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Journal of Hydraulic Engineering, Volume 147; https://doi.org/10.1061/(asce)hy.1943-7900.0001920

Abstract:
Previous research has shown that local scour at bridge piers is severely increased by the accumulation of woody debris around piers. However, due to the unavailability of accurate information regarding the characteristics of formed debris jams, the shape and dimensions of accumulations tested in previous laboratory experiments have had to be assumed. This article provides an assessment of debris-induced scour based on recently available knowledge about the relation between the potential dimensions of debris accumulations, the characteristics of flow, and debris elements. Clear-water scour experiments (with and without debris accumulation) were conducted using debris models with shape and size that correspond to the particular flow characteristics of each experiment. The results showed that scour depths obtained with flow-dependent debris accumulations were larger than without accumulations by a factor ranging from 1.18–2.19. The analysis of the scour depths affected by the accumulations suggested similar characteristics as well as dependence on the flow intensity, blockage area ratio, and depth ratio.
Hao Wu, Jie Zeng,
Journal of Hydraulic Engineering, Volume 147; https://doi.org/10.1061/(asce)hy.1943-7900.0001919

Abstract:
A numerically based investigation is carried out to determine the minimum median diameter of the riprap stone needed to avoid shear failure inside the riprap apron used to protect spill-trough abutments against erosion. The study considers identical spill-through abutments placed on the floodplains of a compound channel. Several series of Reynolds-averaged Navier-Stokes (RANS) simulations are conducted with varying floodplain width, Bf, ratio between the abutment length and the floodplain width, La/Bf, mean diameter of the riprap stone, D50, and channel curvature, R, to estimate the maximum Froude number, Fr, at which riprap stones in aprons placed at the base of spill-through abutments will resist shear failure by the flow. A design formula for riprap size selection in aprons protecting spill-through abutments is proposed. The formula is expressed as D50/y=C0.5α*Frα, where y is the flow depth next to the toe of the abutment. The two model parameters are C and α. Results show that α is only a function of Bf for abutments that do not extend until close to the main channel and α=1.85 for abutments extending over the whole width of the floodplain.
José M. Díaz Lozada, Carlos M. García, Graciela Scacchi, Kevin A. Oberg
Journal of Hydraulic Engineering, Volume 147; https://doi.org/10.1061/(asce)hy.1943-7900.0001922

Abstract:
The selection of optimum sampling configurations to measure the aspects of turbulent flow of water depends on the variable being measured, the applied measurement technique, the degree of environmental noise, and flow characteristics in and near the sampling location. This work presents a method to dynamically select the exposure time (SET) during the flow-velocity measurement at each sampling location on the basis of the moving block bootstrap (MBB) technique. The MBB enables near real-time estimation of the confidence intervals and, subsequently, the COV for turbulence parameters. The dynamic SET method has been tested in this work using time series of synthetic turbulent flow-velocity signals. This method was implemented using actual flow-velocity signals recorded with acoustic Doppler velocity (ADVs) instruments and acoustic Doppler current profilers (ADCPs). The results obtained from the implementation of the dynamic SET method show that the sampling time to achieve a defined uncertainty threshold is not the same for different turbulence parameters. Consequently, using the dynamic SET method, the exposure time can be optimized to obtain the turbulence parameters with the required uncertainty level. The dynamic SET method can be implemented in the instrument’s data logger to dynamically select the exposure time during flow measurements for a given uncertainty of the required turbulence parameter.
Xerxes Mandviwalla,
Journal of Hydraulic Engineering, Volume 147; https://doi.org/10.1061/(asce)hy.1943-7900.0001898

Abstract:
Protection layers are often used to prevent scour and erosion, e.g., prevention of scour around wind turbine foundations. However, several cases exist where installed scour protection has settled, where loss of sediment through the armor layer can explain the failure. This paper presents the use of a detailed large eddy simulation–discrete-element method (LES-DEM) model to study sediment particles in porous media. First, a simple idealized case of the removal of sediment from an idealized cavity beneath a smooth turbulent boundary layer was set up. The model showed the penetration of turbulence, mainly in the form of sweep events, into the cavity. This high momentum would at times reach the bottom and entrain the fine sediments. The sediment would subsequently roll over and form a pile and at times be suspended from the return flow of the penetrating turbulence. Finally, a more realistic armor layer was set up with a series of closely packed spheres. Fine sediments were seeded at the bed. A hydraulically rough boundary layer was developed over the armor layer, where turbulent statistics from the model compared well against experiments. Turbulent structures characteristic of the bursting process were identified in the rough wall case. The penetration of sweep events’ entrainment and suspending the finer sediments is detailed. The flushing of cavities from passing ejection events is also presented.
Harry E. Schulz, Jakobus E. van Zyl, Tingchao Yu, Iran E. Lima Neto, Francisco A. S. Filho, Nivaldo A. Correa, Igor M. Benites, Huaqing Wang
Journal of Hydraulic Engineering, Volume 147; https://doi.org/10.1061/(asce)hy.1943-7900.0001911

