Author(s): Sikandar Yosufzai; Subhojit Kadia; Zulfequar Ahmad; Nils Ruther
Linked Author(s): Subhojit Kadia, Zulfequar Ahmad, Nils Rüther
Keywords: Piano Key Weir; Rectangular Weir; Plunge pool; Scour; Apron
Abstract: Piano Key Weirs (PKWs) are a preferred spillway type for passing floods at existing low-head dams with limited available spillway length. The associated high specific discharge and three-dimensional flow patterns can increase downstream scour. Despite recent studies, there is still a need for specific design guidelines to mitigate scour associated with these structures. An experimental investigation was conducted under several hydraulic conditions to evaluate the scour reduction achieved by a plunge pool downstream of a laboratory-scaled type-A PKW. Without a plunge pool, significant scour depths are observed, exceeding twice the weir height, with distinct hydraulic phenomena identified. Upon the installation of a plunge pool, there is a substantial reduction in the scour depth, averaging a 79.1% reduction in the maximum scour depth. This initial study and the findings underscore the critical role of a plunge pool in minimizing scour depth downstream of PKWs. The follow up study will cover varied plunge pool geometry and tailwater submergence to enhance the current understanding and provide valuable insights for the design and implementation of effective scour countermeasures, enhancing the safety and longevity of these hydraulic structures.
Year: 2024