Journal of Hydraulic Engineering

The relationship between the mixing‐length theory and the nonlinear theory is analyzed. The equation of motion for open‐channel flows can be obtained by the Gyarmati integral, which includes the linear and nonlinear terms of dissipation potential. The velocity distribution for laminar and turbulent flows in an open channel can be deduced by this integral. The relationship between the theory of minimum energy dissipation rate and the Gyarmati principle is analyzed. It shows that the constitutive structure of the mixing‐length model is valid in principle from the thermodynamic point of view. For the simple case of quasi‐uniform river flow, the Gyarmati integral of maximization should be reduced to the theory of minimum energy dissipation rate.

Decisions on the timing and location of pumping or recharge in aquifers are in general subjected to physical and operational constraints. The physical constraints are determined by the hydrologic behavior, and the operational constraints by the rules of operation of water allocation and use. The determination of the best strategy of operation requires the simulation of both the physical and operational behavior. In a model designed for interactive decision making, the user can interact with the simulator using a video terminal that graphically displays the simulated state of the system. An interactive simulation model based on the “Discrete Kernel Approach” is presented. The response functions due to unit pulse excitations are generated, using a mainframe computer. After these response functions are generated and stored, the simulation reduces to a simple discrete convolution. These relatively efficient simple computations are done on a microcomputer. Color computer graphics are used to project the simulated state.

The concept of entropy based on probability has been applied in modeling the vertical distributions of the velocity, shear stress, and (suspended) sediment concentration in open‐channel flows. A velocity distribution equation derived by the entropy‐maximization principle has advantages over the Prandtl‐von Karman universal velocity distribution equation. The (maximized) entropy functions derived for the velocity distribution and sediment transport are effective in reflecting the effects of the size of suspended sediment, coarseness of bed material, and sediment concentration. They can, therefore, be used as variables for characterizing and comparing various open‐channel flows. Through their sensitivities to the various parameters needed to describe the flow and sediment transport characteristics, the entropy functions can also be used to obtain much‐needed, new equations for the estimation of parameters difficult to determine owing to insufficient numbers of equations available. The entropy concept provides an excellent vehicle for introducing probability into hydraulics, and such an introduction makes dealing with uncertainties inherent in hydraulic processes possible and help developing sampling schemes, in addition to the modeling and parameters estimation mentioned earlier.

A general planning methodology has been developed for use in the planning of dual‐purpose detention basins. The methodology employs continuous simulation, statistical analysis, and a general design heuristic to obtain an integrated system of detention basins. Both water quantity and water quality constraints may be considered. The methodology developed is used to examine two potential strategies for the design of stormwater management facilities for multiple design frequencies. These two strategies are applied to a synthetic watershed constructed from average geomorphic parameters for the state of Indiana.

Available data on the initial dilution of a horizontal round buoyant jet in a perpendicular crossflow are successfully interpreted using length scales and mathematical models. The database consists of in situ measurements of surface dilution in the sewage boil at a number of sea outfalls in the United Kingdom, as well as limited laboratory experimental data. Simple equations for the prediction of minimum initial dilution in an ambient current are well‐supported by the collective data. The dilution constants obtained are comparable to but greater than those derived from previous laboratory experiments of a vertical negatively buoyant jet in a crossflow. A correlation for the downstream location of minimum dilution is also provided. The results reported herein can be readily used in outfall design.

The properties of buoyant and dense discharges in a horizontal mixing channel are evaluated analytically and experimentally. The mixing channel is shallow, of specified length and roughness, and connected to a reservoir or stream. The flow in the channel consists of a mixing zone and a gradually varied counterflow. Mixing modes associated with four possible interactions are described. A hydraulic theory is formulated and used to develop synthesized dilution curves. Experiments conducted in a laboratory flume confirmed the existence of four mixing modes, and dilution measurements are consistent with predicted trends. In practice, the theory would be useful in the design and operation of such a facility.

Summarized are findings of a computer‐based study of the mud‐flows on Mt. St. Helens following its eruption on May 18, 1980. Analyses were made of the start‐up dynamics and flow of mud down various drainages of the mountain, and of the surge wave generation in Swift Reservoir when the mudflow down East Pine Creek entered the reservoir. Viscosities of mudflows in the Muddy Creek and Pine Creek drainages were evaluated in order to establish a basis for general analysis of mudflow phenomena. Starting with estimates of snow deposition on the mountain, and incorporating the characteristics of the pyroclastic blast of the eruption, initiation of flow was approximated. Subsequent flow down different drainages was modeled, and time sequencing of the flows into Swift Reservoir was compared with measured reservoir elevations recorded on the morning following the eruption. Additional kinematics of the flows were compared with corresponding field measured data where possible.

This experimental study concentrates on the behavior of an axisymmetric jet with an unsteady discharge flow rate. Results show that it is possible to categorize unsteady jets with a linear ramp time-discharge variation into quasi-steady and steady groups based upon the fluid travel time to a fixed downstream station.

This note presents the results of an experimental study on the hydraulics of two-level Denil fishways. The two-level Denil appears to be particularly suitable for situations with large values of d/b for which the simple Denil would create fish passage problems because of its high velocities.