Transitional flow in channel junctions

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Transitional flow in channel junctions

Transitional flow in channel junctions

01 Jan 2004-Vol. 16, Iss: 4, pp 464-467

TL;DR: In this article, a simple one-dimensional formulation was proposed to predict the transitional flow at an open-channel junction, based on energy and continuity equations, and an empilical relation between the junction losses, the junction angle, and the discharge ratio was suggested which agrees well with the experimental results.

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Abstract: On the basis of energy and continuity equations a simple one-dimensional formulation was proposed to predict the transitional flow at an open-channel junction. An empilical relation between the junction losses, the junction angle, and the discharge ratio was suggested which agrees well with the experimental results. The results calculated by the present formulation for the depth ratio were compared with the results of earlier one-dimensional formulations and experiments. It is found that the present results coincide better with experiments than those of others.

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Journal Article•DOI•

Experimental modelling of urban flooding: a review.

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Emmanuel Mignot¹, Xuefang Li², Benjamin Dewals²•Institutions (2)

University of Lyon¹, University of Liège²

01 Jan 2019-Journal of Hydrology

TL;DR: This review aims at helping computational modellers to pinpoint the most suitable dataset for validating their numerical approaches and laboratory modeller to identify gaps in current experimental knowledge of urban flooding.

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123 citations

Journal Article•DOI•

Experimental study of the dividing flow in steep street crossings

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Leonardo S. Nanía¹, Manuel Gómez², José Dolz²•Institutions (2)

University of Granada¹, Polytechnic University of Catalonia²

01 Jan 2004-Journal of Hydraulic Research

TL;DR: In this paper, a scale model of a street crossing has been built and a series of tests has been conducted for studying the flow pattern in the crossing when the flow in the streets is supercritical.

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Abstract: A first approach to the experimental study of the dividing flow in steep street crossings is presented. A scale model of a street crossing has been built and a series of tests has been conducted for studying the flow pattern in the crossing when the flow in the streets is supercritical. It has been found that the inflow power ratio at the entrance of the crossing can be used as a non-dimensional parameter for predicting the flow distribution as well as the flow pattern. On the basis of these relationships a one-dimensional formulation can be developed in order to predict the dividing flow in crossings.

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44 citations

Journal Article•DOI•

Local scour at open-channel junctions

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S. Mahmood Borghei¹, Aidin Jabbari Sahebari¹•Institutions (1)

Sharif University of Technology¹

08 Sep 2010-Journal of Hydraulic Research

TL;DR: In this article, the scour patterns at the junction of two loose bed channels were studied under clear-water conditions, where the main dimensionless variables were the angle between the two approach flow branches, the discharge and width ratios of the tributary to the downstream channel branches, and the ratio of the mean downstream velocity to the threshold velocity.

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Abstract: High bed-shear stress resulting from secondary flows and velocity increase at a channel junction cause local erosion and deposition in natural rivers and earth-lined channels. Herein, the scour patterns at the junction of two loose bed channels were studied under clear-water conditions. The main dimensionless variables are the angle between the two approach flow branches, the discharge and width ratios of the tributary to the downstream channel branches, and the ratio of the mean downstream velocity to the threshold velocity. The results indicate that the position of the maximum scour depth temporally moves to the outer wall and upstream to the main channel, as affected by the dimensionless variables. The effects of these variables are given in graphs and are expressed with a formula for maximum scour depth.

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31 citations

Cites background or result from "Transitional flow in channel juncti..."

...The test results indicate that the flow depth downstream of the junction decreases with increasing u, Qbd and V/Vc, in agreement with Taylor (1944), Gurram et al. (1997) or Weber et al. (2001). Only the results for u 1⁄4 508 are presented here, while the results from all three test angles are considered in Section 4....
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...…(Taylor 1944, Best and Reid 1984, Hager 1989, Paola 1997, Hsu et al. 1998, Rhoads and Kenworthy 1998), flow depth along the branches (Hager 1989, Gurram 1993, Gurram et al. 1997, Hsu et al. 1998), shear layer along mixing interface (Bradbrook et al. 2000, Sukhodolov and Rhoads 2001, Rhoads and…...
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...The test results indicate that the flow depth downstream of the junction decreases with increasing u, Qbd and V/Vc, in agreement with Taylor (1944), Gurram et al. (1997) or Weber et al....
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Journal Article•DOI•

