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Numerical simulations of free-surface flows are important to provide a prediction tool for the optimal management of irrigation canals. Here, we consider an alternative to solving the shallow-water equations. We propose a free-surface model in which the vertical component of the water current is fully resolved. We believe that such a detailed description can be useful to model the flow around gates or in other situations where the vertical structure of the flow will be important such as in the case of sediment transport and deposition. Our approach is based on a two-fluid lattice Boltzmann model. We compare the predictions obtained from numerical simulation and experiments performed on a laboratory microcanal facility. DOI: 10.1061/(ASCE)IR.1943-4774.0000260 CE Database subject headings: Irrigation; Open channels; Numerical models; Two-dimensional models; Gates; Flow simulation. Author keywords: Lattice Boltzmann models; Free-surface hydraulic; Irrigation channels; Numerical two-dimensional models; Gates equations.

The exchange flow through the Burlington Ship Canal connecting Hamilton Harbour with Lake Ontario is investigated, using a two-layer internal hydraulics model. The summer exchange features an upper layer of polluted Harbour Water flowing from the harbour into the lake, whereas a lower layer of fresh Lake Ontario Water flowing from the lake into the harbour. We predict this exchange, taking into account the effects of both friction and barotropic forcing of multiple frequencies. Predictions of density interface and volume flux compare well with experimental and field data. The interface varies non-linearly with distance along the canal, with and without barotropic forcing. Our results indicate that the exchange flow is highly frictional. The barotropic forcing comprises oscillation modes of different frequency; these individual forcing modes cause the interface and layer velocities to fluctuate significantly in time, but their influence on the time average flows through the canal is minimal. Key words: exchange flow, two-layer hydraulics model, Burlington Ship Canal, Hamilton Harbour, Lake Ontario, density stratified flow. L'ecoulement d'echange dans le canal maritime de Burlington reliant le Port de Hamilton et le Lac Ontario est etudie en utilisant un modele hydraulique interne a deux couches. L'echange estival comporte une couche supeerieure d'eau pollueee du port s'ecoulant du port vers le lac, alors qu'une couche infeerieure d'eau douce du Lac Ontario s'eecoule du lac vers le port. Nous predisons cet echange en tenant compte des effets du frottement et du forcage barotrope a multiples frequences. Les previsions de l'interface de densite et du volume d'ecoulement se comparent bien aux donneees experimentales et celles obtenues sur le terrain. L'interference varie de maniere non lineeaire avec la distance le long du canal, avec et sans forcage barotrope. Nos resultats montrent que l'ecoulement d'echange a un tres fort coefficient de frottement. Le forcage barotrope comprend des modes d'oscillation a differentes frequences. Ces modes individuels de forcage feront beaucoup fluctuer l'interface et les vitesses des couches dans le temps, mais leur influence est minimale sur les ecoulements pondereis dans le temps dans le canal. Mots-cles: ecoulement d'echange, modele hydraulique a deux couches, canal maritime de Burlington, Port de Hamilton, lac Ontario, stratification d'ecoulement lieee a un gradient de densite;. [Traduit par la Redaction], Introduction The Burlington Ship Canal is a straight, rectangular channel that connects Lake Ontario with Hamilton Harbour (Figs. 1a,1b). The harbour has been receiving a large amount of industrial and [...]

Fluid loads on a variety of hydraulic structures and the free surface profile of the flow are important for design purposes. This is a difficult task because the governing equations have nonlinear boundary conditions. The main objective of this paper is to develop a procedure based on the natural element method (NEM) for computation of free surface profiles, velocity and pressure distributions, and flow rates for a two-dimensional gravity fluid flow under sluice gates. Natural element method is a numerical technique in the field of computational mechanics and can be considered as a meshless method. In this analysis, the fluid was assumed to be inviscid and incompressible. The results obtained in the paper were confirmed via a hydraulic model test. Calculation results indicate a good agreement with previous flow solutions for the water surface profiles and pressure distributions throughout the flow domain and on the gate. Key words: free surface flow, meshless methods, meshfree methods, natural element method, sluice gate, hydraulic structures. Les charges de fluides sur les structures hydrauliques et le profil de la surface libre de l'eecoulement sont importants aux fins de conception. Cette conception est une tache difficile puisque les equations principales presentent des conditions limites non lineeaires. Cet article a comme objectif principal de developper une procedure basee sur la methode des elements naturels (NEM) pour calculer les profils de la surface libre, les distributions de vitesse et de pression ainsi que les debits pour un ecoulement gravitaire bidimensionnel sous les panneaux de vannes. La NEM est une technique numeerique dans le domaine de la meecanique computationnelle et peut etre consideree comme etant une methode sans maillage. Dans la presente analyse, le fluide etait presume etre exempt de viscosite et incompressible. Les resultats obtenus ont ete verifies par un essai du modele hydraulique. Les resultats des calculs montrent une bonne correlation entre les solutions d'ecoulement anterieures pour les profils de surface de l'eau et les distributions de pression dans tout l'ecoulement et sur la vanne. Mots-cles: ecoulement de surface libre, meethodes sans maillage, methode par elements naturels, panneaux de vanne, structures hydrauliques. [Traduit par la Redaction], Introduction The analysis of two-dimensional gravity affected flows involving a free surface is an important area of research in hydraulic engineering. Examples include flows over hydraulic structures such as spillways, [...]

Quantitative relationships between soil structure, especially macropore characteristics, and soil hydraulic properties are essential to improving our ability to predict flow and transport in structured soils. The objectives of this study were to quantitatively relate macropore characteristics to saturated hydraulic conductivity ([K.sub.sat]) and dispersivity ([lambda]) and to identify major macropore characteristics useful for estimating soil hydraulic properties under saturated condition. Large intact soil columns were taken from two land uses (cropland and pasture) of the same soil type (a Typic Hapludalf), with four replicates for each land use. The soil columns were scanned using X-ray computed tomography (CT) to obtain macropore parameters including macroporosity, length density, mean tortuosity, network density, hydraulic radius, path number, node density, and mean angle. The [K.sub.sat] of the whole soil column, as well as each soil horizon within the column, and solute breakthrough curve (BTC) of Ca[Br.sub.2] were determined for each column. For all eight soil columns studied, macroporosity and path number (the number of independent macropore paths between two boundaries) explained 71 to 75% of the variability in the natural logarithm of [K.sub.sat] values of the whole soil columns as well as of individual soil horizons. The traditional convection--dispersion equation (equilibrium model) simulated the BTCs well for all soil columns except one with an earthworm hole passing through the entire column, for which the two-region model (non-equilibrium model) was required. The path number, hydraulic radius, and macropore angle were the best predictors for [lambda], explaining 97% of its variability. Correlation between), of the whole soil columns and [K.sub.sat] values of the Bt horizons (but not A horizons) implied that the dispersivity was mainly controlled by the horizon with the lowest [K.sub.sat] in the soil columns. These results indicate that the most useful macropore parameters for predicting flow and transport under saturated condition in structured soils included macroporosity, path number, hydraulic radius, and macropore angle. doi: 10.2136/sssaj2010.0062

Turbulent momentum and velocity always have the greatest gradient along wall-normal direction in straight channel flows; this has led to the hypothesis that surplus energy within any control volume in a three-dimensional flow will be transferred toward its nearest boundary to dissipate. Starting from this, the boundary shear stress, the Reynolds shear stress, and the velocity profiles along normal lines of smooth boundary may be determined. This paper is a continuous effort to investigate depth-average shear stress and velocity in rough channels. Equations of the depth-averaged shear stress in typical open channels have been derived based on a theoretical relation between the depth-averaged shear stress and boundary shear stress. Equation of depth mean velocity in a rough channel is also obtained and the effects of water surface (or dip phenomenon) and roughness are included. Experimental data available in the literature have been used for verification that shows that the model reasonably agrees with the measured data. DOI: 10.1061/(ASCE)HY.1943-7900.0000271 CE Database subject headings: Boundary shear; Reynolds stress; Velocity distribution; Open channel flow; Turbulent diffusion; Shear stress. Author keywords: Boundary shear; Reynolds stress; Velocity distribution; Open-channel flow; Turbulent diffusion.

