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Estimation of the soil-water retention curve, [theta](h), on undisturbed soil samples is of paramount importance to characterise the hydraulic behaviour of soils. Although a method of determining parameters of the water retention curve ([alpha], a scale parameter inversely proportional to mean pore diameter and n, a measure of pore size distribution) from saturated hydraulic conductivity ([K.sub.s]), sorptivity (S) and the [beta] parameter, using S and [beta] calculated from the inverse analysis of upward infiltration (UI) has been satisfactorily applied to sieved soil samples, its applicability to undisturbed soils has not been tested. The aim of the present study was to show that the method can be applied to undisturbed soil cores representing a range of textures and structures. Undisturbed soil cores were collected using stainless steel cylinders (5 cm internal diameter x 5 cm high) from structured soils located in two different places: (1) an agricultural loam soil under conventional, reduced and no tillage systems; and (2) a loam soil under grazed and ungrazed natural shrubland. The [alpha] and n values estimated for the different soils using the UI method were compared with those calculated using time domain reflectometry (TDR) pressure cells (PC) for pressure heads of -0.5, -1.5, -3, -5, -10 and -50kPa. To compare the two methods, [alpha] values measured with UI were calculated to the drying branch of [theta](h). For each treatment, three replicates of UI and PC calculations were performed. The results showed that the 5-cm high cylinders used in all experiments provided accurate estimates of S and [beta]. Overall, the [alpha] and n values estimated with UI were larger than those measured with PC. These differences could be attributed, in part, to limitations of the PC method. On average, the n values calculated from the optimised S and [beta] data were 5% larger than those obtained with PC. A relationship with a slope close to 1 fitted the n values estimated using both methods ([n.sub.PC] = 0.73 [n.sub.UI] + 0.49; [R.sup.2] = 0.78, P < 0.05). The results show that the UI method is a promising technique to estimate the hydraulic properties of undisturbed soil samples. Additional keywords: hydraulic conductivity, soil tillage, sorptivity., Introduction Water flow in the vadose zone is primarily regulated by the unsaturated hydraulic conductivity, K, which is related to the water retention curve, [theta](h) (van Genuchten 1980). These parameters [...]

Crayfish of the species Orconectes virilis inhabit two distinct types of hydrodynamic environments: lakes and rivers. Odor cues in these habitats convey chemical information differently due to dispersion by different physical processes. In the laboratory we examined orientation strategies of crayfish collected from lake and river habitats to an odor source dispersed in either a lotic (river) or lentic (lake) manner. Our results showed lake crayfish had variable responses under both flow regimes whereas river crayfish oriented similarly under both flow regimes. Lake crayfish increased walking speeds, decreased heading angles, and decreased turn angles while orienting under lotic versus lentic conditions. Conversely, river crayfish oriented similarly under both flow regimes and reflected lake crayfish behavior in lotic flow. We conclude lake and river crayfish show differences in their orientation strategies due to influences from sensory signals in their source habitat. These results show crayfish show behavioral plasticity with respect to the hydrodynamic and signal structure from their native environments and may be an example of sensory bias., INTRODUCTION In freshwater systems two major types of flow environments exist: lakes with low average or inconsistent flow (termed lentic) and rivers consistent uni-directional flow (termed lotic). Because flow characteristics [...]

Extremes of flow and patterns of flow variability limit the distribution and abundance of riverine species via a natural disturbance regime. Using a habitat template approach, we describe the distribution and characteristics of natural flow regimes in Canada based on the severity of flows, flow predictability, and flow variability. Bayesian clustering was used to group 888 gauged watersheds across Canada into 10 classes. Some flow classes were found in all provinces, whereas others showed greater regional grouping related to land physiography (e.g., Canadian Shield and ecozones). Ontario and British Columbia had the greatest diversity of flow classes. Larger river systems tended towards less harsh flow regimes and greater flow regularity than small systems. A stream-lake network pattern, particularly the presence of lakes, decreased the severity of flow. The flow metric flood-free interval was found to be a potentially misleading indicator of reduced disturbance for high-latitude streams in Canada where ice formation and persistence are important stress factors for biota. Most flow stations had an 80% or higher chance of belonging to their primary membership class. Quantifying uncertainty in class assignment can help fellow scientists and resource managers appropriately apply our findings. Les debits extremes et les motifs de variabilite des debits limitent la repartition et l'abondance des especes fluviales en produisant un regime de perturbation naturel. En employant une approche reposant sur les gabarits d'habitat, nous decrivons la repartition et les caracteristiques des regimes d'ecoulement naturel au Canada en fonction de l'ampleur des debits, de leur previsibilite et de leur variabilite. L'agregation bayesienne a ete utilisee pour regrouper 888 bassins versants jauges a la grandeur du Canada en 10 classes. Certaines classes de debits etaient presentes dans toutes les provinces, alors que d'autres presentaient des concentrations regionales associees a la physiographie (p. ex. Bouclier canadien) et aux ecozones. L'Ontario et la ColombieBritannique presentaient la plus grande diversite de classes de debits. Les reseaux hydrographiques plus importants avaient tendance a presenter des regimes d'ecoulement moins extremes et une plus grande regularite des debits que les reseaux plus petits. Le motif du reseau fluviolacustre, particulierement la presence de lacs, se traduisait par des debits moins extremes. Il a ete observe que le parametre associe a l'ecoulement, les jours sans inondation, etait un indicateur potentiellement trompeur de perturbation moindre pour les cours d'eau de haute latitude au Canada, oU la formation et la persistance de la glace sont d'importants facteurs de stress pour les etres vivants. La plupart des stations hydrometriques presentaient une probabilite de 80% ou plus de faire partie de leur classe d'appartenance primaire. La quantification de l'incertitude de l'affectation aux differentes classes peut aider les scientifiques et les gestionnaires de ressources a appliquer adequatement les resultats de cette etude. [Traduit par la Redaction], Introduction Flow regime is a key determinant of physical processes in streams, freshwater biodiversity, life history characteristics, and many ecological traits (Poff et al. 1997; Bunn and Arthington 2002). The [...]

