Local scour by multiple slit-type energy dissipaters
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Local scour by multiple slit-type energy dissipaters * Li Yao1, Jian-hua Wu2 1. College of Water Conservancy and Ecological Engineering, Nanchang Institute of Technology, Nanchang 330099, China 2. College of Water Conservancy and Hydropower Engineering, Hohai University, Nanjing 210098, China (Received July 30, 2020, Revised October 3, 2020, Accepted October 5, 2020, Published online November 23, 2020) ©China Ship Scientific Research Center 2020 Abstract: Energy dissipation and scour control are all the key issues for the design of hydraulic structures. On the basis of the high energy dissipation for the multiple slit-type energy dissipaters (M-STED) developed by the authors, in this work, the characteristics of the scour hole for the M-STED were experimentally investigated through three sets of those physical models with five cases and a scour hole form index was proposed. The results show that, the M-STED results in not only the high energy dissipation but also the mild upstream slope of the scour hole thanks to the scour hole form index of larger than 0.5, which is in favor of the safety of the release works. Key words: Energy dissipation, scour, scour hole form index, multiple slit-type energy dissipater
In order to carry out the high energy dissipation and effective scour control, many kinds of flip buckets of the outlets for the release works have been designed and used in the high dam projects. Where the change of the outlet width was concerned, all those flip buckets could be divided into three types, i.e., constant width type, expansion or contraction type[1]. The slot-type flip bucket[1-2] or partial-flip bucket[3-4] is just the new development of the constant width type ones, which produce significant extension of the flow in the direction of the flow through the buckets. The deflector[5-6], the flaring pier[7], the slit-type[8], or the beveled edge of the outlet[9], in the way of contraction or expansion of the flip buckets, aim at the increasing of the dimension of the flow, either in the flow section or in the flow direction. Thus, the energy of the flow is greatly dissipated due to the decrease of the average velocity of the flow section. For the various flip buckets mentioned-above, many works have been conducted about the flow regime, the energy dissipation, and the jet trajectory etc.. The geometries of the flip buckets have been
* Project supported by the National Natural Science Foundation of China (Grant No. 51879129). Biography: Li Yao (1985-), Female, Ph. D., Lecture, E-mail: [email protected] Corresponding author: Jian-hua Wu, E-mail: [email protected]
developed and improved in order to increase the energy dissipation. It is well known that, the local scour control of the river bed downstream of the release works is a serious concern when the energy of the flow is dissipated effectively[10]. The energy dissipation and scour control are the two different aspects of the design of hydraulic structures. Slit-type energy dissipater (STED) has been widely used in many high dam projects thank
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