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Energy dissipation structures, particularly stilling basins, are critical for defining the hydraulic jump characteristics that are suitable. Appropriate sill geometry for abruptly expanding stilling basins has been investigated and a central rectangular sill has been proposed in the literature. This study has examined the suggested central sill and alternative flip buckets for abruptly expanding stilling basins. A series of experimental and numerical studies were carried out for two different heights of the central sill and two different flip buckets. Simulations have been evaluated using experimental data of laboratory scale, which indicated that they were acceptably precise. For the simulations, the k−ε turbulence model RNG module was preferred using the volume of fluid methods. The PISO approach was chosen to resolve this equation system numerically. The results showed that the hydraulic jump characteristics are strongly influenced by sill geometry. For the Type-3 sill negative static pressures have not occurred and performs better at energy dissipation than other geometries examined in the study. Higher pressures occurred on the rectangular prism-shaped sills. Maximum static pressure happened on the Type-2 sill. The least static pressure was seen in the Type-4 sill type. [ABSTRACT FROM AUTHOR]

Study of hydraulic jumps following aerated supercritical flow has been limited, although this is a common scenario in stilling basins preceded by open-channel spillways. New experiments were performed in a concrete stilling basin model downstream of a sloping stepped chute, where hydraulic jumps were generated on the horizontal stilling basin bed and characterized by bubbly approach flow with Froude numbers 7.6 and 9.3 and Reynolds numbers in the order of 105. Measurements were focused on the jump toe oscillations, jump roller length, and air–water flow property distributions. Comparison of the results with literature data under non-aerated inflow conditions suggested overall insignificant pre-aeration effects on the investigated air–water flow properties, although some comparative analyses were subject to scale effects. The streamwise evolution of air flux suggested that the pre-entrained air did not intrude deeply into the jet-shear layer beyond 1/5 to 1/3 roller length from the jump toe. [ABSTRACT FROM AUTHOR]

When a river channel is narrow, bifurcated, or intersected, or when extreme weather or geological disasters cause shed rock masses to occupy a river flood channel, local hydraulic jumps may develop in the channel. Natural disasters such as landslides, floods, and debris flows occur upstream, will result in large transport rate of large-sized gravel particles. Those particles may be blocked in hydraulic jump areas, causing river channel water depth to rise. In this study, the effect of local hydraulic jumps on the sediment deposition rate was investigated in flume experiments. The ratio of upstream and downstream Froude numbers, particle size, Sediment supply intensity, and flow discharge all affected the sediment deposition rate. With increases in the ratio of upstream and downstream Froude numbers, particle size, and sediment supply intensity, the sediment deposition rate increased. The sediment deposition rate decreased with an increase in flow discharge. Approach hydraulic conditions and particle properties jointly determined the sediment deposition rate in a hydraulic jump section, and an empirical formula was developed using those parameters to calculate the sediment deposition rate. Thus, to identify risks and prevent disasters in mountain rivers, local changes in hydraulic conditions and particle properties need to be jointly evaluated. [ABSTRACT FROM AUTHOR]

In this study, to simulate open channel flows, an explicit incompressible mesh-free method is employed in which the pressure field is obtained by explicitly solving the pressure Poisson equation. To capture the velocity information in open channel flows, the source term in the pressure Poisson equation is modified while the spatial discretization of gradient and Laplacian models is based on the moving particle semi-implicit (MPS) method. The inflow boundary condition is treated by injecting fluid particles into the domain according to the inlet discharge, and the outflow condition is handled by prescribing the pressure distribution and removing the fluid particles beyond the domain. The explicit incompressible mesh-free method is then used to simulate open channel flows, including weir flow, hydraulic jump, and flow over an obstacle. In the simulations, velocity distribution and flow pattern are examined. The simulated results are compared to available experimental measurements and other numerical results. There is a good agreement between the simulated results and the experimental measurements. It shows that the explicit incompressible mesh-free method can reproduce the flow characteristics in the open channel flows. [ABSTRACT FROM AUTHOR]