Abstract:
Theoretical and experimental results for the evolution of cavities generated by upward vertical leakage jets in porous media are presented. The formulation is based on the conservation principles of mass, momentum, and energy. Two conditions were considered: two-dimensional isotropic medium and three-dimensional isotropic medium. The results of the cavity height are given in nondimensional form and related to the Froude number that considers the inlet flow characteristics (width of the slot or diameter of the orifice, and inlet velocity). Both the two-dimensional and the three-dimensional cases provided theoretical results for the length of the cavity limited by a maximum Froude number. This characteristic implies that the cavity destabilizes for Froude numbers higher than this maximum critical value. It was observed that parameters of the porous medium (soil parameters) not present in the conservation formulation must be added a posteriori to cover a larger spectrum of soil possibilities. The experimental results show that the theoretical proposition follows the main characteristics of the observations.
Roger A. Kuhnle, ,
Journal of Hydraulic Engineering, Volume 147; https://doi.org/10.1061/(asce)hy.1943-7900.0001930

Abstract:
Experiments were conducted in a laboratory flume in which gravel and total bed-load rates were measured continuously using independent methods that allowed evaluation of the effect of four antecedent flow conditions on the transport of bed load under standard flow. It was found that both mean total bed-load rate and gravel transport rates are related to the magnitude of antecedent flow. The changes in mean bed-load rates were attributed to changes in the stability of the coarsest fractions of the bed material, caused by the previous high-flow event. This work indicates that long-term mean bed-load transport rates for a sand and gravel bed are not just a function of grain size and flow rate but also vary with the magnitude of antecedent flow.
Elias Sebastião Amaral Tasca, , Edevar Luvizotto
Journal of Hydraulic Engineering, Volume 147; https://doi.org/10.1061/(asce)hy.1943-7900.0001914

Abstract:
A central element of a pipeline’s air management infrastructure is typically its set of air exchange valves (AEVs), a designation that includes air release and air/vacuum valves. Knowledge of the air mass flow rate as a function of pressure difference is essential for AEV selection and design, a relationship expressed by its somewhat complex and certainly nonlinear characteristic curve (CC). However, both measurement and simulation of this CC are often nonintuitive and, for various practical and theoretical reasons, problematic. To provide greater insight, several helpful performance scaling analyses are undertaken here with the goal of aiding system investigation, design, and operation. To this end, a performance similarity relation (PSR) for different-sized AEVs is developed and its effectiveness demonstrated in the light of commonly available air mass flow data. Also, the PSR is successfully applied to aid in the interpretation of published experimental air expulsion data. Additionally, the interaction of the CC with basic pipeline parameters on system performance is explored in the context of common hydraulic transient events. For this second application, the water-hammer pressures generated by a pump trip scenario are numerically simulated for several test pipelines, considering four AEV sizes each having three possible characteristic curves.
, Andrew Brooks, Bofu Yu, Jon Olley,
Journal of Hydraulic Engineering, Volume 147; https://doi.org/10.1061/(asce)hy.1943-7900.0001935

Abstract:
Hydraulic models used to simulate floods through riparian forests along rivers need to account for flow resistance caused by tree drag. Tree drag formulations have been developed for this purpose in previous studies, using drag force measurements on several broad-leaved, temperate species at tree scale to calibrate model parameters. However, tree reconfiguration and reduction in drag force in response to increased flow velocity are still not fully understood, particularly for subtropical tree species with sclerophyllous foliage. An established towing tank method was adapted to a field setting using a motorboat to tow submerged she-oak and tea trees through still water. Drag coefficients for both genera decreased with increasing velocity due to stem and foliage reconfiguration, except for the lowest velocity measurements on some she-oak trees, indicating the emergence of a rigid regime. The rigid regime has also been observed in previous studies and is important for flood modeling because drag forces could otherwise be overestimated at low velocities. Therefore, a new Cauchy number has been formulated and tested to predict regime transition for she-oak trees.
, Fengjie Zhang, Xin Liu, , Jianmin Zhang,
Journal of Hydraulic Engineering, Volume 147; https://doi.org/10.1061/(asce)hy.1943-7900.0001928

Abstract:
Solutions for dam-break flow mainly developed for rectangular channels are not applicable to prediction of the propagation of the dam-break wave in frictional triangular channels. This study presents an approximate solution considering the frictional effect on the dam-break flow in a dry horizontal triangular channel. Wave tip velocity is solved by an implicit formula for the product of time and resistance coefficients. All other hydraulic properties in the wave tip region can be expressed as explicit functions of wave tip velocity. Meanwhile, laboratory experiments have been performed for obtaining water surface profiles of dam-break flow from which the position and velocity of the wave tip front have been derived. Results show that retardation of the wave front position is more significant with the increases in both resistance and time. The proposed analytical solution shows satisfactory agreement with measurements, and clarifies how the behavior of the dam-break wave tip is affected by channel geometry.
Barbara Zanchi,
Journal of Hydraulic Engineering, Volume 147; https://doi.org/10.1061/(asce)hy.1943-7900.0001923

Abstract:
We present the results of laboratory experiments specifically designed to quantify the height and migration rate of an aggrading gravel front. The experiments were performed in sediment feed mode with constant water and sediment supply. Particular care was put into the experimental procedure and the methods to determine the quantities of interest to ensure reproducibility of the results. The celerity and height of an aggradation front were modeled as functions of the Froude number of the flow for the initial bed profile and of a load ratio defined as the ratio of the sediment feed rate to the transport capacity of the flow for the initial bed. The two control parameters (Froude number and load ratio) also determined the translational or dispersive nature of a sediment front. Two predictors were provided to estimate the dimensionless height and celerity of an aggradation front. The former was an increasing function of the load ratio and a decreasing function of the Froude number, and the latter was roughly proportional to the squared Froude number and had no evident relationship with the load ratio. The present results are of interest for scholars and practitioners needing to determine the key properties of swift gravel fronts as those developing, for example, during flash floods.
, Anneliese Sytsma, Octavia Crompton, Sally Thompson
Journal of Hydraulic Engineering, Volume 147; https://doi.org/10.1061/(asce)hy.1943-7900.0001900

