Journal of Hydraulic Engineering

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December 2006

Volume 132, Issue 12, pp. 1247-1370

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2006—Year of Continuity and Momentum

Dennis A. Lyn

J. Hydraul. Eng. 132, 1247 (2006); http://dx.doi.org/10.1061/(ASCE)0733-9429(2006)132:12(1247) (1 page)

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Hunter Rouse—His Work in Retrospect

Robert Ettema

J. Hydraul. Eng. 132, 1248 (2006); http://dx.doi.org/10.1061/(ASCE)0733-9429(2006)132:12(1248) (11 pages) | Cited 3 times

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Experimental Study of Surcharged Flow at Combining Sewer Junctions

Can-Hua Zhao, Ph.D., David Z. Zhu, and Nallamuthu Rajaratnam

J. Hydraul. Eng. 132, 1259 (2006); http://dx.doi.org/10.1061/(ASCE)0733-9429(2006)132:12(1259) (13 pages) | Cited 3 times

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The results of a laboratory investigation on surcharged flow in combining sewer junctions are presented in this paper. Experiments were conducted in a 90° model junction and the 25.8° Edworthy model junction. The study confirmed the existence of three flow regimes in sewer junctions with a steep outgoing pipe: Regime I denotes the open-channel flow through the junction chamber; Regime II flow is partially surcharged flow featured by orifice flow into the outlet pipe; and Regime III flow is fully surcharged flow with all connecting pipes running full. The transition flow from Regimes II to III was investigated, and it may be related to the inlet waves at the entrance of the outlet pipe. Criteria for the transition were provided. Theoretical analyses were conducted based on one-dimensional momentum equation. The derived equations are able to estimate the water depth in the junction chamber. Energy loss in Regime III flow was studied and predictions based on the momentum equation were evaluated.

Flow Resistance and Momentum Flux in Compound Open Channels

Zhixian Cao, Jian Meng, Gareth Pender, and Steve Wallis

J. Hydraul. Eng. 132, 1272 (2006); http://dx.doi.org/10.1061/(ASCE)0733-9429(2006)132:12(1272) (11 pages) | Cited 5 times

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New formulations are presented for flow resistance and momentum flux in compound open channels. As implemented in the St. Venant equations, these formulations facilitate a physically enhanced approach to evaluating conveyance, roughness, stage-discharge relationship, and unsteady flood routing in compound open channels. An analysis using steady flow data from the well-controlled experiments at the large-scale Flood Channel Facility, HR Wallingford, demonstrates the ability of the present approach to properly resolve the discontinuity of overall roughness across the main-channel bankfull level. Also, the proposed formulations are shown to be conducive to obviating the long-standing computational difficulty in unsteady flood routing due to small flow depths over flat and wide floodplains. The present work should find general applications in one-dimensional computation of river flows.

Particle Image Velocity Measurements of Undular and Hydraulic Jumps

J. M. Lennon and D. F. Hill

J. Hydraul. Eng. 132, 1283 (2006); http://dx.doi.org/10.1061/(ASCE)0733-9429(2006)132:12(1283) (12 pages) | Cited 8 times

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Measurements of the mean and turbulent flow fields in undular and hydraulic jumps have been acquired with single-camera particle image velocimetry (PIV). Three Froude numbers, ranging from 1.4 to 3.0, were studied, and in each case data were collected at numerous streamwise locations. The data from these streamwise locations were subsequently compiled into spatially dense ( ∼ 80,000 grid points) “mosaic” images encompassing both the supercritical and subcritical portions of the flow. The measured mean and turbulent velocity fields provide more detailed views inside undular and hydraulic jumps than were previously available from studies using pointwise measurement techniques. The two-dimensional spatial density of the measurements provides for the determination of gradient-based quantities such as vorticity. The potential for determining boundary shear stress from the velocity data is evaluated with several methodologies. The results are found to be consistent with recent measurements made using Preston tubes. Discussion of the technical aspects of and difficulties involved with applying PIV to hydraulic jumps is provided. These challenges included the identification and tracking of the free surface through image analysis and the scattering of laser light by entrained air bubbles in the roller region.

Effects of Velocity Gradients and Secondary Flow on the Dispersion of Solutes in a Meandering Channel

Andrea Marion and Mattia Zaramella

J. Hydraul. Eng. 132, 1295 (2006); http://dx.doi.org/10.1061/(ASCE)0733-9429(2006)132:12(1295) (8 pages) | Cited 1 time

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Two contrasting mechanisms, created by channel curvature which strongly affect longitudinal dispersion of solutes in rivers are examined. In natural channels the large cross-sectional variability of the primary velocity component tends to increase longitudinal dispersion by providing a large difference between adjacent fast and slow moving zones of fluid. By contrast secondary circulation tends to decrease longitudinal dispersion by enhancing transverse mixing. A series of tests have been carried out in a very large flume containing a meandering water-formed sand bed channel to measure the longitudinal dispersion coefficient at various locations around a meander. These experimental observations are compared with experimental data obtained from meandering channels with smooth, fixed sides and regular cross-sectional shapes. All the data has been compared against predictions from two current modeling approaches. Finally, the significance of the two competing mechanisms in curved channels is discussed with regard to their relative influence on longitudinal mixing.

