Journal of Hydraulic Engineering

The paper presents the results of the calibration, by means of a microgenetic algorithm, of the mechanical parameters of high-density polyethylene pipes, to reproduce experimental unsteady flow runs in an installation consisting primarily of a steel pipe and of an additional polyethylene pipe. The mechanical parameters of viscoelastic models are estimated using both one-dimensional and quasi-two-dimensional models. Two sets of runs carried out at a distance of about 12 years are considered. The calibration of a three-parameter Kelvin-Voigt model provides evidence of the impossibility of obtaining general results. The use of a model with a single Kelvin-Voigt element (two-parameter model) gives good results in terms of comparison between numerical and experimental results for both pressure head and velocity. The calibration for the second series of tests shows increased deformability of the material (the reduction of the elastic modulus is more than 30%). The calibrated values of the retardation time result linearly correlated to the oscillations period, increasing with time due to the reduction of the elastic modulus. The obtained results allow evaluation of the viscoelastic parameters starting only with the knowledge of the equivalent elastic modulus.

This work introduces a simple and straightforward approach for the creep function determination in viscoelastic pipes on the basis of transient flow analysis. The governing equations are expanded and analytically solved for the first half period of the transient. This solution results in a direct formula for the viscoelastic Joukowsky pressure head as a function of the creep function coefficients which are a priori unknown. Utilizing the measured data, only in the first half water hammer period and the proposed viscoelastic Joukowsky formula, the problem unknowns are determined. To investigate the method’s merits and limitations, two experimental polyethylene pipes are taken into account from the literature. The results show that the proposed approach works very well for long enough pipelines which are completely crept in the half period of the transient flow. The method is found to be computationally efficient and easy to implement in comparison with traditional inverse transient analysis techniques.

Pressure gradients were measured for shear-thinning (5% CMC), Bingham plastic (7% bentonite), and viscoplastic (6% kaolin) fluids in pipe diameters of Ø40 to Ø200 mm, in laminar and turbulent flow. The fluids were characterized as power law, Bingham plastic, and Herschel-Bulkley fluids respectively, and additionally as Casson fluids. The study considered the effect of the rheological model in reproducing experimental laminar flow, and on transitional velocity and turbulent flow predictions. For the fluids tested, the model was found to have little effect on laminar flow calculations. Transitional velocities were predicted using three well-known techniques and found to depend on the model, although no preferences were apparent. Errors in transitional velocity predictions varied from 2.5 to 31%. Turbulent predictions too were made using three common and widely published methods, and varied significantly with rheology. All the methods, however, predicted turbulent flow similarly when using the Casson model, with errors of between 4 and 11%. It is concluded, at least for the types of time-independent, homogeneous/pseudohomogeneous, non-Newtonian fluids investigated, that for pipe flow in the practical range $40{\mathrm{s}}^{-1}<(8V/D{)<\mathrm{1,000}\mathrm{s}}^{-1}$, laminar flow pressure gradient predictions are insensitive to the rheological model. Transitional velocity and turbulent flow pressure gradient predictions, however, are significantly affected by the rheological model used, so care must be taken to correctly characterize fluids for which these predictions are required.

This paper presents large eddy simulations (LES) and experimental results of buoyant jets in cross-flow (JICF). Mixing behavior of buoyant JICF is governed by the velocity ratio ($\gamma$) and the jet Richardson number (Ri). Four buoyant JICF cases are studied with $0.68<\gamma <1.28$ and $0.31<\mathrm{Ri}<1.83$. In this range, both initial buoyancy and initial momentum are important; the release of overflow dredging plumes is a practical example within this range. The shape, size, and vertical location of simulated jet concentration cross sections compare well to measured ones. The LES results are also compared with semiempirical formulas for buoyant JICF. Those formulas use an added mass coefficient ($k_n$) and a spreading rate ($\beta$) as calibration parameters. In the present study, it is found that path, dilution, and spreading can be well predicted by applying $k_n=0$ and $\beta =0.7$; those values result in better predictions than when using the advised values—namely, $k_n=1$, $0.34<\beta <0.62$. Cross contours for concentration ($C/C_{\max }$) and fluctuations ($C^{\prime }/C_{\max }$) show self-similar behavior. The maximum value for a buoyant JICF is $C^{\prime }/C_{\max }=0.45–0.65$. The intriguing discovery is made that the jet of a buoyant JICF overtakes its own cross-flow: the average horizontal streamwise velocity of the jet of a buoyant JICF is slightly larger than the cross-flow velocity. This effect is found for all four buoyant JICF cases considered in this study, but is strongest for the deepest buoyant JICF trajectories. The increased horizontal streamwise velocity of the jet originates from zones with increased velocity next to the initially vertical jet, which acts as a vertical cylindrical obstacle.