Abstract:
The Rational Method remains one of the most widely used approaches for estimating peak discharge in small catchments. In one widely used interpretation of the Rational Method, the maximum possible peak discharge produced by a storm with a given return period is predicted by setting the storm duration equal to the time of concentration. Whether the time of concentration maximizes peak flow for a rainfall return period, however, depends on the relationship between contributing area and storm duration. Here, we show that under many conditions, using the time of concentration in the Rational Method leads to an underestimation of peak discharge. This underestimation is illustrated using two case studies on idealized hillslopes on which runoff occurs as sheet flow. We suggest that practitioners should become cognizant of the differences between the critical duration (the storm duration that maximizes peak discharge) and the time of concentration within the Rational Method and be alert to morphology and land-use patterns that are likely to cause these timescales to diverge.
Kevin Flora, Christian Santoni,
Journal of Hydraulic Engineering, Volume 147; https://doi.org/10.1061/(asce)hy.1943-7900.0001912

Abstract:
Vegetation can have an appreciable impact on the hydrodynamics and scour potential in natural rivers, but this effect is generally unaccounted for in high-fidelity computational fluid dynamic models. In this study, we have incorporated trees into the flow domain using two different approaches to study the hydrodynamics of the American River in Northern California under flood conditions. In the first approach, we resolved numerous trees as discrete objects. The second method incorporated a vegetation model into our in-house numerical model to treat the vegetation as a momentum sink along the banks. The flood flow of both cases was modeled using the large-eddy simulation. The computed hydrodynamics results of the cases were compared with a baseline case, which did not include any trees. Although both the tree-resolving and vegetation model approaches compared well with one another with respect to the flow field, they significantly altered the computed river flow dynamics and bed shear stress near the banks and the midwidth of the river compared with that of the no-tree case. Both methods that accounted for the resistance of the trees obtained lower and higher bed shear stresses and velocities along the banks and the midwidth of the river, respectively, than that of the baseline case. This research identified the important role that vegetation plays in natural rivers and provided researchers and engineers with the conceptual tools needed to incorporate vegetation into numerical models to improve the accuracy of the model results.
, Arno Talmon, Cees van Rhee
Journal of Hydraulic Engineering, Volume 147; https://doi.org/10.1061/(asce)hy.1943-7900.0001913

Abstract:
Hydraulic two-phase transport applied in the dredging, mining, and deep-sea mining industries involves the transportation of sand, gravel, polymetallic nodules, or other particulate tailings as a solids phase and water as a liquid phase. Regardless of the type or size of the granular material, the slurry flow is always subject to transient behavior. Most transient behavior can be attributed to the centrifugal pump as variations in pump pressure and mixture velocity over time, but transients can also be caused by microscopic slurry mechanisms, specifically the amplification of density waves in a pipeline. Density wave amplification in horizontal pipelines at mixture velocities just above the deposition limit velocity was reported and researched in the 1990s. New experiments showing a density wave amplification in a system with combined vertical and horizontal pipelines and at mixture velocities far above the deposition limit suggest that another type of density wave amplification mechanism exists. The newly proposed density wave amplification mechanism is hypothesized to be caused by a change in average particle velocity as the slurry flows from a vertical pipe into a horizontal pipe. Density waves that grow too large cause system blockages or possibly a failure of the pump drive. This article considers centrifugal pump–induced transients and density wave amplification effects separately and how these effects influence each other. Three case studies showing density wave amplification are analyzed, one from the literature and two from new data sets. Furthermore, the causes of these transients are discussed, and where possible, solutions are proposed to avoid these undesirable instabilities.
Shima Kasaei, Ephraim Bryski, Ali Farhadzadeh
Journal of Hydraulic Engineering, Volume 147; https://doi.org/10.1061/(asce)hy.1943-7900.0001915

Abstract:
Floodborne debris impact loads depend on several factors, including debris orientation and velocity. Due to the random nature of turbulent flood flows, debris motions are inherently random. This study presents a probabilistic characterization of debris motions in steady-state currents with relatively high Reynolds numbers. An item of debris was released, multiple times, in the open channel flows, at two angles and three current velocities. The debris motions were recorded via a camera. The characteristics of the debris motions including the trajectory, orientation, and velocity were extracted using image processing and were analyzed statistically. The results indicate that the debris orientation and lateral displacement followed a Gaussian distribution. The current velocity and release angle had a smaller effect on the debris lateral displacement than did the orientation. The analysis also highlights the combined effect of the current velocity and release angle on the lateral displacement and orientation of the debris. Empirical relationships were developed for estimating the mean trajectory and orientation of debris in steady currents, as a function of the release angle, and Froude number.
, Thorsten Stoesser, Junqiang Xia
Journal of Hydraulic Engineering, Volume 147; https://doi.org/10.1061/(asce)hy.1943-7900.0001910

