ABSTRACT
Weirs are widely used hydraulic structures in rivers for water-level elevation, flood control, and discharge measurement. Flows upstream of the weirs are separated due to the adverse pressure gradient, and it produces a recirculating zone. The recirculating zone plays a crucial role in sediment entrainment, discharge capacity, and contaminant transport. In this study, the characteristics of separation flow under various hydraulic conditions were investigated by laboratory experiments. Finite crest length weir with a vertical front wall and a downstream ramp is installed at the experimental flume. Particle Image Velocimeter (PIV) was used to measure the 2D velocity field. Acceleration, deceleration, reverse flow, and separation were found upstream of the weir from the mean flow fields. Separation points were found from the streamlines calculated by mean flow fields. The location of highest unsteadiness estimated by Root-Mean-Square fields is located at the upstream edge of the weir and the center of the recirculation.