Copyright of Water Conservancy Science & Techonlogy & Economy is the property of Water Conservancy Science & Technology & Economy Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This paper numerically investigates the physical features of hydraulic jump oscillations at an abrupt drop with high Froude numbers reaching values up to 9.92. In order to emphasize the importance of the bottom shape, different relative step heights in the range between 0.9 and 3.4 have been analysed, leading to the occurrence of different jump regimes (A-wave, A-jump, B-wave and B-jump). For the case of the B-jump type, the jump toe is drifted downstream when the Froude number increases. For the A-jump type with high Froude, the surface roller is made up of an increasing several number of vortices and thus the jump toe is drifted upstream, when the Froude number increases. In particular, for the case of the A-jump type at the highest simulated Froude number, when the toe of the jump is at its most upstream location, the maximum number of anticlockwise vortices (with decreasing sizes) is observed. At the same time, the turbulence levels decrease much faster due to the dominance of viscous forces at the small scales. Instead, when the toe of the jump is moving downstream, the neighbouring vortices tend to influence each other with their rotation and to coalesce into one larger vortex and the turbulence levels increase rapidly due to the dominance of inertial forces. A statistical analysis indicates that turbulent pressure fluctuations increase rapidly from the toe of the jump and reach a peak in the roller region, downstream of which they decrease again. The structure of the turbulent pressure fluctuations depends on the Froude number. [ABSTRACT FROM AUTHOR]

There are multiple initiatives aimed at strengthening coastal communities against tsunami disaster risks, such as growing vegetation belts, construction of embankments, moats, and different hybrid alternatives. To find a solution for strengthening the coastal buildings themselves, we firstly reviewed the flow phenomena around a single emergent (circular and rectangular) cylinder (case C1), which was considered as a piloti-type column under different Froude conditions, and evaluated the formation of surface bow-waves, hydraulic jump detachment, and wall-jet-like bow-waves. Secondly, the flow characteristics were investigated under the same Froude conditions with side-by-side two-cylinder (case C2) and four-cylinder (case C4) arrays in an open channel. Surface bow-wave length ( L B w ) increased by 7–12% over the rectangular cylinders (RCs) compared to the circular cylinders (CCs) with a subcritical flow. For the supercritical flow with a 1/200 bed slope, hydraulic jump detachment was observed in relation to the Froude number. The observed length of the hydraulic jump detachment ( L j u m p ) varied between 3.1–8.5% and 4.2–12.9% for the CCs and RCs in the supercritical flow with a 1/200 bed slope. In addition, the wall-jet-like bow-wave height ( h j e t ) over the CCs was increased by 37% and 29% compared to the RCs with a supercritical flow and zero bed slope (orifice-type flow). For case C4, a hydraulic jump was observed for the supercritical flow over the horizontal channel bed. Finally, empirical equations were defined concerning the geometrical shape and arrangement based on the experiment data for the single and side-by-side configurations of the cylinders to validate the height of the wall-jet-like bow-wave as the most critical flow property. [ABSTRACT FROM AUTHOR]

Sluice gates are utilized in dams and irrigation channels as regulating structures in the channel have the role of regulating the water level for proper water intake of upstream intakes. As high velocity and energy of the flow issuing from these hydraulic structures scour occurred in erodible downstream beds. Occurrence of the hydraulic jump is very possible, and when it forms, therefore the necessity of investigating the flow condition increases. The scouring phenomenon is a time evolution and a long-time procedure. This research focused on time effects on experimental data received by a sediment bed profiler at different times from the experimental setup conducted in a laboratory. The maximum scour depth (dse), the maximum dune height (hd), the horizontal distance of the maximum scour depth from the beginning of the sedimentary bed (xse), and the horizontal distance of the maximum dune height from the beginning of the sedimentary bed (xd) were investigated. Laboratory observations show that the extension of the location of the maximum scour depth and the maximum height of the dune formed with time is evident. The laboratory data for the dimensionless conditions of 4 scour profiles characteristics including dse/b0, hd/b0, xse/b0, and xd/b0 were analyzed by the nonlinear regression method, and separate equations were proposed for each characteristic. RMSE=0.045, 0.0677, 0.358, and 2.146 respectively, and the R² =0.996, 0.975, 0.974, and 0.977 respectively. [ABSTRACT FROM AUTHOR]

