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The Journal contains scientific and technical material of broader interest in the areas of theoretical, experimental and computational hydraulics and fluid mechanics in various fields of application (rivers, coasts, environment, structures and industrial flows). This may also include results of field studies and interdisciplinary studies. Further included is publication of state-of-the-art papers, information which is suitable for the end-user (design and consultancy) and forum articles. Discussions to papers and technical notes are welcomed. The scope of the Journal covers the fields in which IAHR is active.
The Journal of Hydraulic Research has been published (currently six issues per year) since 1964 by IAHR and is distributed to all IAHR Members as part of the Membership Subscription, together with the IAHR HydroLink newsletter. JHR is published in print and electronic format. Abstracts are available on-line from 1996,and Full papers from 2001.

Abstract of Papers - JHR Volume 42 Issue 5

Performance Characteristics of Water Wheels  
by G. Müller and K. Kauppert  

Vol: 42 / Issue: 5

  
During the eighteenth, nineteenth and the first half of the twentieth century, water wheels were important hydraulic energy converters. It is estimated that in England 25,000–30,000 wheels were in operation around 1850; in Germany 33,500 water wheels were recorded as late as 1925. Today, only very few water wheels are still in use. Low head hydropower is seldom exploited, since cost-effective energy converters for these conditions are not available. A small number of companies are currently again manufacturing apparently economically attractive over- and undershot water wheels; the performance characteristics of these wheels are however unclear so that the assessment of the potential of a site as well as their design and efficient operation relies on estimates. A number of engineering textbooks and three detailed experimental studies of water wheel design and performance were published between 1850 and 1935, but nowadays appear to be virtually unknown. A detailed study of these reports was conducted, and the performance characteristics of overshot water wheels were analysed in order to assess the application of such wheels for electricity generation. It was found that water wheels have to be designed for a given flow rate, head difference and intended operating regime. Properly designed overshot wheels have an efficiency of 85%, undershot wheels of approximately 75% for 0.2 < Q/Qmax < 1.0, making this type of energy converter suitable for the exploitation of highly variable flows.Water wheels must, however, be operated within certain parameter ranges in order to be able to perform efficiently; they appear to offer an efficient and cost-effective solution for the exploitation of low head hydropower sources.  

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Environmental Impacts of Coordinated Sediment Flushing  
by J. Liu, S. Minami, H. Otsuki, B. Liu and K. Ashida    

Vol: 42 / Issue: 5

  
The environmental impacts of sediment flushing are predicted by a one-dimensional model for prediction and evaluation of sediment flushing (PESF1D). The model computes one-dimensional unsteady flow and non-equilibrium transport of non-uniform sediment mixtures. In the sediment transport module, bed material load is taken as sediment mixtures for calculating the bed evolution and wash load concentration is computed in consideration of the mixing action between the fine sediments in the flowing water and bed porewater. The influences of tributaries on the concentrations are taken into account in diffusion equations of wash load and suspended load. The non-uniform property of the bed material load is modeled by introduction of a mixing layer, transition layer and deposition strata. PESF1D was calibrated on the basis of the observations during the concerted flushing at Dashidaira and Unazuki reservoirs in 2001. The suspended solid concentrations predicted for potential flushing in 2002 are in good agreement with the measurements during the concerted flushing in July 2002. The dissolved oxygen concentration of the lower Kurobe River would not have strong relationship to the suspended solid concentration. The sediment budget shows the riverbed has been eroded after completion of Unazuki dam in 2001.  

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Rapidly Varying Transient Flows in Alluvial Rivers  
by A. K. Singh, U. C. Kothyar and K. G. Ranga Raju  

Vol: 42 / Issue: 5

  
Extensive changes can occur in alluvial river morphology over relatively short time periods due to such extreme events as a flash flood or flood resulting due to dam break or dike failure. In the present paper the results obtained through the application of a fully coupled one-dimensional alluvial river model are presented for simulation of such sharp hydraulic and bed transients in an alluvial river. Here the governing system of partial differential equations was discretized by making use of the generalized Preissmann finite difference scheme. The resulting set of non-linear partial difference equations was solved by using Newton–Raphson iterative procedure in which the solution for banded matrix of Jacobians was obtained through a hexa-diagonal solution algorithm. The model presented herein has been validated through a number of proofs of the concept tests and by simulating the Quail Creek Dike failure which occurred on 31 December 1988 and 1 January 1989 in Washington County, Utah, USA. The present model was further extended to simulate the processes of grain sorting, wash load transport and non-equilibrium sediment transport. The results obtained from these simulations are presented in this paper.  

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Simulation Study of Flow through a reach of the Chattahoochee River  
by J. Huang, V.C. Patel, Y. G. Lai and L. J. Weber  

Vol: 42 / Issue: 5

  
A three-dimensional numerical hydrodynamic model was developed by the writers to simulate flows through natural river reaches. The model has been successfully applied to and validated for a number of open channel flows. In this study, it is further applied to a flow through a reach of the Chattahoochee River, near Atlanta, GA, for which field and laboratory measurements were performed. The region of interest contains two piers of the Holcomb Bridge, a pier of an abandoned bridge, an old in-stream water intake, and six pump intakes. Good agreement is obtained between the model simulation and the experimental measurements demonstrating the ability of the model to capture important flow features.  

