采用临界流量计后，流量计下游压强的变化不会影响流量的测量。
If the critical flow meter is used, the measure isn t affected by the variation.
导出了U形渠道正常水深、临界水深水力计算的迭代公式，并给出了判别水深范围的界限流量计算公式。
The iteration equation of U-shaped channel normal depth and critical water depth in hydraulic calculation is deduced. The equation of boundary discharge to criterion water depth range is given.
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