The present experimental study analyzes the effects of lateral jet flow (LJF) in a stilling basin with abruptly expanding channels on the stabilization and the significant characteristics of spatial hydraulic jump. The experiments were carried out with three different inflow Froude numbers (8.77, 9.56, and 10.87), three different distances of the LJF from the abruptly expanding channel (0 m, 0.25 m, and 0.5 m), and one and two LJF (i.e., the number of active orifices in the LJF system). According to the results, the distances of the LJF from the narrow channel and the number of LJF improve the hydraulic jump's stabilization and flow pattern enhancement in the tailwater channel. Additionally, the average sequent depth and the spatial jump length decreased by 14% and 20%, respectively, compared to no LJF. Also, using LJF increases relative energy dissipation by 12.45% on average. HIGHLIGHTS Using lateral jet flow (LJF) to stabilize spatial hydraulic jump.; Reduction of sequent depth by LJF.; Reduction of hydraulic jump length by LJF.; Increasing energy dissipation in spatial hydraulic jump using LJF.;

Abstract In the present study, series of laboratory experiments were conducted to investigate the effectiveness of perforated screens as energy dissipators in mixed triple wall mode in the case of small hydraulic structures. The shapes of openings for each layer of screens were either circular, square or triangular. Every layer of the screen had a porosity of 45% per unit depth of the screen. The experiments were conducted to dissipate the energy for supercritical flows of Froude number F 1 ranging from 3.2 to 19.3. The screens were placed vertically with the first screen 1.5 m from the sluice gate and consecutive screen at a gap of 25 mm. The experiments showed that the energy of the supercritical flows can be dissipated effectively by using perforated screens. The difference in energy dissipation between the upstream and downstream of the screen was more significant than the energy dissipation caused by classical hydraulic jumps. Comparing the results of the present study with the previous researchers it is found that the energy loss in case of present study more than the previous researchers. The relative energy loss in the present study was found to be varying from 74 to 94%. The value of the Froude number downstream of the screen, F 2, was varying from 1.1 to 1.81, with an average value of 1.35. Tailwater deficit parameter, D, if found to be varying from 0.66 to 0.90.

The current research investigates experimentally the flow passing through combined hydraulic structure consists of V-notch sharp crested weir and inverted V-shaped sharp gate installed in straight channel as a control structure. Nine structure models were used considering three different vertex angles simultaneously used for the weir and the gate (θ = 60°, 90° and 120°). Eighty-one experimental runs were executed to explore the influence of the combined structure geometry, the upstream head, and the tailwater depth on the conveyed flow, the discharge coefficient and the downstream flow pattern with special emphasize on the hydraulic jump characteristics. The outcomes were analyzed and graphically presented. The results proved that the simultaneous flow through the combined structure regardless the vertex angles conveyed more discharge with less downstream water disturbance on account the classical V-notch weir and the inverted V-shaped gate. The flow discharge increased up to 10 times, and the discharge coefficient increased by around 26% for combined structure of 120° vertex angle under similar hydraulic conditions. The conveyed discharge was influenced by the gate angle than the weir angle. The downstream flow characteristics were more sensitive to the weir angle than the gate angle under similar hydraulic conditions. The measured hydraulic jump lengths were compared to other formulas and showed good agreement. Also, the weir and gate vertex angles effectively influenced the hydraulic jump characteristics. The outcomes were used to develop empirical equations for predicting the discharge coefficient and dimensionless jump length associated to the combined structure. The results and analysis in this research are limited to tested data range.

Several studies indicate that using hydraulic structure results in some adverse effects that affect the stability of these structures, including scouring the floor. Many researchers resorted to using defensive means to reduce the flow's speed and energy as much as possible. One of these means is the use of screen walls. Therefore, the current study focused on reviewing different types of research that dealt with the help of screen walls by changing the location of the screen and geometric shape, such as the diameter of the holes, thickness of the screen wall, porosity, changing the geometric arrangement of the gaps such as the square, triangle and hexagon, as well as the use of a screen inclined at a certain angle, use of triangular meshes and use Artificial intelligence programs to simulate and compare results.

