mean flow的用法和樣例：
例句
- The average flow of the river is 200 cubic metres per second.
這條河平均流量為每秒二百立方米。 - 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.
存在邊界條件導致非均勻飽和的平均流量，而這反過來又導致非平穩性的統計速度場。
