Entrainment of density flows is a key parameter in constructing predictive models of global climate, ocean flows, and turbidity currents. Our numerical experiment, which included 10 subaqueous dilute density flows with a steady sustained inflow (SSI) on a 2D channel bed slope varying from 0.1° to 90°, showed that in the slope range of 0.1–20°, there is a linear relationship between the ambient fluid

ABSTRACT Accurate calculation of air demand is fundamental in the design of air ducts in a spillway tunnel. However, it was often underestimated by empirical formulas in previous studies. In this paper, an air–water stratified flow model, in which the air and water are coupled by a new interfacial shear stress formulation, is proposed. The model is verified by using prototype data and numerical CFD

Under large unit discharges, cavitation damage may occur and energy dissipation may remarkably decline in stepped chutes due to absence of air entrainment. Herein, a pre-aeration device, entraining air by contracting the flow locally by walls without special air vent, is proposed for increasing the maximum available unit discharges. The test results demonstrate that the aerator proposed in this paper

This study investigates the effects of wildlife activities by beavers, muskrats, gophers, and ants on seepage through Barr Lake, Commons Pond, Lake Elizabeth, Village Pond, and Walden Place Dams in South Carolina, USA, using a numerical seepage model. Data was collected from all dam sites for geotechnical testing, and observations were made for animal activities. The laboratory results were used for

A model for the subsurface flow and associated oxygen transfer induced by surface flow and slip velocity is presented in a gravel bed river. The shear velocity (U *) and hydraulic conductivity (K) were used to characterize the surface flow and subsurface flow, respectively. The subsurface flow field was described by using the Darcy and the Brinkman equations. The interaction between surface and subsurface

The transient behaviour of the pump-turbine in load rejection is very complex, and slight changes in runner blade shape may have great influence on it. To understand the underlying flow mechanisms, the load rejection processes of two model pump-turbines with the same specific-speed but different in the runner blade inlet shape were investigated by a three-dimensional numerical simulation method. The

ABSTRACT Numerical models are used increasingly to tackle aerated flows for example in spillway design. However, these models are usually empirical and often lack thorough calibration. Herein a mixture model is calibrated with experimental data on uniform aerated flow from literature. A commercial code was used to solve the mixture Reynolds-averaged Navier–Stokes equations. Air entrainment was modelled

ABSTRACT Flow patterns around three widely used instream rock structures in an open-channel flume were investigated using high-resolution large-eddy simulations. Specifically, rock vanes at two different installation angles, a J-hook vane, and bendway weirs at two different angles, with realistic geometries, were studied. Velocity fields in the wake of these instream structures were measured using

A series of experiments were conducted beneath simulated partial ice covers to investigate the turbulent flow behaviour using a particle image velocimetry system. The velocity data were used to assess predictive capabilities of some bed shear stress models developed for open channels. Specifically, the abilities of the Ludwieg–Tillmann, quadratic stress law and Prandtl's seventh power law techniques

(2020). Correction. Journal of Hydraulic Research. Ahead of Print.

Self-cleansing is a hydraulic design concept for drainage systems for mitigation of sediment deposition. Experimental studies in the literature have mostly been performed in circular channels. In this study, experiments were conducted in five cross-section channels: trapezoidal, rectangular, circular, U-shape and V-bottom to investigate the non-deposition condition of sediment transport in rigid boundary

In this paper, the Spalart–Allmaras turbulence model, very popular for compressible aerospace applications, is adapted for incompressible free surface environmental flows. The Spalart–Allmaras model is a Reynolds-averaged Navier–Stokes model which solves for one transport equation of a viscosity-like variable. Besides its efficiency and reasonable computational cost, the model can take into account

Owing to the complexity of the load rejection process, the accompanied complex low frequency pressure fluctuations and their sources have not been determined. Herein, the load rejection transient process of a pump-turbine was simulated with a three-dimensional (3-D) large eddy simulation method and a dynamic mesh technology. The simulation results were validated against the experimental data. Through

This paper presents a vegetated flow and sediment transport model for investigating flow–vegetation–sediment interactions. Vegetation-induced turbulence is simulated by a k − ε turbulence closure, in which shear and stem-scale wake turbulent kinetic energies are solved separately. The model simulates both unidirectional and oscillatory flows as well as turbulence structures reasonably well with the

We present an experimental analysis of hydraulic roughness variations due to changes in alluvial cover in a mixed bedrock-alluvial meandering channel with larger bedrock roughness than alluvial roughness. Three sets of experiments were conducted in a highly sinuous flume: one with bare bedrock, and two with enough sediment to cover 21% and 78% of the bedrock respectively. We compare our results with

