Journal of Hydraulic Engineering

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August 2006

Volume 132, Issue 8, pp. 753-874

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Some Recent Additions to the Editorial Board

Dennis A. Lyn

J. Hydraul. Eng. 132, 753 (2006); http://dx.doi.org/10.1061/(ASCE)0733-9429(2006)132:8(753) (1 page)

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Hans Albert Einstein in South Carolina

Robert Ettema and Cornelia F. Mutel

J. Hydraul. Eng. 132, 754 (2006); http://dx.doi.org/10.1061/(ASCE)0733-9429(2006)132:8(754) (5 pages) | Cited 1 time

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Innovative Energy-Dissipating Hood

Michael C. Johnson, M.ASCE and Rajesh Dham, M.ASCE

J. Hydraul. Eng. 132, 759 (2006); http://dx.doi.org/10.1061/(ASCE)0733-9429(2006)132:8(759) (6 pages) | Cited 1 time

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Fixed-cone valves are generally used to regulate flow under medium to high head conditions because of their ability to safely and efficiently pass the flow. By design, fixed-cone valves, also known as Howell–Bunger valves, emit a large-diameter conical spray. The spray is effective in spreading and dissipating energy, although in some conditions where space is limited, it may be desirable to contain the spray. Containing the spray may be achieved by using a hood; however the result is a high velocity hollow jet that focuses the energy in the stilling basin. Depending on the size of the stilling basin downstream of the valve and the sensitivity to environmental factors, it may be necessary to dissipate some energy of the concentrated jet prior to impingement in the stilling basin. This paper discusses the development of a baffled hood that is capable of dissipating over 92% of the power available upstream from the fixed-cone valve. Practicing engineers will find the information of this study helpful in assessing alternative means of dissipating energy when utilizing fixed-cone valves to regulate and control discharge.

Mean Flow and Turbulence Structure in Vertical Slot Fishways

Minnan Liu, Nallamuthu Rajaratnam, F.ASCE, and David Z. Zhu, M.ASCE

J. Hydraul. Eng. 132, 765 (2006); http://dx.doi.org/10.1061/(ASCE)0733-9429(2006)132:8(765) (13 pages) | Cited 14 times

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This paper presents the results of an experimental study on the mean and turbulence structures of flow in a vertical slot fishway with slopes of 5.06 and 10.52%. Two flow patterns existed in the fishway and for each one, two flow regions were formed in the pools: a jet flow region and a recirculating flow region. The mean kinetic energy decays rapidly in the jet region and the dissipation rate in most of the areas in the pool is less than 200 W/m3. For the jet flow, the nondimensional mean velocity profile across the jet agrees very well with that of a plane turbulent jet in the central part of the jet with some scatter near its boundaries. Its maximum velocity decays faster compared to a plane turbulent jet in a large stagnant ambient. The jet presents different turbulence structure for the two flow patterns and for each pattern, the turbulence characteristics appear different between the left and right halves of the jet. However, the turbulence characteristics show some similarity for each case. The normalized energy dissipation rate shows some similarity and has a maximum value on the center of the jet. The results are believed to provide useful insight on the turbulence characteristics of flow in vertical slot fishways and can be used to verify numerical models and also for guidance in the design of fishways in the future.

Modeling Ventilation Phenomenon in Sanitary Sewer Systems: A System Theoretic Approach

S. Edwini-Bonsu, A.M.ASCE and P. M. Steffler, A.M.ASCE

J. Hydraul. Eng. 132, 778 (2006); http://dx.doi.org/10.1061/(ASCE)0733-9429(2006)132:8(778) (13 pages) | Cited 3 times

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Municipal wastewater collection systems, due to the nature of their functions, carry varying concentrations of odorous gases. The production rate and transport of these gases within and out of sewer systems depend on air flow rate in the system piping. However, municipal sewers are generally designed to only transport sewage flow without giving consideration to the air flow field. As a consequence, the movement of air into, along, and out of collection systems is for the most part uncontrolled. The purpose of this paper therefore is to provide a new design protocol based on system theoretic techniques to be used by municipal engineers and environmentalists involved in odor control and sewer foul air transport studies. The modeling formulation accounts for combined wastewater drag and pressure-induced air flows, and manhole pressurization. The developed framework is applied to both hypothetical and real sewer systems to only illustrate the applicability of the modeling formulation.

