Author(s): Pouria Rahmati; Susan Gaskin; S. Y. Lo

Linked Author(s): Susan Gaskin

Keywords: Hydropower; Draft tube aeration; Bubble Dynamic; Dissolved oxygen; Multiphase jet

Abstract: Hydropower, an important renewable energy source for climate change mitigation, presents downstream environmental challenges, particularly regarding low dissolved oxygen levels. Draft tube aeration, a technique injecting air into the draft tube, is a promising remedial solution. Air pocket formation and the bubble dynamics of air injected into the lee of an elbow deflector in a vertical conduit is investigated. Air pocket formation and bubble shedding regimes are influenced by the key parameters of the Reynolds number of the conduit flow and of the air-to-water flow. The experimental investigations show that increasing the air flow rate results in larger bubbles, while increasing the water flow velocity results in a decrease in the bubble sizes shed from the air pocket. In the vertical conduit, in which the buoyancy force and the water flow are codirectional, individual bubbles tend to remain attached to the wall surface after detaching from the air pocket. The study increases understanding of the processes with the ultimate aim to improve draft tube aeration techniques and with it their potential environmental benefits.

DOI: https://doi.org/10.3929/ethz-b-000675921

Year: 2024