Journal of Hydraulic Engineering

Steady recirculating flow is described by means of a mathematical model based on the full unsteady Reynolds equations and the $K‐\epsilon$ model for turbulence closure. The model is applied to the flow in a steep‐sided trench perpendicular to the main flow direction. Inlet profiles are taken with reference to developed channel flow. For the wall boundary a local equilibrium is assumed, yielding among others a logarithmic behavior for the mean flow velocity. The constants of the $K‐\epsilon$ model are related to the roughness conditions. A sensitivity study is reported to identify the relative importance of the various constants and inlet conditions. Numerical results are compared with laboratory experiments.

Six methods for predicting friction factor are evaluated and a new method is presented which better predicts flow depth (and therefore friction factor) when discharge and slope values are known. The goal of the investigation is to define a relationship between depth, discharge, and slope that can be used in a wide range of situations where uniform flow conditions are present, and which can also be adapted for numerical modeling applications. None of the six methods completely satisfy the writer's criteria; therefore a new relationship is presented. The proposed technique is based on dimensional analysis, a statistical analysis of a large body of laboratory and field data, and basic principles of hydraulics. Separate equations are developed for the lower (dune and ripple) and upper (flat bed and antidune) flow regimes. The technique also includes a simple method for flow regime determination. Finally, the proposed method is verified through comparison with data sets not used in the derivation of the technique.

Results of a mathematical model for the, depth‐averaged main flow velocity in shallow river bends are compared with measurements in two consecutive sharply‐curved short bends in the river Dommel, The Netherlands. The computed main velocity distribution agrees rather well with the measured one in the larger part of each bend. Near the bend exits, however, deviations occur which indicate that secondary flow convection should be included in the mathematical model. Also, the present model is used to verify some qualitative explanations for the skewing of the main velocity distribution (towards the inner bank in the first part of a bend, outwards further downstream) and to show the effect of flow stage variations on the streamline pattern.

This paper describes linear partitioning of energy expenditure in curved open channels. An analytical method which predicts energy losses due to longitudinal resistance and transverse circulation is presented; predicted results are compared with measurements. The transverse energy loss is evaluated using the velocity field of transverse circulation which is implicitly dependent on the internal turbulent shear and boundary roughness; thus, direct evaluations of the shear and boundary losses are avoided. Transverse circulation is often referred to as secondary circulation as its velocity component is generally substantially lower than the longitudinal or primary velocity. Such is not the case for the energy expenditure. The loss due to transverse circulation may be of the same order of magnitude as the longitudinal loss at a higher depth to radius ratio or lower channel roughness, or both.

The distribution of precipitation in both time and space in the southern Nevada area is examined. It is concluded that this area can be divided into two zones of precipitation separated by a transition zone on the basis of annual average precipitation. One region, relative to the other area, is defined to be a deficit annual average precipitation region. This observation could have a significant impact on groundwater recharge estimates and on the siting of facilities which must be protected from flash floods. In addition precipitation records at two stations in the southern Nevada area were examined and point intensity/duration relationships were derived for these stations.

A qualitative description of the axial motion of the starting homogeneous round water jet is presented by dividing the jet trajectory in three regions. The jet front accelerates after the exit and reaches a maximum axial velocity at the distance of nine diameters. Beyond an axial distance of twenty diameters the starting jet motion has a constant deccelerating character and an axial velocity constantly less than the steady jet velocity. In the intermediate region the motion has a transitional behavior. The starting homogeneous jet geometry is similar to the starting plume geometry.

An inflatable dam is a tube of flexible material inflated by water or air to impound water. The profile of the water inflated dam is obtained numerically. The relationships between the parameters that govern the shape of dam are presented in the form of charts.

Circular jets with swirl have been used widely in combustion chambers and burners because they achieve better dilution and mixing at small distances from the nozzle. This characteristic of swirling jet has a significant potential for ocean outfall applications in increasing the rapidity of mixing of waste water at small distances from the effluent port. A preliminary experimental study is described which investigated the mixing of a negatively buoyant swirling jet.

This study investigates headwall influence on local scour downstream of culvert outlets. Scour holes produced by discharging jets of varying duration and magnitude through circular culverts onto a horizontal sand bed were observed and mapped. The bed material was a uniform sand with a mean grain diameter d₅₀ = 1.86 mm and a standard deviation σ = 1.33. The culvert diameter was 102 mm (4 in.). A series of expressions are developed describing the depth, width, length, and volume of scour hole as a function of time, discharge intensity, and headwall conditions. Results are presented in equation and graphical form. A criterion is presented for the design depth of a headwall at culvert outlets.

The results of an experimental study on the erosion of sand beds by plane water wall jets with minimum tailwater is presented. A comparison is made with the erosion caused by the corresponding deeply submerged water wall jet.