Dynamics of Air Flow in Sewer Conduit Headspace

S. Edwini-Bonsu, A.M.ASCE and P. M. Steffler, A.M.ASCE

J. Hydraul. Eng. 132, 791 (2006); http://dx.doi.org/10.1061/(ASCE)0733-9429(2006)132:8(791) (9 pages)

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Pressurization in sanitary sewer conduit atmosphere is modeled using computational fluid dynamics techniques. The modeling approach considers both turbulent and laminar flow regimes. The turbulent model takes into consideration the turbulence-driven secondary currents associated with the sewer headspace and hence the Reynolds equations governing the air flow field are closed with an anisotropic closure model which comprises the use of the eddy viscosity concept for the turbulent shear stresses and semiempirical relations for the turbulent normal stresses. The resulting formulations are numerically integrated. The turbulent model outputs are verified with experimental data reported in the literature. Satisfactory agreement is obtained between numerical simulations and experimental data. Mathematical formulas and curves as functions of longitudinal pressure gradient, wastewater velocity, and sewer headspace geometry are developed for the cross-sectional average streamwise velocity.

Godunov-Type Solutions for Transient Flows in Sewers

Arturo S. León, Mohamed S. Ghidaoui, M.ASCE, Arthur R. Schmidt, M.ASCE, and Marcelo H. García, M.ASCE

J. Hydraul. Eng. 132, 800 (2006); http://dx.doi.org/10.1061/(ASCE)0733-9429(2006)132:8(800) (14 pages) | Cited 10 times

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This work is part of a long term project which aims at developing a hydraulic model for real-time simulation of unsteady flows in sewers ranging from gravity flows, to partly gravity–partly surcharged flows to fully surcharged flows. The success of this project hinges on the ability of the hydraulic model to handle a wide range of complex boundaries and to provide accurate solutions with the least central processing unit time. This first paper focuses on the development and assessment of two second-order explicit finite-volume Godunov-type schemes (GTS) for unsteady gravity flows in sewers, but with no surcharging. Traditionally, hydraulic transients have been modeled using the method of characteristics (MOC), which is noted for its ability to handle complex boundary conditions (BCs). The two GTS described herein incorporate BCs in a similar manner to the MOC. The accuracy and efficiency of these GTS schemes are investigated using problems whose solution contains features that are relevant to transient flows in sewers such as shock, expansion, and roll waves. The results show that these GTS schemes are significantly faster to execute than the fixed-grid MOC scheme with space-line interpolation, and in some cases, the accuracy produced by the two GTS schemes cannot be matched by the accuracy of the MOC scheme, even when a Courant number close to one and a large number of grids is used. Furthermore, unlike the MOC solutions, which exhibit increasing numerical dissipation with decreasing Courant numbers, the resolution of the shock fronts was maintained by the GTS schemes even for very low Courant numbers (0.001).

Frazil Ice Blockage of Water Intakes in the Great Lakes

Steven F. Daly and Robert Ettema

J. Hydraul. Eng. 132, 814 (2006); http://dx.doi.org/10.1061/(ASCE)0733-9429(2006)132:8(814) (11 pages) | Cited 1 time

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Each winter, municipal water supply and thermal power plants drawing water from the Great Lakes face the problem of their water intakes becoming blocked by frazil ice formed in the lakes. Little is known about the manner in which frazil forms, how it is drawn down to the depths at which the intakes are located, and how to prevent frazil from fully blocking intakes. This paper presents an overview of frazil formation and intake blockage in the Great Lakes. The paper first reviews the current understanding of the processes of frazil formation and intake blockage, and it adds new insight regarding the processes. It then describes the problem by way of case-study examples of frazil blockage of two intakes in Lake Michigan. Based on the case studies, and experiences with other intakes in the Great Lakes, the paper outlines methods for monitoring and mitigating frazil blockage. Two options are recommended: monitoring rate of water level drop in the pump forebay onshore from the intake, and rate of headloss increase between the intake and the forebay. Laboratory modeling of intake blockage is then presented.