Gravel-bed roughness structures for an unworked bed and a water-worked bed are analysed at different topographic scales measuring the bed surfaces by a 3D terrestrial laser scanner in a laboratory flume. The study represents a novel contribution in assessing the role of water-work on a uniform gravel-bed, demonstrating the development of small-scale bedforms (i.e. clusters). To support these observations

Simulations of shallow-water flows in an open channel with vegetation are considered. The simple formulation of bulk resistance makes numerical realization of vegetation straightforward. Stem-scale eddies due to individual plants are not modelled. While the vegetation resistance parameterization has been frequently used, few studies exist that comprehensively evaluate the modelling skills of such a

(2020). Correction. Journal of Hydraulic Research. Ahead of Print.

This article concerns the turbulent flow of Herschel–Bulkley slurries through circular horizontal pipes; in particular, that of concentrated domestic slurry obtained upon separation of domestic waste water and reduction in the use of water for domestic purposes. Experiments with a rheologically equivalent clay (kaolin) slurry indicated a non-Newtonian behaviour of the Herschel–Bulkley type. A modified

Debris flows are typical two-phase flows that commonly occur with entrainment. By involving sediment materials, the fluid viscosity of debris flow may change significantly along with the variety of solid volume fraction, which further influences debris flow routing. To address this issue, a two-phase model is incorporated with a correlation for the apparent viscosity of the mixture and an entrainment

Hydropower tunnels are generally subject to a degree of rock falls. Studies explaining this are scarce and the current industrial standards offer little insight. To simulate tunnel conditions, high Reynolds number flow inside a channel with a rectangular cross-section is investigated using particle image velocimetry and pressure measurements. For validation, the flow is modelled using large-eddy simulation

We present an experimental study of natural hyperconcentrated flows of fine sediment from Draix-Bleone observatory. Suspensions of volumic concentration ranging from 29 to 44% were tested in a rheometer and exhibit a Herschel–Bulkley behaviour. Suspensions of volumic concentration ranging from 0 to 31% were tested in flume experiments with varying slope and discharge. Velocity profile measurements

The 2D shallow water equations are often solved through finite volume (FV) methods in the presence of irregular topography or in non-rectangular channels. The ability of FV schemes to preserve uniform flow conditions under these circumstances is herein analysed as a preliminary condition for more involved applications. The widely used standard Harten-Lax-Van Leer (HLL) and a well-balanced Roe method

For a channel with a constant discharge, the characteristics of the surge wave entering a junction are obtained from the classical Stoker solution, and then the effect of the junction is analysed by applying the momentum and mass conservation equations. Experimental cases involving different combinations of the tributary lake height and the main channel discharge were tested, and measurements show

Air supply to free-surface water flows in tunnels is a key safety issue for high-head dams. The present study analyses the effects of approach water velocity and area residual of tunnel cross-section on air demand, using the volume of fluid (VOF) method in combination with the k–ε turbulence model. For a tunnel area residual less than 0.4, the attenuation of air velocity above the free-surface water

In the analysis of water distribution networks (WDNs) facing uncertainty, fuzzy set theory is suggested as an applicable stochastic analysis approach when the probability distributions of the information are not available. This technique can recognize the extreme values of unknown variables when uncertain input information varies between pre-specified extremes. Current approaches proposed in the literature

The proper orthogonal decomposition (POD)-Galerkin projection method was applied to the quasi-two-dimensional (quasi-2D) water-hammer problem for achieving a model order reduction. The computation of the axial velocity profile requires a large number of numerical grids that is equal to the number of degrees of freedom (DOFs) in the quasi-2D water-hammer problem. To alleviate the large computational

Transition from laminar to turbulent flow of non-Newtonian fluids is investigated using velocimetry data. These data are obtained by applying particle image velocimetry to images obtained through ultrasound imaging (echography). This yielded the observation of intermittent structures (puffs and slugs) that are formed during transition. Post its observation, transition is characterized using the friction

(2020). Critical shear stress for erosion of sand and mud mixtures. Journal of Hydraulic Research: Vol. 58, No. 3, pp. 548-550.

(2020). Closure to “Critical shear stress for erosion of sand and mud mixtures” by WEIMING WU, CHAMIL PERERA, JARRELL SMITH and ALEJANDRO SANCHEZ, J. Hydraulic Res. 56(1), 2018, 96–110. Journal of Hydraulic Research: Vol. 58, No. 3, pp. 550-551.