The conventional railway substructure in France was built by emplacing ballast directly on subgrade. Over years of operation, the interpenetration of ballast and subgrade created a soil layer between them. Under different conditions, this naturally formed layer, namely interlayer, can contain different quantities of fine particles, becoming more or less sensitive to changes in water content. As the water content changes are governed by the hydraulic behavior of the interlayer soil, assessing the influence of fine particle content on the hydraulic behavior of interlayer soil is of importance. To this end, the hydraulic behavior of an interlayer soil taken from Senissiat (near Lyon, France) was investigated using two infiltration columns, a large-scale column equipped with tensiometers and a time domain reflectometer (TDR) for suction and volumetric water content measurements, respectively, and a smaller column equipped with high-capacity tensiometers only. Different fines contents were considered and wetting-drying cycles were applied to the soil specimens. The hydraulic conductivity was determined by applying the instantaneous profile method. The results obtained showed that (i) hysteresis exists for both the soil water retention curve and the hydraulic conductivity changes with suction; (ii) the effect of wetting-drying cycles is insignificant; (iii) adding 10% fine particles to the natural interlayer soil gives rise to changes in the soil water retention curve but does not induce significant changes in hydraulic conductivity; (iv) the unsaturated hydraulic conductivity of interlayer soil with 10% fine particles added is close to that of soil sieved at 2 mm, suggesting that the unsaturated hydraulic conductivity of interlayer soil is mainly governed by fine particles through the suction effect. By contrast, in a saturated state, the value for the interlayer soil with 10% fine particles added was found to be higher, suggesting that in this case the hydraulic conductivity is mainly governed by the water transfer through macropores. Key words: railway substructure, interlayer soil, fines content, instantaneous profiles method, hydraulic conductivity. La sous-structure des lignes ferroviaires conventionelles en France est construite en pla^ant le ballast directement sur le sol support. Apres plusieurs annees d'operation, l'inter-penetration du ballast et du sol support a cree une couche de sol entre les deux. Cette couche formee de fa^on naturelle, appelee couche intermediaire, peut contenir differentes quantites de particules fines selon differentes conditions, et devient plus ou moins sensible aux variations de teneur en eau. Puisque les variations de teneur en eau sont fonction du comportement hydraulique du sol de la couche intermediaire, il est important d'evaluer l'influence de la teneur en fines sur le comportement hydraulique du sol de la couche intermediaire. A cette fin, le comportement hydraulique d'un sol de la couche intermediaire preleve a Senissiat (pres de Lyon, France) a ete etudie a l'aide de deux colonnes d'infiltration; une colonne a grande echelle equipee des tensiometres et sondes de reflectometrie dans le domaine temps (RDT) pour les mesures de succion et de teneur en eau, respectivement, et une colonne plus petite instrumentee seulement des tensiometres a haute capacite. Differents teneurs en fines ont ete consideres, et des cycles de mouillage-sechage ont ete appliques aux echantillons de sol. La conductivite hydraulique a ete determinee par la methode des profils instantanes. Les resultats obtenus demontrent que (i) l'hysteresis est presente pour la courbe de retention d'eau et la variation de la conductivite hydraulique selon la succion; (ii) l'effet des cycles de mouillage-sechage n'est pas significatif; (iii) l'ajout de 10% de particules fines au sol de la couche intermediaire naturel modifie la courbe de retention d'eau mais n'entraine pas de changements significatifs dans la conductivite hydraulique; (iv) la conductivite hydraulique non saturee du sol de la couche intermediaire avec ajout de 10% de particules fines est pres de celle d'un sol tamise a 2 mm, ce qui suggere que la conductivite hydraulique non saturee est geree principalement par les particules fines via l'effet de succion. Par ailleurs, a l'etat sature, la valeur pour le sol de la couche intermediaire avec ajout de 10% de particules fines est superieure, ce qui demontre que dans ce cas, la conductivite hydraulique est geree principalement par le transfert de l'eau a travers les macro-pores. [Traduit par la Redaction] Mots-cles : sous-structure ferroviaire, sol de la couche intermediaire, teneur en fines, methode des profils instantanes, conductivite hydraulique., Introduction Many railway lines across the world have been in operation for more than a hundred years. In France, conventional lines represent 94% of the whole railway network. As opposed [...]

Backflushing is an efficient alternative for cleaning trash racks at small hydropower plants. The actual debris to trash rack adhesion is measured in situ for the first time by an innovative, custom-made measuring device. Despite large measurement variations caused by unevenness in debris distribution, the adhesion to trash rack for most types of debris and for most sites is relatively modest. There is also a trend where a higher maximum head loss through the trash rack increases the debris adhesion to the trash rack. The hydraulics around the trash rack during a backflushing process is assessed by monitoring the velocity development and the pressure difference through the trash rack in a physical model. As expected, when debris adhesion to the trash rack is high, releasing the attached debris requires a higher pressure difference through the trash rack and a higher approach velocity. Key words: trash rack, backflushing, debris adhesion, small hydropower. Le decolmatage a contre-courant est un choix efficace pour nettoyer les grilles d'entree de petites centrales hydroelectriques. L'adherence reelle des debris aux grilles d'entree est mesuree in situ pour la premiere fois grace a un dispositif de mesure innovant et fait sur mesure. Malgre de grandes variations de mesures en raison de l'irregularite de l'accumulation de debris, l'adherence aux grilles d'entree de la majorite des types de debris et pour la plupart des sites est relativement faible. Il existe egalement une tendance ou une perte de pression maximale a travers la grille d'entree augmente l'adherence des debris a la grille d'entree. Durant le processus de decolmatage, l'hydraulique autour des grilles d'entree est evaluee en surveillant, dans un modele physique, le developpement de la vitesse et la difference de pression a travers la grille d'entree. Tel que prevu, lorsque l'adherence des debris a la grille d'entree augmente, il faut accroitre le differentiel de pression a travers la grille d'entree et la vitesse d'approche afin de liberer les debris. [Traduit par la Redaction] Mots-cles: grille d'entree, decolmatage, adherence des debris, petite centrale hydroelectrique., Introduction With the growing interest in clean and renewable energy, there is an increasing trend towards constructing new small hydropower plants. Many existing and new power plants worldwide are experiencing [...]

In this research, computational fluid dynamic simulation of direct-contact membrane distillation process is carried out. The process consists of a nanoporous flat-sheet membrane as contactor, a saline liquid feed, and permeate phase. The flow pattern is considered to be counter-current. The aim of the process is to produce pure water from saline water. Heat and mass transfer equations are derived and solved for water by finite element analysis. The simulations are then validated by comparing simulation predictions with the experimental data reported in literature. Good agreement was obtained which confirmed the validity of simulation procedure in simulation of water desalination using membrane distillation. Diffusion of water vapor through pores of membrane is simulated by combination of the Knudsen and Poiseuille flow. POLYM. ENG. SCI., 54:660-666, 2014. © 2013 Society of Plastics Engineers, INTRODUCTION Recently, membrane technology has gained wide applications in environment and food industries. In environmental applications, membrane technology is mostly used for treatment of wastewater and control of greenhouse gas [...]

