Characteristics of Large-Scale Coherent Structures on Irregularly Arranged Rough-Bed Open-Channel Flows
Large-scale coherent structures (LSCSs) in rough-bed open-channel flow (OCF) are significant in turbulence research. A recent breakthrough is the bimodal feature of LSCSs on regular rough-bed OCF (i.e., LSCSs exhibit two typical motions: large-scale motions (LSMs) and very-large-scale motions (VLSMs...
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MDPI AG
2023-03-01
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| Series: | Water |
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| Online Access: | https://www.mdpi.com/2073-4441/15/6/1105 |
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| author | Yongqiang Wang Peng Zhang Shengfa Yang Chunhong Hu Jianling Jin Rangang Zhang |
| author_facet | Yongqiang Wang Peng Zhang Shengfa Yang Chunhong Hu Jianling Jin Rangang Zhang |
| author_sort | Yongqiang Wang |
| collection | DOAJ |
| description | Large-scale coherent structures (LSCSs) in rough-bed open-channel flow (OCF) are significant in turbulence research. A recent breakthrough is the bimodal feature of LSCSs on regular rough-bed OCF (i.e., LSCSs exhibit two typical motions: large-scale motions (LSMs) and very-large-scale motions (VLSMs)). However, the presence and characteristics of LSMs and VLSMs in irregularly arranged rough-bed OCF remain unclear. Thus, in this study, high-precision indoor flume experiments were performed under typical irregularly arranged rough-bed conditions, and time-resolved particle image velocimetry was used for velocity measurements. Statistical quantities of velocity fluctuations revealed that the friction Reynolds number and roughness exerted a certain modulation on the velocity fluctuating properties. The spectra of velocity fluctuations provided direct and statistical evidence for the presence of LSMs and VLSMs in irregularly arranged rough-bed OCF. VLSMs contributed more than 60% of the streamwise turbulent kinetic energy and 40% of the Reynolds shear stress in the outer region of the irregularly arranged rough-bed OCF, which was slightly higher than that in the smooth-bed or regular rough-bed OCF scenarios. No apparent dependence of the wavelength of VLSMs on the flow submergence (<i>H/d</i><sub>50</sub>) was observed in the present irregularly arranged rough-bed OCF, which is in contrast to that reported for regular rough-bed OCF. Furthermore, the relationship between the peak wavelength of VLSMs and the aspect ratio did not strictly follow a linear increase, in contrast to that documented in the literature. |
| first_indexed | 2024-03-11T05:46:03Z |
| format | Article |
| id | doaj.art-ace1b1798cae438ba7f73c0b1e497b5b |
| institution | Directory Open Access Journal |
| issn | 2073-4441 |
| language | English |
| last_indexed | 2024-03-11T05:46:03Z |
| publishDate | 2023-03-01 |
| publisher | MDPI AG |
| record_format | Article |
| series | Water |
| spelling | doaj.art-ace1b1798cae438ba7f73c0b1e497b5b2023-11-17T14:26:33ZengMDPI AGWater2073-44412023-03-01156110510.3390/w15061105Characteristics of Large-Scale Coherent Structures on Irregularly Arranged Rough-Bed Open-Channel FlowsYongqiang Wang0Peng Zhang1Shengfa Yang2Chunhong Hu3Jianling Jin4Rangang Zhang5School of River & Ocean Engineering, Chongqing Jiaotong University, Chongqing 400074, ChinaNational Engineering Research Center of Inland Waterway Regulation, Chongqing Jiaotong University, Chongqing 400074, ChinaNational Engineering Research Center of Inland Waterway Regulation, Chongqing Jiaotong University, Chongqing 400074, ChinaState Key Laboratory of Simulation and Regulation of Water Cycle in River Basin, China Institute of Water Resources and Hydropower Research, Beijing 100048, ChinaSchool of River & Ocean Engineering, Chongqing Jiaotong University, Chongqing 400074, ChinaSchool of River & Ocean Engineering, Chongqing Jiaotong University, Chongqing 400074, ChinaLarge-scale coherent structures (LSCSs) in rough-bed open-channel flow (OCF) are significant in turbulence research. A recent breakthrough is the bimodal feature of LSCSs on regular rough-bed OCF (i.e., LSCSs exhibit two typical motions: large-scale motions (LSMs) and very-large-scale motions (VLSMs)). However, the presence and characteristics of LSMs and VLSMs in irregularly arranged rough-bed OCF remain unclear. Thus, in this study, high-precision indoor flume experiments were performed under typical irregularly arranged rough-bed conditions, and time-resolved particle image velocimetry was used for velocity measurements. Statistical quantities of velocity fluctuations revealed that the friction Reynolds number and roughness exerted a certain modulation on the velocity fluctuating properties. The spectra of velocity fluctuations provided direct and statistical evidence for the presence of LSMs and VLSMs in irregularly arranged rough-bed OCF. VLSMs contributed more than 60% of the streamwise turbulent kinetic energy and 40% of the Reynolds shear stress in the outer region of the irregularly arranged rough-bed OCF, which was slightly higher than that in the smooth-bed or regular rough-bed OCF scenarios. No apparent dependence of the wavelength of VLSMs on the flow submergence (<i>H/d</i><sub>50</sub>) was observed in the present irregularly arranged rough-bed OCF, which is in contrast to that reported for regular rough-bed OCF. Furthermore, the relationship between the peak wavelength of VLSMs and the aspect ratio did not strictly follow a linear increase, in contrast to that documented in the literature.https://www.mdpi.com/2073-4441/15/6/1105open-channel flowrough-bedlarge-scale motionsvery-large-scale motions |
| spellingShingle | Yongqiang Wang Peng Zhang Shengfa Yang Chunhong Hu Jianling Jin Rangang Zhang Characteristics of Large-Scale Coherent Structures on Irregularly Arranged Rough-Bed Open-Channel Flows Water open-channel flow rough-bed large-scale motions very-large-scale motions |
| title | Characteristics of Large-Scale Coherent Structures on Irregularly Arranged Rough-Bed Open-Channel Flows |
| title_full | Characteristics of Large-Scale Coherent Structures on Irregularly Arranged Rough-Bed Open-Channel Flows |
| title_fullStr | Characteristics of Large-Scale Coherent Structures on Irregularly Arranged Rough-Bed Open-Channel Flows |
| title_full_unstemmed | Characteristics of Large-Scale Coherent Structures on Irregularly Arranged Rough-Bed Open-Channel Flows |
| title_short | Characteristics of Large-Scale Coherent Structures on Irregularly Arranged Rough-Bed Open-Channel Flows |
| title_sort | characteristics of large scale coherent structures on irregularly arranged rough bed open channel flows |
| topic | open-channel flow rough-bed large-scale motions very-large-scale motions |
| url | https://www.mdpi.com/2073-4441/15/6/1105 |
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