On large-scale flow structures in a gravel-bed river

Buffin‐Bélanger, Thomas; Roy, Alain; Kirkbride, Alistair D.

doi:10.1016/s0169-555x(99)00106-3

Cited by 99 publications

(100 citation statements)

References 14 publications

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“…ACARLAR et SMITH (1987) ont montré que la fréquence d'échappement sans dimension, exprimée par le nombre de Strouhal (S = fd/U où f est la fréquence d'échappement ; d, la hauteur de l'hémisphère ; U, la vitesse moyenne de l'écoulement) était proportionnelle au nombre de Reynolds de l'obstacle lorsque celui-ci est inférieur à 1 600. Au-delà de cette valeur, la fréquence d'échappe-ment oscille fortement entre 0,2 et 0,4, ce qui rejoint le concept du nombre de Strouhal universel pour les écoulements ayant un nombre de Reynolds élevé (LEVl, 1983 ;NAKAMURA, 1996 ;VIOLLET et al, 1998 (BUFFIN-BÉLANGER et al, 2000a).…”

Section: -Introductionunclassified

Interactions entre les structures d'échappement et les structures à grande échelle dans l'écoulement turbulent des rivières à lit de graviers

Buffin‐Bélanger¹,

Roy²,

Levasseur³

2005

rseau

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Dans les rivières graveleuses, il est établi que les structures d'échappement formées dans la zone de recirculation à l'aval d'amas de galets génèrent d'intenses échanges turbulents. Le mécanisme responsable de l'échappement demeure par contre mal connu. Peu d'études sur la dynamique des structures d'échappement ont été réalisées dans des écoulements où le nombre de Reynolds est élevé comme c'est le cas en rivières. De plus, les connaissances actuelles ne tiennent pas compte des découvertes récentes sur la turbulence en rivière à lit de graviers où on a observé des structures de forte et de faible vitesse occupant toute la profondeur de l'écoulement et pouvant durer plusieurs secondes. Ces structures à grande échelle devraient jouer un rôle sur le mécanisme d'échappement étant donné l'influence de la vitesse ambiante sur la dynamique de la zone de recirculation. Nous rapportons les résultats de deux expériences originales sur les liens dynamiques entre les structures à grande échelle et le mécanisme d'échappement en aval d'un amas de galets. La première expérience repose sur l'analyse de corrélations croisées entre des séries de vitesses obtenues au sommet et à l'aval proximal d'un amas de galets. Les résultats montrent que les fortes fluctuations dans le sens de l'écoulement au sommet de l'obstacle sont liées, quelques instants plus tard, à de fortes fluctuations vers l'amont dans la zone de recirculation. La seconde expérience utilise la visualisation des structures d'échappement et la mesure simultanée des vitesses de l'écoulement. L'analyse combinée des images vidéo et de séries de vitesse suggère une relation entre le passage des structures à grande échelle et les manifestations de l'échappement. Ces résultats nous permettent de présenter un modèle où, lors du passage d'un front de haute vitesse, une structure d'échappement se développe et prend de l'expansion vers le lit et vers la surface en se propageant vers l'aval alors que, lors du passage d'un front de faible vitesse, elle s'élève vers la surface de manière plus cohérente. Cette étude propose un nouveau mécanisme d'échappement et révèle le rôle que joue la structure de l'écoulement ambiant sur le développement de structures dans les cours d'eau à lit graveleux.The flow structure in a gravel-bed river is closely related to the presence of protruding clasts and of pebble clusters. It is well known that shedding motions from the lee side of large clasts and clusters are a recurrent process that explains the strong exchanges of momentum in river flows. However, shedding has yet to be fully characterised for high Reynolds number flows such as those found in gravel-bed rivers. Moreover, our current understanding of shedding mechanisms does not include the recent discovery that large-scale flow structures in the form of high- and low-speed wedges occupy the entire flow depth over a gravel-bed river. From two original experiments, this paper investigates the influence of these wedges on the nature of shedding in the lee of a pebble cluster. The interactions b...

