Journal of Hydraulic Engineering

To validate the use of acoustic Doppler velocimeters (ADVs) for the measurement of turbulent flows, experiments were conducted in an axisymmetric turbulent jet and in approximately homogenous isotropic turbulence with zero mean flow. The jet experiments show that the horizontal RMS velocities measured by the ADV were overestimated when compared to both flying hot-film anemometry measurements and the accepted values in the literature. However, the vertical component of the RMS velocity agrees well with those of other studies. This was furthermore confirmed by the ADV measurements in the isotropic turbulence with zero mean flow. Given that the overestimated RMS velocities in the horizontal directions may be caused by Doppler noise and spikes, two postprocessing filters and a Doppler noise–reduction method were applied to the jet data in an attempt to correct the data. Although the RMS velocities decreased, they remained erroneously higher than the accepted values. A noise-reduction method for axisymmetric flows that corrects the RMS velocities to within the range of acceptable values is presented. Lastly, because the Doppler noise is thought to depend on the mean velocity, a series of laboratory experiments were undertaken to relate Doppler noise to the mean velocity. The results showed no clear relationship between the Doppler noise and the mean flow. In addition, subtracting the Doppler noise (measured for a given mean velocity) from the measured RMS velocities (at the same mean velocity) did not significantly decrease the RMS velocities.

Information about the grain-size distribution of the surface layer of sediment exposed on riverbeds is often critical in studies of fluvial hydraulics, geomorphology, and ecology. A variety of sampling and analysis techniques are in common usage that produce grain-size distributions that are not directly comparable. This paper seeks to explore the appropriate conversions between different types of surface grain-size sampling methods. This is particularly timely in the light of increasingly widespread use of automatic and semiautomatic image-based measurement methods, the comparability of which with conventional measurement methods is relatively poorly constrained. For conversions between area-by-number (paint-and-pick) and grid-by-number (pebble-count) samples, the empirically derived conversion factor ($\pm 2.2$) was found to be greater than that predicted by the Kellerhals and Bray model ($\pm 2$), but the errors associated with using the value predicted by the model were small (3.8% in mm). For conversions between areal samples recorded by count and weight, the empirically derived conversion factor was approximately $\pm 2.9$, but the use of the value predicted by the Kellerhals and Bray model ($\pm 3$) resulted in only small errors (5.2% in mm). Similarly, for conversions between image-based grain-size distributions recorded in area-by-number and grid-by number form, the emipirically derived conversion factor was $\pm 1.9$, but using the model value of $\pm 2$ resulted in only small errors (4.1% in mm). Although these results are specific to the data sets analyzed, the variety of sedimentary conditions included gives the authors of this study confidence that the results are representative.

Five series of experiments were performed to study the penetration and dilution properties of vertical negatively buoyant thermal jets (thermal fountains). The flow was turbulent, and the densimetric Froude number $\mathsf{F}$ based on the radius of the discharge varied from 4.7 to 24. The experiments were conducted in the laboratory by discharging hot water vertically downward into a colder-water environment that had a temperature greater than 15°C. Under these conditions, the water equation of state was practically linear, and the downward negatively buoyant thermal jet was dynamically similar to an upwards negatively buoyant dense jet of equal densimetric Froude number. The temperature fields associated with the negatively buoyant jets were measured with arrays of fast responding thermocouples and were used to study the jet penetration and dilution properties. Detailed analyses of the temperature data revealed large fluctuations of jet penetration in the vertical direction. The mean and maximum vertical jet penetrations obtained in this study using temperature data were consistent with the results of previous studies based on visual data. In contrast, smaller fluctuations of jet penetration occurred in the horizontal direction, and the maximum horizontal penetration of the return flow, at the level of the source ($z=0$), was ${\delta }_m=1.40r_0\mathsf{F}$. This value is about one-half of the mean vertical jet penetration. On the other hand, the minimum dilution of the returning fluid at the source height just outside of the nozzle was ${\mu }_{\min }=0.58\mathsf{F}$.

This work presents a modification to steady-state water distribution network (WDN) simulation models to account for directional devices such as check valves (CHVs) and flow-control valves (FCVs). These devices, allowing water flow control in a definite direction, are important to manage the hydraulic system functioning over time by considering the variation of some boundary conditions (e.g., required demands and tank levels). However, the simulation models are built on the assumption that water can flow in both directions of each pipe in the hydraulic system, and the information on directionality of some devices is not automatically allowed. Thus, in WDN models, those devices are currently modeled using a heuristic approach intermixed with solving the problem of steady-state WDN analysis. For this reason, a different approach using content and cocontent theory was recently proposed to define the conditions that guarantee the existence and uniqueness of the solution. The alternative proposed in this paper presents an adjustment of the energy balance equations to account for flow-control valves. Check valves are treated as a special case of flow-control valves, whereas the directionality of pumps, which are equipped with a check valve to avoid reverse flow, is modeled by means of their implicit check valve. Once the status of such directional devices is identified, a topological analysis of the network is performed. The methodology is applied to the demand-driven and pressure-driven analysis of a WDN solved by means of the global gradient algorithm, although it could be easily extended to other algorithms.

