Experimental Observations of Flow and Bed Processes in Large-Amplitude Meandering Flume

Termini, Donatella

doi:10.1061/(asce)hy.1943-7900.0000046

Cited by 99 publications

(60 citation statements)

References 41 publications

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“…Before proceeding further, it seems important to briefly summarize here some peculiar results of investigations performed in the same meandering flume of that considered in this work: -Termini ( [33]) conducted experiments under the hydraulic conditions that are considered in the present work in order to examine the effect of the continuously changing channel's curvature on flow pattern. She verified that, because of the changing channel curvature, the flow accelerates near the outer bank from the beginning of the bend to the inflection section downstream and decelerates near the inner bank.…”

Section: Pertinent Aspects and Summary Of Previous Resultsmentioning

confidence: 99%

“…Such a different behaviour is caused by the secondary circulation that develops more significantly in the case of B/h < 10 than in the case of B/h > 10, and that attenuates the effect of the convective acceleration close to the outer bank (see also in [31]). Water 2018, 10, x FOR PEER REVIEW 4 of 10 channel axis (see details in [33]). Bearing in mind the specific aim of the present work, our attention is focused only on the longitudinal velocity component.…”

Section: Pertinent Aspects and Summary Of Previous Resultsmentioning

confidence: 99%

“…Details of the experimental setup and measurements conditions can be found in previous works (see as an example in [33]) and only features of particular interest for the following analyses are briefly presented here.…”

Section: Experimental Datasetmentioning

confidence: 99%

“…The instantaneous local longitudinal and transverse velocity components were measured in cross-sections spaced about 50 cm or so apart, starting from the first inflection section of the meandering channel (see Figure 1), by using a two-dimensional (2D) side-looking Acoustic Doppler Velocimeter (ADV) manufactured by SonTek Inc. (San Diego, CA, USA), in points spaced of 1-1.5 mm along the verticals of nine transverse abscissas symmetrically to the channel axis (see details in [33]). Bearing in mind the specific aim of the present work, our attention is focused only on the longitudinal velocity component.…”

Section: Experimental Datasetmentioning

confidence: 99%

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Dip Phenomenon in High-Curved Turbulent Flows and Application of Entropy Theory

Termini

Moramarco

2018

Water

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Abstract:The estimation of velocity profile in turbulent open channels is a difficult task due to the significant effects of the secondary flow. The present paper investigates the mechanism of the velocity-dip phenomenon, whereby the location of the maximum velocity appears to be below the free surface. Previous studies conducted in straight channels relate the mechanism of the velocity-dip phenomenon to secondary flow induced by anisotropy of turbulence. This work focuses on high-curved channels where the secondary motion, which is also induced by the channel's curvature, evolves along the bend. The width-to-depth ratio, B/h, is one of the most important parameters that are affecting the secondary motion entity. In particular, the present study aims to investigate the evolution of the velocity-dip along the bend for two values of the width-to-depth ratio and the applicability of the entropic model for the dip-phenomenon estimation. The results show that the velocity-dip is more accentuated for low values of the width-to-depth ratio, where the secondary motion plays a fundamental role in the distribution of the downstream flow velocity, although the velocity-dip is also present when the aspect ratio is higher than 10. Furthermore, the velocity profiles that were estimated by applying the entropic model are in good agreement with the measured ones, especially for B/h < 10.

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Section: Pertinent Aspects and Summary Of Previous Resultsmentioning

confidence: 99%

Section: Pertinent Aspects and Summary Of Previous Resultsmentioning

confidence: 99%

Section: Experimental Datasetmentioning

confidence: 99%

Section: Experimental Datasetmentioning

confidence: 99%

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Dip Phenomenon in High-Curved Turbulent Flows and Application of Entropy Theory

Termini

Moramarco

2018

Water

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“…Firstly, the CCHE2D is calibrated using data measured in two laboratory experiments, including flat-bed (Da Silva, 1995) and deformed-bed (Termini, 2009). Then, two bends with different sinuosity and bed topography are analysed, with deflection angles of 30° and 110° representing 'small' and 'large' sinuosity respectively.…”

Section: Introductionmentioning

confidence: 99%

Distribution of primary and secondary currents in sine-generated bends

2018

WSA

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The secondary circulation in a meandering channel redistributes the velocity over the bend. However, the shift of primary flow by secondary currents is not quantitatively understood, due to the difficulty in isolating the role of curvature-driven secondary flow from that of topography-driven secondary flow in bed-deformed meanders. The influences of curvaturedriven and topography-driven secondary currents on the redistribution of primary flow in sine-generated meandering channels were examined by CCHE2D. The model is calibrated using data measured in two sets of laboratory experiments including flat-bed flow and mobile-bed flow. Analysis indicated that topography-induced current mainly contributes to the redistribution of primary flow from inner to outer bank in the curved channels, rather than the secondary flow driven by curvature.

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Three‐dimensional flow structure and bed morphology in large elongate meander loops with different outer bank roughness characteristics

Konsoer

Rhoads

Best

et al. 2016

Water Resources Research

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Few studies have examined the three‐dimensional flow structure and bed morphology within elongate loops of large meandering channels. The present study focuses on the spatial patterns of three‐dimensional flow structure and bed morphology within two elongate meander loops and examines how differences in outer bank roughness influence near‐bank flow characteristics. Three‐dimensional velocities were measured during two different events—a near‐bankfull flow and an overbank event. Detailed data on channel bathymetry and bed form geometry were obtained during a near‐bankfull event. Flow structure within the loops is characterized by strong topographic steering by the point bar, by the development of helical motion associated with flow curvature, and by acceleration of flow where bedrock is exposed along the outer bank. Near‐bank velocities during the overbank event are less than those for the near‐bankfull flow, highlighting the strong influence of the point bar on redistribution of mass and momentum of the flow at subbankfull stages. Multiple outer bank pools are evident within the elongate meander loop with low outer bank roughness, but are not present in the loop with high outer bank roughness, which may reflect the influence of abundant large woody debris on near‐bank velocity characteristics. The positions of pools within both loops can be linked to spatial variations in planform curvature. The findings indicate that flow structure and bed morphology in these large elongate loops is similar to that in small elongate loops, but differs somewhat from flow structure and bed morphology reported for experimental elongate loops.

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Experimental Observations of Flow and Bed Processes in Large-Amplitude Meandering Flume

Cited by 99 publications

References 41 publications

Dip Phenomenon in High-Curved Turbulent Flows and Application of Entropy Theory

Dip Phenomenon in High-Curved Turbulent Flows and Application of Entropy Theory

Distribution of primary and secondary currents in sine-generated bends

Three‐dimensional flow structure and bed morphology in large elongate meander loops with different outer bank roughness characteristics

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