Low-head dams can be dangerous to recreational river users when a submerged hydraulic jump forms downstream, with recirculating surface flows that repeatedly carry trapped recreationists upstream into the high-velocity jet plunging over the dam crest. The flow endangers those who pass over the dam from upstream and can also entrap those who approach too closely from downstream. A national task force is using a range of methods to identify potentially dangerous structures, but definite determination requires field data and an analysis of the hydraulic conditions for each site's range of likely flow rates. The spreadsheet tool described here determines the submergence created by site-specific tailwater levels and uses previous research results to estimate the associated magnitude of reverse flow velocities. The spreadsheet also determines the crucial tailwater level at which the jet passing over the dam stops plunging into the tailwater pool and instead flips to the surface, creating safer, downstream-directed velocities. The article describes application to specific sites and provides insight about the dangerous flow range of typical low-head dams. [ABSTRACT FROM AUTHOR]

The work proposes and discusses a theoretical approach to predict the behavior of an open-channel supercritical flow that overpasses a step, either forward or backward facing, non-orthogonal to the flow direction. In this case, a sequence of oblique shock waves and expansion fans is generated close to and downstream of the step. The proposed model is verified by comparing the theoretical predictions with the results provided by a two-dimensional, depth averaged numerical model. Applications include the combined use of oblique steps and abrupt wall deflections to suppress wave fronts that characterize supercritical flow in channel bends. Special attention is devoted to the supercritical to subcritical transition (and vice versa) in overpassing a forward-facing step; this is found to be a rather intriguing problem characterized by complex solutions and by hysteresis. Besides the classic smooth (everywhere supercritical) and choked (with a hydraulic jump and a subcritical flow upstream of the step) solutions, an additional intermediated flow configuration can occur for particular characteristics of the supercritical current and step height. The domain of existence of the different solutions, as well as the hysteresis domain, are obtained based on the theoretical and the numerical models. [ABSTRACT FROM AUTHOR]

Laboratory experiments were conducted out to investigate the regimes of submerged flows over the sharp-crested weirs in sand bed Channel. These kinds of flows were classified as five states such as (I) impinging jet, (II) bed surface flow, (III) surface jump, (IV) surface wave, and (V) surface jet based on the depicted vector plots of the regimes. By increasing the submergence ratio, the impinging jet was developed as a downward jet which was impinged from the weir crest to the downstream. By continue the increasing, flow regime was developed as a bed-surface flow which is supposed that the impinging jet is turned as flow near the bed position instead of having a direct impact with the bed. Additionally, increasing constancy of the submergence ratio causes that the bed-surface regime turned to the surface jump which is accompanied by a hydraulic jump at the water surface. Subcritical condition at downstream of the weir which is provided by raising the tailwater due to constant flow discharge causes that the surface wave regime has vanished at the water surface of the downstream of the weir and some oscillating waves were transferred to downstream. Finally, by considering the maximum range of submergence ratio, the flow regime was changed to the surface jet which was accompanied by a big clockwise vortex at the lower water elevation. The present study classifies these flow regimes based on the velocity components (u, v, w). This approach was chosen by the authors to show the different classification between visual inspection and investigating the velocity direction by ADV. Then, an empirical equation was proposed to show the boundaries of the presented regimes. Also, a dynamic restriction was proposed based on experimental and literate data as a non-eroded status that is due to a submerge ratio, the scour hole is not provided at downstream of sharp-crested weir. [ABSTRACT FROM AUTHOR]