The nonaerated region may occupy a large portion of the skimming flow in steep, stepped spillways, particularly for relatively high unit flow rates. In spite of the numerous contributions on the hydraulic properties at both the inception point of air entrainment and the aerated region, much less is known regarding the flow in the nonaerated region. In this paper, new empirical evidence, based on an extensive data set obtained during several years in a large-scale facility, sheds light on the features of the nonaerated-flow region. Diverse ways to locate and estimate the main hydraulic properties at the inception point are first discussed and compared. Then, expressions capable of characterizing the main flow variables along the nonaerated region are presented, namely, the boundary-layer development, the velocity distribution, the equivalent clear-water depth, the characteristic depth taking into account the free-surface unsteadiness due to turbulence, and the energy dissipation. The energy dissipation is observed to be larger than that for smooth spillways, although much smaller than values typically reported for aerated flows at the toe of stepped spillways.

A curb inlet and two combination inlets (with a grate and curb opening) used for storm-water drainage were tested under varying road conditions, and equations were developed for their application. The need for this study arose from a general uncertainty in matching the inlets tested to previously published methods. This uncertainty relates to sizing inlets and in determining the flow captured. A one-third Froude-scale model of a two-lane road section was designed and built for testing. A total of 120 tests were performed for longitudinal street slopes from 0.5 to 4%, cross slopes from 1 to 2%, gutter prototype flow depths from 0.1 to 0.15 m, and prototype inlet lengths from 1 to 4.6 m. Collected test data on inlet efficiency were compared to previously published methods for the inlets and were found to deviate by as much as 45% and an average of 13% at typical design depths of 0.1–0.15 m. Existing methods for the curb inlet were modified, and empirical design equations were developed for the combination inlets. Dimensionless parameter groups developed for empirical equations are based largely upon flow characteristics and may be applicable to other inlets. New methods were found to deviate by as much as 19% and by an average of 5% from the observed test data for typical design depths of 0.1–0.15 m.

Dredging and flow reduction in the Modaomen Estuary in China have had a measurable impact on tidal propagation and damping. This paper includes an assessment of the impacts of these human interventions through the use of a new analytical hydraulic model procedure. The model calculates tidal propagation and damping as a function of bathymetry and river discharge through a simple iterative procedure with explicit analytical equations. The results obtained are accurate and allow both an analysis of the historic development and a sensitivity analysis to assess the effect of possible further dredging and flow reduction. Particularly in the upper reaches of the estuary, tidal damping and wave celerity are sensitive to dredging and flow reduction. Historic analysis shows that due to these activities, since 1993, the tidal amplitude in the Modaomen Estuary has increased by more than 0.1 m, while the travel time of the tidal wave has decreased by 30 min in the middle part of the estuary and up to 80 min in the upper reaches. In the future, the tidal amplitude and the wave celerity will increase even further if flow reduction and dredging continue. Moreover, this development would increase the risk of salinization in the estuary and facilitate the inland propagation of storm surges.

Flow past a spur dyke on a rigid bed meandering channel with a trapezoidal cross section has been studied experimentally. An acoustic Doppler velocimeter (ADV) was used to measure the velocities. The results show that length of the downstream separation zone changes according to the location of the spur dyke. It varies from 4.0 to 22.8 times the spur dyke length. In addition, the separation zone at higher elevations is wider compared to that near the bed for most of the locations of the spur dyke. The effect of contraction ratio and inflow Froude number on separation zone is also presented.

An experimental study was conducted investigating submerged hydraulic jumps with baffle blocks. An extensive series of tests were completed that covered a range of Froude numbers, submergence factors, and block arrangements. Dimensional analysis was used to interpret the results and study the effect of each parameter. Two flow regimes, the deflected surface jet (DSJ) and reattaching wall jet (RWJ), were observed. The occurrence of a particular regime depends on the block shape and location as well as the Froude number and submergence factor. The DSJ regime was found to dissipate more energy due to the formation of the deflected jet and its impingement on the water surface. The DSJ regime is almost as efficient in dissipating energy as the free hydraulic jump. This flow regime also had a smaller reverse flow region compared to the RWJ regime. Empirical equations were derived for predicting the critical values of the submergence factor at which each flow regime forms. The efficiency of the submerged hydraulic jump with blocks in dissipating energy was compared with that of free without blocks as a function of submergence factor.

The present analysis shows that the vertical movement of spring-suspended containers that communicate with a liquid in a reservoir is proportional to the change of the liquid level in that reservoir. It also demonstrates how they could be used as sensitive liquid level measuring devices, which are easy to build, calibrate, and use.