Abstract:
A three-dimensional (3D) numerical study is undertaken to investigate dam-break flows over 3D structures. A two-phase flow model has been developed within the large-eddy simulation (LES) framework. The governing equations have been discretized using the finite-volume method, with the air-water interface being captured using a volume-of-fluid method while the Cartesian cut-cell method deals with complex geometries. The robustness and versatility of the proposed numerical approach are demonstrated first by applying it to a 3D dam-break flow over a cuboid. Good agreement is obtained between the simulation results and the corresponding experimental data and other numerical solutions. Then, a horizontal cylinder and a sphere are subjected to the same dam-break flow. Snapshots of water surface profiles are presented and discussed, and turbulent vortical structures are identified in the flow. In addition, the internal kinematics, hydrodynamic loading on the structure, and energy dissipation during dam-break flow impact are analyzed and discussed, providing more insight into such flows.
James Hart, Fred Sonnenwald, Virginia Stovin,
Journal of Hydraulic Engineering, Volume 147; https://doi.org/10.1061/(asce)hy.1943-7900.0001918

Abstract:
Temporal concentration profiles resulting from an injected pulse of fluorescent tracer were recorded at multiple locations along a pipe during controlled unsteady flow conditions. A linear temporal change in discharge over durations of 5, 10, or 60 s for both accelerating and decelerating flow conditions was studied. Tests were performed for flows that changed within the turbulent range, between Reynolds numbers of 6,500 and 47,000, and for laminar to turbulent flows, between Reynolds numbers of 2,700 and 47,000. Analysis of the data shows the limitations of employing steady-state routing of temporal concentration profiles in unsteady flow. Employing a flow weighted time routing approach, using tracer mean velocity and dispersion coefficients, provides accurate predictions of mixing in unsteady flow. For decelerating flows, longitudinal dispersion coefficients were lower than for the equivalent mean steady discharge. Previously unreported disaggregation of the tracer cloud was observed during all experiments accelerating from laminar to turbulent conditions.
Tanjina Afrin, , Abdul A. Khan
Journal of Hydraulic Engineering, Volume 147; https://doi.org/10.1061/(asce)hy.1943-7900.0001906

Abstract:
This paper examines the relationship between the flow rate and outflow depth for flow in a rectangular pipe with the outflow running partially full of a free nappe through a series of computational fluid dynamics (CFD) simulations. The results are presented for two different upstream inlet conditions, namely, flooded, in which the pipe inlet is fully submerged, and partially full, wherein there is a free surface at the pipe inlet. The results are presented for the outflow normalized brink depth as a function of the nondimensional flow rate q*=(q/gD3). For q* less than 0.575, the outflow conditions are the same regardless of the inflow boundary conditions. However, for larger q*, there is a bifurcation in the outflow behavior. When the pipe inlet is fully submerged and q*>0.575, the flow transitions to the so-called bubble-washout regime, and the brink depth is larger than for the case in which the pipe inlet is only partially full. These results indicate that if the brink depth from a pipe is to be used to quantify the pipe discharge, it is important to know the upstream flow conditions in order to know which flow regime is controlling the outflow.
Narendra Patel, Joshan Shahi,
Journal of Hydraulic Engineering, Volume 147; https://doi.org/10.1061/(asce)hy.1943-7900.0001924

Abstract:
Natural river velocity distributions are often studied by laboratory flume flows because of similarities of the bed shear stress effects between the two flows. Nevertheless, the velocity distributions in natural rivers are often affected by winds over water surfaces, which are often negligible in laboratory flows. The objective of this research is then to study how water surface shear stress and wind-induced turbulent mixing affect open channel velocity distributions in flume flows and natural river flows. To this end, we first introduce the recent second log-wake law from symmetric and antisymmetric channel flows to open channel flows. We then demonstrate that: (1) a laboratory flume velocity distribution is a superposition of a half symmetric channel flow solution and a half antisymmetric channel flow solution, and (2) a natural river velocity distribution is a superposition of a half symmetric channel flow solution and a complete antisymmetric channel flow solution. These solutions are confirmed by both laboratory and field data including velocity dip and inflection phenomena.
, Christopher Homer, Fuqiang Tian, Hongchang Hu
Journal of Hydraulic Engineering, Volume 147; https://doi.org/10.1061/(asce)hy.1943-7900.0001897

Abstract:
Pooled stepped chutes with openings as a design requirement are associated with high flow transmission efficiency and smaller downstream dissipation structures; however, these design openings may negatively affect flow characteristics. In this study, 3D numerical simulations were conducted on large pooled stepped chutes equipped with openings and different pool heights, which benefited from the volume of fluid (VOF) method, to track free-surface configuration, and the use of the k−ε(RNG) turbulence model. Results indicated that, for a pooled stepped chute with θ=8.9°, increasing pool heights increased flow resistance, and for a chute with a steeper slope, θ=26.6°, flow resistance remained quasi-constant. Four configurations for openings were further tested: centered, offset, inline, and staggered configurations. Results demonstrated that the staggered configuration reduces residual head at the end of the chute. Additionally, the data revealed that, as the dimensions of the openings increases, flow resistance decreases. The findings of this research could be used as a general guideline for practical cases where openings should be embedded in pooled stepped chutes.
Zhongtian Bai, Ruidi Bai, Rongcai Tang, , Shanjun Liu
Journal of Hydraulic Engineering, Volume 147; https://doi.org/10.1061/(asce)hy.1943-7900.0001916

