Showing papers in "Journal of Hydraulic Engineering in 1965"

Erosion and Deposition of Cohesive Soils

Abstract: The effects of shear stress, suspended sediment concentration, and shear strength of bed on the erosion rates of a cohesive bed in an open channel with salt water have been investigated. The deposition rates of suspended cohesive sediment and the patterns of bed erosion have been studied to a lesser extent. For the experimental range the erosion rates were found to be independent of the shear strength of the bed and the concentration of suspended sediment. They depend strongly on the bed shear stress. The minimum shear stresses for initiation of erosion were also found to be independent of the shear strength of bed. There seems to exist a critical velocity for the clay part of suspended sediment, above which all such sediment remains in suspension, whereas even for velocities slightly below this critical limit, the suspended clay deposits rapidly. Scouring occurred predominantly within a well defined narrow and relatively straight zone near the center of the flume.

Calculation of Nonuniform Sediment Concentrations

Abstract: A method of calculating sediment concentration and discharge for large range mixtures is presented. An attempt is made to determine that part of hydraulic radii which is responsible for sediment discharge rate for granular beds with channel configurations. A comparison of theoretical calculations using the proposed method with field (nature) measurements and with results of the H. Einstein 1950 method and its modification is made.

Critical Analysis of Open-Channel Resistance

Abstract: Despite continued progress in the analysis of closed-conduit and boundary-layer resistance, many of the results have been slow to find their way into the hydraulics of open channels. In this paper an effort is made to take greater advantage of existing knowledge in related fields, largely through findings from a continuing program of research in which the writer has been engaged for several decades. The general resistance function is examined under the following interdependent categories: Effects of viscosity, roughness, and shape of cross section; effects of boundary nonuniformity; and effects of unsteadiness, particularly free-surface instability. Special attention is given to such matters as integration of the logarithmic velocity law, variation of roughness form and concentration, channel choking in the critical region, and resistance augmentation by both standing and traveling waves.

Mathematical Models of Catchment Behavior

Abstract: After an examination of trends in the modeling of hydrologic systems, a review of some recent studies is given. The authors' preliminary studies on the feasibility and efficiency of the automatic evaluation of catchment model parameters by use of a digital computer are described and some results presented.

Computer Analysis of Overland Flow

Abstract: A method for synthesizing overland flow hydrographs using a high-speed digital computer is presented. The parameters of the flow equations are individually varied and the resulting hydrographs shown. These hydrographs are then used to produce a single dimensionless hydrograph and a general relation for time to equilibrium flow, from which the hydrograph for any combination of parameters encountered in this study may be constructed.

The Hydraulic Jump as a Well Jet

Abstract: An attempt to study the mechanics of the hydraulic jump, treating it as a plane turbulent wall jet under adverse pressure gradient, is presented. Extensive measurements have been made regarding the pressure field, velocity distribution, and the boundary shear stress in the jump for nine supercritical Froude numbers from 2.68 to 9.78. It has been found that the pressure distribution is hydrostatic only in a narrow region near the bed. The velocity distribution in the forward flow is similar. The skin friction coefficient based on the supercritical velocity decreases monotonically with x/y2, in which x is the distance from the beginning of the jump and y2 is the subcritical sequent depth. A more accurate form of the momentum equation for the jump has been developed. Also, a method has been devised to predict the surface and energy profile in the jump.

Submerged Hydraulic Jump

Abstract: This paper presents a study of the submerged hydraulic jump as the case of a plane turbulent wall jet under adverse pressure gradient with backward flow on top. Using the experimental results of the author for the forward flow and those of Liu and Henry for the backward flow, a method has been devised to predict the surface profile, and the fall of the pressure plus momentum and the energy in the submerged hydraulic jump. Also a study has been made of the boundary shear stress that was measured with a Preston tube.

Spurious Correlation in Hydraulics and Hydrology

Abstract: Spurious correlation is the correlation built into ratios, products, or other functions of two sets of random variables when the two sets have some elements in common. In hydraulic and hydrologic literature, many instances may be found of spurious correlations that are mistakenly interpreted as establishing relationships between single elements when such relationships may not exist or may not be as closely defined as they appear to be. Examples are given from technical literature. Tables are presented giving means, standard deviations, and correlation coefficients for ratios and products of variables, for both general and specific cases. Caution is advised in the use of functions with common elements.