Validation of a Large-Eddy Simulation Model to Simulate Flow in Pump Intakes of Realistic Geometry

T. E. Tokyay and S. G. Constantinescu, M.ASCE

J. Hydraul. Eng. 132, 1303 (2006); http://dx.doi.org/10.1061/(ASCE)0733-9429(2006)132:12(1303) (13 pages) | Cited 9 times

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This paper describes efforts toward developing a reliable numerical model to predict pump intake flow and associated vortices. Numerical prediction of these flows characterized by the formation of unsteady (meandering) intermittent vortices and presence of massive separation is very challenging. Successful prediction of these phenomena and their effects on the mean flow fields requires numerical methods and turbulence models that can accurately capture the dynamics of the main coherent structures in these flows. In the present work, large-eddy simulation (LES) in conjunction with an accurate nondissipative nonhydrostatic Navier-Stokes massively parallel solver is used to predict the flow and vortical structures in a pressurized pump intake of complex geometry. The LES model is validated using particle image velocimetry data recently collected on a laboratory model of a realistic geometry pump intake. To better put in perspective the predictive performance of the LES model, results from steady simulations employing the shear stress transport (SST) Reynolds-averaged-Navier-Stokes (RANS) model are presented and compared with LES. It is shown that even if SST can fairly successfully capture the mean velocity distribution and mean vortical structures in some regions, overall LES can more accurately predict the mean flow and turbulence statistics compared to the steady SST model.

Transition from Ripples to Dunes

Arved J. Raudkivi

J. Hydraul. Eng. 132, 1316 (2006); http://dx.doi.org/10.1061/(ASCE)0733-9429(2006)132:12(1316) (5 pages) | Cited 6 times

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The bed forms generated by the flow of water over alluvial beds are predominantly treated in terms of stability concepts. These generally postulate a constant wavelength, and describe the variation of amplitude. Yet, the wavelength is one of the most variable parameters of these features. The features are also described as ripples, dunes, and antidunes. But there is no explanation on how ripples transform into dunes. On the basis of available data, this paper offers a description of the generation of ripples and their transformation into dunes.

ANN and Fuzzy Logic Models for Simulating Event-Based Rainfall-Runoff

Gokmen Tayfur and Vijay P. Singh, F.ASCE

J. Hydraul. Eng. 132, 1321 (2006); http://dx.doi.org/10.1061/(ASCE)0733-9429(2006)132:12(1321) (10 pages) | Cited 7 times

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This study presents the development of artificial neural network (ANN) and fuzzy logic (FL) models for predicting event-based rainfall runoff and tests these models against the kinematic wave approximation (KWA). A three-layer feed-forward ANN was developed using the sigmoid function and the backpropagation algorithm. The FL model was developed employing the triangular fuzzy membership functions for the input and output variables. The fuzzy rules were inferred from the measured data. The measured event based rainfall-runoff peak discharge data from laboratory flume and experimental plots were satisfactorily predicted by the ANN, FL, and KWA models. Similarly, all the three models satisfactorily simulated event-based rainfall-runoff hydrographs from experimental plots with comparable error measures. ANN and FL models also satisfactorily simulated a measured hydrograph from a small watershed 8.44 km2 in area. The results provide insights into the adequacy of ANN and FL methods as well as their competitiveness against the KWA for simulating event-based rainfall-runoff processes.

Erosive Wear of Hydraulic Concrete with Low Steel Fiber Content

X. G. Hu, A. W. Momber, and Y. Yin

J. Hydraul. Eng. 132, 1331 (2006); http://dx.doi.org/10.1061/(ASCE)0733-9429(2006)132:12(1331) (10 pages) | Cited 1 time

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The paper reports on the erosion resistance of two types of hydraulic concrete, a plain concrete and a concrete reinforced with a low volume of steel fibers. Flow velocities ranged up to 230 m/s for water flow and up to 160 m/s for particle-water flow. Flow angles were 15° and 90°, respectively. A general relationship could be found between erosion rate, ER, and process parameters: ER∝vFn∙f(θ), with vF being the flow velocity, and θ being the flow angle. The velocity exponent n varied between 2.1 and 2.3 for water flow and between 2 and 2.9 for particle-water flow. In general, erosion rate decreased if the concrete was reinforced. However, the influence of the fiber reinforcement was more pronounced for the shallow flow angle. This is explained by the formation of a “shadow zone” behind the fibers in the case of shallow flow angle.
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Lateral Variations in Suspended Sediment Concentration over Dunes

R. A. Kuhnle, M.ASCE and D. G. Wren, M.ASCE

J. Hydraul. Eng. 132, 1341 (2006); http://dx.doi.org/10.1061/(ASCE)0733-9429(2006)132:12(1341) (6 pages) | Cited 3 times

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A series of laboratory flume experiments were conducted to characterize lateral variations of suspended sediment over dunes. Forty experimental runs were made using flow depths of 0.328 and 0.127 m in a 1.2-m-wide channel. The Froude number was 0.47 and the median diameter of the bed material was 0.52 mm. Point samples of suspended sediment and depth-integrated values calculated using acoustic backscatter data were collected simultaneously at two lateral positions at spacings of 0.41, 0.20, 0.10, and 0.05 m. Root mean square differences between the paired samples increased from 30 to 94% and from 20 to 45% of the mean concentration for point samples and depth-integrated samples, respectively, as the lateral spacing between samples was increased. Lateral variations in the concentration of suspended sediment should be considered when designing sediment sampling strategies over dune beds.