Modelling of the tributary momentum contribution to predict confluence head losses

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Stéphan Creëlle¹, Laurent Schindfessel¹, Tom De Mulder¹•Institutions (1)

Ghent University¹

04 Mar 2017-Journal of Hydraulic Research

TL;DR: In this paper, the authors proposed a new model to determine the head losses at confluences in one-dimensional models of open channel networks, making use of a momentum conservation approach.

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Abstract: This paper proposes a new model to determine the head losses at confluences in one-dimensional models of open channel networks, making use of a momentum conservation approach Momentum conservation has been applied in several theoretical models for confluence head losses, giving satisfactory results in general However, for larger confluence angles between the main channel and the incoming tributary, the model accuracy diminished Many authors identified that a correct estimation of the tributary momentum contribution is a prerequisite for accurate results This work reports on the development and application of a theoretical model for the tributary momentum contribution, based on similarities with the flow upstream of a circular bend in a straight open channel It describes the two-dimensional depth-averaged flow features in the tributary under the assumption of a 90° angle confluence in which all channels have equal widths, in order to obtain the resulting momentum contribution The proposed mod

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28 citations

Cites background or methods or result from "Transitional flow in channel juncti..."

...Appendix 3 Starting from the conservation of energy between the upstream sections and the contracted section (Hager, 1989), an expression for μ can be derived as follows: HMCS = qHTUS + (1 − q)HMUS (A15) HMCS = q ( YshMCS + μ 2q2hMCS 2Ys2 Q2MDS gμ2W2h3MCS ) + (1 − q) × ( YshMCS + μ 2(1 −…...
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...Furthermore, several authors (Hager, 1989; Hsu et al., 1998; Webber & Greated, 1966) noticed that at large angles between the tributary and the main channel, the inflow angle starts to deviate significantly from the physical confluence angle....
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...…the flow in the entire confluence is subcritical (a7) and (ii) the flow is contracting towards the contracted section (which goes along with negligible head losses (Hager, 1989)), the velocity at the downstream corner is certainly not higher than in the contracted section (see also section 3.3)....
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...As mentioned in the introduction, several authors (Gurram, Karki, & Hager, 1997; Hager, 1989; Hsu et al., 1998; Shabayek, Steffler, & Hicks, 2002; Taylor, 1944; Webber & Greated, 1966) have applied the principle of (streamwise) momentum conservation over a control volume to predict the head losses…...
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...For cases where the flow remains supercritical after the contracted section, the water depth in the separation zone is very small, and its contribution to the momentum balance between the contracted section and the MDS can be neglected (Hager, 1989)....
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Journal Article•DOI•

Comparative study of 1D and 2D flow simulations at open-channel junctions

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Rabih Ghostine¹, José Vazquez, Abdelali Terfous¹, Robert Mosé, Abdellah Ghenaim¹ - Show less +1 more•Institutions (1)

Institut national des sciences appliquées¹

03 Apr 2012-Journal of Hydraulic Research

TL;DR: In this paper, a comparison between the 1D and 2D approaches for simulating combining flows at open-channel junctions is presented, allowing for a full comprehension of flow modelling.

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Abstract: In this paper, a comparison between the 1D and 2D approaches for simulating combining flows at open-channel junctions is presented. The two approaches are described allowing for a full comprehension of flow modelling. For flows in an open-channel network, mutual effects exist among the channel branches at a junction. Therefore, the 1D Saint-Venant equations for the branch flows are supplemented by various junction models. The existing models are of empirical nature and depend on the flow regime and thus are not practical in all cases. The numerical approximation of the two approaches is performed by the Runge–Kutta discontinuous Galerkin scheme and tested using defined flow problems to illustrate the results of the two approaches. Comparisons are conducted for supercritical, transitional and subcritical flows, indicating the validity range of the 1D approach and the advantages of the 2D approach.

