Twin Plate Weir: A Flow Measuring Device (TECHNICAL NOTE)

For efficient use of water, accurate measurement of flow in (field/laboratory) channels is required for many water resource projects. The present work is aimed to study the flow characteristics of a twin plate weir (two sharp-crested plates are placed one behind the other at some distance) under free and submerged flow conditions. Experiments are performed with four spacing of the twin plate weir ranging from 10 cm to 40 cm under free and submerged flow conditions. It was observed that the coefficient of discharge (Cd) is a function of head over the crest (H1) and height of the plate of the weir (P) in free flow condition. The critical submergence (H2/H1) increases as the discharge increases, for a particular spacing of the twin plate weir (L). The critical submergence also increases with the increase in the spacing of the weir plates for any discharge. When some material fills the space between the two plates, the Cd increases as the percentage of filling increase. The device may prove quite useful when siltation occurs between the twin plate weirs. The device could be utilized in laboratory/industry channels for the discharge measurement.