Flow Measurement Using Full Width Weir : Comparison of ISO, JIS and His Formulae

A series of flow measurement tests were carried out, as the activity of the Research Committee of the JSME, by using a weir of 1.5m width to verify which formula of ISO, JIS and HIS Standards is the most accurate, and to clarify effects of a short approach channel with a flow straightener on the accuracy, where the crest height tested was 0.8, 1.4 and 2m for the purpose of investigating the accuracy of a weir measuring a large flow rate. The first ISO formula showed, on an average, a deviation of -1.5%, the second -0.4%, the third -1% and the fourth +l%. The JIS formula gave a deviation of +0.1% and HIS -1%. All the formulae showed almost constant deviation in the head range between 0.15 and 0.45m. The tests also confirmed the validity of a shortened approach channel provided with a flow straightener