Abstract:
This paper presents a case study of a prototype B-type hydraulic jump produced downstream an irrigation-regulating gate in a natural river. The inflow Froude number is Fr1=5.1 and the Reynolds number is Re=9×105. Detailed air–water flow properties and free-surface fluctuating features are investigated on site in the central flow region using intrusive phase-detection probes and nonintrusive acoustic displacement meters. Challenges in employing the phase-detection probe in high-momentum natural water are addressed, including the necessary postprocessing for uncertainty mitigation. While good agreement between the present data and previous laboratory measurements is achieved for the air concentration and interfacial velocity distributions, scale effects are observed for bubble frequency, challenging the validity of previous empirical prediction deriving from laboratory experiments. A greater percentage of large bubbles are detected in the full-scale jump. The free-surface fluctuating characteristics are investigated together with the surface wave propagation in the tailwater. The jump length and roller length in the B-jump are discussed with comparison to existing model equations. Although the investigation is limited to one case, it provides the first physical data obtained in full-scale natural water and an important benchmark data set for future study of scale effects in self-aerated open channel flows.
Robin Julian, , Sébastien Ollivier, Philippe Blanc-Benon
Journal of Hydraulic Engineering, Volume 147; https://doi.org/10.1061/(asce)hy.1943-7900.0001905

Abstract:
This paper aims at improving the weighting function based-method (WFB) for modeling the transient behavior of a laminar flow in cylindrical pipes in a one-dimensional approach. Two improvements for the numerical computation of the unsteady friction term are presented. First, a rational approximation of the weighting function in the Laplace domain is preferred instead of an exponential series fit in the time domain. It allows the WFB method to be improved in terms of validity for small time steps, accuracy, and computational efficiency. Second, the use of auxiliary differential equations to compute convolution makes the high order time-integration of the frequency-dependent friction term straightforward, without the assumption of a constant acceleration during the time step. The simulation results for a well-known experimental test case show a good agreement of the derived methods with the experiment. Finally, the time stability of the discretized problem is fully analyzed, and a stability condition for the WFB method is brought out.
Walid Bouchenafa, , Arnaud Lefevre,
Journal of Hydraulic Engineering, Volume 147; https://doi.org/10.1061/(asce)hy.1943-7900.0001904

Abstract:
A drag reduction method by polymer additives was tested for the first time in a large scale open-channel watercourse. Ten and a half tons of a water soluble polymer were injected during 15 consecutive hours in the upstream section of an irrigation canal in steady state, leading to a 20 ppm concentration of polymer in the water. The evolution of the water depth was measured every 10 min for 18 h along ten sections further downstream, up to a distance of 26.3 km from the injection section. The water depth at all sections remained constant until the arrival of the polymer, at which time it strongly decreased, sometimes with a slight water-depth increase beforehand; the depth then remained constant as long as the polymer injection remained. A maximum water depth reduction of 26 cm (i.e., 17%) was measured at the first cross section (2 km downstream from injection). The water depth reduction decreased to 10% and 3% at 10 and 20 km downstream from the injection, respectively. However, further downstream, at a distance of 26.3 km, the water depth increased by 5%. This paper also discusses the environmental impacts of polymer injection through analysis of samples taken from the water and bed material before and during the experiments.
Journal of Hydraulic Engineering, Volume 147; https://doi.org/10.1061/(asce)hy.1943-7900.0001899

Abstract:
Vertically assembled ring meshes serve as barriers against explosive threats, in particular when overflowing water completely covers the mesh. The author measured the flow velocity over these structures using Surface Structure Image Velocimetry and subsequently determined the water layer thickness by taking into account discharges in the range 1.0 L/s≤Q≤4.5 L/s. The water proceeds through and over the mesh and forms surface surges at lower discharges. The surges disappear for higher discharges and induce plain water curtains. Based on a momentum balance equation, a theoretical approach was derived to describe the flow dynamics. The free parameters, e.g., the surface roughness of the metal rings and the deflection angle at the rings, were analyzed and compared with the experimental data. The main finding of this study was that the flow velocity remained constant at w≈0.54 m/s, whereas the water thickness increased linearly between 1.0 and 4.6 mm with increasing discharge. As a consequence, ring meshes should be supplied with the highest possible discharge to achieve the greatest mitigating effect against blast wave threats.
, , Sajjad Salam, Bryan Scholl,
Journal of Hydraulic Engineering, Volume 147; https://doi.org/10.1061/(asce)hy.1943-7900.0001891

Abstract:
Understanding the complex flow and sediment transport on vegetated slopes is important for ecological restoration and conservation projects. This study quantifies the erodibility of sand infill through densely vegetated engineered turf on steep slopes. Flume testing was conducted on four different sand infill materials. The initially lain bed material had artificially high mobility due to the infill application method. Grains were elevated by the vegetation and protruded into the flow. Then, the bed material gradation during subsequent flows became progressively coarser. Two regimes were identified. Poorly sorted infill soils underwent noticeable changes to gradation and had decreasing mobility with increasing shear stress. Conversely, well-sorted soils had minimal changes to gradation and resulted in the expected trend of increasing sediment flux with increasing shear stress. Existing predictive formulas performed poorly, in particular for the soils with evolving gradation. An updated formulation to predict sediment flux is proposed based on a reduction to the effective bed shear stress and dimensionless parameters relating to the flow, sediment, and vegetation characteristics. The proposed modification results in greatly improved predictions for both sediment flux magnitude and trend.
Jie Zhang, Magnus Larson
Journal of Hydraulic Engineering, Volume 147; https://doi.org/10.1061/(asce)hy.1943-7900.0001907