To investigate the hydraulic behaviour of the fine-grained embankments along the mid-course of the Po River, research was carried out on a full-scale physical model, built on the floodplain along the existing embankment and forming a pond. The pond was filled to reproduce historical floods. The prototype was built according to recommendations formulated by the Po River Management Authority. The engineering properties of the foundation soils were investigated by in situ tests and complemented by some suction-controlled laboratory tests. Pore-water pressure was measured in the embankment and in its foundation before, during, and after the experimental reproduction of two floods that occurred in 1976 and 2000. Atmospheric variables were monitored at the prototype site. Monitoring data refer to 6 months of experimental activities. Pore-water pressure measurements were first presented and subsequently interpreted through an isothermal two-dimensional flow approach where boundary flow rates express the evolution of atmospheric variables. The distribution of the pore water provided by this interpretation was used for stability analyses of the prototype. Results from the experimental activities and their interpretation indicate that the river embankment remains extensively unsaturated during floods. Typical suction trends within the embankment, suction- associated soil strength, and the resulting slope stability safety factors are also shown. Key words: embankments, partially saturated soil, in situ measurements, numerical analysis, hydraulic conductivity. Un projet de recherche a ete realise afin d'etudier le comportement hydraulique de berges de materiaux fins placees a mi-chemin de la riviere Po, grace a un modele physique a l'echelle reelle construit sur la plaine inondable le long d'une berge existante et formant un etang. L'etang a ete rempli pour reproduire des inondations historiques. Le prototype a ete construit selon les recommandations formulees par l'Autorite de gestion de la riviere Po. Les proprietes d'ingenierie des sols de fondation ont ete evaluees par des essais sur le terrain et completes par quelques essais de controle de succion en laboratoire. Les pressions interstitielles dans la berge et dans sa fondation ont ete mesurees avant, pendant, et apres les reproductions experimentales de deux inondations survenues en 1976 et 2000. Les variables atmospheriques ont ete mesurees sur le site du prototype. Les donnees de suivi recueillies couvrent 6 mois d'activites experimentales. Les mesures de pression interstitielle sont d'abord presentees et ensuite interpretees a l'aide d'une approche d'ecoulement isotherme en 2D dans laquelle les conditions frontieres de taux d'ecoulement expriment revolution des variables atmospheriques. La distribution des pressions interstitielles obtenue par cette interpretation est utilisee pour des analyses de stabilite du prototype. Les resultats des activites experimentales et leur interpretation indiquent que les berges de la riviere demeurent fortement non saturees durant les inondations. Les tendances typiques de succion a l'interieur de la berge, la resistance du sol associee a la succion, et les facteurs de securite de stabilite de pente sont aussi presentes. [Traduit par la Redaction] Mots-cles: berges, sols partiellement satures, mesures in situ, analyse numerique, conductivite hydraulique., Introduction The Po River, which crosses northern Italy from west to east (Fig. 1), is Italy's main water course in terms of length and capacity. Past flooding of the main [...]

Experimental results on the nature-like fishway induced flow field and its relation to fish behaviour are presented. A rocky-ramp with 5% slope was built along a8.9mx0.9mx0.6m laboratory flume, and acoustic Doppler velocity measurements were taken in a grid with 186 points for low, middle, and high discharges. The flow is characterized applying spatial and point analysis techniques. Point analysis consistently shows that the boulder to boulder distance is small enough to disrupt turbulent coherent structures. At boulder wakes no predominance of sweep and ejection events occur, evidencing a good resting place for fish migration. The nature-like rocky-ramp offers a diversity of flow conditions controlled by the boulders geometry that might allow a variety of fishes to develop their preferred paths characterized by flow properties with different magnitudes depending on the particular species. Obtained results compare well with similar ones reported for other standard fishways. Key words: ADV, fish habitat, fish passage, flow, nature-like fishways, turbulence. Cet article presente les resultats d'experiences concernant le champ de courant induit dans une passe migratoire d'aspect naturel et sa relation avec le comportement des poissons. Une rampe rocheuse ayant une pente de5%aete construite le long d'un canal jaugeur de laboratoire mesurant 8,9 x 0,9 x 0,6 m; des mesures de vitesse ont ete prises au debitmetre acoustique selon une grille de 186 points a des debits faibles moyens et eleves. L'ecoulement est caracterise en appliquant des techniques d'analyse spatiale et par points. L'analyse par points montre de maniere uniforme que la distance de rocher a rocher est suffisamment petite pour perturber les structures coherentes de turbulence. Il n'y a aucune predominance de balayage et d'ejection dans les sillages des rochers, prouvant qu'il s'agit d'un bon endroit de repos pour les poissons en migration. La rampe rocheuse d'aspect naturel offre une diversite de conditions d'ecoulement controlees par la geometrie des rochers, ce qui pourrait permettre a plusieurs especes de poissons de developper leur chemin prefere selon les proprietes d'ecoulement de differentes amplitudes propres aux especes particulieres. Les resultats obtenus se comparent bien a d'autres resultats similaires rapportes pour d'autres passes migratoires standards. [Traduit par la Redaction] Mots-cles : debitmetre acoustique, habitat du poisson, passe migratoire, ecoulement, passes migratoires d'aspect naturel, turbulence., 1. Introduction Fishways are hydraulic structures enabling fish to negotiate river obstructions such as dams, weirs, and under-road culverts. According to their design, one can distinguish standard and nature-like fishways. [...]