Evaluating the vulnerability of buildings lying in flood-prone areas is an essential component of the assessment of flood-induced risk, particularly because of the severe consequences that damage and collapse of building may have on loss of life during most extreme events. Despite its importance, a comprehensive methodology for use in the assessment of the potential damage to buildings caused by dynamic

Formation of an air-entraining vortex in the vicinity of an intake structure is considered to be a major problem of the intake. These vortices are not acceptable as they decrease the efficiency of the intake structures. Adequate submergence above the intake can effectively halt the formation of such vortices. The present study deals with the analytical and experimental works carried out on a horizontal

(2020). Symmetric junction manholes under supercritical flow conditions By Juan Saldarriaga, Gina Rincon, Gloria Moscote and Maria Trujillo. Journal of Hydraulic Research: Vol. 58, No. 1, pp. 182-185.

This paper explores continuous pressure wave characteristics and flow features in a periodic transient flow induced by a rotary pressure wave generator. A three-dimensional CFD model based on the realizable k-ϵ turbulence model is established to conduct the simulations. The results show that the turbulent kinetic energy evolution in the periodic transient flow is similar to that in an instantaneous

A new 3D hydrodynamic model was developed to simulate water quality transport in surface waterbodies. The governing equations are the continuity equation, free surface equation, momentum equation and transport equation. The 2D numerical scheme of CE-QUAL-W2 was expanded in three dimensions and modified to solve for the free surface elevation. A time splitting technique was employed to solve the momentum

ABSTRACT The double-averaging methodology is used in this paper for deriving equations for the second-order velocity moments (i.e. turbulent and dispersive stresses) that emerge in the double-averaged momentum equation for incompressible Newtonian flows over mobile boundaries. The starting point in the derivation is the mass and momentum conservation equations for local (at a point) instantaneous variables

Well-resolved detached eddy simulation (DES) and unsteady Reynold-averaged Navier–Stokes (URANS) simulations are conducted for a water pump-intake bay. Three cases are analysed: a high-submergence, low discharge case (Case 1), a low-submergence, low-discharge case (Case 2) and a low-submergence, high-discharge case (Case 3). The numerical model uses the volume of fluid (VOF) to account for the free

ABSTRACT In order to analyse the flow characteristics of free-surface vortexes and to validate the Burgers vortex model by using stereo particle image velocimetry, experiments are conducted in a 600 mm diameter vortex tank. Measured axial velocities indicate that 10–25% of the flow is transported through the vortex core. The velocity profiles show that the axial flow is concentrated in a domain bounded

Hydropower plant units operating in off-design conditions are subject to cavitation flow instabilities, potentially inducing hydro-acoustic resonances under certain conditions. They can be predicted by using one-dimensional numerical models of hydropower plants that rely on a proper modelling of the draft tube cavitation flow in off-design conditions. The latter is based on hydro-acoustic parameters

This paper presents the experiments performed on a high head model Francis turbine during start-up. Synchronized time dependent pressure and velocity measurements were performed to investigate the instabilities in the turbine. A total of four steady state operating points, namely synchronous load, part load, best efficiency point, and high load are considered to perform the turbine start-up. The runner

This paper focuses on the transient stability of a hydro-turbine governing system with three kinds of tailrace tunnels. As the transfer coefficients change with operation conditions, the dynamic transfer coefficients which can describe the transient characteristics of the hydro-turbine governing system are introduced. Then, the transient stability of the hydro-turbine governing system is analysed.

Using the recently developed bottom-tilting wave maker, run-ups of very long waves are investigated on an adjustable plane beach. Both leading-elevation waves and leading-depression waves are considered, in which the experimental results are compared with the numerical solution of the nonlinear shallow water equations. A surf similarity parameter based on the steepness of the accelerating phase of

ABSTRACT To better understand individual violent wave overtopping, of significance for coastal defence design, three breaking wave types (steep-fronted, plunging and broken) based on focused wave groups, were generated in laboratory and numerical models. High-speed video captured overtopping events and produced velocity vector maps by means of bubble image velocimetry (BIV). Results were compared with

ABSTRACT By the late nineteenth century, the scientific study of bedload transport had emerged as an offshoot of hydraulics and geomorphology. Since then, computing bedload transport rates has attracted considerable attention, but whereas other environmental sciences have seen their predictive capacities grow over time, particularly thanks to increased computing power, engineers and scientists are

This paper outlines the various approaches used to calculate bedload transport. As bedload transport exhibits considerable spatial and temporal variations, computing the bedload transport rates and morphological changes experienced by streambeds is difficult. A large body of experimental work has revealed scaling laws relating the mean transport rate qs to hydraulic conditions (that is, water discharge