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Conveyance in a two-stage Meandering Channel with a Mobile Bed  
by P.R.Wormleaton, R.H.J. Sellin and T. Bryant  

Vol: 42 / Issue: 5

  
A series of experiments are reported on the conveyance of over-bank mobile bed meandering channels, using the UK Flood Channel Facility at HR Wallingford. The sides of the inner channel were fixed whilst the bed was formed of graded material with a d50 of 1.6 mm. The floodplains were either smooth or, for most experiments, artificially roughened using expanded metal strips. Three floodplain planforms were used, these being straight, sinuous and narrow berms parallel to the inner channel. Inner channel discharges were measured using integrated point values from a 3-D Acoustic Doppler Velocimeter. Most discharge calculation methods for meandering channels employ a horizontal division between the main channel and floodplain meander zone. The results of several of these were compared with the observed data and were shown to be unsatisfactory when the floodplain is rough. This led to the development of a method using vertical interfaces between the inner channel and floodplains, based upon a force–momentum flux balance for the inner channel. This vertical interface method is shown to give improved results for both total and sub-sectional discharges in cases where the floodplain is rough.  

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Evaluation of some Flux-limited high-resolution Schemes for Dam-break Problems with Source Terms  
by M. Tseng and C. Yen  

Vol: 42 / Issue: 5

  
Four approximate Riemann solvers from first-order up to third-order accuracy are presented and compared in this paper for solving one-dimensional rapidly varied unsteady dam-break problems with source terms over wet and dry beds. The effects of tailwater depth, channel width and channel cross-section are also explored. Simulated results are compared with analytical solution and experimental measurements to assess the performances of first-order entropy-satisfying Roe scheme, second-order TVD scheme, second-order ENO scheme, and third-order ENO scheme. For dam-break problems with source terms, the differences in accuracy of simulated results are not so significant among the four solvers. The present study integrates the four approximate Riemann solvers in a formulation together that it is convenient to obtain a suitable solution by evaluating their numerical solutions for engineers to solve different practical problems.  

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The Dynamic Effect of Pipe-wall Viscoelasticity in Hydraulic Transients. Part I— Experimental Analysis and Creep Characterization  
by D. Covas, I. Stoianov, J. F. Mano, H. Ramos, N. l Graham, and C. Maksimovic  

Vol: 42 / Issue: 5

  
The mechanical behaviour of the pipe material determines the pressure response of a fluid system during the occurrence of transient events. In viscoelastic pipes, typically made of polyethylene (PE), maximum or minimum transient pressures are rapidly attenuated and the overall pressure wave is delayed in time. This is a result of the retarded deformation of the pipe-wall. This effect has been observed in transient data collected in a high-density PE pipe-rig, at Imperial College (London, UK). Several transient tests were carried out to collect pressure and circumferential strain data.  

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The Effect of Background Turbulence on Jet Entrainment: an Experimental Study of a Plane Jet in a Shallow Coflow  
by S.J. Gaskin, M. Mckernan and F. Xue  

Vol: 42 / Issue: 5

  
Many effluents are released into water bodies or into the atmosphere, and dilution is relied on to minimize the toxic effects of the pollutants on the environment. Dilution occurs due to entrainment and subsequent mixing of the “clean” (or cleaner) ambient fluid and the effluent stream. In the near field, dilution occurs due to momentum or buoyancy driven entrainment into the effluent stream, which is proportional to a characteristic velocity of the jet or plume. Whereas in the far field, dilution occurs due to turbulent diffusion at a rate dependent on the level of turbulence in the receiving fluid. In order to predict the expected dilution of an effluent stream, it is necessary to answer the question, at what point does the dilution mechanism change and how does it affect dilution rates. An experimental study examining the velocity and concentration decay of plane jets released into shallow coflows with increasing levels of external turbulence, indicated that levels of external turbulence just large enough to disrupt the jet structure reduced dilution rates significantly.  

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Experimental Investigation of Bed-load and suspended-load Transport over Weirs  
by C. Lauchlan  

Vol: 42 / Issue: 5

  
An experimental investigation was undertaken to model the transport of bed-load and suspended-load sediment over steep slopes such as dikes and weirs. Six tests were performed using a vertical wall weir and a sloped (1 : 4) wall weir. Measurements were made of bed-load and suspended-load transport rates upstream and downstream of the test section. It was found that upstream of a vertical weir a strong down-flow vortex forms. This vortex creates a scour hole at the base of the weir and entrains sediment entering the region so that all of the sediment is transported in suspension over the weir. Downstream of the weir a strong reverse vortex traps a proportion of the material in suspension and creates a deposition zone. The sediment supply and flow rate control the temporal development of this deposit. For a sloped weir the down-flow vortex is eliminated at the upstream weir face.  

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Combined-free Flow over Weirs and below Gates By A.M. Negm, A.M. Al-Brahim and A. A. Alhamid  
by Discussers: B. Altan Sakarya, I. Aydin and A. M. Ger  

Vol: 42 / Issue: 5

  
Discussion  

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Exact Solutions for Normal Depth Problem  
by PRABHATA K. SWAMEE PUSHPA N. RATHIE  

Vol: 42 / Issue: 5

  
Normal depth is a key parameter occurring in the design of canals. It also occurs in the analysis of varied flow in canals and natural streams. The open channel resistance equation involves implicit form for all the practical canal sections. The solution of the implicit equation for normal depth involves tedious method of trial and error. Presented herein are the exact equations for normal depth for various open channel sections.  

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