Turbulence is the fundamental mechanism governing energy transfer in river flows that was conventionally examined in laboratory flumes. Recently, a trend has been observed for constructing larger scale and outdoor facilities that tend to avoid the problems of upscaling of experimental results. This paper presents the results of an experimental study performed on a river reach used as an environmental field laboratory. The study is focused on the understanding of the spatial arrangement of the flow structure and its dependency on the temporal variability of the flow. Detailed measurements were taken using acoustic Doppler velocimeters and their analysis was completed applying the theory of open-channel flows. The obtained results reveal that the flow structure on the river reach resembles characteristics of a typical three-dimensional open-channel flow. Away from the riverbanks, the flow behaves as a quasi-two-dimensional fully developed turbulent open-channel flow thus providing conditions favorable for field experimental studies of shallow mixing layers and flows over patches of submerged aquatic plants. An interesting observation in the seasonal dynamics of turbulent shear stress patterns was that the height of the roughness layer was reduced in the central part of the flow, though the overall roughness coefficient was increased. At the same time, the structure of the secondary flow near the banks was also substantially altered as the secondary circulations observed at low water levels were replaced by flow separation and internal boundary layers at medium water levels. DOI: 10.1061/(ASCE)HY.1943-7900.0000267 CE Database subject headings: Turbulence; Rivers; Hydrodynamics; Field tests; Shear stress; Fluid dynamics. Author keywords: Turbulence; River hydrodynamics; Field study; Turbulent shear stresses.

Vortex drop shafts are used in urban drainage systems to connect two sewers located at considerably different elevations. After their introduction in 1947, these were studied with particular reference to subcritical approach flow. Vortex shafts for supercritical approach flow can also be used, but the intake structure may have relatively high cost due to the complex geometry. The present study includes experimental results of a specific investigation on the changes to be made in the supercritical approach channel if a subcritical vortex intake is used. The experimental investigation analyzes the effect of a hydraulic jump on the performance of vortex intake structure to define appropriate technical solutions, essentially consisting in a negative step to be located along the supercritical approach channel. Design criteria are finally presented for the evaluation of the step height and its distance from the vortex intake structure. DOI: 10.1061/(ASCE)HY.1943-7900.0000249 CE Database subject headings: Energy dissipation; Hydraulic jump; Sewers; Shafts; Drop structure; Critical flow; Intake structures. Author keywords: Energy dissipation; Hydraulic jump; Sewer hydraulics; Vortex shaft; Drop structure.

An exponential distribution of the bed-pressure fluctuations is used to estimate the depth within a porous gravel bed from which fine sediment of a given size can be removed. The coarsest grain size of the fine sediment that might be washed out is of O([10.sup.-1]) in relation to both the gravel grain size and the equivalent grain roughness. A higher equivalent grain roughness results to a larger absolute cleaning depth, whereas the averaged gravel grain size is seen to be less important. The results are successfully tested for plausibility against the grain size distributions of an armored gravel bed and its underlaying bimodal layer as found in situ in the river Rhine. However, qualitative and quantitative experimental data for an in-depth validation remain to be performed. DOI: 10.1061/(ASCE)HY.1943-7900.0000263 CE Database subject headings: Open channel flow; Gravel; River beds; Turbulence; Sediment. Author keywords: Open-channel flow; Gravel bed; Turbulence; Flushing flows; Fine sediment.

The statistics of pressure fluctuations above and within three types of porous granular beds such as in gravel bed streams, rivers, and man-made canals are investigated by data gained via laboratory flume experiments. The flow conditions examined include a diversity of hydrodynamic loads that increase up to the point where single grains are moving from time to time, without causing severe modification to the bed texture and the related positions of the pressure sensors. Analysis is performed by means of histograms and spectral techniques and vertical intensity profiles. Two simplified equations are found that describe the vertical decrease for the standard deviation of the measured fluctuations indicating drag and lift, respectively, nondimensionalized by the mean bed shear stress. The former fluctuation is described by a crude linear fit, whereas the latter clearly shows that the lift intensity decreases exponentially in the porous bed with a decay distance of one to two times the equivalent grain roughness. Within the subsurface layer the standard deviation reaches a nonzero constant, mainly dominated by long-wave pressure fields that are convected in the outer flow. These findings can be used in future sediment transport models that use force balance approaches to determine incipient motion conditions. DOI: 10.1061/(ASCE)HY.1943-7900.0000251 CE Database subject headings: Open channel flow; Gravel; Turbulence; Power spectral density; Laboratory tests; River beds. Author keywords: Open-channel flow; Gravel bed; Turbulence; Pressure fluctuation; Spectral density; Interstitial.

A model for the production of isovel contours in a normalized form, which can be used for estimation of discharge in artificial and natural channels by using a single point of measurement, has been introduced previously by Maghrebi in 2006. Herein, for the first time, application of the model to a tidal river with partially reverse flow, which is caused by opening a sluice gate located asymmetrically close to the right bank of the Ohta floodway in Hiroshima, Japan, is presented. An acoustic Doppler current profiler was used to measure the velocity profiles at different verticals (with several points at each vertical) and then discharge was calculated. In addition, estimated discharge based on each measured point with the aid of the model was obtained. For the measured points away from the low magnitude of isovel values, the predicted discharges are comparable with the measured one. Due to the fluctuations of the measured velocities, instead of a single point of measurement, vertical and horizontal groupings of the measured points were used to estimate the discharge. It is generally proposed to select the measured points from the regions with the corresponding high values of isovels in the range of u/V 0.5. The overall results have shown that minimum errors are associated with the horizontal groupings. DOI: 10.1061/(ASCE)WW.1943-5460.0000049 CE Database subject headings: Tidal currents; River flow; Water discharge. Author keywords: ADCP; Discharge estimation; Isovel contours; Reverse flow; Tidal river; Couette flow.