Wind Driven Water Currents

Abstract: Flow induced in a body of water by wind blowing over the surface is studied in a series of experiments in a laboratory channel. Results are coordinated by dimensional analysis and general principles of turbulent flow. For large Reynolds number, mean and turbulent velocities when related to shear velocity follow an outer law distribution. Effects of vertical and lateral channel contraction are also considered.

Potential Evaporation and River Basin Evaporation

Abstract: Potential evaporation is a measure of the energy available for evaporation, whereas the evaporation from the water, soil, and vegetation surfaces of a region is controlled by the availability of both energy and water. A recent analysis of the regional energy balance has suggested that the potential evaporation is a measure of the extent of regional evaporation that does not occur because of the control imposed on the availability of water by soil moisture and vegetation processes. The suggestion is incorporated into a method for computing regional evaporation from climatological observations. The method is tested by comparing computed potential evaporation—one of its principal components—with observed pan evaporation and by comparing computed regional evaporation—its end product—with river basin evaporation derived from rainfall and runoff records. It is concluded that changes in regional evaporation caused by changes in the availability of water are reflected in the potential evaporation and that the method formulated by the writer may be used as a working hypothesis for computing regional or river basin evaporation from climatological observations.

Turbulent Flow in a Three-Dimensional Channel

Abstract: The results of tests to define the Reynolds stress tensor in one corner of a straight, smooth, closed conduit of rectangular cross section were presented. The measurements are used in conjunction with a simplified version of the equations of motion to conclude that secondary motions will be present in any established flow in a conduit of noncircular section. One of the boundaries may be a free surface. The sustaining mechanism for the secondary motion is shown to depend on the horizontal and vertical components of the turbulent motion. A physical justification for the measured behavior of these components is obtainable from the consideration that the magnitude of a velocity fluctuation normal to a boundary is inhibited by proximity to the boundary, whereas a similar restriction on the component parallel to the boundary does not exist. Direct measurements of the secondary motions were obtained.

Theoretical Aspects of Seepage from Open Channels

Abstract: Seepage from open channels was evaluated by analog in relation to depth and shape of the channel, position of the water table, and the saturated and unsaturated permeability of the soil. Subsoil conditions included an impermeable layer and a permeable layer at varying depth. The case of clogged bottoms and banks was treated analytically. For trapezoidal canals with 1:1 side slopes, a bottom width W\Db\N, and a surface width W\Ds\N, soil conditions at distances more than 5 W\Db\N below the bottom have little effect on seepage. Lowering the water table increases the seepage, but when the water table at a horizontal distance of 10 W\Db\N has reached a depth of 2.5 Ws below the water level in the channel, the seepage is already near that at infinite depth of the water table. Seepage increases with increasing water depth, but at a slower rate than the discharge for uniform flow. Therefore, canals convey water more efficiently when deep than when shallow. Other analyses refer to the effect of bottom treatment for seepage reduction, and to the effect of unsaturated flow on seepage.

Horizontal Jets in Stagnant Fluid of Other Density

Abstract: The influence of the density difference between a jet and the surrounding fluid on the diffusion caused by a circular horizontal submerged turbulent jet is studied theoretically on the basis of the similarity principle. A theoretical solution is given on the basis of the assumption that the local variation of density in the jet is small in comparison with the density of the ambient fluid. The theoretical results show how the coordinates of the axis of the jet and the rate of mixing, and the velocity at the axis of the jet depend on the initial density difference between the jet and the stagnant ambient fluid and on the velocity of the jet when it issues from a nozzle. The theoretical solution agrees fairly well with experimental data available in literature. Only three dimensional, circular horizontal jets are considered in this study.

