西南涡暴雨过程进行了数值模拟,并利用模拟结果分析了暴雨过程中西南涡的演变特征,结果表明:高层200 h Pa西风急流入口区、中层500 h Pa西太平洋副热带高压位置、中纬度短波槽、东北亚强冷涡的适当配...基于AREM模式对发生在华南地区的3次西南涡暴雨过程进行了数值模拟,并利用模拟结果分析了暴雨过程中西南涡的演变特征,结果表明:高层200 h Pa西风急流入口区、中层500 h Pa西太平洋副热带高压位置、中纬度短波槽、东北亚强冷涡的适当配置,中低层孟加拉湾和南海暖湿气流的持续输送,是有利于西南涡东移发展,从而造成华南地区持续性强降水的典型环流形势;降水落区与低涡位置密切相关,一般集中在西南涡中心南侧,雨带延伸方向与低涡移动路径一致;而其强度则与低涡中心区域位势高度等值线梯度及低层大气风场强度息息相关。西南涡中心低层为东风和弱北风,中层以南风为主,高层为强西风和弱北风,低层辐合、高层辐散及正涡度结构特征显著。涡度平流项和辐合辐散项的作用集中体现在中低层大气,涡度对流项、扭转项的作用则在中高层更为明显,而涡度辐合辐散项对西南涡的发展加强起最主要的作用。展开更多
2013年7月4—7日江淮地区出现了入梅以来的第一次持续性暴雨,造成江淮地区严重的洪涝灾害。利用欧洲中期天气预报中心(ECMWF)逐6 h的1°×1°再分析资料、FY-2F卫星云量资料和江淮地区72个气象站逐日降水资料,对此次暴雨过...2013年7月4—7日江淮地区出现了入梅以来的第一次持续性暴雨,造成江淮地区严重的洪涝灾害。利用欧洲中期天气预报中心(ECMWF)逐6 h的1°×1°再分析资料、FY-2F卫星云量资料和江淮地区72个气象站逐日降水资料,对此次暴雨过程的成因进行分析。结果表明:在500 h Pa以径向环流为主的背景形势下,江淮地区上空缓慢移近梅雨锋的西南涡是此次降水过程的关键系统。高空急流、500 h Pa高空槽、西南低空急流、西南涡、边界层急流和梅雨锋共同作用形成深厚的辐合层,低层辐合、高层辐散的垂直结构增强了大气的抽吸作用,造成强烈的垂直运动。边界层强的垂直风切变触发了对流不稳定能量的释放。来自孟加拉湾和南海的水汽通过西南超低空急流向江淮地区输送,为江淮地区带来水汽和热力条件。南方暖空气和北方冷空气交汇于江淮地区,形成假相当位温密集带,产生天气尺度的上升运动,雨带主要位于密集带的南侧,可作为雨区预报的参考。展开更多
基金Sponsored by National Natural Science Foundation of China(51210007,51004029)
文摘An Eulerian-Eulerian two-fluid model was developed to study the vortex flow inside a slab continuous casting mold with argon gas injection. Interracial momentum transfer that accommodated various interracial forces including drag force, lift force, virtual mass force, and turbulent dispersion force was considered. Predicted results agree well vaith experimental measurements of the water model in two-phase flow pattern and vortex flow structures. Three typical flow patterns with different argon steel ratios （ASRs） have been obtained： ＂double roll＂, ＂three roll＂, and ＂single roll＂. The flow pattern inside the mold alternates among the three types or it may attain some intermedi ate condition. With increasing ASR, the positions of vortices move from the submerged entry nozzle to the narrow face of the mold, and the sizes of vortices are reduced gradually. The rotating directions of vortices are all from high velocity area to low velocity area. Two mechanisms of vortex formation on the top surface have been suggested, i. e. , congruous shear flow and incongruous shear flow.
文摘基于AREM模式对发生在华南地区的3次西南涡暴雨过程进行了数值模拟,并利用模拟结果分析了暴雨过程中西南涡的演变特征,结果表明:高层200 h Pa西风急流入口区、中层500 h Pa西太平洋副热带高压位置、中纬度短波槽、东北亚强冷涡的适当配置,中低层孟加拉湾和南海暖湿气流的持续输送,是有利于西南涡东移发展,从而造成华南地区持续性强降水的典型环流形势;降水落区与低涡位置密切相关,一般集中在西南涡中心南侧,雨带延伸方向与低涡移动路径一致;而其强度则与低涡中心区域位势高度等值线梯度及低层大气风场强度息息相关。西南涡中心低层为东风和弱北风,中层以南风为主,高层为强西风和弱北风,低层辐合、高层辐散及正涡度结构特征显著。涡度平流项和辐合辐散项的作用集中体现在中低层大气,涡度对流项、扭转项的作用则在中高层更为明显,而涡度辐合辐散项对西南涡的发展加强起最主要的作用。
文摘2013年7月4—7日江淮地区出现了入梅以来的第一次持续性暴雨,造成江淮地区严重的洪涝灾害。利用欧洲中期天气预报中心(ECMWF)逐6 h的1°×1°再分析资料、FY-2F卫星云量资料和江淮地区72个气象站逐日降水资料,对此次暴雨过程的成因进行分析。结果表明:在500 h Pa以径向环流为主的背景形势下,江淮地区上空缓慢移近梅雨锋的西南涡是此次降水过程的关键系统。高空急流、500 h Pa高空槽、西南低空急流、西南涡、边界层急流和梅雨锋共同作用形成深厚的辐合层,低层辐合、高层辐散的垂直结构增强了大气的抽吸作用,造成强烈的垂直运动。边界层强的垂直风切变触发了对流不稳定能量的释放。来自孟加拉湾和南海的水汽通过西南超低空急流向江淮地区输送,为江淮地区带来水汽和热力条件。南方暖空气和北方冷空气交汇于江淮地区,形成假相当位温密集带,产生天气尺度的上升运动,雨带主要位于密集带的南侧,可作为雨区预报的参考。