The flow problem of an incompressible axisymmetrical quasisteady translation and steady rotation of a porous spheroid in a concentric spheroidal container are studied analytically. The same small departure from a sphere is considered for each spheroidal surface. In the limit of small Reynolds number, the Brinkman equation for the flow inside the porous region and the Stokes equation for the outside region in their stream functions formulations and velocity components, which are proportional to the translational and angular velocities, respectively, are used. Explicit expressions are obtained for both inside and outside flow fields to the first order in a small parameter characterizing the deformation of the spheroidal surface from the spherical shape. The hydrodynamic drag force and couple exerted on the porous spheroid are obtained for the special cases of prolate and oblate spheroids in closed forms. The dependence of the normalized wall-corrected translational and rotational mobilities on permeability for a porous spheroid in an unbounded medium and for a solid spheroid in a cell on the particle volume fraction is discussed numerically and graphically for various values of the deformation parameter. In the limiting cases, the analytical solutions describing the drag force and torque or mobilities for a porous spheroid in the spheroidal vessel reduce to those for a solid sphere and for a porous sphere in a spherical cell. PACS Nos: 47.15.G-, 47.56.+r Nous etudions analytiquement le probleme de la translation incompressible, axysimeetrique et en rotation stationnaire d'un spheroide poreux dans un contenant spheroidal concentrique. Le meme petit ecart d'une sphere est etudie pour chaque surface spheroidale. Dans la limite des petits nombres de Reynolds, nous utilisons l'eequation de Brinkman pour l'ecoulement a l'inteerieur d'une region poreuse et l'eequation de Stokes pour la region exterieure dans leurs formulations de la fonction de courant et des composantes de la vitesse, qui sont proportionnelles aux vitesses de translation et de rotation respectivement, tel qu'utilisee. Nous obtenons des expressions explicites pour les ecoulements a la fois interieur et exterieur, au premier ordre du parametre definissant la non sphericite des surfaces spheroidales. Nous derivons analytiquement la force de trainee hydrodynamique et le couple exerces sur le spheroide poreux pour les cas speeciaux de spheroides allonges et aplatis. Nous discutons numeriquement et graphiquement pour un spheroide poreux la deependance des mobilites translationnelle et rotationnelle, normaliseies pour la correction due au mur, sur la permeiabilite; dans un milieu non borne; et pour un spheroide solide dans une cellule, la dependance sur la fraction de volume de la particule. Dans les cas limites, les solutions analytiques decrivant la force de trainee et le torque ou les mobilites pour un spheroide poreux dans un contenant spheroidal se reduisent a celles pour une sphere solide et pour une sphere poreuse dans une cellule spherique. [Traduit par la Redaction], 1. Introduction The problems of uniform flow past and through porous media have several important applications, notably in the flow of oil through porous rocks, extractions of energy from geothermal [...]

The six-degrees-of-freedom ship motions of a ship at speeds other than zero are always measured in terms of encounter frequency, and often, the incident waves in experimental data are also measured only in the encounter frequency domain. Using these measured data to obtain transfer functions from irregular following sea ship motions is complicated by the combined effects of very low encounter frequencies and the 'folding' of the sea spectra. This results in having both overtaking and encountered waves of the same encounter frequency bur different wavelengths. Computing transfer functions becomes untenable when the ship speed approaches the wave phase velocity, where the encounter spectrum has a mathematical singularity. St. Denis and Pierson (1953, 'On the Motions of Ships in Confused Seas,' Soc. Nav. Archit. Mar. Eng., Trans., 61, pp. 280-357) suggested the basic relationships between response ship motions or moments that can be developed in the wave frequency domain at the outset. The St. Denis-Pierson method is based on a linear theory and works well when the ship response regime is linear or weakly nonlinear. However, for high-speed craft operating at different headings where the problems are nonlinear, especially strongly nonlinear, the St. Denis-Pierson assumptions will break down inducing error (1953, 'On the Motions of Ships in Confused Seas,' Soc. Nav. Archit. Mar. Eng., Trans., 61, pp. 280-357). Furthermore, using the frequency resolution method to remove the singularity point may also induce errors, especially when the singularity point is located near the peak of stationary frequency. How to obtain the correct frequency resolution in the local region of singularity point is still an unsolved problem. In this study, we will propose a new method capable of predicting ship response motions for crafts with nonlinear or strongly nonlinear behaviors quantitatively. For example, using this method, one can use measured ship motion data in head seas to predict the motions of the ship at high speed in following seas. The new method has six steps, including using a filter to eliminate those unexpected modes that are not from incident waves, inertial motions, or nonlinear interactions, and applying a higher-order Taylor expansion to eliminate the singularity point. We refer to the new method as the Lin-Hoyt method, which agrees reasonably well with computations of the nonlinear 'digital, self-consistent, ship experimental laboratory ship motion model,' also known as DiSSEL (2006, 'Numerical Modeling of Nonlinear Interactions Between Ships and Surface Gravity Waves H: Ship Boundary Condition,' J. Ship Res., 50(2), pp. 181-186). We also use experimental head sea data to validate the simulations of DiSSEL. The Lin-Hoyt method is fast and inexpensive. The differences in the results of the numerical simulations obtained by the Lin-Hoyt method and other linear methods diverge rapidly with increased forward ship speed due to the nonlinearity of ship motion responses. [DOI: 10.1115/1.4000502]

The transverse vibratory response of a long, slender vertical top tension riser, subject to an ocean current, is studied. The problem is treated as a coupled fluid flow/vibration problem, which is solved numerically. The fluid flow part is represented by the 2D Navier-Stokes equations, with large-eddy simulation turbulence modeling and strip theory, which are solved numerically to obtain the flow field and determine the vortex-shedding behavior in the flow. The approach flow is a shear flow ranging in Reynolds number from 8000 to 10,000. Given the flow field and vortex-shedding behavior, the transverse fluid forcing function can be determined at a given instant, which becomes the input to the Euler-Bernoulli beam equation to calculate the displacement of the riser, using a technique that involves the Wentzel-Kramers-Brillouin (WKB) method and modal decomposition. The boundary conditions for the fluid flow equations are updated each time step as the cylinder moves. The natural frequency of the riser is tension dominated, not bending-stiffness dominated. With the decrease in tension with increasing depth, the natural frequency is affected. Therefore, the solution will be influenced by the depth-dependent tension. This study has indicated some interesting features regarding the vortex-induced vibration of a variable-tension riser. The vibrational response is greater for a variable-tension riser than for a constant-tension riser, when the variable-tension riser is assumed to have the same top tension as the constant-tension riser. Thus, this is one reason why it is important to take into account the variable tension when estimating fatigue failures of marine risers. [DOI: 10.1115/1.4000500]

This paper advanced our recent effort (Li and Calisal, 2007, 'Preliminary Result of a Discrete Vortex Method for Individual Marine Current Turbine,' The 26th ASME International Conference on Offshore Mechanics and Arctic Engineering, Jun. 10-15, San Diego, CA) to study the behavior of tidal-current turbines. We propose a discrete-vortex method with free-wake structure (DVM-UBC) to describe the behavior of a stand-alone tidal-current turbine and its surrounding unsteady flow and develop a numerical model to predict the performance and wake structure of the turbine based on DVM-UBC. To validate this method, we conducted a series of towing tank tests. DVM-UBC is then validated with several kinematic and dynamic results. When we compared the results obtained with DVM-UBC with our towing tank test results, published results, and the results obtained with other numerical methods, we achieved good agreements. Our comparisons also suggested that DVM-UBC can predict the performance of a turbine 50% more accurately than the traditional discrete-vortex method (traditional DVM) with comparable computational effort and will produce results comparable to the Reynolds averaged Navier-Stokes equation with much less computational effort. [DOI: 10.1115/1.4000499] Keywords: tidal power, tidal-current, discrete-vortex method, unsteady flow, viscous effect, numerical simulation, kinematic and dynamic validation, towing tank test