The accurate prediction of the dilution and motion of the produced denser water (e.g., discharge of concentrated brine generated during solution mining and desalination) is of importance for environmental protection. Boundary conditions and ambient stratification can significantly affect the dilution and motion of gravity currents. In this study, a multiphase model was applied to simulate the gravity current descending a slope into a linearly stratified ambient. The $k\text{-}\omega$ turbulence model was used to better simulate the near-bed motion. The mathematical model, the initial and boundary conditions, and the details of the numerical scheme are described here. The time-dependent evolution of the gravity current, the flow thickness, and the velocity and density field were simulated for a range of flow parameters. Simulations show that the Kelvin–Helmholtz (K-H) billows are generated at the top of the trailing fluid by the interfacial velocity shear. The K-H instability becomes weaker with the slope distance from the source because of the decrease in interfacial velocity shear along the slope. The ambient stratification restricts and decreases the current head velocity as it descends the slope, which differs from the situation in the homogenous ambient while the head velocity remains in an approximately steady state. Motion of the descending flow into the stratified ambient has two stages: initial acceleration and deceleration at a later stage based on the balance of inertial, buoyancy, and friction forces. When the descending current approaches the initial neutral position at a later stage, it separates from the slope and spreads horizontally into the environment. The simulated results, such as vertical velocity and density profiles and front positions, agree well with the measurements, indicating that the mathematical model can be successfully applied to simulate the effect of the boundary conditions and ambient stratification on the dilution and propagation of gravity currents.

Numerous research contributions have been made on the hydraulic properties for steep, stepped chutes. Stepped chutes applied to more moderate slopes like those for aging embankment dams are a growing trend, and research activities as a result have increased in this arena. Although numerous stepped chute design guidelines are available, some of them are complicated and somewhat cumbersome to use. A multiyear, large-scale physical model study was conducted for a broad range of step height ($h$) to critical flow depth ($d_c$) ratio and chute slope ($\theta$) (i.e., ${0.035\le h/d}_c\le 2.27$ and $14°\le \theta \le 26.6°$). The objectives of the study were to (1) evaluate the step height to critical flow depth ratio and the chute slope affect on the surface inception point, clear water and bulked flow depth, air concentration, and energy coefficient; and (2) develop practical, straight-forward design relationships for practicing engineers. Detailed flow measurements were collected during testing, and the results were compared in terms of free-surface inception point, air-water flow properties, and energy dissipation. Free-surface inception point relationships were validated for a broader range of use. Relationships for air concentration, clear water flow depth, and energy coefficient were developed, and findings showed these relationships are a function of (1) the length from the downstream edge of the broad-crested weir to the point of interest to the characteristic length from the downstream edge of the broad-crested weir to the free-surface inception point (${L/L}_i$) ratio, (2) the step height to critical flow depth (${h/d}_c$) ratio, and/or (3) the chute slope ($\theta$).

This study explores the comprehensive calibration potential of impedance-based methods implementing several unsteady friction models for a pipeline system with or without leakage. The corresponding response functions in the frequency domain approach have been derived by the impulse response method and incorporated into the genetic algorithm-based calibration method. Unsteady models addressed either frequency-dependent friction or acceleration-based frictions. Parameter calibration exercises with experimental data have shown that the impedance-based approach provides a versatile and feasible optimization framework via the fitting of an objective function based on the predicted and measured pressure head variation. To check the impact of pressure pulsation and noise, extended calibration tests were performed using oscillated and disturbed pressure data bounded by the frequency and amplitude of a pump system and the measurement error of a conventional pressure transducer. The performance of the integrated optimization examples demonstrates the robustness of the impedance-based approach, both in the representation of a real-life system and the configuration of various system characteristics.

A comprehensive hydraulic modeling effort that was applied to two rural watersheds in southern Virginia is presented in this paper. The 10-, 50-, 100-, and 500-year storms and the probable maximum flood (PMF), are considered in this study with the objectives of assessing the impact of extreme hydrologic events through the generation of inundation maps, characterizing the sediment transport process under severe flooding conditions, and quantifying the uncertainty associated with the floodplains boundary roughness and its influence on the results. The employed methodology includes the construction of a river terrain model that combines geospatial and field-collected data, a calibration procedure based on regression equations and developed stage-discharge predictor curves, and unsteady flow simulations utilizing discharge hydrographs produced by an event-based hydrologic model. The results highlight the severe flooding conditions associated with the PMF and the necessity of considering it as the worst-case scenario in regions with relatively wet and humid climate. The modeling effort presented in this paper aims to serve as a reference framework for the development, implementation, and validation of hydraulic models intended to simulate extreme hydrologic events, as well as to provide guidance for the interpretation of the results for similar studies.

Radio frequency identification technology (RFID) has allowed for tracking of individual clasts implanted with passive integrated transponder (PIT) tags through sedimentary systems, providing recovery rates much higher than older sediment tagging methods such as painted or magnetic clasts. However, preparation of natural clasts for PIT tag implantation has been time-consuming and dangerous with rates of catastrophic failure of clasts of $\sim 66\%$ or more. Moreover, failure rates increase as clast size decreases. The authors present an improved methodology that provides nearly 100% success rates and allows for drilling of clasts down to 23 mm along the intermediate diameter. The gripping and binding device (GABI) prevents clasts from rotating and is effective when used in conjunction with the rhythmically applied pressure drilling technique. GABI is simple and inexpensive to build and can be used in a field setting. The improved safety and effectiveness of the method will allow for greater application of RFID tracking of natural sediment. Additionally, the ability to drill smaller clasts opens up new possibilities for research in sediment transport.