Journal of Hydraulic Engineering

The results of a study on the effect of ice cover on oil slicks contained by booms in rivers are presented. Experimental observations on velocities in the oil slick obtained by laser doppler anemometry are found to agree well with theoretically predicted profiles. The effect of the ice cover is to increase the thickness of the ponded slick by one‐third. It also increases the stability of the oil water interface.

A computer model based on both the energy and momentum equations is developed. This generalized model can be used for the computation of water surface profiles through hydraulic jumps. It also allows computation of water surface profiles regardless of whether the bed slope is steep, mild, horizontal, adverse or a combination of these. The control section can be a lake, weir, gate or a natural river section. The Manning, Chezy or Darcy‐Weisbach equations, can be used for head loss computation. A detailed description of methods used and a step‐by‐step computation procedure is given. Examples are used to demonstrate the applications of this generalized model for water surface profile computations.

Labyrinth‐crest spillways provide an economical flood‐handling structure provided the operating head is small. This paper describes the design of A spillway with a labyrinth crest for which published discharge characteristics were uncertain for higher heads. To verify the design, a model study was conducted which indicated that actual discharge would be at least 20% lower than originally estimated. Details are presented for the design criteria for the spillway crest and for the flow conditions downstream including the chute, the energy dissipator, and the receiving channel.

The need for skimming of fresh groundwater above a saline water body without producing an unacceptable contamination in the pumped water calls for the investigations carried out in this research work. Two axisymmetric models, namely the steady state and the transient upconing models, are developed with the assumption of an abrupt interface. Finite element method with an iterative scheme is employed in solving the steady state model whereas a method of finite element in space and finite differences in time is used with iterative schemes for the transient model. The models are calibrated with the analytical solutions for the case of radial flow to a fully penetrating well in an unconfined aquifer. A method of superimposing the effects of hydrodynamic dispersion on the upconing is discussed. The simulation results of both models, together with the technique of dimensional analysis, provide information for establishing design criteria for optimal pumping or choice of well depth or both.

An analytical diffusion model for flood routing which can take into account backwater effect and lateral flows has been developed. The model is applied to route the floods in a hypothetical rectangular channel with different upstream, downstream, and lateral boundary conditions. Different channel characteristics are assumed and the results obtained are found to check well with those obtained by the finite difference method of implicit scheme based on the complete Saint‐Venant equations for unsteady open channel flow. The model shows good results when applied to simulate flood flow conditions in 1980 and 1981 in the Lower Mun River, in Northeast Thailand. The model cannot be incorporated with detailed data of cross sections or river bed geometry but requires only their average values. The Chézy, C and the diffusivity, k due to channel irregularities are used in the model and are determined by trial and error during model calibration. The model provides an excellent means to analyze individual or overall effects of the boundary conditions and requires much less effort and time for computation at a particular station.

A closed‐form solution is obtained with the help of the seepage theory and the Schwartz‐Christoffel transformation for determination of average uplift pressures for any section of hollow gravity dam. The average uplift pressure is calculated numerically from the derived equations and plotted to facilitate the use of the results for design purposes. It is seen that the average uplift pressures drop almost linearly to about 5–22% near the head of the cavity. The average uplift pressure opposite the cavity head decreases with an increase in the value of $l_1/b\text{,}$ and decreases in the value of $b_1/b\text{.}$ The average uplift pressures beyond the cavity head drop to approximately negligible value at a distance of about $\mathrm{2b}$ from the head of the cavity. By shifting the cavity head towards downstream, the average uplift pressures increase in the entire upstream portion.

A nonequilibrium formula in terms of the depression cone volume is used to predict the drawdown variations in a fully penetrating large diameter well discharging from a leaky aquifer. The derivation of the formula is based on the continuity and Darcy laws. Sets of type curves are presented to find the aquifer and aquitard hydraulic properties. The asymptotic curves, as the leakage diminishes to zero, approximate the type curves for large diameter wells in confined aquifers. Leaky aquifer type curves for drawdowns in the producing well have three distinctive portions. The initial portion is a straightline and it reflects the effect of the well storage. It does not provide any relevant information about either the aquifer or the semipervious layer hydraulic properties. The second portion is a transition from the well storage effect to the complete leakage effect only. The last portion is a horizontal line corresponding to the steady state flow due to leakagev. In fact, the second portion is the most significant one from the aquifer parameters determination point of view. Comparison of these type curves with the point source solution indicates that the deviations are larger for small times but large leakages. However, for large times and small leakages, these deviations reduce to practically acceptable limits.

The paper presents results of harmonic analysis in studying particle motion in oscillating flows. An approximate equation is derived to solve the zeroth harmonic equation, which governs the effective fall velocity $\overline{\nu }{}_s\text{,}$ of particles in oscillating flows. The equation reveals that the drag force on the particles is significantly modified by the instantaneous relative velocity between particles and fluids. Three major factors that govern the variation of $\overline{\nu }{}_s$ (as compared to the terminal velocity in still water are the terminal velocity Reynolds number, the phase lag, and the velocity amplitudes of the flow and particle oscillations. The dimensionless equation is given. Applying to the sediment suspension under wave action, the analysis suggests that an enhancement of suspension should occur.

The regime geometry and channel patterns of alluvial rivers are analyzed Wing an energy approach together with physical relationships of flow continuity, flow resistance, and sediment transport. Because of the discontinuity in flow resistance, and thus in power expenditure, between lower and upper flow regimes, the adjustment in river regime consists of sudden changes in channel geometry, channel pattern, and sometimes silt‐clay content, when such a discontinuity is crossed. Thresholds or discontinuities in river morphology are obtained in the analysis. In accordance with such thresholds, rivers of distinct morphological features are classified into four regions based upon the bankfull discharge, channel slope, and median size of bed sediment. Their respective features are described, and certain regime relationships for channel width and depth are established. The predicted channel geometries are compared with river data.

The available information on incipient sediment motion criteria for both unidirectional and oscillating flow motions is summarized and analyzed according to the Shields diagram for incipient motion. The Shields diagram is extended for large and small particle sizes, on the basis of data collected in China. Design guides prepared by the U.S. Army Corps of Engineers and the California Department of Transportation are compatible with the extended Shields diagram for incipient motion.

Plane flow with moderately curved and involved bounding streamlines is investigated by accounting for the transverse variations of the velocities. The result is a highly nonlinear version of the corresponding Boussinesg relation (valid only for weakly curved and sloped stream lines). Applications include the computation of the cnoidal and solitary wave profiles and indicate a clear advantage of the present formulation over previous ones.

To compute groundwater solute transport, the CPU memory requirement can be drastically reduced by using the subregion iteration of the orthogonal-upstream weighting finite element method. The use of an orthogonal-upstream weighting function results in an irreducible and diagonally dominant coefficient matrix. These properties provide sufficient conditions for the convergence of block iteration methods. Computer runs for a test problem were carried out for 10 × 10, 30 × 30, and 50 × 50 grid systems with 2, 3, and 4 subregions. The CPU memory and CPU time were monitored during each run. The number of iterations required for the convergent solution in each time step was also recorded. The results are useful for determining the number of subregions required for a given computer memory capacity, and for estimating the CPU time when using the subregion iteration method.