Recently, some riser vortex-induced vibrations (VIVs) experimental data have been made publicly available (oe.mit.edu/VIV/) including a 10 m riser VIV experiment performed by Marintek, Trondheim, Norway, and donated by ExxonMobil URC, Houston, TX, USA. This paper presents our numerical simulation results for this 10 m riser and the comparisons with the experimental results in uniform current. The riser was made of a 10 m brass pipe with an outer diameter of O.02 m (L/D = 482) and a mass ratio of 1.75. The riser was positioned vertically with top tension of 817 N and pinned at its two ends to the test rig. Rotating the rig in the wave tank would simulate the uniform current. In the present numerical simulation the riser's ends were pinned to the ground and a uniform far field incoming current was imposed. The riser and its surrounding fluid were discretized using 1.5 x [10.sup.6] elements. The flow field is solved using an unsteady Reynolds-averaged Navier-Stokes (RANS) numerical method in conjunction with a chimera domain decomposition approach with overset grids. The riser is also discretized into 250 segments. Its motion is predicted through a tensioned beam motion equation with external force obtained by integrating viscous and pressure loads on the riser surface. Then the critical parameters including riser VIV amplitude (a) to the riser outer diameter (D) ratio (a/D), vorticity contours, and motion trajectories were processed. The same parameters for the experimental data were also processed since these data sets are in 'raw time-histories' format. Finally, comparisons are made and conclusions are drawn. The present numerical method predicts similar dominant modes and amplitudes as the experiment. It is also shown that the cross flow VIV in the riser top section is not symmetric to that of the bottom section. One end has considerably higher cross flow vibrations than the other end, which is due to the nondominant modal vibrations in both in-line and cross flow directions. The computational fluid dynamics (CFD) simulation results also agree with the experimental results very well on the riser vibrating pattern and higher harmonics response. The higher harmonics were studied and it is found that they are related to the lift coefficients, hence the vortex shedding patterns. It is concluded that the present CFD approach is able to provide reasonable results and is suitable for 3D riser VIV analysis in deepwater and complex current conditions. [DOI: 10.1115/1.4000498]

Empirical downstream hydraulic geometry equations for consolidated clay-dominated cohesive bed (nonalluvial) natural streams are presented using data from six rivers in eastern Ontario, Canada and four rivers from other regions. The width exponent (0.57) was comparable to the exponents reported for previous studies; however, the depth exponent (0.52) was greater for clay- dominated cohesive bed than for typical alluvial gravel-bed and sand-bed rivers. The width to depth ratio of smaller channels ([Q.sub.bf] < 20 [m.sup.3]/s) was greater for consolidated clay bed than for either sand-bed or gravel-bed channels. This study suggests that the concept of hydraulic geometry and bankfull (channel forming) discharge can be extended to nonalluvial consolidated clay-bed channels. DOI: 10.1061/(ASCE)HY.1943-7900.0000199 CE Database subject headings: Clays; River beds; River flow; Geometry; Channels; Design; Fluvial hydraulics; Geomorphology; Canada. Author keywords: Clay; River beds; River flow; Geometry; Channel design; Fluvial Hydraulics; Geomorphology.

This study presents experimental results on the flow of magnetorheological grease (MRG) through microchannels. MR materials flowing through microchannels create microvalves. The flow is controlled by injecting the MRG through microchannels with controlled adjustable rates. To study the effect of different channel diameters and surface roughnesses, microchannels made of stainless steel, PEEK, and fused silica materials with nominal internal diameters ranging from 1 mm to 0.075 mm (75 [micro]m) are tested. A magnetic field is applied perpendicular to the microchannel flow and is controlled by an input electric current. The pressure drop of the flow is measured across the length of the microchannels. The dynamic pressure drop range and surface roughness effects are also discussed. The Herschel--Bulkley model for non-Newtonian fluid flow is employed to the experimental results with good agreement. The results show a significant pressure drop for different magnetic field strengths. [DOI: 10.1115/1.4000922]

Displacement of isotopic compositions at boundary layers across strata of contrasting composition is commonly used to investigate hydrothermal fluid flow during orogeny. This study investigates whether hydrothermal fluid flow was focused along the Islay Anticline, Islay, SW Highlands of Scotland, as shown in the axial zone of the neighbouring Ardrishaig Anticline. Four localities from the limb to the axial plane of the Islay Anticline were investigated for isotopic homogenization of metacarbonate units to silicate values. At Mull of Oa on the limb of the anticline, metacarbonate samples show limited isotopic resetting and the fluid flux is estimated to be doi: 10.1144/0016-76492009-135.

The coupling and interactions between ship motion and inner-tank sloshing are investigated by a potential-viscous hybrid method in the time domain. For the time-domain simulation of vessel motion, the hydrodynamic coefficients and wave forces are obtained by a potential-theory-based 3D diffraction/radiation panel program in the frequency domain. Then, the corresponding simulations of motions in the time domain are carried out using the convolution-integral method. The liquid sloshing in a tank is simulated in the time domain by a Navier--Stokes solver. A finite difference method with SURF scheme assuming the single-valued free-surface profile is applied for the direct simulation of liquid sloshing. The computed sloshing forces and moments are then applied as external excitations to the ship motion. The calculated ship motion is in turn inputted as the excitation for liquid sloshing, which is repeated for the ensuing time steps. For comparison, we independently developed a 3D panel program for linear inner-fluid motions, and it is coupled with the vessel-motion program in the frequency domain. The developed computer programs are applied to a barge-type floating production storage and offloading (FPSO) hull equipped with two partially filled tanks. The time-domain simulation results show reasonably good agreement when compared with Maritime Research Institute Netherlands (MARIN's) experimental results. The frequency-domain results qualitatively reproduce the trend of coupling effects, but the peaks are in general overpredicted. It is seen that the coupling effects on roll motions appreciably change with filling level. The most pronounced coupling effects on roll motions are the shift or split of peak frequencies. The pitch motions are much less influenced by the inner-fluid motion compared with roll motions. [DOI: 10.1115/1.4000391] Keywords: sloshing and motion interactions, filling level versus sloshing effect, coupled dynamic analysis, Navier--Stokes solver with SURF, peak frequency shift and split, time-domain potential-viscous hybrid method, frequency-domain coupled analysis

Drag-reducing flow of dilute surfactant solution in the two-dimensional channel is investigated experimentally by using particle image velocimetry (PIV) system. Five hundred instantaneous velocity frames of u-v in the x-y plane are taken by PIV for every condition. Fluctuation intensity and instantaneous velocity distributions are discussed in order to study the turbulence transport in the drag-reducing flow. As compared with water, the results show that wall-normal velocity fluctuations in the drag-reducing flow are suppressed significantly, and instantaneous velocity distributions display different features. Moreover, the drag-reducing flow exhibits the reduced inclination angle of turbulence transport and appearance of 'zero Reynolds shear stress.' High shear dissipation also appears in some solutions. Based on the analysis of the balance of mean and mean turbulent kinetic energies, it is found that the complex rheology, i.e., the elasticity and viscosity of the solution, is considered as the main factor that change the characteristics of turbulence transport. [DOI: 10.1115/1.4001631]

The effect of the flood recession time on the local scour depth at bed sills in gravel deposits is examined. Experiments were carried out to study the development of scour holes under time-varying hydraulic conditions with no upstream sediment feed. Triangular-shaped hydrographs, having recession times up to three times the duration of the rising limb, were used. Traditionally, the peak water discharge in any flood event is used as a design value in estimating the final depth of scour formed by a flood. This approach is overly conservative when the flow hydrograph is steep, i.e., during the occurrence of flash floods. The actual reduction of the scour depth from this estimated value is dependent on both the characteristics of the flood event and the characteristics of the stream. The results show that the maximum potential scour depth can be achieved only for hydrographs with long recession times, while the rate of this process can be estimated as a function of the ratio between a characteristic flood time and the steady-state temporal scale of scour development. A method is proposed for the prediction of the scouring process under unsteady flows in terms of two dimensionless temporal parameters. Results obtained for clear-water boundary conditions can be extended to sediment-supply tests if specific supply input conditions hold. DOI: 10.1061/(ASCE)HY.1943-7900.0000164 CE Database subject headings: Erosion; Scour: Drop structures; Unsteady flow; Flash floods. Author keywords: Erosion; Scour; Drop structures; Unsteady flow; Flash floods.

