Journal of Hydraulic Engineering

The measurement of suspended sediment, particularly in field settings, is important in the documentation of sediment transport and deposition. Many measurement techniques have been used with varying degrees of success. The techniques, including their operating principles, advantages, and disadvantages are discussed. The techniques discussed include acoustic, bottle, pump, focused beam reflectance, laser diffraction, nuclear, optical backscatter, optical transmission, and spectral reflectance. Emphasis is placed on instrumentation techniques, as this is the area of suspended-sediment measurement that has the greatest potential for improving sediment data. Acoustic technology (if further developed) emerges as a promising technology because of its ability to measure the concentration profile without intruding into the flow. This technology-transfer information will be valuable to practitioners and researchers needing to choose a means of measuring suspended sediment. The choice of a measurement technique has implications for sampling efficacy and expense.

Based on a method of combining stochastic processes with mechanics, a new bedload formula for the arbitrary kth size fraction of nonuniform sediment is theoretically developed by using a stochastic model of sediment exchange and the probabilistic distribution of fractional bedload transport rates. The relations, proposed recently by Sun, for the probability of fractional incipient motion and for the average velocity of particle motion are introduced to bedload formula. Plenty of experimental data for the bedload transport rate of uniform sediment are used to determine two constants. The theoretical bedload formula for any fraction of nonuniform sediment possesses several advantages, including a clear physical concept, a strict mathematical derivation, and a self-adaptability to uniform sediment. The formula is verified with natural data expressing the transport of nonuniform sediment under full motion in laboratory flume. The result shows that the experimental observations agree well with the predicted fractional bedload transport rates. Comparison of the theory with field data finds that the proposed formula still applies to partial transport of bedload in gravel-bed streams as long as the immobile percentage of bed material is taken into account.

A method for determining the flow carrying capacity of a channel system, capable of accounting for the interacting backwater effect among channel reaches and incoming lateral flow, is presented here. The method makes use of hydraulic performance graphs—a new tool for dealing with open-channel-flow problems. The hydraulic performance graph summarizes all the backwater profile information for a channel reach. As an illustration, the method is applied to evaluate the channel capacities of a portion of Boneyard Creek in the city of Urbana, Ill. The example demonstrates that the channel flow capacity is a function of the exit water level, of which the maximum normal flow capacity and the absolute maximum carrying capacity are special cases.

In the framework of the present study, 2D and 3D finite-difference procedures have been developed and applied with regard to flow, heat, and contaminant transport in the marine environment, where a shallow aquatic environment can be assumed. The common characteristic of such a type of environment is that the water depth is much smaller than a typical length in the horizontal direction. Conditions of this environment allow 2D or shallow water 3D numerical models to be applied instead of a more expensive and time consuming full 3D solution. Such an approach is almost obtained without loss of accuracy. By reference to a practical case of a wind dominated environment, the requirements and possible use of the 2D or 3D numerical codes are identified and analyzed. It is shown that the applicability of the 2D model mainly depends on the wind direction. Considerations are made with regard to recirculation of thermal effluent into the inlet of a power station. It is shown that, even in an extremely complicated geometry of the simulated domain, the 2D and 3D simulations can provide the same order of magnitude of results for some wind directions, particularly in the case of wind blowing parallel to the shoreline. On the other hand, for a wind direction nearly perpendicular to the shoreline, the 2D model produces unreliable or simply nonphysical results, whereas the 3D model provides reliable results. These conjectures are of great practical importance because most of the previous thermal effluent studies have been carried out by using the 2D modeling. It is considered that the performance of the 2D and shallow water 3D simulations provide an adequate description and understanding of basic transport phenomena in the simulated domain

New data describing the longitudinal dispersion of a solute tracer due to a surcharged manhole structure are presented. The increase in both travel time and dispersion caused by this structure is quantified over ranges of discharge and surcharge. Discharge variations exhibit clear trends, whereas surcharge variations are less evident. The results are presented as both Taylor dispersion coefficients and values of parameters used in aggregated dead zone modeling. The limitations of using surcharged averaged parameters with each technique for describing mixing due to a surcharged manhole structure are illustrated. The study shows that the presence of manhole structures within urban drainage schemes has a significant effect on both the travel time and mixing processes of a solute. It is suggested that these processes should be included for the accurate modeling of urban drainage schemes.

A theoretical analysis and an experimental study on the efficiency of water jet pumps, where water is used for both the primary and secondary flows, are presented in this paper. The theoretical efficiency equations for such jet pumps were first derived based on one-dimensional formulation, and the theoretical maximum ideal efficiency of 100% was obtained. An experimental rig was designed and constructed to conduct the experimental study in which a commercial water jet pump was used. The effects of different area ratios of nozzle to mixing throat as well as different nozzle cross sections, which include square and triangular nozzles, on the jet pump performance were then investigated. The best nozzle cross section for the jet pump was found to be circular, and for high efficiency, the area ratio was found to be around 0.30.