Abstract:
The aim of this technical note is to present methods that allow for direct computation of the bed roughness due to sediment transport based on a formula developed in the literature for cases involving current or waves separately. The methods result in approximate nondimensional expressions for the exact solutions in terms of polynomials determined by least-square fits, where the accuracy of the polynomials is high. Using the present methods may significantly reduce calculation times of roughness due to sediment transport in numerical models of morphological change.
Yuan Hui, , Joseph F. Atkinson, , Yanping Feng
Journal of Hydraulic Engineering, Volume 147; https://doi.org/10.1061/(asce)hy.1943-7900.0001908

Abstract:
The validation of numerical models for large lakes is difficult because of sparse field observations. In this study, a Froude-Rossby scaled physical model of Lake Ontario, North America, is used to support numerical simulations. Experimental data are consistent with available field observations and provide a more comprehensive view of lake-wide features that include, in the absence of wind, strong eastward flows along both northern and southern shorelines, a large cyclonic gyre in the Rochester basin, and smaller midlake cyclonic eddies. With a west wind (most common direction), a well-defined westward flow in the middle of the lake separates an anticyclonic gyre in the north from a cyclonic gyre in the south. A review of numerical models shows that most models can capture general features of these observed patterns but do not always reproduce all details, especially in nearshore regions. A numerical model based on the Environmental Fluid Dynamics Code (EFDC), with a 200-m resolution in nearshore regions, is developed.
Sanjeeta N. Ghimire, Joseph W. Schulenberg
Journal of Hydraulic Engineering, Volume 147; https://doi.org/10.1061/(asce)hy.1943-7900.0001889

Abstract:
Dam operators often do not know whether an auxiliary spillway will fail until it is loaded, which can be infrequent. Such failures have the potential to result in overall dam failure, leading to loss of life and substantial property damage. The purpose of this paper is to develop a screening technique to identify potentially risky auxiliary spillways. The paper uses the National Inventory of Dams (NID) data and analyzes a sample of 400 earthen dams with auxiliary spillways. The main innovation of the paper is to employ code to create multiple input files and analyze them in the Windows Dam Analysis Modules (WinDAM) C software. This technique is more efficient than the current functionality of WinDAM C, which evaluates one dam at a time. The proposed method serves as a quick screening and decision-making tool for multiple embankments for extreme flooding events by identifying potentially risky auxiliary spillways that may require in-depth analysis. The results of this screening found 75% of spillways are likely to sustain heavy damage. Additionally, heavy damage was related to narrower spillway widths.
Farzad Farvizi, Bruce W. Melville, Asaad Y. Shamseldin, SeyedReza Shafiei
Journal of Hydraulic Engineering, Volume 147; https://doi.org/10.1061/(asce)hy.1943-7900.0001901

Abstract:
Tsunamis are among the most destructive natural disasters. Recent major tsunamis in Indonesia (2004), Chile (2010), and Japan (2011) resulted in significant loss of human lives and damage to coastal structures. Damages to lifeline infrastructure caused by these disasters have highlighted the need for much more attention from the engineering community to the investigation of tsunami interactions with coastal bridges. Therefore, developing resilient infrastructure that can withstand and remain operational against tsunami bores will significantly improve the postdisaster recovery of the affected areas. In this study, a series of experiments have been conducted in a 15 m long, 1.2 m wide, and 1.2 m deep wave flume equipped with an automatic gate to generate a tsunami bore in order to quantify tsunami-induced loads on a deck girder section bridge. The results of the experiments carried out with a bridge model to investigate the effects of the bridge deck skewness on the tsunami wave-induced forces and moments are presented. The bore height, bore velocity, resulting forces, and moments were measured. It was found that the skewed bridge deck is subjected to additional force and moment components, namely the lateral force (Fy) and the rolling and yawing moments (Mx and Mz). These components are nonexistent for the unskewed bridge deck. Based on the experimental results, equations were proposed for estimating the tsunami horizontal, lateral, and uplift forces for a deck girder section bridge.
Journal of Hydraulic Engineering, Volume 147; https://doi.org/10.1061/(asce)hy.1943-7900.0001909

Abstract:
There exist many bed-load functions in the literature to calculate bed-load transport rates, but none of them fit data from low to high shear stress conditions. This research presents a generalized bed-load function based on empirical data. Specifically, the classic power law in high shear stress conditions is extended to low shear stress conditions by applying a complimentary error function (or logistic function) and using Coles’ mathematical idea for the wake law in turbulent boundary layer velocity distribution. The resulting generalized bed-load function agrees well with the classic data sets; it reduces to Huang’s 5/3 power law in the very low and the high shear stress conditions, and it is numerically close to Paintal’s 16th power law in the transitional regime. It is found that the maximum turbulence-induced lift force and the minimum critical shear stress in the Shields diagram correspond to the inflection point (in terms of logarithmic scale) in the Einstein bed-load diagram, resulting in the most efficient bed-load transport rate. After that, this paper discusses the effects of turbulence-induced lift force, critical shear stress, viscosity, nonlinearity, and uncertainty on bed-load transport. Finally, an example with uncertainty analysis is illustrated for applications.
Minna Ho, Jeroen M. Molemaker, , ,
Journal of Hydraulic Engineering, Volume 147; https://doi.org/10.1061/(asce)hy.1943-7900.0001896