Culvert design must account for a large range of flow rates but most of the time culverts convey flows that are smaller than the design flow. Repeated high flows passing through the culverts lead to a gradual increase of the sediment deposits in the culvert vicinity, eventually resulting in reduced flow and sediment capacity. Sedimentation at culverts is quite an involved process due to the combined effect of flow non-uniformity and unsteadiness, as well as of the flow-sediment interaction. This paper reports results from a series of laboratory experiments aimed at understanding the hydro and morpho-dynamic changes occurring in the vicinity of a three-box culvert. For this purpose, velocity and turbulence characteristics upstream of the culvert were mapped globally and locally during the transition from an original flatbed to equilibrium sediment transport condition using contemporary acoustics, light detection and ranging, and image-based technologies. The experimental results reveal flow complexities not currently accounted for in the design of the multi-barrel culverts, but which can be detrimental for their long-term operation. Considerations on practical approaches to efficiently model the complexities were formulated. Key words: culvert, non-uniform flow, LSPIV, LiDAR, acoustic instrument. La conception des ponceaux doit tenir compte d'une grande plage de debits mais, la plupart du temps, les ponceaux font passer des debits qui sont inferieurs au debit prevu. Les debits eleves passant a repetition dans les ponceaux engendrent une augmentation graduelle du depot de sediments aux environs du ponceau, ce qui conduit eventuellement une capacite reduite de debit et de transport solide. La sedimentation aux ponceaux est un processus complexe en raison de l'effet combine de la non-uniformite et de l'instabilite du debit ainsi que de l'interaction debit-sediments. Le present article presente les resultats d'une serie d'experiences en laboratoire visant a comprendre les changements hydrodynamiques et morpho-dynamiques survenant aux environs d'un ponceau tricorps. A cette fin, les caracteristiques de vitesse et de turbulence a l'amont du ponceau ont ete cartographiees globalement et localement durant la transition d'un lit plat initial a une condition de transport a l'equilibre de sediments en utilisant l'acoustique contemporain, le LiDAR et les technologies basees sur les images. Les resultats experimentaux revelent des complexites de debits dont on ne tient pas presentement compte dans la conception de ponceaux multitubes, mais qui pourraient nuire a leur fonctionnement a long terme. Nous avons formule des recommandations concernant les approches pratiques afin de modeliser efficacement ces complexites. [Traduit par la Redaction] Mots-cles: ponceau, debit non uniforme, LSPIV, LiDAR, instrument acoustique., 1. Introduction Culverts are common hydraulic structures for secondary roads crossing small streams in the rural US Midwestern area. In this region, the sedimentation at culverts is a chronic problem [...]

Hydraulic geometry and resistance to flow of headwater streams in the Northwest Territories of Canada are presented in this paper. Power functions describe at-a-station hydraulic geometry relationships very well, where positive exponents of width, depth, and velocity have mean values of 0.14, 0.17, and 0.65, respectively. These values were found to be lower, much lower, and higher than corresponding mean values of width, depth, and velocity exponents found in the literature. The mean velocity exponent is greater than mean width and depth exponents combined, demonstrating the dominant role of velocity in accommodating varying discharge in all streams evaluated in this study. Darcy-Weisbach resistance factor (f) and Manning's n individually vary over three orders of magnitude, 1.0-267 and 0.085-1.37, respectively. Despite large ranges, hydraulic relations are described effectively through power equations and Keulegan function curves fitted for each section. Key words: hydrotechnical engineering, fluid mechanics and hydrodynamics, hydraulic geometry, resistance to flow. Cet article presente la geometrie hydraulique et la resistance a l'ecoulement de ruisseaux de tete dans les Territoires du Nord-Ouest du Canada. Les fonctions de puissance decrivent tres bien les relations de geometrie hydraulique a la station ou les exposants positifs de largeur, de profondeur et de vitesse valent respectivement 0,14, 0,17 et 0,65. Ces valeurs se revelent plus basses, beaucoup plus basses, et plus elevees que les valeurs moyennes correspondantes des exposants de largeur, de profondeur et de vitesse trouves dans la litterature. L'exposant de vitesse moyenne est superieur aux exposants combines de largeur et de profondeur moyennes, demontrant la dominance de la vitesse pour traiter de la variabilite de la decharge dans tous les ruisseaux evalues lors de cette etude. Le facteur de resistance (f)de Darcy-Weisbach et le n de Manning varient individuellement de trois ordres de grandeur, respectivement 1,0-267 et 0,085-1,37. Malgre de larges plages, les relations hydrauliques sont decrites efficacement par l'utilisation d'equations de puissance et les courbes de fonction de Keulegan ajustees a chaque section. Mots-cles: hydraulique, mecanique des fluides et hydrodynamique, geometrie hydraulique, resistance a l'ecoulement. [Traduit par la Redaction], 1. Introduction The term 'hydraulic geometry' (downstream and at-a-station) quantitatively describes the relationship among principal hydraulic variables of river width, depth, and velocity with changing discharge. Downstream hydraulic geometry deals [...]

We studied the diel variation of in situ coral temperature, irradiance and photosynthetic performance of hemispherical colonies of Porites lobata and branching colonies of Porites cylindrica during different bulk water temperature and tidal scenarios on the shallow reef flat of Heron Island, Great Barrier Reef, Australia. Our study presents in situ evidence that coral tissue surface temperatures can exceed that of the surrounding water under environmental conditions typically occurring during low tide in shallow reef or lagoon environments. Such heating may be a regular occurrence on shallow reef flats, triggered by the combined effects of high irradiance and low water flow characteristic of low Spring tides. At these times, solar heating of corals coincides with times of maximum water temperature and high irradiance, where the slow flow and consequent thick boundary layers impede heat exchange between corals and the surrounding water. Despite similar light-absorbing properties, the heating effect was more pronounced for the hemispherical P. lobata than for the branching P. cylindrica. This is consistent with previous laboratory experiments showing the evidence of interspecific variation in coral thermal environment and may result from morphologically influenced variation in convective heat transfer and/or thermal properties of the skeleton. Maximum coral surface warming did not coincide with maximum irradiance, but with maximum water temperature, well into the low-tide period with extremely low water flow in the partially drained reef flat, just prior to flushing by the rising tide. The timing of low tide thus influences the thermal exposure and photophysiological performance of corals, and the timing of tidally driven coral surface warming could potentially have different physiological impacts in the morning or in the afternoon., Introduction Diurnal fluctuations in irradiance affect the photophysiology of the endosymbiotic dinoflagellates (zooxanthellae) of corals (Brown et al. 1999; Ralph et al. 1999; Jones and Hoegh-Guldberg 2001; Winters et al. [...]

