Journal of Hydraulic Engineering

The synoptic behavior of a two‐dimensional turbulent surface jet is experimentally investigated. Single‐point hot‐film data were obtained for mean and root‐mean‐square velocities in the developing jet to a distance of 240 characteristic lengths downstream of the origin. The growth rates of the length and velocity scales are found to resemble more closely those observed in wall jets than those in free jets. The effects of jet confinement are to retard the ability of the jet to entrain fluid, to decrease the growth rate of the length scale, and to increase the decay rate of the velocity scale. Mean velocity‐profile similarity is still observed when the data is nondimensionalized with the reduced scales. Jet momentum will appear to have been lost due to momentum exchange with the return flow. An approximate analysis provides a means to estimate the momentum loss due to limited‐depth and is shown to correlate well with scale development in several jet configurations for these and prior experiments.

In free‐surface water flows the hydraulic jump has usually been considered a turbulent reverse roller supported by an underlying and expanding stream. The air‐entrainment aspect of the water surface at the jump is normally a predominant feature. In this investigation the character of the turbulence in the jump, and therefore of the air‐entrainment mechanism, is controlled by the use of drag‐reducing soluble additives. The resulting lower level of entrained air permits photographic and visual observation of a jump in a small glass‐sided laboratory flume. The photographs presented in the paper show that the remaining air bubbles act as flow tracers and reveal a turbulent structure in the upper part of the jump very similar in appearance to that observed for a turbulent mixing layer in a wind tunnel using shadow refractography. Measurements of expansion angles for the turbulence structures in the jump agree well with wind‐tunnel measurements of expansion angles for the turbulent mixing layer between coflowing airstreams with a velocity difference.

Conventional multilayered riprap and filter protections around bridge piers can be substituted by one thick single layer of riprap. Because of this simpler construction, field installations are less likely to be defective. An analytical description was derived relating the mean flow velocity, which causes initiation of erosion of the base material, to characteristics of the single‐layer protection and the base material. The governing dimensionless parameters describe suitable thickness of the riprap layer, grain size of riprap material, grain size of base material, and mean flow velocity. The diameter of the pier does not influence initiation of erosion. The theoretical expression was verified by means of comparative largescale laboratory experiments. In most design conditions the simplified riprap protection requires a thinner protective layer than the conventional riprap and filter protection.

We use a saturated‐unsaturated flow model (UNSAT2) to study the effect of soil cementing and channel widening on infiltration and recharge in two idealized profiles along the Rillito River of southern Arizona. The channel sections associated with the profiles are 202‐ft (61.6‐m) and 326‐ft (99.4‐m) wide. A synthetic 10‐yr runoff in the river provides head values for generating infiltration before and after bank protection in these two sections. Results from the two base simulations are combined to produce four additional cases. Soil cementing the banks of the river without widening the channel reduces infiltration and recharge by 15% for the 326‐ft wide (99.4‐m) channel and by 25% for the 202‐ft wide (61.6‐m) channel. Increasing channel width together with bank protection increases infiltration 25% for our two sections. Increasing channel width without bank protection, however, increases infiltration by 46% for our conditions. Channel narrowing with bank protection markedly increases infiltration rates, about 50% for the two sections.

A set of type curves has been derived for aquifer test analysis in horizontally fractured rock environments by using the volumetric approach. The validity of this approach has been confirmed with the numerical as well as analytical results in the literature concerning the multiaquifer wells that are similar to multihorizontal fracture wells. In the general formulation, each fracture is assumed to have different aperture and roughness. Various simplifications of the formulation are given to cover some theoretical as well as practical interests. The volumetric method relates especially the fracture aperture and roughness to other hydraulic quantities through the type curve expressions. The well storage effect has been taken into consideration and as a result the initial portions of type curves appear as straight lines on the double logarithmic paper that implies power law relation. The final portions of type curves are also straight lines, but on semilogarithmic paper, implying an exponential type of relation. The practical applications of the developed methodology has been presented for the time‐drawdown data obtained from the main well that is in horizontally fractured rock aquifer at Halifax County, Nova Scotia, Canada.

Type curve expressions are derived analytically for drawdowns around a fully penetrating well in vertically graded hydraulic conductivity aquifers. A linear increase in the hydraulic conductivity with depth is adopted in this paper. Solution of the relevant groundwater movement equations are achieved by the application of Boltzmann transformation individually for the continuity and laminar flow law equations. Necessary type curves are presented for determining the aquifer parameters from an aquifer test performed in the field. The analytical results show that the conventional Theis and Jacob methods are not applicable in the cases of vertically graded hydraulic conductivity aquifers. In addition, a straight line method is proposed for the late time‐drawdown data. However, both type‐curve and straight‐line procedures developed in the paper yield the Theis and Jacob method equivalents, respectively. The application of the methodology is given for fissured and fractured hard‐rock aquifer test data obtained in the field.

A method is proposed to calculate the interaction between an oscillating body and the water surrounding it for low values of the Keulegan‐Carpenter number and in laminar flow conditions. Rather than dividing the viscous forces originated by the unsteady motion into an added mass inertia force and a frictional, energy dissipating, component, the interaction is here evaluated through a “Basset term” style convolution integral of the expression of the force calculated for impulsively started flow. A numerical procedure is employed to show that, for simple motions, the method herein proposed yields solutions similar to those obtainable by the classical approach, while it can efficiently deal with problems involving complex forcing actions or very short impulses, where the traditional approach fails to provide satisfactory results. The applicability of this technique is limited to purely laminar flows, thus including most of the problems related to the hydrodynamic damping of vibrating structures and excluding the whole domain of wave induced forces.

Pump sampling can be an accurate method of measuring suspended sand concentrations. When the flow velocity through the pumping nozzle does not match the local stream velocity, however, an error is introduced. A simple equation is presented that can be used to produce correction factors for this source of error. The equation is successfully compared to data that was not used in the development of the theory. The predictive equation is also adapted to include misalignment of sampling nozzle; the adapted equation is checked against data and used to show that these errors are very small.

The US P-61 suspended-sediment sampler has an electrically operated valve in the nozzle and samples isokinetically the entire mass of water and sediment entering its nozzle. The Delft Bottle (DB) is a continuous flow-through device that collects by deposition most of the coarse sediment entering its nozzle but allows the water and finer sediments to pass through it. The minimum size of particle that deposits in the DB increases with increasing stream velocity. When the samplers were compared on the basis of computed total sand transport (material > 0.062 mm), the transport rates computed from samples collected by the P-61 were about twice those of the DB. DB transport rates in the 0.062–0.125 mm size fraction were much lower than P-61 rates for the same size. In the 0.125–0.250 mm size fraction, the DB and P-61 rates were nearly equal for transport, less than 200 g/m²/s. The DB rates fell below the P-61 rates for four greater transport rates in this size fraction. For a larger size fraction, the two devices gave fairly good agreement.

Lynch and Gray present a number of analytic solutions for computer flow model testing. They derive detailed analytic solutions of the linearized shallow water equations, including bottom friction, wind stress, and variable bathymetry in Cartesian and polar geometry. This paper makes corrections for cases where the bathymetries are reverse quadratic. Some graphic results from the reverse quadratic bathymetry are included.

Concise closed-form equations for the mean transverse velocities and Reynolds shear stresses in the fully developed region of axisymmetric and two-dimensional jets are presented. These equations were derived from the Navier-Stokes equation and the Gaussian distribution of mean longitudinal velocity. The derived equations for Reynolds stresses agree with experimental measurements. The closed-form solutions are suitable for substitution into other equations for further investigation. Reynolds stresses are needed for numerical modeling of turbulent flows.