Journal of Hydraulic Engineering

A layer‐averaged model for steady, spatially developing turbidity currents laden with poorly sorted sediment is presented together with laboratory experiments conducted to test several assumptions involved in the model development and to gather basic information about such flows and the sediment deposits that they generate. Measured flow velocity and sediment concentration profiles displayed a good degree of similarity and facilitated the evaluation of shape factors. The amount of sediment deposition and grain size of the deposits were found to decrease monotonically with distance from the source. The ability of the theoretical model to reproduce the depositional pattern and grain‐size variation with distance was tested using data from a strongly depositional current. The laboratory observations were reproduced fairly well by the model.

Dispersion processes in the near‐shore coastal waters 15 km south of the Hudson‐Raritan estuary of New Jersey are investigated using measurements of velocity and salinity profile at two locations, one 600 m offshore in a 10.7‐m‐deep water and the other 1,200 m offshore in 12.8‐m‐deep water. Following the traditional approach, we seek to quantify dispersion coefficient $K$, representing the various mechanisms responsible for alongshore dispersion. The velocity and salinity measurements are decomposed into spatial and temporal averages and deviations from the averages. Using the various correlation terms, contributions to the salt flux in the alongshore direction—such as the mean advection, the residual circulation, and the oscillatory shear flow induced by wind variations—are determined. These contributions are then employed in the estimation of the horizontal (alongshore) dispersion coefficient. The time variation in the coefficient over the 30‐day study period is presented, revealing a high degree of variability, with magnitudes ranging from 360 to 2,700 m²/s. This variability is attributed to the extremely variable wind speed and direction observed during the study period, with the freshwater discharge of the esturary also playing an important role.

Strong convection can be produced by placing a V‐shaped plate in a horizontal flow. Vortices that shed from the plate coalesce with neighboring ones to form a horseshoe‐shaped vortex. The self‐induced upward motion produced due to the shape and the flow converging and surmounting the plate raises the vortex head, resulting in the vertical convection. The dependence of the motion of the three‐dimensional vortex filaments on the dihedral angle of the V‐shaped dihedral plate and Reynolds number of the mean flow have been numerically simulated. It was found that the maximum vortex raising height can be attained with a dihedral angle of about 90°

The present paper provides an experimental study of standing waves generated by piers in chute spillways. The wave pattern is described with the coordinates at the wave beginning, at the section of maximum wave height, and at the wave end. Wave 1 refers to the immediate tailwater zone of the pier, whereas wave 2 may appear at the chute wall farther downstream. Both waves tend to become independent of the approach Froude number provided $F_0>5$. Wave 1 is shown to depend exclusively on the ratio of approach flow depth to pier width, whereas wave 2 is also affected by the relative wall distance. The flow is described both analytically and by selected photographs. Means to reduce the wall waves are presented. The principle of wave reduction involves a shift of wave phases of the flows originating from either pier side. The optimum length of pier extension length is discussed and a design procedure is represented. As a result, standing chute pier waves can practically be inhibited.

Recent attempts have been made to reduce scour around solid circular piers. Such attempts use riprap, a circular collar around, a rectangular slot through, and a delta wing‐like fin ahead of piers. Providing another scour reduction device, the present paper replaces the solid pier by a group of three smaller piers. A pier group starting from its foundation and extending fully into the flow depth is termed a “full pier group” and one extending partially into flow depth a “partial pier group.” The scour due to a pier group in its best orientation is compared with that due to a solid pier of diameter equal to the circumscribing circle diameter of the pier group. It was observed that the scour reduction due to a full pier group is about 40%, and 75% of this reduction can be realized by a partial pier group extending into half the flow depth only. Also, the full pier group is seen to be more effective than a solid cylinder with a full slot of width equal to half its diameter and as effective as a solid cylinder with a collar 3.5 times its diameter. A collar on a pier group is much more effective than on a solid pier.

Besides discharge $Q$ and sediment characteristics (size $D_{50}$ and concentration $C$), the third physical factor governing hydraulic geometry of an alluvial canal is resistance to erosion of bank material. Lacey formulas provide one set of the parameters of hydraulic geometry through the wetted perimeter $P$, hydraulic mean radius $R$, and slope $S$, with implied values of sediment concentration $C$ and maximum safe boundary shear stress t\ds. But with varying values of $C$ and t\ds, many other sets of $P$, $R$, and $S$ are possible. Defining Lacey divergence as the ratio of actual value to value obtained with the Lacey formula and designating this ratio by subscript $r$, Lacey Divergence relations were obtained for velocity $V$ and $C$. Velocity ratio V\dr was found related only to slope ratio S\dr, whereas sediment concentration ratio C\dr was related to both S\dr and boundary shear stress ratio t\dr. Equations were then derived for P\dr, R\dr and S\dr in terms of C\dr and t\dr, which permit determination of $P$, $R$, and $S$ when design data in respect of $Q$, $D_{50}$, $C$, and t\ds are given.

Complete vertical velocity profiles were measured at 13 streamflow‐gaging stations across the northern United States to evaluate streamflow‐velocity adjustment coefficients and discharge‐measurement procedures under an ice cover. Adjustment coefficients at several common vertical positions varied significantly from station to station and from measurement to measurement at some stations. The ice‐cover roughness was the primary factor affecting the profiles at most stations. Several discharge‐measurement procedures were developed using one‐half of the data collected, and the accuracy of the procedures were evaluated using the other half of the data. The relative error for each method was computed by comparing estimated discharge to discharge computed using complete vertical‐profile information. Two procedures—a one‐point method with velocity measured at $0.4D$ (where $D$ is the effective depth of flow) using a site‐specific adjustment coefficient and a two‐point method using velocity measured at $0.4D$ and $0.8D$—were found to be the most accurate in terms of bias and root‐mean‐squared error. Further study is needed to evaluate the efficiencies of these two methods.

Theoretical solutions are proposed for the hydrodynamical characteristics of mining pits in erodible beds. These solutions are derived from the linear St. Venant equations of momentum and continuity for appropriate initial and boundary conditions. Pits of trapezoidal and rectangular shapes and discussed, although it is indicated that pits of any regular geometric shape can be considered for solution. Solutions are also given for two trapezoidal and rectangular pits in the same bed. Theoretically, solutions can be developed for any number of pits of any regular geometric shape in the same bed. Numerical results are plotted for one and two trapezoidal pits, respectively, in an erodible bed.