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Aspects of the Bed Geometry and Flow in Meandering Streams at Incipient and Later Stages.

Record Type:	Electronic resources : Monograph/item
Title/Author:	Aspects of the Bed Geometry and Flow in Meandering Streams at Incipient and Later Stages./
Author:	Cheng, Yunshuo.
Description:	1 online resource (175 pages)
Notes:	Source: Dissertations Abstracts International, Volume: 84-06, Section: B.
Contained By:	Dissertations Abstracts International84-06B.
Subject:	Viscosity. -
Online resource:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=30168730click for full text (PQDT)
ISBN:	9798358407534

Aspects of the Bed Geometry and Flow in Meandering Streams at Incipient and Later Stages.
Cheng, Yunshuo.

Aspects of the Bed Geometry and Flow in Meandering Streams at Incipient and Later Stages. - 1 online resource (175 pages)

Source: Dissertations Abstracts International, Volume: 84-06, Section: B.

Thesis (Ph.D.)--Queen's University (Canada), 2022.

Includes bibliographical references

This thesis consists of two parts. In the first part (Chapter 2 and 3), two new empirical equations for the length and height of alternate bars at the fully developed (or equilibrium) state are introduced. The equations are developed on the basis of dimensional considerations and all available laboratory data; the formulations incorporate also findings by stability analyses of the phenomenon. The equations correlate bar height normalized by flow depth and bar length normalized by flow width to the excess width-to-depth ratio with regard to the threshold, or critical, value of width-to-depth ratio at which alternate bars occur as well as the relative depth and the grain size Reynolds number. It is shown that when compared with previous empirical equations, the present equations produce a considerably improved alignment of the data with the perfect agreement line and a significantly larger percentage of data falling within the 20% error range (nearly twice more data in the case of the height equation, and 1.5 times more in the case of the length equation). In contrast to previous methods, the present equations were found to produce realistic estimates of bar height and length when extrapolated to field conditions. In the second part of the thesis (Chapter 4), one of the most fundamental questions related to meandering streams is addressed and shed light on, namely 'Where and why is more energy lost in a meandering stream when compared to a straight stream?' Answering this question involves a work/energy analysis founded on the equations of motion, and facilitated by a series of numerical simulations of meandering flows carried out with a three-dimensional (3D) solver of the Reynolds Averaged Navier-Stokes (RANS) equations. The laboratory experiments carried out by da Silva et al. (2006) in five sine-generated meandering streams with q0 = 30°, 50°, 70°, 90° and 110°, were used as basis for the analysis. The energy/work terms were quantified throughout the flow domain on the basis of the simulated flows and then presented and analyzed in their vertical- and channel- averaged values. Particular attention was paid to the following aspects:1- how much more energy is dissipated in meandering streams when compared to their equivalent straight channel counterparts; and 2- what are the mechanisms determining the additional losses and what are their individual contributions.

Electronic reproduction.
Ann Arbor, Mich. :
ProQuest,
2023

Mode of access: World Wide Web

ISBN: 9798358407534Subjects--Topical Terms:

1050706
Viscosity.
Index Terms--Genre/Form:

542853
Electronic books.

Aspects of the Bed Geometry and Flow in Meandering Streams at Incipient and Later Stages.
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100 1 $a Cheng, Yunshuo. $3 3695361
245 1 0 $a Aspects of the Bed Geometry and Flow in Meandering Streams at Incipient and Later Stages.
264 0 $c 2022
300 $a 1 online resource (175 pages)
336 $a text $b txt $2 rdacontent
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500 $a Source: Dissertations Abstracts International, Volume: 84-06, Section: B.
500 $a Advisor: da Silva, Ana Maria F.
502 $a Thesis (Ph.D.)--Queen's University (Canada), 2022.
504 $a Includes bibliographical references
520 $a This thesis consists of two parts. In the first part (Chapter 2 and 3), two new empirical equations for the length and height of alternate bars at the fully developed (or equilibrium) state are introduced. The equations are developed on the basis of dimensional considerations and all available laboratory data; the formulations incorporate also findings by stability analyses of the phenomenon. The equations correlate bar height normalized by flow depth and bar length normalized by flow width to the excess width-to-depth ratio with regard to the threshold, or critical, value of width-to-depth ratio at which alternate bars occur as well as the relative depth and the grain size Reynolds number. It is shown that when compared with previous empirical equations, the present equations produce a considerably improved alignment of the data with the perfect agreement line and a significantly larger percentage of data falling within the 20% error range (nearly twice more data in the case of the height equation, and 1.5 times more in the case of the length equation). In contrast to previous methods, the present equations were found to produce realistic estimates of bar height and length when extrapolated to field conditions. In the second part of the thesis (Chapter 4), one of the most fundamental questions related to meandering streams is addressed and shed light on, namely 'Where and why is more energy lost in a meandering stream when compared to a straight stream?' Answering this question involves a work/energy analysis founded on the equations of motion, and facilitated by a series of numerical simulations of meandering flows carried out with a three-dimensional (3D) solver of the Reynolds Averaged Navier-Stokes (RANS) equations. The laboratory experiments carried out by da Silva et al. (2006) in five sine-generated meandering streams with q0 = 30°, 50°, 70°, 90° and 110°, were used as basis for the analysis. The energy/work terms were quantified throughout the flow domain on the basis of the simulated flows and then presented and analyzed in their vertical- and channel- averaged values. Particular attention was paid to the following aspects:1- how much more energy is dissipated in meandering streams when compared to their equivalent straight channel counterparts; and 2- what are the mechanisms determining the additional losses and what are their individual contributions.
533 $a Electronic reproduction. $b Ann Arbor, Mich. : $c ProQuest, $d 2023
538 $a Mode of access: World Wide Web
650 4 $a Viscosity. $3 1050706
650 4 $a Turbulence models. $3 3682363
650 4 $a Flow velocity. $3 3564851
650 4 $a Creeks & streams. $3 3685269
650 4 $a Civil engineering. $3 860360
650 4 $a Sediment transport. $3 555890
650 4 $a Energy. $3 876794
650 4 $a Grain size. $3 3682362
650 4 $a Canals. $3 3560045
650 4 $a Mechanics. $3 525881
650 4 $a Rivers. $3 519737
650 4 $a Reynolds number. $3 3681436
650 4 $a Hydraulics. $3 669758
650 4 $a Aquatic sciences. $3 3174300
650 4 $a Engineering. $3 586835
650 4 $a Fluid mechanics. $3 528155
650 4 $a Hydraulic engineering. $3 613609
650 4 $a Physics. $3 516296
655 7 $a Electronic books. $2 lcsh $3 542853
690 $a 0791
690 $a 0543
690 $a 0346
690 $a 0792
690 $a 0537
690 $a 0204
690 $a 0218
690 $a 0605
710 2 $a ProQuest Information and Learning Co. $3 783688
710 2 $a Queen's University (Canada). $3 1017786
773 0 $t Dissertations Abstracts International $g 84-06B.
856 4 0 $u http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=30168730 $z click for full text (PQDT)