Formation Processes and Configuration of Channel-Flow Dominated Alluvial Deltas by Numerical Simulation

Chih-Ming Tseng, Shaohua Marko Hsu, and Chjeng-Lun Shieh

J. Hydraul. Eng. 132, 825 (2006); http://dx.doi.org/10.1061/(ASCE)0733-9429(2006)132:8(825) (14 pages) | Cited 1 time

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A horizontal two-dimensional mobile bed model for simulating the formation of river-dominated deltas in the river mouth or reservoir is presented, which is composed of shallow water equations, sediment transport formula, and a sediment continuity equation. Geometry similarity of river deltas during the processes of formation is discussed. Stability analysis and sensitivity analysis of parameters in the model are analyzed, which indicates that bed configuration is sensitive to the incipient-motion criteria of bed–load particles. The effect of gravity component on the initiation of sediment movement, therefore, is recommended to be considered in the modeling. The bed configuration including the reverse slope in the longitudinal profile and concave in the transverse profiles are correctly simulated with help from the correction of incipient-motion criteria. Simulation results are verified with a series of experiments and are consistent with series geometric functions and dimensionless profiles inducted from experimental data. This reflects the great reliability of the model. Historical topographical records of two typical in-land deltas depicting their earlier developmental stages are discussed to show the usefulness of this study.

Multilayer Averaged and Moment Equations for One-Dimensional Open-Channel Flows

Cenling Xia and Yee-Chung Jin, A.M.ASCE

J. Hydraul. Eng. 132, 839 (2006); http://dx.doi.org/10.1061/(ASCE)0733-9429(2006)132:8(839) (11 pages) | Cited 2 times

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A model is developed to account for the vertical distribution of velocity and nonhydrostatic pressure in one-dimensional open-channel flows. The model is based on both classical multilayer models and depth-averaged and moment equations. The establishment of its governing equations and the flow simulation are performed over a number of flow layers as in classical multilayer models. However, the model also allows for vertical distributions within a flow layer by including both Boussinesq terms and effective stress terms due to depth-averaging operations. These terms are evaluated on the basis of vertically linearly approximated profiles of velocity and pressure. The resulting additional coefficients can be solved by the moment equations for the relevant layers. Three verifications demonstrate satisfactory simulations for water surface profile, as well as vertical distributions for horizontal velocity, vertical velocity, and nonhydrostatic pressure. Sensitivity analysis shows that the model can be applied with fewer flow layers, more flexibility of layer division, and less computational cost than classical multilayer models, without a remarkable compromise in accuracy.
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Bottom Aeration of Stepped Spillways

Michael Pfister, Willi H. Hager, F.ASCE, and Hans-Erwin Minor

J. Hydraul. Eng. 132, 850 (2006); http://dx.doi.org/10.1061/(ASCE)0733-9429(2006)132:8(850) (4 pages) | Cited 5 times

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The upstream reach of stepped spillway flows may become prone to cavitation damage for large specific discharges because of the absence of air close to its bottom, until the point of bottom self-aeration is reached. This study considers the effect of two aerator types located at the first vertical step face to add air to the chute bottom. Compared to standard stepped spillway flow, considerable differences may be observed closely downstream of the aerator, whereas no significant deviations occur in the far-downstream chute reach. The characteristics of bottom air concentration curves on stepped chutes are investigated with an experimental approach. The results are then compared with flows on both smooth chutes and standard stepped chutes. The data analysis results in design equations that may be applied to usual stepped spillways of chute angles around 50∘. In addition, a sinusoidal variation of air concentration about the average value as a novel phenomenon is described relating to a local instability in the minimum bottom air concentration reach.