The flow exponent greatly determines the hydraulic performance of drip emitters. The objective of this study is to reveal the change of flow exponents with different water pressures. Laboratorial experiments of the relationship between discharges and water pressures were conducted with five types of drip emitters used for surface drip irrigation systems. The regression for calculating flow exponents was done with different segment pressures. The results showed that the flow exponent reduced gradually with the increase of the pressure segment except a brief increase in the early stage of pressure increasing due to the channel expansion. The eddy drip-arrow is most suitable for the pressure ranges of 2-8 and 8-14 m[H.sub.2]O. The effect of the use of the small diameter drip-tube is best in the high-pressure range of 17-25 m[H.sub.2]O. The relation between average flow velocities and water pressures is characterized by the flow exponent, the same as that between emitter discharges and water pressures. The eddy drip-arrow and the in-line drip-tape with a low discharge but a high flow velocity can meet the requirements of both prominent anticlogging and long-distance use. The Reynolds numbers of the five types of drip emitters range from 200 to 1,800. below the critical value of the turbulent transition of a conventional scale flow. The small diameter drip-tube needs the lowest Reynolds number required for full turbulence transition which assures a lower flow exponent when the emitter runs with a relatively low discharge. DOI: 10.1061/(ASCE)IR.1943-4774.0000181 CE Database subject headings: Trickle irrigation; Experimentation; Water flow. Author keywords: Drip irrigation; Emitter; Multisegment; Flow regime; Flow exponent.

An experimental study was conducted to investigate the use of a temperature-control curtain in selective withdrawal from a two-layer stratified reservoir. This study focused on the case where cool water at a depth was forced to flow under the curtain. The evolution of the mean flow, the withdrawal water quality, and the mean velocity field were studied using particle image velocimetry and laser-induced fluorescence. Practical relationships were developed for predicting the withdrawal water quality and the interface height as a function of time. The structures of the flow field in both the upper and lower layers are discussed in detail. The flow in the lower layer was dominated by the recirculation eddy induced by the jet flow under the curtain and a relation between the eddy length and the interface height was obtained. Close to the intake, within about 3d (where d=intake diameter), the velocity field can be well described by the potential flow theory. Beyond 3d, however, the flow field considerably deviated from the potential flow theory due to the jet expansion and stratification. A general discussion of the results and engineering applications are also provided. DOI: 10.1061/(ASCE)HY.1943-7900.0000165 CE Database subject headings: Temperature effects; Water flow; Water quality; Reservoirs. Author keywords: Temperature control; Selective withdrawal; Two-layer flows; Water quality; Stratified reservoir.

Microbeads are used to track fluid flow over microband electrode arrays to investigate fundamentals of redox magnetohydrodynamics (redox-MHD) in a confined solution. The results may lead toward the design of micro total analysis systems with microfluidics based on the redox-MHD concept. Ion flux was generated by reduction and oxidation of electroactive potassium ferri- and ferrocyanide at selected individually addressable microelectrodes in the array. An external magnetic field was produced by a small, permanent magnet (0.38 T) placed directly below the array with its field perpendicular to the plane of the array. The cross product of ion flux and magnetic field produces a magnetic force (a portion of the Lorentz force equation) that causes the fluid to rotate around the active electrodes. Velocities up to 1.4 mm/s are demonstrated here. The effects on velocities were obtained for different concentrations of redox species, widths of electrodes, gaps between electrodes, and combinations of anodically- and cathodically polarized electrodes. The microbeads allowed mapping of flow patterns and velocities, both parallel and perpendicular to the array chip. The influence of counteracting shear forces, drag along the walls, and reinforcing flow are discussed. A significant result is the fairly fiat flow profile across 650 [micro]m, attained between electrodes that are oppositely biased. 10.1021/ac9020177

Doubts have been expressed about the validity of the critical depth defined in terms of the minimum specific energy head of the free-surface streamline when dealing with developing open-channel flows. This note examines the two approaches for defining critical flow, that based on the minimum specific energy of the free-surface streamline and that based on the mean energy head of the whole flow section. Large differences for the dimensionless critical depths are obtained with the two methods due to each critical depth proving to be a different control point on the free-surface profile. It is argued that both methods are different alternatives, although the critical depth concept was different in each case. Theoretical support to critical flow computations based on the free streamline is provided. An alternative approach for computing the discharge characteristics of broad-crested weirs based on the energy loss inside the boundary layer is also proposed. DOI: 10.1061/(ASCE)HY.1943-7900.0000142 CE Database subject headings: Open channel flow; Boundary layers; Critical flow; Weirs. Author keywords: Open channels; Boundary layers; Critical flow; Weirs.

The Cartesian cut-cell method can be used to represent irregular and complex computational domains with less computational efforts by cutting the grid cells on the boundary surfaces in a background uniform Cartesian mesh. In this study, a modified Cartesian cut-cell grid technique is proposed to better represent complex physical geometries. A point shifting treatment was employed to determine the start and end points of a line segment in cut-cell grids. This led to an improved representation of sharply-shaped corners in surface polygons. Numerical simulation to solve a set of shallow-water equations was performed by incorporating a finite volume approach into the Cartesian cut-cell mesh. The advective fluxes at intercells were first estimated by a Harten, Lax and van Leer for contact wave approximate Riemann solver. In order to improve the model accuracy to the second order, a total variation diminishing- weighted average flux method was applied to work adaptively with the cut-cell mesh. The numerical model was then employed to simulate darn-break flow propagation in a small channel with a rectangular obstacle or a 45[degrees] bend. The numerical results show good agreement with available laboratory measurements. DOI: 10.1061/(ASCE)EM. 1943-7889.0000065 CE Database subject headings: Dam failures; Shallow water; Water flow; Simulation. Author keywords: Cut-cell approach; Dam-break flows; TVD-WAF method; Approximate Riemann solver; Shallow-water flows.

Governing underground water flow, hydraulic properties such as hydraulic conductivity or coefficient of consolidation are major geotechnical parameters. Determination of hydraulic properties, however, is traditionally time consuming and expensive. This research proposes an easy and economical way of determining the hydraulic properties of soils through piezocone penetration tests. Pore pressure responses of soils from piezocone penetration tests are numerically analyzed herein by the coupled theory of mixtures, which is based on the large strain elastoplasticity. Using the numerical results, the effects of input parameters are evaluated. Simple equations are also derived for a faster estimation of the hydraulic conductivity or the coefficient of consolidation of soils. The hydraulic properties predicted by these derived equations agree reasonably with the measured results. DOI: 10.1061/(ASCE)1090-0241(2010)136:3(456) CE Database subject headings: Hydraulic conductivity; Cone penetration tests; Soil consolidation; Elastoplasticity; Hydraulic properties. Author keywords: Piezocone; Hydraulic conductivity; Coefficient of consolidation; Elastoplasticity.