The gravity-driven free surface flow problems for which both the solid and free surface boundaries are highly curved are very difficult to solve. A computational scheme using a variable domain and a fixed domain natural element method (NEM) is developed in the present study for the computation of the free surface profile, velocity and pressure distributions, and the flow rate of a 2D gravity fluid flow through a conduit and under a radial gate. The problem involves two highly curved unknown free surfaces and arbitrary curved-shaped boundaries. These features make the problem more complicated than flow under a sluice gate or over a weir. The fluid is assumed to be inviscid and incompressible and the results obtained are confirmed by conducting a hydraulic model test. The results are in agreement with other flow solutions for free surface profiles and pressure distributions. Key words: free surface flow, natural neighbour interpolation, numerical methods, hydraulic gates. Les problemes d'ecoulement gravitaire en surface libre oU les limites imposees par les parois solides et la surface libre sont tres courbes sont tres difficiles a resoudre. Un modele informatique utilisant une methode d'elements naturels a domaine variable et a domaine fixe est developpee dans la presente etude afin de calculer le profil de la surface libre, les distributions de vitesse et de pression ainsi que le debit d'un ecoulement gravitaire bidimensionnel d'un fluide dans un conduit et sous une vanne a segment. Le probleme implique deux surfaces libres inconnues tres courbees et des limites courbes arbitraires. Ces caracteristiques rendent le probleme plus complique que celui de l'ecoulement sous une vanne register ou par-dessus un deversoir. Il est presume que le fluide est incompressible et non visqueux; les resultats obtenus sont confirmes par un essai utilisant un modele hydraulique. Les resultats concordent avec les autres solutions d'ecoulement pour les profiles a surface libre et les distributions de pression. Mots-cles : ecoulement en surface libre, interpolation du voisin naturel, methodes numeriques, ecluses hydrauliques. [Traduit par la Redaction], Introduction Various types of hydraulic structures are commonly used in rivers and channels as control structures. Examples of these control structures include spillways, weirs, and various types of gates. The [...]

In Georgia, there are three distinct populations of black bears (Ursus americanus, including two subspecies americanus and floridanus). The Middle Georgia population has been shown to exhibit high genetic similatities within the population and we wanted to determine if the Ocmulgee River was a barrier to bear movements. One out of 9 collared females and 7 of 17 collared males crossed the Ocmulgee River. River flow (bear = 70.7 cubic m/sec, random = 92.7 cubic m/sec) and river depth (bear = 2.6 m, random = 2.8 m) were significantly lower when bears crossed the river than random samples. The river did appear to be a barrier to females but not males. Females may be less likely than males to cross the river because of behavioral differences (e.g., cub rearing) and smaller home ranges., INTRODUCTION Throughout North America, American black bear populations have been reduced from past historical records (Dickson, 2001; Pelton, 2001). Habitar conversion, degradation, fragmentation and past unregulated harvest have contributed to [...]

A simple method for evaluating the discharge at a narrow compound sewer is proposed, based on the entropy concept. The entropy parameter can be obtained from a single pair of mean and maximum velocities at the channel section. This study proved the entropy parameter to be constant in the two real field sites for any hydraulic condition. The linear relation between the mean and maximum velocities was found effective in evaluating the discharge, using the value of the maximum instead of the mean velocity in the channel. The validation of the method was carried out by comparing the estimated results with the measured findings at the field sites. Key words: discharge, measurement, mean velocity, maximum velocity, entropy. Une methode simple, basee sur le concept de l'entropie, pour evaluer le debit dans des canalisations etroites est proposee. L'entropie peut etre calculee par le seul couple (vitesse moyenne, vitesse maximale) dans la section mouillee. Cette etude a demontre sur deux sites reels que le parametre d'entropie est constant, quelques soient les conditions hydrauliques. La linearite de la relation entre les vitesses moyenne et maximale permet d'evaluer le debit efficacement en utilisant uniquement la valeur de la vitesse maximale. La comparaison entre les resultats et les valeurs effectivement mesurees sur le terrain a permit de valider la methode. Mots-cles : debit, mesure, vitesse moyenne, vitesse maximale, entropie., 1. Introduction In urban hydrological management, the measurement of discharge in sewer networks is always an important task. Flow data are needed for multiple purposes, such as control of networks, [...]

This article proposes a hydraulic performance index to assess objectively and precisely the capacity of a culvert to drain the design flow without exceeding its inlet rating. As for the design, the proposed method is to apply a hydrological model to calculate the corresponding design flow for a given return period then use a hydraulic model to calculate the proposed hydraulic performance index. This index is then used to assess and compare the impacts of various external elements on the hydraulic performance of the culvert. The elements analysed and compared are the impact of climate changes, land use changes, settling, wear by corrosion and abrasion and the downstream influences. Key words: index, rehabilitation, performance, hydraulic, flood, route. [Journal translation] Le but du travail presente ici est de proposer un indice de performance hydraulique pour evaluer objectivement et precisement la capacite d'un ponceau a drainer le debit de conception sans depasser la cote maximale permise a son entree. La methodologie proposee consiste a appliquer, comme lors de la conception, un modele hydrologique pour calculer le debit de design correspondant a une periode de retour donnee, puis utiliser un modele hydraulique pour calculer l'indice de performance hydraulique propose. Cet indice a ete ensuite utilise pour evaluer et comparer les impacts de divers elements externes sur la performance hydraulique d'un ponceau. Ainsi, les impacts des changements climatiques, du changement d'occupation du sol, de la sedimentation, de l'usure par corrosion et abrasion et des influences avales sur la performance hydraulique d'un ponceau ont ete analyses et compares. Mots-cles : indice, rehabilitation, performance, hydraulique, inondation, route., 1. Introduction generale Il est de plus en plus reconnu que le rechauffement de la planete peut induire des temperatures estivales plus elevees entrainant plus d'evaporation durant l'ete et par [...]

