Study of flow with gravel size sediment through bottom racks: Relation of effective void ratio with hydraulic parameters

© 2016 Taylor & Francis Group, London. An experimental campaign in a bottom intake system is carried out for two different void ratio racks, adopting several approximation flows, varying longitudinal slopes and flow with three gravel sized sediments. Results such as the effective void ratio due to the gravel deposition over the rack were obtained. Length of rack necessary to derive an inlet flow considering occlusion effects is calculated and compared with existing design criteria. The effective void ratio is related to several hydraulic parameters calculated at the beginning of the rack, e.g. shear stress, Froude number, drag force, square of densimetric Froude number, velocity at the beginning of the rack, etc. From this, a formulation is proposed to predict the effective void ratio as a function of the hydraulic values at the beginning of the rack. This will allow calculate the wetted rack length in case of flows with gravel sized sediments.