The helical flow behind the bottom threshold kinematic structure analysis for the purpose of controlling its mass transfer characteristics and sediment transport

by

E. Shchodro1, S.M. Sidorov1, 2

1Institute of Natural and Technical Systems, RF, Sevastopol, Lenin St., 28

2Sevastopol State University, RF, Sevastopol, Universitetskaya St., 33

DOI: 10.33075/2220-5861-2024-1-92-102

UDC 532.5.032                                                          

EDN: https://elibrary.ru/ndjkly

Abstract:

The operation of sediment control and hydroecological structures made as a bottom threshold, ledge or half-dam depends on the kinematic structure of the spatial helical flow that arises behind such structures. The paper describes the structure of such a flow and analyzes the influence of a number of factors affecting mainly the distribution of pressure along the axis of a helical flow: – longitudinal slope of the crest of the structure; – holes at the beginning of the helical flow, creating the possibility of free flow of water edge flow; – the presence of a barrier installed behind the threshold, ledge or in front of it, on the approach to it, on the effectiveness of work as a sediment control or environmental structure and some other factors. Relationship between the above factors and changes in the kinematic structure and patterns of mass transfer between the transit flow and the conditionally closed region of the helical flow is established. Conclusions are drawn about the role of each of them. The main conclusion from the experimental part of the work is that the planned dimensions of the separation zone, the speed of translational movement of the flow in the roller, the speed of twist of the flow in it, as well as the specific flow rates of the flows flowing into the zone and flowing out of it change consistently along the length of the helical flow. It is also concluded that they should be used depending on the purpose of the designed structures of this type.

Keywords: sediment transport, wastewater mixing, bottom thresholds, buoys, half-dams, kinematics of helical flows.

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