Use of Interrelated Records to Simulate Streamflow

Abstract: Streamflow simulation is usable in water resources design for the purpose of extracting pertinent information from streamflows at recorder locations and using that information to generate additional values for those locations, and values for additional locations, that could as reasonably occur in the future as could repetition of past events. An electronic computer procedure is described that extracts a maximum degree of pertinent information from monthly streamflow data and generates values whose statistical characteristics are consistent with those of the observed monthly streamflow. Multiple linear regression of the data transformed to unit normal standard deviates is used. A procedure is described for using data that are not simultaneous at all recorder locations and that would permit formulating an interrelated-streamflow generator for ungaged locations.

Flow Over a Vertical Sill in an Open Channel

Abstract: An investigation of a particular case of flow over a vertical sill is reported. This flow consists of a definite nonuniform reach between two flow sections, the entrance section upstream of the sill at which a supercritical flow exists and the surface roller of a forced hydraulic jump begins, and the exit section downstream of the sill at which uniform subcritical flow is reached. The flow is described by five dimensionless variables, the Froude number, and four similarity criteria for flow geometry. The relationships among the variables are given by graphs based on experimental data. The boundary values and the similarity concepts for the flow have been defined. The results are applicable to the design of hydraulic jump stilling basins.

Withdrawal from Two-Layer Stratified Flow

Abstract: Theoretical and experimental studies at the Massachusetts Institute of Technology Hydrodynamics Laboratory and TVA's Engineering Laboratory have established the general flow and design relationships involved in the controlled withdrawal from the bottom layer of fluid in a two-layered flow system having a discrete interface. These data allow the design of skimmer wall structures which make possible such controlled withdrawal. This paper describes the theoretical considerations, the test arrangements used to obtain the laboratory data, and presents a comparison of the laboratory and theoretical results.

Yearly sea level variations for the United States

Abstract: Yearly mean sea level series from 44 Coast and Geodetic Survey (U. S. Environmental Science Service Administration) tide stations are analyzed. An empirical classification is obtained from the relationship of series trend to yearly variability that uniquely groups specific geographical areas. The groups, together with their average trends for the longest common series, 1940 to 1962, are as follows: Northern Atlantic, 0.011 ft per yr; Southern Atlantic, 0.009 ft per yr; Pacific, 0.002 ft per yr; Gulf, 0.007 ft per yr; Southeast Alaska, -0.023 ft per yr. Significant changes in trend with time are not evident at the representative stations of New York since about 1950 and Fort Pulaski and Cedar Key since about 1953. The longest continuous series, New York, begins with 1893. The mean initial year for the 44 series is 1925.

Secondary Currents in a Corner

Abstract: The weak secondary current that occurs in flow through noncircular conduits is studied. Equations giving the magnitude of the secondary velocities near a corner are developed. These equations are based on empirical data of primary velocity distribution. Experimental measurements of the secondary current tend to confirm the validity of the relationships and solutions.

Ground-Water Models Solved by Digital Computer

Abstract: Ground-water data may be stored conveniently on punched cards or magnetic tapes. Ground-water problems may be solved by analyzing the stored data using digital-computer programs that describe finite-difference models of aquifer performance. The methods were used to predict the effect of a proposed reservoir on water levels in the Old Bridge Sand Member of the Raritan Formation of New Jersey.

Channel Gradients Above Gully-Control Structures

Abstract: Regression techniques are used to determine some significant factors affecting the slope of the sediment deposition profile above gully-control structures and debris dams. Analyses of field data on gully-control structures in Wisconsin and debris dams in California show that the original channel slope, the width of the channel at the structure, and the height of the spillway crest above the original thalweg are statistically significant variables.

Boundary Layer Development and Spillway Energy Losses

Abstract: Recent studies of the mechanics of the turbulent boundary layer development have resulted in knowledge applicable to the spillway energy loss problem. The significance of the boundary layer, displacement, momentum, and energy thicknesses is studied relative to the spillway energy losses. The results of a laboratory investigation on the turbulent boundary layer development are correlated with limited prototype data and extended to include the concept of energy thickness. A design procedure is included that should provide more accurate estimates of spillway energy losses than procedures previously published. Design charts are also included. In most cases of high structures the turbulent boundary is probably not fully developed before the design flow reaches the energy dissipators. Therefore, the described procedure should serve as a useful design tool.