Submarine depressions are common features on the eastern Bahamian seafloor but the genesis of the deepest ones (>4000 m in water depth) is not well understood. We conducted a morphometric analysis and compared them to a worldwide database of rounded depressions, whatever their genesis is. The deep Bahamian depressions are large elongated structures, among the largest on Earth, with a width greater than 1000 m and a depth sometimes greater than 200 m. They extend at the toe of the Blake Bahama Escarpment (BBE), one of the tallest escarpments on Earth. Some of them align parallel to the BBE. Other depressions align along large submarine canyon axes. When aligned along canyon axes, the depressions closest to the canyon head are flanked by a topographic high interpreted as a slope-break deposit, i.e., sediment deposited after flow expansion following a hydraulic jump. Turbidity currents in the carbonate canyon system are not permanent processes, but are rather triggered during sea-level highstands when the carbonate platform is flooded. In addition, some depressions are not located in canyon axes. Consequently, the size and location of the depressions are not likely explained by a simple plunge pool mechanical erosion. Rather, our data suggest that all depressions could be initiated by giant karstic dissolution structures (dolines or sinkholes). Under interpretation, those located in canyon axes are sporadically refreshed by carbonate-laden turbidity currents. The height of the outsized chutes marking the crossing of the BBE by the canyon mouth generates a hydraulic jump allowing sediment deposition toward the bottom of the depression. Large depressions observed at this location in the Bahamas were the result of an initial dissolution phase related to retreat of the BBE and the more recent sediment-laden flow activity. The depressions orientated along canyon axes facilitated the regressive erosion that formed the canyons. At present, the depressions located at canyon mouths act as regular plunge pools. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Water & Soil Conservation is the property of Gorgan University of Agricultural Sciences & Natural Resources and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The main problem presented in this paper is the safety inlet navigation of the waterway below the bridge in the city of Kaunas in Lithuania. The analyzed reach is located in the Nemunas river downstream of the Kaunas dam. It is a part of the waterway E–41 leading to the Klaipeda harbor on the southern coast of the Baltic Sea. The work was initiated by the Lithuanian company UAB "Inžinerinis projektavimas" with funds from the project called European Union Trans-European Transport Network (EU TEN-T). The main requirement imposed along this reach is to keep sufficient depth even in the range of the lowest flows. The depth is sufficient if it is not lower than 1.15 m for minimum flows such as Q95% and Q95% with ice. The hydraulic conditions for maximum flow Q50%, Q5%, and Q1% are also taken into account for control because the threat of hydraulic jump generation was also noticed. The research is based on georeferenced data from public and non-public sources. The hydrologic data were received from the Lithuanian Hydrometeorological Service. The physical model was created in the Water Laboratory of the Department of Hydraulic and Sanitary Engineering at Poznan University of Life Sciences, Poland. The preprocessing of spatial data in ArcGIS 10.8.2 and rules of hydraulic similarity were implemented in the process of physical model preparation. Three experiments were conducted in the laboratory with scaled values of Q95%, Q5%, and Q1%. The measurements of the water surface and evaluations of the average velocity were used to validate the 2D numerical model prepared in HEC-RAS 6.3.1. The basic layers of the HEC-RAS model were preprocessed in ArcGIS 10.8.2 by ESRI company. The numerical model was implemented to test different values of unknown roughness of the channel bottom. The simulations were conducted for the real values of Q95% and Q95% with ice and Q50%. The results of the simulations were depth and Froude number maps. These maps were classified into zones of no risk, middle risk, and high risk. ArcGIS in the post-processing phase was applied to identify the locations of the hazards. The magnitude of risk was expressed in terms of minimum depth achieved, maximum Froude number, as well as the length of the reaches with high risk related to these two factors. The threat of hydraulic jump formation below the bridge was also noticed. Conducted results confirmed that the combination of hydrodynamic simulations and geoprocessing in the pre- and post-processing stages could be a powerful tool in hydraulic engineering analyses. Additionally, it is worth noting that numerical modeling enables a wider analysis of potential conditions than could be possible with a physical model only. [ABSTRACT FROM AUTHOR]

We show that interfacial gravity waves comprising strong hydraulic jumps (bores) can be described by a two‐layer hydrostatic shallow‐water (SW) approximation without invoking additional front conditions. The theory is based on a new SW momentum equation which is derived in locally conservative form containing a free parameter α. This parameter, which defines the relative contribution of each layer to the pressure at the interface, affects only hydraulic jumps but not continuous waves. The Rankine–Hugoniot jump conditions for the momentum and mass conservation equations are found to be mathematically equivalent to the classical front conditions, which were previously thought to be outside the scope of SW approximation. Dimensional arguments suggest that α depends on the density ratio. For nearly equal densities, both layers are expected to affect interfacial pressure with approximately equal weight coefficients, which corresponds to α≈0$\alpha \approx 0$. The front propagation velocity for α=0$\alpha =0$ agrees well with experimental and numerical results in a wide range of bore strengths. A remarkably better agreement with high‐accuracy numerical results is achieved by α=5−2$\alpha =\sqrt {5}-2$, which yields the largest height that a stable gravity current can have. [ABSTRACT FROM AUTHOR]

