A combined numerical model for computing mixing areas of pollution vertical jet discharging into tidal flows has been developed. This numerical model is composed of a 2-D depth-averaged dynamic far-field numerical mod...A combined numerical model for computing mixing areas of pollution vertical jet discharging into tidal flows has been developed. This numerical model is composed of a 2-D depth-averaged dynamic far-field numerical model and a 2-D vertical dynamic near-field numerical model. The former uses finite node method to compute velocity, and improved finite node method to compute pollutant concentration distribution; the latter is a k-e turbulence model, and uses SIMPLE (Semi-Implicit Method for Pressure Linked Equations) method to compute velocity. At the same time, the former provides boundary conditions for the latter. This model can simulate both far- field pollutant concentration distribution and near-field vertical recirculation quickly and precisely. This model has been verified by measured data of pollutant F of the Dachang reach of the Changjing River and test data presented by Chen el al. (1992). On the basis of verification, the authors use a designed hydrograph to compute this mixing area for a certain amount of wastewater discharging into the river.展开更多
为研究湍流积分尺度对高层建筑风荷载大小和分布的影响,研究其合理取值,基于大涡模拟开展了B类地貌不同湍流积分尺度下CAARC(commonwealth advisory aeronautical research council)标准高层建筑模型绕流模拟,并将模拟结果与风洞试验进...为研究湍流积分尺度对高层建筑风荷载大小和分布的影响,研究其合理取值,基于大涡模拟开展了B类地貌不同湍流积分尺度下CAARC(commonwealth advisory aeronautical research council)标准高层建筑模型绕流模拟,并将模拟结果与风洞试验进行了比较.研究结果表明:大涡模拟能较好地反映高层建筑周围风场绕流特性和表面风压分布.随着湍流积分尺度的增大,平均运动的变形率向湍流脉动输入能量,以致平均风速降低、湍流强度增大;侧面风压脉动性降低15%、分离流附着提前出现;基底扭矩谱和弯矩谱的峰值及高频段幅值均减小;层斯托罗哈数在0.4倍建筑高度以下基本相同,随高度的增加其值下降20%~30%;层平均阻力系数下降5%~10%;迎风面风压系数平均值下降2%~5%,侧面和背面下降12%~17%.湍流积分尺度对迎风面和侧面上风向的风压水平相关性、层升力和0.8倍建筑高度以下的层阻力相关性的影响可以忽略.随湍流积分尺度的增大,风压水平相关系数增大,背风面增大5%~10%,侧面下风向增大15%~25%,0.8倍建筑高度以上层阻力相关性系数增大25%~50%.B类地貌湍流积分尺度的调整系数为0.4时,计算得到的风荷载与试验结果趋于一致.展开更多
文摘A combined numerical model for computing mixing areas of pollution vertical jet discharging into tidal flows has been developed. This numerical model is composed of a 2-D depth-averaged dynamic far-field numerical model and a 2-D vertical dynamic near-field numerical model. The former uses finite node method to compute velocity, and improved finite node method to compute pollutant concentration distribution; the latter is a k-e turbulence model, and uses SIMPLE (Semi-Implicit Method for Pressure Linked Equations) method to compute velocity. At the same time, the former provides boundary conditions for the latter. This model can simulate both far- field pollutant concentration distribution and near-field vertical recirculation quickly and precisely. This model has been verified by measured data of pollutant F of the Dachang reach of the Changjing River and test data presented by Chen el al. (1992). On the basis of verification, the authors use a designed hydrograph to compute this mixing area for a certain amount of wastewater discharging into the river.
文摘为研究湍流积分尺度对高层建筑风荷载大小和分布的影响,研究其合理取值,基于大涡模拟开展了B类地貌不同湍流积分尺度下CAARC(commonwealth advisory aeronautical research council)标准高层建筑模型绕流模拟,并将模拟结果与风洞试验进行了比较.研究结果表明:大涡模拟能较好地反映高层建筑周围风场绕流特性和表面风压分布.随着湍流积分尺度的增大,平均运动的变形率向湍流脉动输入能量,以致平均风速降低、湍流强度增大;侧面风压脉动性降低15%、分离流附着提前出现;基底扭矩谱和弯矩谱的峰值及高频段幅值均减小;层斯托罗哈数在0.4倍建筑高度以下基本相同,随高度的增加其值下降20%~30%;层平均阻力系数下降5%~10%;迎风面风压系数平均值下降2%~5%,侧面和背面下降12%~17%.湍流积分尺度对迎风面和侧面上风向的风压水平相关性、层升力和0.8倍建筑高度以下的层阻力相关性的影响可以忽略.随湍流积分尺度的增大,风压水平相关系数增大,背风面增大5%~10%,侧面下风向增大15%~25%,0.8倍建筑高度以上层阻力相关性系数增大25%~50%.B类地貌湍流积分尺度的调整系数为0.4时,计算得到的风荷载与试验结果趋于一致.