Rounded stepped spillway experimental results are introduced and compared with the traditional sharp spillway. A shooting flow is recognized and introduced as a transition to the skimming flow. A quick attainment of the skimming flow is observed for rounded steps. The rounded stepped spillway is characterized by a 3% increase in the rate of energy dissipation. An increase in inception length is observed for the rounded spillway conveying small discharges, which indicates more flow stability and quicker transition to skimming flow. For high velocities (high discharges), increase in the mixed air-water length, which prevents the cavitation risk damage, is observed in rounded spillway. More inception depth and less training wall height are observed for rounded spillway. Training wall height for rounded chute is found to be 20% less than the sharp spillway. Generally, the study recommends using rounded steps for initial transition steps or for the main spillway steps rather than the sharp stepped traditional configuration. Key words: rounded stepped spillway, sharp stepped spillway, shooting flow, skimming flow, energy dissipation, two phase flow, flow characteristics, inception point, training wall. Les resultats experimentaux d'un deversoir en marches d'escalier arrondies sont presentes et compares a ceux d'un deversoir conventionnel a crete aceree. Un ecoulement torrentiel est reconnu et presente comme une transition vers un ecoulement extremement turbulent et, dans ce cas, l'ecoulement de surface est extremement turbulent. L'ecoulement extremement turbulent est rapidement atteint avec les marches arrondies. Le deversoir a marches arrondies se caracterise par une augmentation de 3 % du taux de dissipation d'energie. Une augmentation de la longueur de formation est remarquee pour les deversoirs en marches d'escalier arrondies sur lequel s'ecoulent de faibles debits, ce qui indique une plus grande stabilite de l'ecoulement et une transition plus rapide vers un ecoulement extremement turbulent. Pour les grandes vitesses (forts debits), l'augmentation de la longueur de melange air-eau, qui empeche les dommages par cavitation, est remarquee dans le deversoir en marches d'escalier arrondies. Une plus grande profondeur de formation et une hauteur inferieure des murs de direction sont observees dans les deversoirs en marches d'escalier arrondies. La hauteur des murs de direction pour les coursiers arrondis est de 20 % inferieure a celle du deversoir a crete aceree. L'etude recommande generalement d'utiliser des marches d'escalier arrondies pour les escaliers de transition initiale ou pour les marches d'escalier principales du deversoir plutot que d'utiliser la configuration conventionnelle a marches d'escalier a crete aceree. Mots-cles : deversoir en marches d'escalier arrondies, deversoir a escalier a crete aceree, ecoulement torrentiel, ecoulement extremement turbulent, dissipation d'energie, ecoulement diphasique, caracteristique de l'ecoulement, point de formation, mur de direction. [Traduit par la Redaction], Introduction As a consequence of using roller-compacted concrete (RCC) in dam construction, stepped spillways were built substituting smooth conventional spillways. A large reduction in the specific residual energy for stepped [...]

The main cause of rockfill and embankment dam failures is overtopping due to insufficient outlet works. During the last 15 years, the Civil Engineering Department: Hydraulics and Energy of the Technical University of Madrid has been studying the overtopping failure process of rockfill dams. One of the aims of this research is to develop design criteria of cost-effective rockfill dam protections to avoid failure due to such overtopping. Among the different types of known protection, this analysis has focused on downstream rockfill toes. The objective of this study is to achieve stability of the downstream shell of rockfill dams to prevent mass slides. This article summarizes the results of the preliminary experimental and numerical tests developed during the year 2008. Preliminary conclusions show the feasibility of this protection to mitigate partially or totally the serious consequences of overtopping in rockfill dams. Key words: overtopping, rockfill dams, slope protection, dams, cofferdams, embankments, earth dams, reinforcement, through-flow. La principale cause de defaillance des barrages en enrochement et en terre est le debordement en raison du manque d'ouvrages de decharge. Depuis 15 ans, le Departement de genie civil: hydraulique et energie, de l'Universite technique de Madrid, etudie le processus de defaillance des barrages en enrochement par debordement. L'un des objectifs de recherche est de developper des criteres de conception de protection rentable des barrages en enrochement afin d'eviter la defaillance par debordement. Parmi les divers types de protection actuellement connus, l' analyse a porte sur les pieds en enrochement en aval des barrages. L'objectif de la presente etude est de stabiliser la coquille aval des barrages en enrochement afin de prevenir les glissements. Cet article resume les resultats d'essais experimentaux et numeriques preliminaires developpes en 2008. Les conclusions preliminaires montrent la faisabilite de cette protection pour partiellement ou totalement attenuer les consequences graves du debordement des barrages en enrochement. Mots-cles: debordement, barrages en enrochement, protection des pentes, barrages, batardeaux, digues, barrages de terre, renforcement, ecoulement. [Traduit par la Redaction], 1. Background 1.1. Dam safety While there has been significant technological progress in the history of dam engineering, earthfill and rockfill dams remain vulnerable to overtopping, whereas safety requirements have [...]

Due to streamline curvature, non-hydrostatic pressure distribution, and nappe adherence on the weir wall, the discharge coefficient of weirs is less than 1.0. However, in cylindrical weirs, the discharge coefficient extends to values more than 1.0 due to the different pressures and velocity distributions. In this study, pressure and velocity distributions of different circular weirs are simulated by computational fluid dynamics (CFD) and Fluent software and compared with experimental results. The numerical results of CFD show a significant correlation with measured data from manometers and a laser Doppler velocimeter (LDV). Experimental observations show that the critical flow depth forms before and after the crest for greater and smaller discharge coefficients, respectively. Nappe separation depends on overflow discharge and will shift to the downstream face of the cylinder in high discharges. To recognize the location of critical flow and nappe separation, analytical formulations are proposed depending on weir size and inflow conditions. The results show good agreement between the analytical predictions and experimental observations. Key words: laboratory model, CFD, critical depth location. En raison de la courbe dans la ligne d'ecoulement, de la distribution non hydrostatique de la pression et de l'adherence de la lame deversante sur le mur du deversoir, le coefficient de debit des deversoirs est inferieur a 1,0. Toutefois, dans les deversoirs cylindriques, le coefficient de debit atteint des valeurs superieures a 1,0 en raison des pressions et des repartitions des vitesses differentes. La presente etude simule les repartitions des pressions et des vitesses de differents deversoirs circulaires en utilisant Fluent, un logiciel de dynamique numerique des fluides, et les compare aux resultats experimentaux. Les resultats numeriques de la dynamique numerique des fluides indiquent une correlation importante avec les donnees mesurees a partir de manometres et d'un velocimetre Doppler a laser. Les constatations des experiences montrent que la plus profondeur critique d'ecoulement se forme respectivement avant et apres la crete pour des profondeurs critique respectivement superieurs et inferieurs. La separation de la lame d'eau depend de la surverse et se deplacera vers la face aval du cylindre lors de grands debits. Afin de reconnaitre l'emplacement de l'ecoulement critique et de la separation de la lame d' eau, des formules analytiques sont proposees selon la dimension du deversoir et les conditions du debit entrant. Les resultats montrent une bonne correlation entre les previsions analytiques et les observations experimentales. Mots-cles: modele de laboratoire, dynamique numerique des fluides, emplacement de la profondeur critique. [Traduit par la Redaction], 1. Introduction Circular-crested or cylindrical weirs are one of the oldest hydraulic structures for discharge measurement. The advantages of the circular weirs include their stable overflow pattern compared to sharp-crested [...]