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26 citations

Cites background or methods or result from "Transitional flow in channel juncti..."

...The numerical results obtained by the two approaches were compared with the data of Hager (1989a). His tests were conducted in horizontal and smooth branches, 0....
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...The numerical results obtained by the two approaches were compared with the data of Hager (1989a)....
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...ISSN 0022-1686 print/ISSN 1814-2079 online http://www.tandfonline.com 164 Greated 1966, Ramamurthy et al. 1988, Hager 1989a, 1989b, Christodoulou 1993, Gurram 1994, Gurram et al. 1997, Hsu et al. 1998a, 1998b, Shabayek et al. 2002), laboratory experiments (Rice 1985, Schwalt and Hager 1995, Hsu et…...
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...The experimental results of Hsu et al. (1998a, 1998b), Hager (1989a), Rice (1985) and Christodoulou (1993) were used to compare the two approaches....
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References

PDF

Open Access

More filters

Journal Article•DOI•

Experimental modelling of urban flooding: a review.

[...]

Emmanuel Mignot¹, Xuefang Li², Benjamin Dewals²•Institutions (2)

University of Lyon¹, University of Liège²

01 Jan 2019-Journal of Hydrology

...read moreread less

123 citations

Journal Article•DOI•

Local scour at open-channel junctions

[...]

S. Mahmood Borghei¹, Aidin Jabbari Sahebari¹•Institutions (1)

Sharif University of Technology¹

08 Sep 2010-Journal of Hydraulic Research

...read moreread less

31 citations

Journal Article•DOI•

Modelling of the tributary momentum contribution to predict confluence head losses

[...]

Stéphan Creëlle¹, Laurent Schindfessel¹, Tom De Mulder¹•Institutions (1)

Ghent University¹

04 Mar 2017-Journal of Hydraulic Research

TL;DR: In this paper, the authors proposed a new model to determine the head losses at confluences in one-dimensional models of open channel networks, making use of a momentum conservation approach.

...read moreread less

28 citations

Journal Article•DOI•

Comparative study of 1D and 2D flow simulations at open-channel junctions

[...]

Rabih Ghostine¹, José Vazquez, Abdelali Terfous¹, Robert Mosé, Abdellah Ghenaim¹ - Show less +1 more•Institutions (1)

Institut national des sciences appliquées¹

03 Apr 2012-Journal of Hydraulic Research

TL;DR: In this paper, a comparison between the 1D and 2D approaches for simulating combining flows at open-channel junctions is presented, allowing for a full comprehension of flow modelling.

...read moreread less

26 citations

Dissertation•

Simulations des écoulements en milieu urbain lors d'un évènement pluvieux extrême

[...]

Quentin Araud

30 Nov 2012

TL;DR: In this article, le manque de donnees experimentales sur des geometries urbaines rend la validation and l'encadrement de l'utilisation of ces derniers difficile.

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Abstract: Les ecoulements en milieu urbain sont complexes et a l’heure actuelle estimes a l’aide d’outils informatiques. Pourtant, le manque de donnees experimentales sur des geometries urbaines rend la validation et l’encadrement de l’utilisation de ces derniers difficile. Cette these presente les resultats obtenus sur un modele physique d’un quartier urbain. La distribution des hauteurs d’eau ainsi que la repartition des debits en sortie du quartier experimental sont mesurees. Leur etude a mis en evidence certains comportements caracteristiques des ecoulements. Les donnees experimentales ont ete comparees aux simulations numeriques generees avec un code 3D (Ansys-Fluent®) et un outil de recherche (Neptune 2D) mis au point durant cette these. Ce dernier resout les equations de Barre de Saint Venant 2D a l’aide d’un schema EVR-DG, associe a une modification des solveurs de Riemann qui rend le code de calcul well-balanced.Les ecarts observes entre Ansys-Fluent® et l’experimental sont majoritairement en-dessous de 10%. Le code Neptune 2D apparait quant a lui legerement moins precis : les ecarts peuvent atteindre 20 a 30%. Diverses hypotheses sont avancees pour expliquer ces ecarts.

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13 citations