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Section: -Introductionunclassified

Interactions entre les structures d'échappement et les structures à grande échelle dans l'écoulement turbulent des rivières à lit de graviers

Buffin‐Bélanger¹,

Roy²,

Levasseur³

2005

rseau

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“…Profiles of mean and turbulent flow properties in gravel bed rivers show consistent patterns in spite of the roughness and heterogeneity of gravel beds (Buffin-Bélanger and Roy 1998; Roy et al 2004). The consistent vertical patterns and the relative stability of the average turbulent variables on a vertical profile are due to the presence of macroturbulent flow structures that occupy the entire depth of the flow and that dominate turbulence production (Buffin-Bélanger et al 2000;Roy et al 2004). These structures are narrow wedges of low-and high-speed fluid that scale with flow depth.…”

Section: Discussionmentioning

confidence: 99%

Habitat Choice by Atlantic Salmon Parr in Relation to Turbulence at a Reach Scale

Enders

Roy

Ovidio

et al. 2009

N American J Fish Manag

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Abstract.-The variables commonly used to describe the physical habitat of Atlantic salmon Salmo salar parr are average velocity, water depth, and substrate. A variety of micro-and mesohabitat models have been developed using these variables to assess habitat quality. However, Atlantic salmon parr live in highly turbulent streams and rivers in which intense fluctuations of water velocity occur. Laboratory experiments have shown that turbulence affects the behavior and energetics of fish. Nevertheless, habitat use in relation to the strong temporal variability of velocity in natural environments has rarely been studied. In this study, Atlantic salmon parr habitat was examined in relation to turbulence in the Patapédia River, Quebec. Rather than taking the usual approach of surveying a large population at one point in time, we used an intensive radiotelemetry tracking survey that focused on the habitat use of a few individual fish over an extended period. We analyzed habitat use in relation to several dynamic hydraulic variables. Our results revealed that under naturally turbulent conditions, the parr displayed high individual variability in their habitat use. Such heterogeneous use of habitat suggests that individuals are not constrained to a single habitat type. Furthermore, no differences were observed in habitat use among the four daily periods (dawn, day, dusk, and night) for individual parr.

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“…Compared with biologists, hydraulic engineers view the fluvial environment through the application of computational fluid dynamic (CFD) models, routing water mass and momentum among a modeler defined numerical mesh space [99]. Turbulence modeled at a micro-scale are a function of Reynolds stresses of fluid motion and boundary layer resistance are scaled to topography and in stream structures [254][255][256][257][258][259]. Discipline differences are best exemplified by the use of the term "turbulence", where biologists refer to it as "wavy" surface waters as criteria for mesohabitat classification and hydraulic engineers apply CFD at the micro-scale noted above [58,63].…”

Section: Framework For Classification Of Multi-stage Ecohydraulics-bamentioning

confidence: 99%

Use of Ecohydraulic-Based Mesohabitat Classification and Fish Species Traits for Stream Restoration Design

Schwartz

2016

Water

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Stream restoration practice typically relies on a geomorphological design approach in which the integration of ecological criteria is limited and generally qualitative, although the most commonly stated project objective is to restore biological integrity by enhancing habitat and water quality. Restoration has achieved mixed results in terms of ecological successes and it is evident that improved methodologies for assessment and design are needed. A design approach is suggested for mesohabitat restoration based on a review and integration of fundamental processes associated with: (1) lotic ecological concepts; (2) applied geomorphic processes for mesohabitat self-maintenance; (3) multidimensional hydraulics and habitat suitability modeling; (4) species functional traits correlated with fish mesohabitat use; and (5) multi-stage ecohydraulics-based mesohabitat classification. Classification of mesohabitat units demonstrated in this article were based on fish preferences specifically linked to functional trait strategies (i.e., feeding resting, evasion, spawning, and flow refugia), recognizing that habitat preferences shift by season and flow stage. A multi-stage classification scheme developed under this premise provides the basic "building blocks" for ecological design criteria for stream restoration. The scheme was developed for Midwest US prairie streams, but the conceptual framework for mesohabitat classification and functional traits analysis can be applied to other ecoregions.

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On large-scale flow structures in a gravel-bed river

Cited by 99 publications

References 14 publications

Interactions entre les structures d'échappement et les structures à grande échelle dans l'écoulement turbulent des rivières à lit de graviers

Interactions entre les structures d'échappement et les structures à grande échelle dans l'écoulement turbulent des rivières à lit de graviers

Habitat Choice by Atlantic Salmon Parr in Relation to Turbulence at a Reach Scale

Use of Ecohydraulic-Based Mesohabitat Classification and Fish Species Traits for Stream Restoration Design

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