To test for threshold effects in the response of coral physiology to increasing seawater flow, field and laboratory experiments were conducted in Moorea. First, the growth of juvenile massive Porites spp. and branching P. irregularis was compared among habitats differing in water motion. Growth of massive Porites spp. responded to flow in a pattern consistent with a threshold effect, whereas growth of P. irregularis increased linearly with flow. Second, a recirculating flume was used to test the effect of flow on photophysiology ([increment of F]/[F.sub.m] effective photochemical efficiency) for massive Porites spp.; [increment of F]/[F.sub.m]' displayed a threshold response at 23 cm [s.sup.-1] and 28 ° C, but not at 31 ° G. Finally, intra-colony variation in the response of AF/Fm' to flow and temperature was explored to evaluate the functional significance of colony shape in small corals. [increment of F]/[F.sub.m]' on the top and upstream surfaces of massive Porites spp. responded with a threshold effect of flow at 28 ° C (but not 31 ° C), but [increment of F]/[F.sub.m]' on downstream surfaces was unresponsive to flow. [increment of F]/[F.sub.m]' for P. irregularis was less responsive to flow than for massive Porites spp., suggesting that the photophysiological response of corals to varying flow speeds may differ between species and morphologies. Together, these results emphasize that flow can have diverse effects on the physiology of corals, with the outcome depending on flow speed, temperature, location on the colony, and perhaps morphology., Introduction Over the last 25 years, large-scale bleaching of scleractinian corals through the loss of Symhiodinium algae, their chlorophyll, or both has become common (Fitt et ai, 2001), and is [...]

We report the first numerical tests of the two-dimensional vertically-averaged and moment (VAM) equations to simulate scour and deposition along alluvial meandering rivers with fixed banks. The VAM hydrodynamic model assumes a linear vertical distribution of the velocity profile and provides estimates of the magnitude and direction of the both near-bed and surface velocity vectors in a quasi three-dimensional (3D) fashion, reproducing at a very basic level some of the 3D effects of the secondary flow in bends. By assuming that the bed shear stress direction along the bed was given by the VAM's near-bed velocity direction, it was possible to successfully reproduce the scour and deposition observed in a curved experimental flume and a meandering river reach. Although the VAM model is more general and does not require a secondary flow correction, as needed by conventional depth-averaged models, the results were not significantly better for the two cases analyzed. Key words: curved open channels, meandering rivers, sediment transport, two-dimensional. Cet article traite des premiers essais numeriques d'equations bidimensionnelles a moyenne verticale et de moment (VAM) utilisees pour simuler l'affouillement et la deposition le long de rivieres alluviales a meandres avec des rives fixes. Le modele hydrodynamique VAM presume une distribution verticale lineaire du profil des vitesses et estime l'amplitude et la direction des vecteurs de vitesse pres du lit et a la surface de maniere quasi tridimensionnelle, reproduisant en gros certains des effets tridimensionnels de l'ecoulement secondaire dans les coudes. En presumant que la direction de cisaillement du lit le long du lit est donne par la direction de vitesse pres du lit tel qu'etablie par la VAM, il a ete possible de reproduire adequatement l'affouillement et la deposition observes dans un canal experimental courbe et dans un troncon de riviere a meandres. Bien que le modele VAM soit plus generaliste et ne demande pas de correction pour l'ecoulement secondaire, tel que requis par les modeles conventionnels avec moyenne par rapport a la profondeur, les resultats n'etaient pas bien meilleurs pour les deux cas analyses. Mots-cles: canaux courbes a surface libre, rivieres a meandres, transport de sediments, bidimensionnel. [Traduit par la Redaction], Introduction Modeling flow in alluvial bends Meandering is a common planform geometry found in many alluvial rivers, characterized by a sinuous channel pattern of alternating bends. Along these bends, in [...]

The flow recovery in the wake of a surface-mounted flat plate is investigated in an open channel. The plate with a thickness-to-chord ratio (t/c) of 0.12 is placed with the chord parallel to the flow. The characteristics of the mean velocity and higher-order statistics obtained along the wake axis upstream and downstream of the plate are discussed in the presence of bed roughness. Inner scaling of the mean velocity profile shows a depression in the outer region of the flow. The near-wall portion of the velocity profile in the plate wake region was found to recover faster to the upstream state. The profiles of the turbulent intensity in the plate wake deviate from the upstream profiles and recover gradually with downstream distance. The upstream turbulent intensities for the wire-mesh rough surface peak at farther wall normal locations compared to those of the sand grain and smooth surfaces. A similar roughness effect was observed at the downstream locations amidst the distorted flow, especially, in the intermediate and far wake regions. In the near- and intermediate-wake regions, both the velocity skewness and flatness factors data for the rough walls were higher compared to the data for the smooth surface. For all surfaces, even at the last measuring station (x = 200t) considered in the study, the skewness and flatness factors were found to be still recovering to the upstream condition. Key words: open channel flow, rough wall boundary layer flow, flow recovery, flat plate, wake flow. Le retablissement du debit dans le sillage d'une plaque plane installee en surface est examine dans un canal a surface libre. La plaque, dont le rapport de l'epaisseur a la corde est de 0,12, est installee avec la corde parallele a l'ecoulement. Les caracteristiques de la vitesse moyenne et les statistiques de niveau superieur obtenues le long de l'axe de sillage en amont et en aval de la plaque sont abordees en rapport avec la rugosite du lit. La mise a echelle du profil de vitesse moyenne interne montre une depression dans la region externe de l'ecoulement. La portion du profil de vitesse pres de la paroi dans la region du sillage de la plaque revient plus vite a l'etat present en amont. Les profils de l'intensite de la turbulence dans le sillage de la plaque s'eloignent des profils en amont et reprennent graduellement plus loin en aval. Les intensites turbulentes en amont de la surface rugueuse du grillage metallique atteignent une intensite maximale plus loin aux emplacements normaux sur le mur par rapport a celles observees pour les surfaces en sable et lisses. Un effet de rugosite similaire a ete remarque aux endroits en aval dans l'ecoulement deforme, plus particulierement dans les regions intermediaires et eloignees du sillage. Dans les regions intermediaries et rapprochees du sillage, les donnees des facteurs d'asymetrie de la vitesse et de planeite des murs rugueux etaient plus elevees que les donnees pour une surface lisse. Il a ete revele que les facteurs d'asymetrie et de planeite de toutes les surfaces, meme a la derniere station de mesure (x = 200t)del'etude, etaient toujours en recuperation des conditions en amont. Mots-cles : ecoulement en canal a surface libre, ecoulement de la couche limite a une paroi rugueuse, retablissement du debit, plaque plane, sillage. [Traduit par la Redaction], 1. Introduction The flow field behind surface mounted objects has been studied extensively. Examples of such flows are many and include the fluid-structure interaction involving flow past buildings, mixing of [...]

