Flow measurements with portable cut-throat flume and broad crested weir in flat gradient channels

Abstract

A study was conducted to evaluate the reliability of flow measurements with portable cut-throat flumes and broad-crested weirs during 1988–89 at the field hydraulic laboratory of the National Agricultural Research Centre, Islamabad. Data of flow measurements were recorded under free and submerged flow conditions with a cut-throat flume and a broad-crested weir as compared to a standard ‘V’ notch. The results indicated that for free flow conditions cut-throat flumes can be used with –2.2 to 8.6% error. However, the use of cut-throat flumes under flat gradient channels may cause problem of over-topping at the upstream end. Under submerged flow conditions, the percent error in the flow measurements of −3.2 to 14.6% was observed. Therefore, cut-throat flumes cannot provide reasonable flow measurements under submerged flow conditions. For accurate flow measurements broad-crested weirs should be used with percent error of −1.5 to 5.8. Such flumes can be easily manufactured in Pakistan to suit different flow regimes and flat gradient channels.