Downstream Hydraulic Geometry of Alluvial Channels

Jong-Seok Lee, A.M.ASCE and Pierre Y. Julien, M.ASCE

J. Hydraul. Eng. 132, 1347 (2006); http://dx.doi.org/10.1061/(ASCE)0733-9429(2006)132:12(1347) (6 pages) | Cited 6 times

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This study extends the earlier contribution of Julien and Wargadalam in 1995. A larger database for the downstream hydraulic geometry of alluvial channels is examined through a nonlinear regression analysis. The database consists of a total of 1,485 measurements, 1,125 of which describe field data used for model calibration. The remaining 360 field and laboratory measurements are used for validation. The data used for validation include sand-bed, gravel-bed, and cobble-bed streams with meandering to braided planform geometry. The five parameters describing downstream hydraulic geometry are: channel width W, average flow depth h, mean flow velocity V, Shields parameter τ*, and channel slope S. The three independent variables are discharge Q, median bed particle diameter ds, and either channel slope S or Shields parameter τ* for dominant discharge conditions. The regression equations were tested for channel width ranging from 0.2 to 1,100 m, flow depth from 0.01 to 16 m, flow velocity from 0.02 to 7 m/s, channel slope from 0.0001 to 0.08, and Shields parameter from 0.001 to 35. The exponents of the proposed equations are comparable to those of Julien and Wargadalam (1995), but based on R2 values of the validation analysis, the proposed regression equations perform slightly better.

Physical and Numerical Comparison of Flow over Ogee Spillway in the Presence of Tailwater

Michael C. Johnson, M.ASCE and Bruce M. Savage, M.ASCE

J. Hydraul. Eng. 132, 1353 (2006); http://dx.doi.org/10.1061/(ASCE)0733-9429(2006)132:12(1353) (5 pages) | Cited 2 times

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Data obtained from two physical models were compared to the results obtained from numerical model investigations of two ogee-crested spillways. In 2001, Savage and Johnson investigated ogee-crested spillways without the effect of tailwater; the present study includes the influence of tailwater on the spillway. The comparison showed that numerical modeling can accurately predict the rate of flow over the spillway and the pressure distribution on the spillway. The results of this study provide users of numerical models performance information that can be used to aid them in determining which tool to use to effectively analyze dams and their associated spillways.

Bat Echolocation Interfering with Ultrasonic Sensors

J. Puertas, Aff.ASCE, E. Peña, Aff.ASCE, F. Sánchez-Tembleque, J. Rabuñal, and E. Sixto

J. Hydraul. Eng. 132, 1358 (2006); http://dx.doi.org/10.1061/(ASCE)0733-9429(2006)132:12(1358) (3 pages)

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The collection of field data is essential to monitoring in river basins to prevent flooding in areas with intense rainfall. A network of stations equipped with ultrasonic sensors was installed in a wet basin in Northwest Spain to monitor the water surface elevation of the rivers in the area. At one of these stations during the summer months, interference and anomalies were detected, presenting a regular pattern. After ruling out other hypotheses, the frequency and intensity of the echolocation calls emitted by bats at specific time intervals was investigated. It was concluded that bat echolocation was the cause of the interference detected.
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Closure to “Decay of Turbulence Downstream of a Stilling Basin” by A. L. Urban, S. C. Wilhelms, and J. S. Gulliver

A. L. Urban, S. C. Wilhelms, and J. S. Gulliver

J. Hydraul. Eng. 132, 1362 (2006); http://dx.doi.org/10.1061/(ASCE)0733-9429(2006)132:12(1362) (1 page)

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Review of River Engineering in Switzerland, Vol. 6, by H.-E. Minor and W. H. Hager

Pierre Y. Julien, Reviewer

J. Hydraul. Eng. 132, 1363 (2006); http://dx.doi.org/10.1061/(ASCE)0733-9429(2006)132:12(1363) (1 page)

Online Publication Date: 15 November 2006

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Papers of Interest

J. Hydraul. Eng. 132, 1364 (2006); http://dx.doi.org/10.1061/(ASCE)0733-9429(2006)132:12(1364) (1 page)

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Reviewers

J. Hydraul. Eng. 132, 1365 (2006); http://dx.doi.org/10.1061/(ASCE)0733-9429(2006)132:12(1365) (6 pages)

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