Wave-Induced Oscillations in Harbors

Abstract: The problem of wave induced oscillations of a small rectangular harbor that is connected to a larger rectangular wave basin is treated. This model system, without artificial energy dissipators, was studied experimentally and theoretically to determine how accurately this arrangement could predict the resonant modes of oscillation of a similar harbor connected to the open sea. The effects of energy dissipators on the harbor response characteristics are discussed briefly. Because of the high degree of coupling between the rectangular harbor and its attendant wave basin, the response characteristics of the model harbor as a function of incident wave period were radically different from a similar prototype connected to the open sea. Efficient wave absorbers and wave filters in the main wave basin are necessary to reduce this coupling effect.

Vertical Drainage of an Unsaturated Soil

Abstract: The general equation describing vertical unsaturated flow of soil water is solved by numerical approximation for several cases. The computer programs are described. The results show: (1) The intermediate belt of a well-drained unsaturated soil approximates field capacity during times of small evapotranspiration and intermittent penetrating rainfall; (2) infiltrated rainfall moves as a pulse with a steep wetting front; (3) the belt of soil water drains from saturation to approximately field capacity within two days for zero evapotranspiration.

Total Bed-Material Transport

Abstract: A method of estimating the bed-material discharge of sand-bed flumes, canals, and rivers is presented. The method uses a group of curves developed from flume data that relate intensity of transport, intensity of shear, and the median fall diameter of the bed material. Also, these curves illustrate that the intensity of transport varies with regime of flow and form of bed roughness. Application of the method yields good results for sand-bed channels when the depth of flow is less than 4 ft.

Sequential Generation of Rainfall and Runoff Data

Abstract: A practical procedure is demonstrated by applying sequential generation techniques to rainfall and runoff data for stochastic, hydrological analysis of drainage basin systems. In this method, the stochastic process is formulated by several major components including the hourly annual storm rainfalls, the abstractions, the routing model, the baseflow, the direct runoff, and the total runoff. As a practical example, 28 annual storms and the corresponding runoff data recorded in the French Broad River Basin at Bent Creek, North Carolina, are used in the analysis. Conventional models are adopted for separations of the abstractions and the baseflow. The hourly storm rainfalls are represented by a Markov-chain model. The basin system is simulated by a series of equal linear reservoirs. The nonlinearity of the system is considered by varying system parameters. From the historical data, 1,000 annual storms are generated sequentially by the Monte Carlo methods and then routed through the simulated basin system to produce 1,000 generated floods which are represented by stochastic flow-duration curves for use in water resources planning and design.

European Concepts of Sediment Transportation

Abstract: Recent investigations indicated that the various aspects of sediment movement are more closely related than was originally thought. Establishment of a sound criterion for determination of the regime of sediment movement offers, at the same time, the possibility of solving individual problems of sediment transportation. A brief review of the European studies will suffice to show more definitely that the stage of incipient motion, the various boundary conditions of sediment movement, and the sediment-transporting capacity are all governed by the same set of variables. These variables are interrelated and their simultaneous inclusion is not necessary for the solution of a given problem. The relationship defining certain stages of sediment movement may become extremely simple if the parameters are suitably selected, and at the same time the effect of numerous variables involved in sediment transportation can be allowed for. European practice distinguishes between sediment studies conducted on a natural watercourse and those conducted experimentally under laboratory conditions. Relationships among parameters describing regimes of sediment movement in many European investigations are presented and analyzed.

Economics of Ground-Water Recharge

Abstract: Benefits and alternatives to artificial recharge are summarized, cost components are reviewed, and costs of selected projects are presented. The value of water is reviewed and the direct and indirect benefits of recharging are considered. Institutional and financial arrangements for artificial recharge projects are studied. Particular attention is given to California's Water Replenishment District Act and to the use of the replenishment assessment as a means for financing projects. Some data on costs of water wells and pumping ground water are presented because extraction of ground water is a part of the total recharge cost. Generalized cost estimates of various items involved in recharge projects are tabulated, including costs of actual projects in California and Illinois. Because of the variability of size, purpose, and method of operation, together with a wide range in land and water costs, no concise summary of recharge costs is possible.