Sewer bend manholes are frequent elements of urban drainage systems. Any deviation of straight-lined supercritical flow, as within the manhole, generates shock waves, possibly impinging at the manhole end or imposing a hydraulic jump. Then the free-surface flow regime abruptly breaks down and backwater effects occur. Thus it is important to know the maximum discharge that safely can pass across a bend manhole, as a function of its geometry, without generating collapsing flow. This study conducted calibrated numerical simulations to assess the hydraulic features of supercritical bend manholes with variable deflection angles, curvature radii, and lengths of straight downstream extension elements. The numerical model was validated previously with data from analogous physical model tests documented in the literature. The combined data from the numerical simulation and from the physical model indicated a hydraulic capacity of the bend manholes for different geometrical setups. It was demonstrated that the hydraulic capacity of a bend manhole increases with increased curvature radii and straight extension lengths, whereas the effect of the deflection angle is less significant. A multiple regression technique provided an empirical equation indicating the normalized discharge capacity of supercritical bend manholes as a function of the governing geometrical parameters, along with the approach flow filling ratio. [ABSTRACT FROM AUTHOR]

To improve the single wafer process for wafer edge yield performance, the liquid film thickness is the key indicator to be investigated. The traditional measurement of liquid film thickness is difficult to execute, due to wafer spinning. The numerical method becomes essential to simulate the process. This paper uses the multiple flow level set method to simulate single wafer spin process. An inlet hydraulic jump is approximated by a two-dimensional axisymmetric approach with a collar inlet. Various spin rotation speeds, variable flow rates, different liquid types and contact angles are simulated. The results indicate liquid film discontinuity at a certain radius and a lower shear rate at the wafer edge. After modifying the process recipe based on the level set simulation result, the wafer edge yield shows improvement. This level set simulation model provides useful information for single wafer wet process control. The level set simulation results can estimate the liquid distribution on the wafer surface before the real process and can avoid experiments on production wafers and hence lead to a lower cost. [ABSTRACT FROM AUTHOR]

Some basic characteristics of a classic hydraulic jump flow over a pebbled rough bed, as well as on a smooth bed as a reference, are presented in this experimental study. For the experiments, an inflow Froude number Fr1 from 1.54 to 4.94 and inflow Reynolds number Re1 from 42 000 to 230 000 were considered. Visual observations and measurements suggested some differences between the formation of a hydraulic jump on rough and smooth bed configurations, including different air entrainment processes, larger vortical structures in the roller length and stronger backward flow in the upper layer. Furthermore, the jump roller and aerated flow lengths were shorter on a pebbled rough bed than on a smooth bed, while the dimensionless advection velocity of large vortices was the same for both bed types. The instantaneous jump toe perimeter showed the largest variation at the largest Fr1 and was generally larger on rough bed than on smooth bed. Larger oscillations of the free-surface profile were observed on smooth bed, highlighting that roughness resulted in smaller free-surface oscillations, suggesting the higher rate of energy dissipation. [ABSTRACT FROM AUTHOR]

Prototype hydraulic jump experiments were conducted at the Pei-bridge Gates in the Bao River, China. Two D-jumps formed on the 14° slope downstream one of the 5-m-wide sluice gates, followed by a sudden expansion of flow cross-section in the stilling basin. With the Froude numbers Fr = 7.47 and 3.18, the Reynolds numbers reached Re = 1.16 × 106 and 1.88 × 106, respectively. The fluctuating jump toe and free-surface characteristics were analysed and compared with existing model tests of classic and D-type jumps. The air–water flow properties were measured intrusively with phase-detection probes and compared to the laboratory data. The prototype jumps exhibited three-dimensional roller motions with shorter roller lengths than classic hydraulic jumps in prismatic channels. Scale effects were noted for the bubble frequency and bubble size distributions among the influences of other measuring factors, implying the need to revisit the model-based prediction relationship at prototype conditions. [ABSTRACT FROM AUTHOR]

In recent decades, stepped chutes followed by a stilling basin became a standard for spillways of dams. The comprehensive knowledge of stepped chute approach flows on internal air–water flow properties of the hydraulic jump is still too limited for an appropriate design of stilling basins. Therefore, an experimental campaign was performed on a large-scale physical model of a plain stilling basin preceded by a 30° sloping smooth or stepped chute. Stepped chute approach flows induce lower deaeration rates along the jump roller as compared to smooth chute approach flows, indicating longer dimensionless jump lengths, normalized by the tailwater depth. Pronounced bottom air concentrations were observed within the first 40% of the jump length in the stilling basin downstream of the stepped chute. Thus, despite the significantly higher pressure fluctuations, this zone seems better protected against cavitation damage than in stilling basins following a smooth chute. [ABSTRACT FROM AUTHOR]