Abstract:
Marine outfalls discharge wastewater on the inner shelf and are designed to encourage rapid effluent mixing sufficient to maintain a submerged wastefield. A high-resolution nonhydrostatic Regional Ocean Modeling System (ROMS) model was used to resolve concomitantly the intermediate- and far-field submarine plume development. ROMS simulations were validated with cross-flow laboratory experiments. Generally, results showed that the nonhydrostatic high-resolution ROMS is capable of resolving plume dynamics in typical cross-flow conditions. Top-of-plume elevation was quantified and found to be highly variable. The ROMS model is relatively insensitive to changes in horizontal effluent input parameterization. Multiple grid resolutions were tested, and good model–data agreement was achieved in low to medium cross-flow experiments. Additional resolution improved high cross-flow results. This intermediate- and far-field three-dimensional nonhydrostatic model resolves plume development over multiple spatiotemporal scales and can include natural oceanic processes currently absent in many plume models. Integrated outfall plume and marine process modeling will advance future wastewater management.
, Robert Ettema
Journal of Hydraulic Engineering, Volume 147; https://doi.org/10.1061/(asce)hy.1943-7900.0001903

Abstract:
This paper presents observations on clear-water and live-bed contraction scour caused by subcritical flow along a large rectangular channel. Three contraction ratios (contraction width/approach–channel width) were used: 0.25, 0.50, and 0.75. Each ratio included a 45° transition linking the contraction to the approach channel. Contractions scour relates to three categories of contraction length: length shorter than flow-separation length at contraction entrance, length exceeds flow-separation length, and length is sufficiently long to develop uniform flow in contraction. Flow-choking was avoided. The experiments focused on the second category, herein termed intermediate-length contractions. Light detection and ranging (LiDAR) scans showed that maximum scour depths occurred at a flow vena contracta (formed within the contraction entrance), the entrance corners, and the contraction exit. The observed sour depth in the vena contracta exceeded the depths estimated using the existing HEC-18 equations for contraction-scour. The deepest scour occurred at entrance corners except for the smallest ratio, which produced a step scour.
Tony L. Wahl, Christopher C. Shupe, Hajrudin Dzafo, Ejub Dzaferovic
Journal of Hydraulic Engineering, Volume 147; https://doi.org/10.1061/(asce)hy.1943-7900.0001902

Abstract:
Coanda-effect screens exclude coarse and fine debris from a variety of water intakes. Water overflows an inclined wedge-wire screen with tilted wires that shear high velocity flow from the bottom of the water column. The screens hydraulically self-clean, making them ideal for remote, nonpowered sites. Flow conditions vary widely over the length of most screens. Previous testing related flow capacity to gravitational, surface tension, and viscous forces, but the range of flow conditions was limited versus potential applications. This study tested small sections of prototype-scale screens at varying slopes, and discharge coefficients were related to Froude and Weber numbers. Tests with variable water temperatures proved that screen performance is independent of Reynolds number and viscosity, but depends strongly on surface tension. Several screen geometries (i.e., wire size, shape, and slot size) were tested, and the performance of all screens could be modeled with power curve functions of the Weber number modified by the Froude number. Individual screens exhibited some unique performance characteristics, but 10 of the 13 screens could be modeled effectively as a group.
Chieh-Ying Chen, Dimitrios K. Fytanidis, Marcelo H. García
Journal of Hydraulic Engineering, Volume 147; https://doi.org/10.1061/(asce)hy.1943-7900.0001890

Abstract:
Bubbly Creek is the historical name given to the West Fork of the South Branch of the Chicago River (SBCR). Even though its base flow is small, during extreme storm events Bubbly Creek becomes an important tributary to the Chicago Area Waterway System (CAWS). During extreme storm events, combined sewer overflows (CSOs) discharged by the Racine Avenue pumping station (RAPS), located at the head of the creek, can result in large flow velocities, potentially entraining into suspension bottom sediments, which contain abundant organic muck and buried waste. Under normal storm flow conditions, the flow discharge from Bubbly Creek flows first into the SBCR and then is conveyed by the Chicago Sanitary and Ship Canal (CSSC) towards Lockport, Illinois. However, during extreme rainfall events the conveyance capacity of the CSSC is exceeded, so there is a flow reversal, and Bubbly Creek water and sediments flow north, along the SBCR and then towards Lake Michigan via the Chicago River controlling works (CRCW). Due to lack of field observations during storms, the entrainment, transport, and fate of sediments from Bubbly Creek during reversed-flow conditions, cannot be easily assessed. This motivated the use of numerical modeling to evaluate the erosion, transport, and deposition of sediments from Bubbly Creek on the CAWS. The public-domain three-dimesional (3D) environmental fluid dynamics code (EFDC) was used to simulate hydrodynamics and sediment transport for two storm events with normal and reversed flow directions and high CSO discharge. Results show that RAPS discharge picks up sediment from Bubbly Creek, causing high-suspended sediment concentrations due to high rates of bottom material resuspension. In the September 2008 storm, approximately 8% the sediment reached CRCW and went into Lake Michigan during flow reversal, while 83% of the sediment went south along the CSSC towards Lockport, Illinois. Herein, the novelty is in shedding light on applying a 3D cohesive sediment module to evaluate the erosion, transport, and fate of organic muck and cohesive sediments originating in Bubbly Creek along the CAWS. The flow and sediment partitioning, bed morphology, and its potential impact on the system could be analyzed under normal and reversed flow conditions for both recently deposited as well as legacy sediments accumulating since RAPS went into operation almost a century ago. Capping of legacy sediments together with periodic dredging of sediments deposited after a CSO event could be an alternative worthwhile considering for urban streams like Bubbly Creek, where flow only takes place after extreme rainfall events.
Yongshun Zeng, Zhifeng Yao, Fujun Wang, Ruofu Xiao, Chenglian He
Journal of Hydraulic Engineering, Volume 147; https://doi.org/10.1061/(asce)hy.1943-7900.0001894

