如果水流状态随时间变化而变化，则称为非恒定流。
If the current status change with time, intitules as the unsteady flow.
一个点上的水流状态，如压力、流速和流量不随时间变化而变化，称为恒定流。
The current status of one point, such as pressure, flow rate and flow don t change with time, intitules as the steady flow.
并根据膜孔灌水流现象，把膜孔灌过程划分为四个阶段，进而分析了各阶段的水流状态。
Repending on the phenomena of film hole irrigation, the authors divide irrigation procedure into four stages, and fully analyse water's state of each stage.
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