A novel approach quantitatively describing two-dimensional displacements of placed riprap stones exposed to overtopping flows is developed and validated, coupling experimental data with Euler’s buckling theory for columns. Past studies investigating the failure mechanisms of placed ripraps with toe support have analysed unidirectional displacements of riprap stones parallel to the slope. 2D description

Turbulence in open channel flows is ubiquitous to hydro-environmental applications and has recently increased in importance with the deployment of tidal stream turbines, as turbulence impacts both the turbine performance and the blade fatigue life. Tidal turbine analysis requires fully developed turbulence characteristics at the inlet of numerical simulations where generally the length scale information

In the last five decades much research has been devoted to the development of predictive formulae to quantify the maximum local-scour depth developing around hydraulic structures (e.g bridge piers). Owing to the complexity of the problem, most of the proposed formulae were developed on empirical grounds, which made them susceptible to scale issues. Recently, a new theoretical approach was proposed

The protection of the marine environment is of growing concern, and the development of hydrodynamic models is required to study ocean processes. In this work, a two-dimensional hydrodynamic lattice Boltzmann model was developed to study wave–current coupling problems that combine wave radiation, bed shear stress and wind shear stress. The model is based on nonlinear shallow water equations and two

When soil surfaces are exposed to high shear stresses induced by high-velocity water flows, they erode. Erosion consists of the detachment, entrainment and transport of soil particles. When exposed to high shear stresses the process of soil detachment is no longer given by the pick-up of individual particles but by the continuous shear failure of layers of soil. The understanding of how soil properties

Flow overtopping can lead to the initiation of breaching and failure of fluvial dikes, causing severe inundations and damage in the protected areas. For flood risk management and prevention, the accurate estimate of flow discharge across the fluvial dike breach is paramount, requiring precise understanding of the breach expansion. Laboratory experiments were conducted to analyse the effects of fine

While the literature on transverse beams in open channels is broad, there is comparatively less understanding of the hydrodynamics of channels with streamwise ribs. In the current study, an asymmetrical canal with a sidewall longitudinal beam was studied experimentally to gain some fundamental understanding of the implications in terms of turbulence and environmental applications. The sidewall beam

This paper presents the hydraulic study of a new manhole geometry, designed to allow the installation of separate sewer systems in narrow streets. The new manhole design comprises two chambers in one structure to manage separate flows. The new shape of the manhole generates a new flow pattern for stormwater. It is therefore important to understand the hydraulic properties of sewer systems using the

This paper provides an evaluation of a hydro-acoustic technique for efficient quantification of the bedload transport in riverine environments. Stationary bedload measurements were conducted simultaneously at different study sites, using three different acoustic Doppler current profilers (ADCP) working at four different frequencies. The raw apparent bedload velocities were de-spiked and filtered in

This paper describes the experiments carried out on flood hydrodynamics in a river-network-floodplain set-up for validating numerical models. Fluvial floods in the set-up are generated due to overbank flow. The flood extent is extracted by processing overlapping images of the flooded set-up. The steady-state flow depths and velocities are measured by a point gauge and acoustic Doppler velocimeter (ADV)

ABSTRACT The current geometric designs of fish guidance structures with vertical bars for run-of-river hydropower plants result in high head losses and asymmetric turbine admission flow. To address these issues, we develop innovative curved bar designs and experimentally investigate different rack configurations with curved bars in a laboratory flume. The present paper (Part II) focuses on the hydraulic

The application of the acoustic Doppler velocimetry (ADV) technique to backward-facing step flows is very scarce in the literature. This work aims at investigating the applicability of the ADV technique to flows over a backward-facing step, at various Reynolds numbers to capture different flow regimes, and to provide reliable data which can be used to validate numerical models. The ADV V e c t r i

Experiments on gravity currents produced from full-depth two-layer stratified buoyancy sources propagating in the slumping phase are presented in the paper. The Froude number in the slumping phase, F S = U f / g 0 ′ H , where U f is the front velocity, g 0 ′ is the average reduced gravity and H is the lock height, is influenced by the density difference ratio, R R = ( ρ U − ρ 0 ) / ( ρ L − ρ 0 ) ,

A three-dimensional numerical model was developed to better understand the hydrodynamics and sediment processes near the water intake of the Cardinal power plant. Sediment is represented with particles that are suspended, deposited or transported as bed load depending on particle size, flow turbulence and local bed shear stress, neglecting morphological changes. Validation against field velocity data

This study focuses on the formulation of a spectral approach to obtain the transmission coefficient (Ct) of floating breakwaters (FB) in irregular waves based on Ct in regular waves. Additionally, it provides a performance comparison of two quite similar rectangular and circular pontoons as FB. It starts with the comparison of Ct and extends to motions in regular waves by experiment. Overall, the rectangular