Oblique weirs are commonly used in urban drainage systems to remove excess flow from a sewer, in particular, a combined sewer system that has limited conveyance capacity. It is important to understand the hydraulics of these weirs to properly monitor the amount of the overflows as well as to design and improve sewer systems. The Rat Creek structure in Edmonton, Alberta, is a combined sewer overflow structure with a weir at an oblique alignment to the centerline of the sewer. A physical model study of the structure was conducted. The results show that both the approach flow conditions and the chamber geometry can significantly affect the hydraulic performance of the weir and invalidate the application of standard weir equations, A unique flow regime with a linear head-discharge rating curve was observed. The effects of modifying the weir and the hanging baffle wall downstream of the weir were also studied and reported. The results of this case study help to improve the understanding of the hydraulics of oblique weirs in sewer systems. Key words: combined sewer overflow, oblique weirs, hydraulics, rating curve, urban drainage. Des deversoirs obliques sont souvent utilises dans les reseaux de drainage urbains afin d'eliminer l'excedent d'un reseau d'egout, plus particulierement d'un reseau unitaire d'assainissement ayant une capacite limitee de transport. Il est important de bien comprendre l'hydraulique de ces deversoirs afin de mieux surveiller la quantite de debordement et de concevoir et d'ameliorer les reseaux d'egout. La structure de Rat Creek, a Edmonton, Alberta, est une structure de debordement d'egouts unitaires munie d'un deversoir aligne obliquement par rapport a la ligne mediane de l'egout. Une etude de la structure a ete realisee en utilisant un modele physique. Les resultats montrent que les conditions de 1'ecoulement d'entree et la forme de la chambre peuvent grandement affecter le rendement hydraulique du deversoir et invalider les equations standards des deversoirs. Un regime d'ecoulement unique avec une courbe hauteur-debit lineaire a ete note. Les effets des modifications an deversoir et du mur deflecteur suspendu en aval du deversoir out egalement ete etudies et rapportes. Les resultats de cette etude de cas aident a ameliorer la comprehension de l'hydraulique des deversoirs obliques dans les reseaux d'egout. Mots-cles: debordement d'egouts unitaires, deversoirs obliques, courbe hauteur-debit, drainage urbain. [Traduit par la Redaction], Introduction A weir is a hydraulic control structure commonly built perpendicular to the direction of the approaching flow to measure discharges. An oblique or skewed weir is one placed obliquely [...]

The discharge and stage measurements in a river system are characterized by a number of sources of uncertainty, which affects the accuracy of a rating curve established from measurements. This paper presents a fuzzy set theory based methodology for consideration of different sources of uncertainty in the stage and discharge measurements and their aggregation into a combined uncertainty. The uncertainty in individual measurements of stage and discharge is represented using triangular fuzzy numbers, and their spread is determined according to the International Organization for Standardization (ISO) standard 748 guidelines. The extension principle based fuzzy arithmetic is used for the aggregation of various uncertainties into overall stage-discharge measurement uncertainty. In addition, a fuzzified form of ISO 748 formulation is used for the calculation of combined uncertainty and comparison with the fuzzy aggregation method. The methodology developed in this paper is illustrated with a case study of the Thompson River near Spences Bridge in British Columbia, Canada. The results of the case study show that the selection of number of velocity measurement points on a vertical is the largest source of uncertainty in discharge measurement. An increase in the number of velocity measurement points provides the most effective reduction in the overall uncertainty. The next most important source of uncertainty for the case study location is the number of verticals used for velocity measurements. The study also shows that fuzzy set theory provides a suitable methodology for the uncertainty analysis of stage- discharge measurements. Key words: discharge calculation, fuzzy arithmetic, measurement uncertainly, uncertainly aggregation, velocity-area method. Les mesures de debit et de niveau dans un reseau hydrographique sont caracterisees par plusieurs sources d'incertitudes, ce qui affecte la precision d'une courbe des debits jauges etablis a parlir des mesures prises. Cet article presente une theorie des ensembles flous pour tenir compte des diverses sources d'incertitude dans les mesures de niveau et de debit ainsi que leur regroupemenl dans une incertitude combinee. L'incertilude des mesures individuelles du niveau el du debit est representee en ulilisanl des nombres flous [riangulaires el leur dispersion est deierminee en ulilisanl les lignes directrices ISO 748. L'arilhmelique lloue basee sur le principe d'extension esi utilisee pour le regroupemenl des diverses incertitudes dans l'incertilude globale de la mesure du debit et du niveau. De plus, une forme floue de la formulation ISO 748 est utilisee pour calculer l'incertilude combinee et la comparaison a la methode floue de regroupemenl. La methode developpee dans cet article est illustree par une etude de cas de la riviere Thompson pres du pont Spences en Colombie-Brilannique, au Canada. Les resultats de cede etude de cas montrent que le choix du nombre de points de mesure de la Vitesse sur une verticale est la plus grande source d'incertitude de la mesure du debit. Une augmentation du nombre de points de mesure represente la reduction la plus efficace de l'incertilude globale. La seconde source en importance d'incertitude pour l'emplacement de l'etude de cas est le nombre de verlicales utilisees pour les mesures de vitesse, L'etude montre egalement que la theorie des ensembles flous est appropriee pour l'analyse des incertitudes dans des mesures de debit el de niveau. Mots-cles : calcul du debit, arithmetique floue, incertitude de mesure, regroupement d'incertitudes, methode de la zone de vitesse. [Traduit par la Redaction], Introduction River stage and discharge records are essential for hydrologic and hydraulic analyses. While stage is measured directly, discharge is calculated using the velocity-area method from measurements of flow velocity, [...]

Clear-water scour due to a short vertical (pressure flow) contraction was investigated in a laboratory channel. Two approach velocities were studied for a (nominally) single configuration of depth and degree of contraction, with experiments conducted lot various durations up to a maximum of 48 h, and the evolution of the scour hole over time monitored. The location of maximum scour in both cases was observed to occur downstream of the contraction, with maximum scour depths substantially in excess of values predicted by published models, even though equilibrium scour conditions were not reached. DOI: 10.1061/(ASCE)0733-9429(2010)136:2(137) CE Database subject headings: Contraction; Scour; Channels; Laboratory tests.

The present experimental investigation focuses on energy dissipation and turbulence production in two undeveloped and a partially developed inflow weak hydraulic jumps, measured with micro-ADVs. For the undeveloped inflow jumps, the turbulence production is mostly confined in the shear layer located in the upper part of the water column. For the partially developed inflow jump, two peak turbulence production regions are observed, one in the upper shear layer and the second in the near-wall region. Moreover, the measured energy dissipation distribution in the jumps reveals a similar longitudinal decay of energy dissipation integrated over the flow sections and of maximum turbulence production values from the intermediate jump region toward its downstream section. DOI: 10.1061/(ASCE)HY.1943-7900.0000124 CE Database subject headings: Hydraulic jump; Turbulence; Inflow; Kinetics.