Abstract:
Parallel pumping systems may operate with excessive vibrations as a result of complex hydraulic excitation sources. To remove excessive vibrations, it is essential to understand the relationships between inner hydraulic excitations and outer vibration characteristics. In this investigation, experiments that included pressure and vibration measurements were performed in a parallel operating pumping system. A computational method was evaluated to determine its ability to reproduce the experimental results. The experimental results show that a large-amplitude vibration may occur under two specific conditions. One is when intrinsic single frequencies in pumps fall into the range of the broadband frequencies. The other is the beat phenomenon, which can occur if the blade passing frequencies (BPFs) from different pumps have a slight difference. The resonance condition is most likely satisfied on the floor slab of the pump house because the natural frequencies of the floor slab are relatively close to the BPF. The computational strategy is proven to be appropriate for resonance checks and risk assessment of high-level vibrations at the design stage.
, Yunjie Li, , , Deyou Liu
Journal of Hydraulic Engineering, Volume 147; https://doi.org/10.1061/(asce)hy.1943-7900.0001895

Abstract:
An approach combining the Brunone unsteady friction model and first- and second-order Godunov-type scheme (GTS) is developed to simulate transient pipe flow. The exact solution to the Riemann problem calculates the mass and momentum fluxes while implicitly considering the Brunone unsteady friction factor. The boundary cells can either be computed by applying the Rankine–Hugoniot condition or through virtual boundary cells adapted to achieve a uniform solution for both interior and boundary cells. Predictions of the proposed model are compared both with experimental data and with method of characteristics (MOC) predictions. Results show the first-order GTS and MOC scheme have identical accuracy, but both approaches sometimes produce severe attenuation when used with small Courant numbers. The presented second-order GTS numerical model is more accurate, stable, and efficient, even for Courant numbers less than one, a particularly important attribute for unsteady-friction simulations, which inevitably create numerical dissipation in both the MOC and proposed first-order Godunov-type schemes. In fact, even with a coarse discretization, the new second-order GTS Brunone model accurately reproduces the entire experimental pressure oscillations including their physical damping in all transient flows considered here.
, Beatriz M. Marino
Journal of Hydraulic Engineering, Volume 147; https://doi.org/10.1061/(asce)hy.1943-7900.0001893

Abstract:
The backscatter strength provided by multifrequency acoustic systems is frequently used to characterize suspended elements in water courses in the entire water column on a short time scale with high temporal and spatial resolution. However, in estuarine waters with highly concentrated suspended matter, sound attenuation may hinder the ability of the acoustic method to obtain grain size profiles. This article presents a novel acoustic technique to overcome this limitation by estimating the sound attenuation caused by both fine and coarse suspended matter fractions through an iterative process that starts by introducing discrete values of suspended particle concentration and size obtained from a conventional diffractometer. Results were compared with those obtained by the traditional two frequency method to highlight the substantial improvement achieved. The main advantage of the proposed methodology is the rapid detection of changes in the concentration and size profiles, which remain hidden when measurements are made with instruments that provide discrete values and require longer times. The technique was applied to obtain the particle size and concentration distributions along a cross section of an estuary characterized by zones where a massive convective process of sedimentation occurs.
Amir Golpira, Abul B. M. Baki, David Z. Zhu
Journal of Hydraulic Engineering, Volume 147; https://doi.org/10.1061/(asce)hy.1943-7900.0001892

Abstract:
In-stream boulders significantly affect local flow hydrodynamics, sediment transport, and aquatic habitats. This study experimentally investigates the Reynolds shear stress (RSS) profiles and turbulent events around an intermediately submerged boulder under a wake interference flow regime. The frequency of turbulent events and their contribution to the RSS are quantified at two specific submergence ratios of 1.56 and 1.90 around the boulder in the near-bed and top-boulder regions. Ejection and sweep events were generally dominant in the near-bed and top-boulder regions. The dominance of turbulent events around the boulder varied as the submergence level changed. Relationships are proposed to predict the contribution of the near-bed turbulent events to the RSS around the boulder.
Sherry L. Hunt, Kem C. Kadavy
Journal of Hydraulic Engineering, Volume 147; https://doi.org/10.1061/(asce)hy.1943-7900.0001877

Abstract:
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 m2/s≤q≤0.930 m2/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≤F≤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.
Hao-Chen Yan, Man-Yue Lam, Joseph Hun-Wei Lee
Journal of Hydraulic Engineering, Volume 147; https://doi.org/10.1061/(asce)hy.1943-7900.0001873

Abstract:
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 (∼10 to 60 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.
Shengwei Pei, Haixing Liu, Yan Zhu, Chao Zhang, Mengke Zhao, Guangtao Fu, Kun Yang, Yixing Yuan, Chi Zhang
Journal of Hydraulic Engineering, Volume 147; https://doi.org/10.1061/(asce)hy.1943-7900.0001882

Abstract:
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.
, Sabine Chamoun, Erik F.R. Bollaert, Giovanni De Cesare, Anton J. Schleiss
Journal of Hydraulic Engineering, Volume 147; https://doi.org/10.1061/(asce)hy.1943-7900.0001881

Abstract:
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.
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