Journal of Hydraulics

Journal of Hydraulics

Study of Transverse Flows and Secondary Currents in Compound Meandering Channel under the Effect of Building Arrangements

Document Type : Research Article

Authors
Mohammad Naghavi 1
Mirali Mohammadi 2
Ghorban Mahtabi 3
1 , Department of Civil Eng., Urmia University, P O Box 165, Faculty of Eng., Urmia 57561-15311, Iran.
2 Prof. in Civil Eng. (Hydraulics & River Eng. Mechanics), Department of Civil Eng., Faculty of Eng., Urmia University, Urmia, Iran
3 ,University of Zanjan
10.30482/jhyd.2024.423155.1683
Abstract
In the present study, flow characteristics in compound meandering channels under the changes of building arrangement in the floodplains were investigated using a numerical simulation. A constant sinuosity factor of 1.21 and relative flow depths (Dr) of 0.29 to 0.49 were considered to illustrate the effect of the hydraulic parameters on the variations of the velocity components. Three types of building arrangements, including structural obstacles perpendicular to the flow of the floodplain (MHT, density=18.5%), structural obstacles parallel to the flow of the floodplain (MGT, density=23.7%), and checkered structural obstacles (MFT, density=23.7%), were used. The simulated data were in good agreement with the experimental data indicating the proper ability of the numerical model in simulation. The result reveals that in the concave arc of sections CS1 and CS7 (apex sections), changing the building arrangements has a negligible effect on the change of transverse and secondary flows due to the parallelism of the main channel flow and the floodplain flow as well as the insignificant effect of the floodplain flow on the main channel. But near the convex arc, these changes are more significant. Hence in section CS4, with the increase of the Dr from 0.29 to 0.49, for cases MAT, MGT, and MHT, the maximum value of depth-averaged transverse flow strength increases by 61%, 91%, and 41%, respectively. In section CS1, the secondary flow cells created in the case of MGT1 cover the entire section; however, in cases of MFT1 and MHT1, the size of the cell is small and is located on the left side of the section. In mid-sections, a small secondary cell in the same direction as the transverse flow (clockwise) is formed in the right corner near the bottom of the channel and gradually grows in the mid-sections and reaches its maximum size in section CS7. Along with the building arrangements of cases MFT1 and MHT1, the transverse component of the floodplain flow velocity (at the entrance of the floodplain flow to the main channel y/h=5) is weakened in the middle sections (CS3, CS4, and CS5). The dimensions of the secondary flow cell increase in the next sections and reach its largest value in section CS7.
Keywords
Compound meandering channel
Building arrangements
Transverse flow
Secondary cell

Subjects

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  • Receive Date 02 November 2023
  • Revise Date 17 January 2024
  • Accept Date 20 January 2024