With the increasing availability of low head dam inventories for the United States, the next challenge is discovering how to determine what dams pose the greatest risk to public safety, preferably before a death occurs. Submerged hydraulic jumps create the dangerous current that drowns roughly 50 recreationists each year, and high tailwater is a key element in its formation. Using a simplified approach based on the Manning equation, flat downstream slopes can be a predictor of high tailwater. Stream slopes at low head dams in Colorado, Idaho, Indiana, Maryland, New Mexico, North Carolina, and Pennsylvania were collected from the NHDPlus HR, and dams with recorded fatalities were compared to stream slopes at low head dams with no recorded fatalities. Using the Mann–Whitney U test, there was not enough evidence to reject the null hypothesis that there is no statistically significant difference between the two populations. Until more fatality data are compiled and more low head dam locations are verified, individual testing of dams is recommended to establish each respective flow range that is likely to pose a risk to public safety. [ABSTRACT FROM AUTHOR]

This paper carried out laboratory experiments to study evolution of internal solitary waves (ISWs) over submarine canyons with a combination of PIV (particle image velocimetry) and PLIF (planar laser-induced fluorescence) techniques. Taking canyon angle θ and collapse height ∆H as variables, Froude number Fr, head position, energy loss, vorticity field and turbulence intensity when ISWs propagate to the canyon were analyzed. According to the Froude number Fr values, the study cases can be divided into three types: Fr > 1.7 means complete internal hydraulic jump (IHJ); 1 < Fr < 1.7 denotes wavy IHJ and Fr < 1 represents no IHJ. The greater canyon angle, collapse depth and amplitude of the incident wave more easily generate IHJs, which can lead to more energy loss, greater vorticity and turbulence intensity in the canyon area. Among all canyon cases, vorticity and turbulence intensity of the no IHJ case showing an obvious bimodal distribution are smaller than IHJ cases. For wavy IHJ, the energy dissipation is not obvious, and the average turbulent intensity performs a "sharp unimodal distribution". Complete IHJ cases last for a long time and cause violent mixing, the average turbulent intensity is the largest and its distribution presents a "gentle single peak" pattern. For the 180° conditions (no canyon cases), less energy is delivered to the reflected wave and more energy is dissipated near the terrain, so the energy loss is the largest in comparison to other conditions. These findings will deepen our understanding of the evolution mechanisms of ISWs propagating over submarine canyons. [ABSTRACT FROM AUTHOR]

The present research was conducted to investigate the effect of sill geometry and sill width on the discharge coefficient and hydraulic jump characteristics. For this purpose, sills with semi-cylindrical, cylindrical, pyramidal, and rectangular cube geometries with widths of 0.075, 0.10, 0.15, and 0.2 m were installed under a sluice gate. Results showed that increasing the sill width increased the sluice gate discharge coefficient compared to the no-sill mode. The results of placing a sill with different geometric shapes under a sluice gate indicate that using a semi-cylindrical sill increases the discharge coefficient. The ranked order of other sills, from the largest to smallest discharge coefficient, is: cylindrical, pyramidal, and rectangular cubic sills, respectively. The results show that the use of a sill increases the energy dissipation. Examining sills of different widths indicates that with increasing width, the increase in velocity and consequent decrease in the depth of the hydraulic jump causes an increase in energy loss. When employing sills of maximum width (b = 0.20 m) for pyramidal, semi-cylindrical, cylindrical, and rectangular shapes, the energy loss increased by 125, 119, 116, and 125% in section A, respectively. The semi-cylindrical sill is most effective in increasing the discharge coefficient, while the pyramidal sill is most effective for increasing energy dissipation. [ABSTRACT FROM AUTHOR]