The study deals with the breakup behavior of swirling liquid sheets discharging from gas-centered swirl coaxial atomizers with attention focused toward the understanding of the role of central gas jet on the liquid sheet breakup. Cold flow experiments on the liquid sheet breakup were carried out by employing custom fabricated gas-centered swirl coaxial atomizers using water and air as experimental fluids. Photographic techniques were employed to capture the flow behavior of liquid sheets at different flow conditions. Quantitative variation on the breakup length of the liquid sheet and spray width were obtained from the measurements deduced from the images of liquid sheets. The sheet breakup process is significantly influenced by the central air jet. It is observed that low inertia liquid sheets are more vulnerable to the presence of the central air jet and develop shorter breakup lengths at smaller values of the air jet Reynolds number [Re.sub.g]. High inertia liquid sheets ignore the presence of the central air jet at smaller values of [Re.sub.g] and eventually develop shorter breakup lengths at higher values of [Re.sub.g]. The experimental evidences suggest that the central air jet causes corrugations on the liquid sheet surface, which may be promoting the production of thick liquid ligaments from the sheet surface. The level of surface corrugations on the liquid sheet increases with increasing [Re.sub.g]. Qualitative analysis of experimental observations reveals that the entrainment process of air established between the inner surface of the liquid sheet and the central air jet is the primary trigger for the sheet breakup. [DOI: 10.1115/1.4000737] Keywords: gas-centered coaxial atomizers, liquid sheets, jet/sheet breakup, sprays

The behavior of unsteady velocity profiles in laminar and turbulent water hammer flows is numerically investigated. In this way, the governing equations for the quasitwo-dimensional equations of transient flow in pipe are solved by using the modified implicit characteristics method. A k-[omega] turbulence model which is accurate for two-dimensional boundary layers under adverse and favorable pressure gradients is applied. The numerical results for both steady and unsteady turbulent pipe flows are in good agreement with the experimental data. The results indicate that both decelerating and accelerating flows are produced in a wave cycle of water hammer. During deceleration of the flow, a region of reverse flows and also strong gradients is formed near to the pipe wall. In case of the turbulent water hammer, this region is very close to the pipe wall compared with the laminar water hammer. Moreover, point of inflection and also point of zero velocity are formed in the unsteady velocity profile due to the water hammer problem. The results show that the point of zero velocity does not move very far from its initial location, while the point of inflection moves rapidly from the wall [DOI: 10.1115/1.4000557] Keywords: water hammer, unsteady velocity profile, k-[omega] turbulence model, inflection point

Nutrient cycling and export in streams and rivers should vary with flow regime, yet most studies of stream nutrient transformation do not include hydrologic variability. We used a stable isotope tracer of nitrogen ([sup.15]N) to measure nitrate (N[O.sup.-.sub.3]) uptake, storage, and export in a mountain stream, Spring Creek, Idaho, U.S.A. We conducted two tracer tests of 2-week duration during snowmelt and baseflow. Dissolved and particulate forms of [sup.15]N were monitored over three seasons to test the hypothesis that stream N cycling would be dominated by export during floods, and storage during low flow. Floods exported more N than during baseflow conditions; however, snowmelt floods had higher than expected demand for N[O.sup.-.sub.3]- because of hyporheic exchange. Residence times of benthic N during both tracer tests were longer than 100 d for ephemeral pools such as benthic algae and wood biofilms. Residence times were much longer in fine detritus, insects, and the particulate N from the hyporheic zone, showing that assimilation and hydrologic storage can be important mechanisms for retaining particulate N. Of the tracer N stored in the stream, the primary form of export was via seston during periods of high flows, produced by summer rainstorms or spring snowmelt the following year. Spring Creek is not necessarily a conduit for nutrients during high flow; hydrologic exchange between the stream and its valley represents an important storage mechanism.

Various types of cover systems can be used to control water infiltration into waste disposal sites. One promising option is to combine different types of soil to create a layered cover with capillary barrier effects (CCBE). A CCBE basically involves the placement of a relatively fine-grained soil, which acts as a water-retention layer, over a coarser capillary break material. On slopes, a CCBE promotes lateral water diversion. Inclined CCBEs, however, are relatively complex, as their behaviour is influenced by numerous factors. In this paper, the authors present the key results obtained from a numerical investigation into the response of steeply inclined CCBEs. The study evaluates the behaviour of covers under dry and humid climatic conditions. After a review of the physical processes and background studies, the paper presents simulation results that demonstrate the effect of key factors on the diversion length of covers, including layer thicknesses, material properties, and recharge rates. The results shown here indicate that increasing the thickness of the cover may improve its efficiency, but only up to a certain maximum beyond which the gain becomes minimal. These results should be of help to those involved in the design of inclined CCBEs. Key words: cover, capillary barrier, unsaturated flow, water infiltration, diversion length, waste rock piles, tailings dams. Differents types de systemes de recouvrement peuvent etre utilises pour controler l'infiltration d'eau dans les sites d'entreposage de rejets. Une option prometteuse consiste a combiner differents types de sol pour creer une couverture avec effets de barriere capillaire (CEBC). De facon sommaire, une CEBC implique la deposition d'une couche de sol relativement fin, qui agit comme couche de retention d'eau, au-dessus d'une couche de materiau plus grossier servant de bris capillaire. Sur les pentes, la CEBC permet la diversion laterale de l'eau. Cependant, les CEBC inclinees ont un comportement relativement complexe, puisque celui-ci est influence par plusieurs facteurs. Dans cet article, les auteurs presentent les principaux resultats obtenus lors d'une evaluation numerique du comportment des CEBC inclinees. L'etude evalue le comportement des couvertures soumises a des conditions climatiques seches et humides. Suite a une revue des processus physiques et des etudes anterieures, l'article presente des resultats de simulations qui demontrent l'effet des principaux facteurs, incluant l'epaisseur des couches, les proprietes des materiaux et le taux de recharge, sur la longueur de diversion des couvertures. Les resultats presentes indiquent que l'augmentation de l'epaisseur de la couverture peut ameliorer son efficacite, jusqu'a une certaine epaisseur au-dela de laquelle les gains sont minimes. Ces resultats pourront aider les practiciens impliques dans la conception de CEBC inclinees. Mots-cles : couverture, barriere capillaire, ecoulement non sature, infiltrations d'eau, longueur de diversion, haldes a steriles, digues de residus miniers., Introduction Cover systems are a practical means for controlling the exchange of water and (or) gas at the surface of waste disposal sites. Many different cover configurations and materials have [...]

Analytical solutions are derived for a one-dimensional model of the bulk temperature response of open-channel flow with unsteady and nonuniform heating at the upstream end, the water surface, and the riverbed. The solutions are explicit formulas comprised of transient terms, which play dominant roles in the upstream region, and equilibrium terms, which determine the temperature far downstream. The applicability of the solutions to practical problems is illustrated for two cases: (1) a stream bounded at its upstream end by a dam and with a midreach inflow; and (2) Boulder Creek, Colo., which is impacted by effluent released from a wastewater treatment plant. The model prediction is in reasonable agreement with gauged data. CE Database subject headings: Analytical techniques; Water temperature; Open channel flow; Wave propagation; Thermal factors.

