Author(s): Michael J. Duer
Linked Author(s):
Keywords: Duckbill nozzle; Variable orifice; Jet velocity; Backflow; Outfall; Diffuser; Dilution
Abstract: Duckbill check valve nozzles (DBNs) are utilized extensively in the design of inland and marine multiport outfall diffusers for both industrial and municipal discharges. When duckbill valves were initially utilized on outfall diffusers circa 1980, the sole intended purpose was to prevent the intrusion of sediment and salt water into the outfall pipe. With continuous hydraulic testing, modeling and research and development, other significant practical, physical, and hydraulic benefits of DBNs, such as enhanced initial dilution, improved salt water purging, and uniform flow distribution among ports have been discovered and presented in Lee (1997), Duer (2000), and Duer (2002). Presented herein are physical and hydraulic characteristics of DBNs that may not be well known to outfall designers and modelers currently and therefore will improve their design and analysis efforts. A detailed discussion on the construction and fabrication of DBNs is presented to illustrate the large number of hydraulic variations achievable per nominal size. Guidance on sizing and mixing zone modeling of DBNs is provided. Specification criteria and guidance are presented that can be used by outfall designers to evaluate DBN manufacturers as there is currently no international standard governing the design and construction of DBNs.
Year: 2016