The average flow of the river is 200 cubic metres per second. 这条河平均流量为每秒二百立方米。
The presence of boundary conditions leads to non-uniformity in the mean unsaturated flow, which in turn causes non-stationarity in the statistics of velocity fields. 存在边界条件导致非均匀饱和的平均流量,而这反过来又导致非平稳性的统计速度场。