The present work attempts to investigate the effects of jet obliquity on the spatial patterns formed as a consequence of hydraulic jumps due to the impingement of circular liquid jets on continuously moving but nonaccelerating horizontal flat plates. Both the normal and the oblique impinging jets are considered, in order to characterize the contrasting features of the associated hydraulic jump mechanisms. Theoretical calculations are executed to obtain the locations of the jump, for different jet and plate velocities and jet inclination angles, using a depth-averaged momentum integral equation for shallow-free surface flows. Comparisons are subsequently made between the theoretical predictions and experimental observations reported in the literature, and a good agreement between these two can be observed. Special cases' of a circular hydraulic jump when the target plate is stationary and the impinging jet is vertical, and elliptic' hydraulic jumps when the target plate is stationary and the impinging jet is obliquely inclined, are also discussed. It is conjectured that flow due to impinging jets on a horizontal moving plate can be modeled as an equivalent flow due to an inclined impinging jet on stationary horizontal flat plates, with appropriate alterations in the jet velocity and the jet inclination angles. [DOI: 10.1115/1.3059583] Keywords: hydraulic jump, impinging liquid jet, stagnation point

This paper is concerned with deriving parameters for assessing the effectiveness of fluid additives to improve water flooding during enhanced oil recovery. We focus particularly on the use of rheological modifiers, which do not show monotonic behavior with the shear rate within the rock pores. We derive figures of merit based on (1) relative retardation in high and low permeability, rock, (2) profile flattening, and (3) injectivity index. Only the last of these provides a measure of water flood profile improvement while maintaining sufficient fluid flow and production levels. [DOI: 10.1115/1.3077142]

ABSTRACT Effective watershed management requires accurate modeling of river discharge. Many years of data collection are often required to capture variations in seasonal trends and produce accurate predictive and descriptive [...]

Mussels rely on a strong byssal attachment to persist in a range of habitats with differing rates of water flow. Recent studies, however, suggest that the ability of one mussel species to sense and respond adaptively to the flow in its environment is limited under even modest flow conditions because the process of byssal thread formation is disrupted. This study extends these findings to four mussel species, Mytilus trossulus, M. galloprovincialis, M. californianus, and Modiolus modiolus. Collectively, the response of byssal thread formation decreased with rates of flow above ~25 cm/s and the critical flow threshold was estimated to be

In terraced paddy landscapes, water losses through the bunds surrounding paddy rice (Oryza sativa L.) fields may significantly reduce water use efficiency. The objective of this research was to identify the dominant pathways active for water flow and solute transport in bunds, and to detect differences between the bunds and adjacent field areas. Two earthen bunds aged 20 and 100 yr were investigated by means of dye tracer experiments in Jiangxi Province, China. Most prominently, the bunds were shown to be distinctly more vulnerable to preferential transport of solutes toward the groundwater than the actual paddy fields. The younger bund showed greater water losses than the old one, caused by a greater macroporosity, lower bulk density, and a less effective hard pan. Three successively operating transport processes could be distinguished: (i) dye solution infiltrated vertically into the field and laterally into the bund; (ii) the plow pan underneath the field and the hard pan in the bund then acted as flow barriers, and horizontal spreading occurred on top of the hard pan toward the outer bund and cross-flow to the adjacent field was observed; and (iii) macropore flow occurred through the hard pan and partly in the subsoil down to the groundwater level, initiated on top of the saturated hard pan and routed through earthworm burrows and root channels as well as shrinkage cracks in the younger bund. In conclusion, compaction of a bund may significantly reduce infiltration rates but does not prevent preferential solute losses.

Experimental approaches for directly determining preferential water flow in field soils usually require artificial interruption of the soil matrix's water flow. This interruption may change the quantitative as well as the qualitative nature of the preferential water flow, particularly in soils such as Andisols where matrix water flow is the dominant process of drainage. To overcome this problem, we applied both the one-dimensional form of Darcy's equation and the soil water balance method, during and shortly after each rain event, for characterizing as well as determining the preferential water flow across a depth of 1 m in an Andisol. The volumetric water contents and pressure potentials at different soil depths were monitored by time domain reflectometry and tensiometry during a 7-yr period. Preferential water flow was detected only two to seven times per year; nevertheless, it accounted for 16 to 27% of the annual total drainage. These flows occurred under macroscopically homogeneous soil water conditions, with pressure potentials mostly below the air-entry pressure in the subsoil. The in situ unsaturated hydraulic conductivity at the depth of 1 m, determined to apparently explain the total drainage during a preferential water flow event, varied over more than one order of magnitude, with little change in water content, and the maximum value reached the saturated hydraulic conductivity. This indicates that preferential water flow occurred mainly through the largest macropores at this depth due to pore-scale physical nonequilibrium. Macropore-mediated preferential water flow and solute transport should be considered in unsaturated subsoil of Andisols. Abbreviations: TDR, time domain reflectometry.

The behavior of free surface flow at a rectangular free overfall is studied experimentally to obtain a relation between the brink depth and the flow rate. A series of experiments were conducted in a tilting flume with wide range of flow rates covering subcritical, critical, supercritical regimes, and two different roughnesses in order to develop a relationship between the discharge and the brink depth. An equation is proposed to determine the flow rate using the brink depth for a channel of known roughness and bed slope. DOI: 10.1061/(ASCE)0733-9437(2008)134:1(89) CE Database subject headings: Discharge measurement; Open channel flow; Subcritical flow; Supercritical flow; Weirs.

A new set of depth-averaged equations is introduced to study the flow over an arbitrary three-dimensional (3D) surface. These equations are derived based on a generalized curvilinear coordinate system attached to the 3D bed surface, therefore it allows us to include the effect of centrifugal force due to the bottom curvature. These general equations make it possible to analyze flows over complex terrain without the limitation of mild slope assumption used in conventional depth-averaged models. This new model is then applied to calculate the water surface profiles of (1) flow over a cylindrical surface; (2) flow over a circular surface; and (3) flow with an air-core vortex at a vertical intake. A simple hydraulic experiment is conducted in the laboratory to observe the water surface profile of flow over a circular surface. The results obtained from the model are in good agreement with experimental measurements and calculation by an empirical formula. Consequently, it demonstrates the applicability of the model in cases of flow over a highly curved bottom. DOI: 10.1061/(ASCE)0733-9429(2007)133:4(350) CE Database subject headings: Open channel flow; Shallow waters; Pressure distribution; Water surface profiles; Three-dimensional models.

This paper presents results of the relationship between the degree of saturation and the matric suction head at static equilibrium and during dynamic flow of water using a Buchner funnel anda fully instrumented two-dimensional tank, respectively. The major influences of the dynamic flow on the relationships between the suction head and the degree of saturation are highlighted and discussed. The experimental results show that dynamic flow of water strongly affects the volume of entrapped air. The results also reveal that any scanning curve can be described as two parts, namely, transition and coinciding. The transition curve starts from the recent reversal degree of saturation and continues up to the previous reversal degree of saturation. The shape of the transition curve and the amount of hysteresis are not only a function of the reversal degree of saturation but ate also a function of the saturation path history. The experimental results are used to examine the validity of the proposed analytical model by Parker and Lenhard in 1987 for describing the relationships between the degree of saturation and the matric suction head. It was found that Parker and Lenhard's model provides a good prediction of the relations provided that care should be taken for the value of the reversal degree of saturation at zero suction head. DOI: 10.1061/(ASCE)1090-0241(2007)133:3(286) CE Database subject headings: Unsaturated soils; Suction; Soil water; Water flow.

The mixed convection of rarefied gas in a vertical asymmetrically heated microchannel between two parallel plates is investigated. The mixed convection parameter, (Gr/Re), the Knudsen number (Kn) and the ratio of wall temperature difference ([r.sub.T]) are studied and their effects on the heat and fluid flow phenomena are determined.

The thermal and hydraulic performances of silicon-based, low aspect ratio micropin-fin cold plates are studied under cross flow conditions. The results have shown that the average Nusselt number (Nu) based on the fin diameter varies with varying Reynolds number (Re), which is based on maximum velocity and fin diameter.