Journal of Hydraulic Engineering

Pressure reducing valves (PRVs) and high-density polyethylene (HDPE) pipes are commonly used in urban water supply systems (UWSS). To study the joint effect of PRV and viscoelasticity on transient wave propagation, extensive experiments have been conducted in a field-scale reservoir-PRV-viscoelastic pipeline system covering a wide range of internal pressure heads ($\mathrm{\sim }\mathrm{10}\mathrm{t}\mathrm{o}\mathrm{60}\mathrm{m}$) and air temperatures (12°C–33°C). In addition, a one-dimensional method of characteristics (MOC) based model that incorporates a PRV model and the generalized Kelvin-Voigt (K-V) model for pipe viscoelasticity is developed and validated against field data for the first time. The simulated transient pressures are in good agreement with field measurements. The K-V parameters exhibit a clustered distribution and the mean value for each element can provide a satisfactory simulation. The PRV in hydraulic transients can be interpreted as a quasi-dead-end with a self-adjusting opening, and causes additional positive pressure wave reflections that are gradually damped due to viscoelasticity. The dynamic changes in PRV opening, head loss, pressure wave reflection, and transmission induced by an incident pressure surge are predicted. Due to the joint action of PRV and pipeline viscoelasticity, the pressure oscillations in an intact pipe settle to a value that is considerably higher than the initial PRV set pressure. In a leaking pipe, the downstream pressure reverts to the original set pressure within a few wave cycles. Leaks can be detected by wave reflections in the time domain signals. The existence of leaks is also found to be associated with the the amplification and damping of the frequency response function (FRF) of the system at certain resonance peaks. This study provides new insights into wave propagation in HDPE pipeline with PRV interaction and an original data set for validation of leakage detection methods.

Air pockets trapped in water pipelines are a common phenomenon and can lead to different air-water two-phase flow patterns: stratified, blowback, plug, and bubbly flows. The two former flows contain a large amount of air and should be carefully monitored for pipeline safety, while the two latter flows have relatively low air fractions and can be regarded as normal operating states of pipelines. Hence, flow pattern identification is key to diagnosing the operating state of pipelines. In this paper, a new data analysis method based on complex network theory is proposed to identify the features of flow patterns using pressure signals. The pressure signals of different flow patterns, collected from an experimental facility, were used to characterize the nodes and edges (i.e., connections) in the complex network. The closely linked nodes with dense edges could be aggregated to form a cluster (i.e., community). An unsupervised machine learning technique is then used for community clustering in the network. The results show that the complex network constructed from pressure signals can be divided into several communities, representing different phases (i.e., air, water, or mixed phases) of the air-water flows. Therefore, the flow patterns can be identified in terms of the cluster features and topological features, which are represented by indicators including modularity, graph density, average path length, and transitivity. The impacts of two structural parameters of the complex network, i.e., window size and sliding step, are analyzed. Sliding step is shown to have a more significant impact on the flow pattern identification than window size. This study shows that the complex network approach is effective for flow pattern identification in air-water two-phase flows and could be potentially used for identification of pipeline operational states.

Chancy-Pougny is a run-of-river dam on the Swiss–French border constructed in the early 1920s. Since its commissioning, the operation of the four spillway gates has been responsible for a progressive erosion of the stilling basin. The future scour potential of the unlined stilling basin of the Chancy-Pougny dam was assessed by hybrid modeling, combining both a physical and a numerical model. The physical model investigated the flow structure in the basin as well as the dynamic pressure fluctuations exerted by the flow on the rocky bottom of the stilling basin. The presence of a large gyre, generated by a flow recirculation in the nonsymmetrical basin, was found to be one of the main causes of significant scour formation. The numerical model used the pressure recordings to reconstitute the observed scour since 1924, predicting significant additional long-term erosion in the stilling basin. As such, a series of scour mitigation measures, including a free-standing wall and various configurations of concrete prisms for scour protection, were tested on both models. A tailor-made solution containing a layer of randomly distributed concrete prisms laid on the basin’s current bottom was identified through this study, proving the importance of both numerical and physical approaches in hydraulic engineering.

Scientists at the USDA Agricultural Research Service (ARS) Hydraulic Engineering Research Unit (HERU) conducted research on physical models of stilling basins (i.e., Types I, II, III, and IV) associated with stepped chutes to evaluate performance. Tests were conducted with naturally developing unit discharges ($0.236{\mathrm{m}}^2/\mathrm{s}\le q\le 0.930{\mathrm{m}}^2/\mathrm{s}$) descending a 3(H):1(V) stepped chute flume designed with 0.15-m step heights at near prototype scale and Froude numbers near the stepped chute toe ranging from $4.1\le \mathsf{F}\le 4.6$. Data and visual observations indicated that dissipation features like floor blocks, the end sill, or a dentated end sill effectively reduced wave oscillations and lessened the impact of propagating waves downstream. The study data appear to agree with other published data for stilling basins associated with smooth chutes; thus, design engineers should have confidence in applying the US Bureau of Reclamation (USBR) stilling basin design criteria to basins associated with stepped chutes. Pressure profiles indicated positive values relative to stilling basin floor elevation along the length of all stilling basins. Additionally, pressure peaked near the basin entrance, the floor blocks, and the end sill.