Water is a primary control on the generation of acidic ([H.sub.2]S[O.sub.4]) effluent from commercial-scale sulphur ([S.sup.0]) blocks. Although clean [S.sup.0] is strongly hydrophobic, microbial colonization of fracture faces and friable [S.sup.0] generates localized hydrophilic conditions. Infiltration occurs preferentially along discrete fractures and in areas of friable [S.sup.0]. Surface evaporation rates are low (mean 0.2 mm/day), and >90% of rainfall infiltrates and rapidly drains from the blocks. A conceptual model to describe the flow and storage of water at the base of [S.sup.0] blocks was developed and tested. The [S.sup.0] blocks were represented as a hydrophilic equivalent porous medium, and lateral drainage through the base of the blocks was quantified using a two-dimensional numerical model. Specific yield ([S.sub.y]) and saturated hydraulic conductivity ([K.sub.s]) values were estimated to be ~4%-7% and ~1x[10.sup.-2] m/s, respectively, by comparing measured and modelled pore-water pressure head and outflow responses to rainfall events. Given that commercial-scale [S.sup.0] blocks are constructed in a similar manner worldwide, the results of this study are considered widely applicable in designing [S.sup.0] block storage facilities that minimize water availability and [H.sub.2]S[O.sub.4] production in [S.sup.0] blocks. Key words: sulphur blocks, dye tracer, infiltration, hydrophobic, fractured, acidic drainage. L'eau est le principal element controlant la generation d'effluents acides ([H.sub.2]S[O.sub.4]) provenant de blocs de soufre ([S.sup.0]) des installations commerciales. Meme si le [S.sup.0] propre est fortement hydrophobe, la colonisation microbienne des faces des fractures et du [S.sup.0] friable genere des conditions localement hydrophiles. Le taux d'evaporation a la surface est faible (moyenne de 0,2 mm/jour) et plus de 90 % des precipitations s'infiltrent et sont rapidement drainees des blocs. Un modele conceptuel decrivant l'ecoulement et l'emmagasinage de l'eau a la base des blocs de [S.sup.0] a ete developpe et teste. Les blocs de [S.sup.0] sont representes par un medium poreux hydrophile equivalent, et le drainage lateral a travers la base des blocs a ete quantifie par un modele numerique en deux dimensions. Le debit specifique ([S.sub.y]) et la conductivite hydraulique ([K.sub.s]) ont ete estimes a ~4-7 % and ~1x[10.sup.-2] m/s, respectivement, en comparant les valeurs mesurees et modelisees des pressions de l'eau interstitielle et les debits a la sortie suivant des periodes de pluie. Puisque les operations commerciales de fabrication de blocs de [S.sup.0] utilisent une procedure similaire d'un pays a l'autre, les resultats de cette etude sont applicables de facon generale a la conception d'installations d'entreposage des blocs de [S.sup.0] qui minimisent la disponibilite de l'eau et la production de [H.sub.2[S[O.sub.4] des blocs de [S.sup.0]. Mots-cles : blocs de soufre, encre traceur, infiltration, hydrophobe, fracture, drainage acide. [Traduit par la Redaction], Introduction Elemental sulphur ([S.sup.0]) has been stockpiled over the past 20 years due to a global [S.sup.0] surplus (Ober 2002). Increased [S.sup.0] production at petroleum refineries, natural gas plants, coking [...]

Techniques for modelling marine pollution have been studied for decades. Specialized modelling methods have been used to simulate pollutant dispersion resulting from offshore outfall. These include empirical and analytical methods, particle tracking method, finite difference and finite element solutions for solving the advection-diffusion equations, and jet integral methods. In the application of these methods, various models have been developed to address ocean discharge problems. This paper reviews modelling techniques associated with simulation of wastewater dispersion discharged from offshore outfalls based on type of method and the physical process of the ocean discharge, such as near-field and far- field modelling. The advantages and limitations of the major mathematical methods are analyzed, as well as their functionality and the availability of modelling software. The development of numerous modelling approaches and software, both commercial and academic, reflects the growing importance and interest in ocean environmental assessment. This review also discusses future trends for development in this field. Key words: fate, transport, offshore discharge, modelling, wastewater, review. On a etudie les techniques de modelisation de la pollution marine depuis des decades. Les methodes de modelisation specialisees ont ete utilisees pour simuler la dispersion de polluants marins provenant de rejets au large des cotes incluant des methodes analytiques, la methode de suivi des particules, la difference definissable et les solutions elementaires definissables pour resoudre les equations d'advection-diffusion, ainsi que les methodes integrales de jet. Dans l'application de ces methodes, on a developpe divers modeles pour traiter des problemes de rejets dans l'ocean. Les auteurs passent en revue les techniques de modelisation associees a la dispersion des eaux usees deechargees lors de rejets au large des cotes, selon le type de la methode, et le processus physique de la decharge oceanique, tel le modelage de champ rapproche et de champ eloigne. On analyse les avantages et la limitation des principales methodes mathematiques et leur fonctionnalite, ainsi que la disponibilite de logiciels. Le developpement de nombreuses approches de modelisation et de logiciels, commerciaux aussi bien qu'academiques, reflete l'importance croissante et Tinteret de revaluation environnementale des oceans; cette revue discute les tendances futures de developpement dans ce domaine. Mots-cles: devenir et transport, decharges au large des cotes, modelisation, eaux usees, revue. [Traduit par la Redaction], 1. Introduction Increasingly, offshore outfalls are being used for the disposal of wastewater in coastal areas. Because the discharged effluents generally exert different velocity, temperature, and density compared with the [...]