Refinement Indicator for Mesh Adaption in Shallow-Water Modeling

Jennifer N. Tate, R. C. Berger, and Richard L. Stockstill

J. Hydraul. Eng. 132, 854 (2006); http://dx.doi.org/10.1061/(ASCE)0733-9429(2006)132:8(854) (4 pages) | Cited 7 times

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Automatic mesh refinement can create suitable resolution for a hydrodynamic simulation in a computationally efficient manner. Development of an automatic adaptive procedure will rely on estimating and/or controlling computational error by adapting the mesh parameters with respect to a particular measurement. Since a primary source of error in a discrete approximation of the shallow-water equations is inadequate mesh resolution, an adaptive mesh can be an efficient approach to increase accuracy. This paper introduces a simple indicator for the shallow water equations that measures the error in a norm of mass conservation to determine which elements require refinement or coarsening. The resulting adaptive grid gives results comparable to a much higher resolution (uniformly refined) mesh with less computational expense.

Formulas for Sediment Porosity and Settling Velocity

Weiming Wu, M.ASCE and Sam S. Y. Wang, F.ASCE

J. Hydraul. Eng. 132, 858 (2006); http://dx.doi.org/10.1061/(ASCE)0733-9429(2006)132:8(858) (5 pages) | Cited 9 times

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Several existing formulas for the initial porosity and settling velocity of sediment have been tested by using extensive data collected from different countries and regions, and modified to achieve better reliability or convenience in use.

Turbulent Flow Friction Factor Calculation Using a Mathematically Exact Alternative to the Colebrook–White Equation

Jagadeesh R. Sonnad and Chetan T. Goudar

J. Hydraul. Eng. 132, 863 (2006); http://dx.doi.org/10.1061/(ASCE)0733-9429(2006)132:8(863) (5 pages) | Cited 4 times

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We present a novel, mathematically equivalent representation of the Colebrook–White equation to compute friction factor for turbulent flow in rough pipes. This new form is simple, no iterative calculations are necessary, and is well suited for accurate friction factor estimation. A limiting case of this equation provided friction factor estimates with a maximum absolute error of 0.029 and a maximum percentage error of 1% over a 20×500 grid of ε/D and R values (10−6 ⩽ ε/D ⩽ 5×10−2; 4×103<R<108). This was more accurate than the best currently available noniterative approximation of the Colebrook–White equation (maximum absolute error of 0.058; maximum percentage error of 1.42%). The superior accuracy, however, was obtained at the expense of a 30% increase in computational effort over the noniterative approximation. The novel equation presented in this study is theoretical and eliminates the need for best fit parameters or complicated initial guesses that are a characteristic of various empirical approximations proposed to date. The simplicity with which this new equation can be solved, coupled with its smooth and predictable error behavior, should make it the method of choice for estimating turbulent flow friction factor in rough pipes.
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Discussion of “Design and Calibration of a Compound Sharp-Crested Weir” by J. Martínez, J. Reca, M. T. Morillas, and J. G. López

Chyan-Deng Jan, M.ASCE, Chia-Jung Chang, and Ming-Hsi Lee

J. Hydraul. Eng. 132, 868 (2006); http://dx.doi.org/10.1061/(ASCE)0733-9429(2006)132:8(868) (4 pages) | Cited 5 times

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Closure to “Design and Calibration of a Compound Sharp-Crested Weir” by J. Martínez, J. Reca, M. T. Morillas, and J. G. López

J. Martínez, J. Reca, M. T. Morillas, and J. G. López

J. Hydraul. Eng. 132, 871 (2006); http://dx.doi.org/10.1061/(ASCE)0733-9429(2006)132:8(871) (1 page) | Cited 1 time

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Review of Turbulent Jets and Plumes— A Lagrangian Approach by Joseph H. W. Lee and Vincent H. Chu

N. Rajaratnam

J. Hydraul. Eng. 132, 873 (2006); http://dx.doi.org/10.1061/(ASCE)0733-9429(2006)132:8(873) (1 page)

Online Publication Date: 14 July 2006

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Papers of Interest

J. Hydraul. Eng. 132, 874 (2006); http://dx.doi.org/10.1061/(ASCE)0733-9429(2006)132:8(874) (1 page)

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