U形渠道机翼形量水槽水跃数值模拟与试验研究

量水槽是灌区常见的特设量水设备,而槽后水力特性是判断其选型是否合理的重要指标之一。以某小型灌区末级灌溉渠系改造工程为原型,针对两种不同工况,采用基于TruVOF方法跟踪自由液面、Favor技术实现网格优化的湍流数学模型,对U形渠道机翼形量水槽水跃问题进行三维数值模拟,分析了水跃的时均流场、共轭水深、发生位置、跃长、断面流速分布以及水跃段能量损失等相关水力特性。采用与原型1：1比尺的水工模型试验资料对模拟结果进行验证,结果表明,二者吻合较好。通过对实测与数值仿真的共轭水深数据进行统计分析,得到了适用于U形渠道机翼形量水槽水跃共轭水深的近似计算公式。研究结果对机翼形量水槽在平原缓坡灌区末级渠系的应用研究提供了一定的参考和建议。     

Time variations of the total electron content in the Southeast Asian equatorial ionization anomaly for the period 2006–2011

This study presents the time variations of the total electron content in the South East Asian equatorial ionization anomaly. The time variation of the TEC is analyzed through the period 2006–2011 by using a latitudinal chain of GPS stations extending in the northern and southern hemisphere. The data shows that the shape of the diurnal variation of the TEC depends on the latitude: a plateau is observed at the stations near the equator and a Gaussian at the station distant from the equator. We observe a semiannual pattern in all the stations with maxima at equinox. In both hemispheres, the amplitude of the crest is larger in spring than autumn from 2006 to 2008 and smaller in spring than in autumn from 2009 to 2011. We also observe an asymmetry between the amplitude and the position of the two crests of ionization. There is a very high level of correlation between the amplitude of the TEC at the two crests and the sunspot number: ∼0.88. During the deep solar minimum 2008–2009, the amplitude of crests of ionization becomes small during several months in summer and winter. The results show that both crests move significantly equatorward in winter than other seasons and there is a tendency for both crests to appear earlier in winter and later in summer.     

U形渠道机翼形量水槽水跃数值模拟与试验研究

量水槽是灌区常见的特设量水设备,而槽后水力特性是判断其选型是否合理的重要指标之一.以某小型灌区末级灌溉渠系改造工程为原型,针对两种不同工况,采用基于TruVOF方法跟踪自由液面、Favor技术实现网格优化的湍流数学模型,对U形渠道机翼形量水槽水跃问题进行三维数值模拟,分析了水跃的时均流场、共轭水深、发生位置、跃长、断面流速分布以及水跃段能量损失等相关水力特性.采用与原型1∶1比尺的水工模型试验资料对模拟结果进行验证,结果表明,二者吻合较好.通过对实测与数值仿真的共轭水深数据进行统计分析,得到了适用于U形渠道机翼形量水槽水跃共轭水深的近似计算公式.研究结果对机翼形量水槽在平原缓坡灌区末级渠系的应用研究提供了一定的参考和建议.     

导弹尾喷流形成的碰撞流场数值模拟

采用计算流体力学方法,从曲线坐标NS方程出发,取用NND2M差分格式,对导弹发射时与地面形成碰撞喷流流场进行数值模拟,计算结果和实验数据符合较好。在此基础上,分析了碰撞喷流的流场结构及特性。