This paper presents the research data on the study of the basic equation and the length of the perfect hydraulic jump, which lasted for a total of more than 500 years. The perfect hydraulic jump is a unique natural phenomenon, which is expressed in a sharp increase in the depth of the flow from h < hcr to h > hcr (where hcr – critical depth) on a small stretch of land with the formation of a surface whirlpool. Having experimental data of conjugate depths, the length of the hydraulic jump was found according to known empirical formulas. This study applied the theoretical equation of Professor Abduramanov to determine the length of a perfect hydraulic jump. As a result, according to the comparison of experimental data, the equations of Professor Abduramanov turned out to be more suitable, giving the most accurate values. However, since the equation of the length of a perfect hydraulic jump is theoretical, the study suggests an empirical formula obtained experimentally based on this equation. [ABSTRACT FROM AUTHOR]

In this work, we analyze the flow of a thin layer of viscous liquid over the outer surface of a sphere due to inertia and gravity. We use the classical problem of a circular hydraulic jump as a starting point and observe the changes in the flow structure as the gravity component along the surface becomes significant. We assume that the flow is stationary and axisymmetric, the curvature of the spherical surface is small, and the capillary forces are negligible. The depth-averaged thin-layer equations describe the flow. We perform a qualitative analysis using a one-parametric representation of the longitudinal velocity distribution and find the necessary conditions for the hydraulic jump existence. The intensity of the jump monotonically decreases, and its radius grows to a certain finite value. The jump vanishes at a finite distance from the axis of symmetry. Using a two-parametric representation, we locate zones of recirculating flow and find the condition of their existence. We find the optimal strategy of averaging by comparing the results of our calculations with the data obtained experimentally and by using simulations in the framework of the full Navier–Stokes equations. [ABSTRACT FROM AUTHOR]

The present study aimed to investigate and compare the laboratory results of energy dissipation and length of vertical Drops equipped with horizontal Screens with the results of standard stilling basins of type one, two, three and four simple vertical Drops. For this purpose, 64 different experiments were performed on vertical Drops equipped with a horizontal Screen at relative distances of 0, 0.25, 0.5, and 0.75 from the edge of Drops, with a porosity of 40 and 50% of the Screen and a height of 20 cm .The results showed that in all experiments and at a constant flow, increasing the distance of the Screen from the edge of Drops does not have much affect the energy dissipation of the current. On average, the downstream energy dissipation for the present study has increased by more than 20% compared to the simple vertical Drop, which can be an excellent alternative to the downstream stilling basin. Among the models of the present study, the most significant reduction in the relative length of the Drops was achieved by the vertical Drops model with a horizontal Screen with a relative distance of 0.75. On average, when using horizontal Screen at four relative distances from the edge of Drops, the relative length of the Drops is reduced by more than 73% compared to the vertical Drops equipped with a standard stilling basin. [ABSTRACT FROM AUTHOR]

This paper focuses on air–water interactions during pipe filling. The air–water mixed flow is related to a mobile hydraulic jump in the horizontal pipe section. The trapped water–air front at the crown of the pipe bridge determines the upstream boundary conditions for the stratified flow, suppressed hydraulic jump, and slug flow regions in the horizontal pipe section. The velocity field, the water level, and the pressure were measured at different stages of the transitional flow process. A full-scale two-phase computational fluid dynamics model, with two-equation eddy viscosity turbulence to account for small scales of motion, was used to predict the air pocket dynamics. The paper suggests that in the case of a frozen upstream water–air front, the formation of a hydraulic jump downstream can be explained by long-wave-type instability, which is confirmed by the free-surface supercritical flow Froude number condition. The hydraulic jump that merges stratified flow and slug flow is characterized by the speed of the surge wave, which is determined by the pressure, cross-sectional area of water flow, and density changes. A mixing efficiency parameter was introduced to explain the dissipation of turbulent energy due to the air–water mixing front of the suppressed hydraulic jump. [ABSTRACT FROM AUTHOR]

In the last two decades, the hydraulic jump has been extensively studied. In this article, attempt is made to have a comprehensive look at different characteristics of this complicated phenomenon. The aim of the present work is classification, comparison, and analysis of many research works on hydraulic jumps during the past years. It was found that there was no significant difference between jump characteristics such as the sequent depth and surface profile with developed or undeveloped approach flow, but air–water characteristics such as void fraction and bubble count rate are significantly affected. The present study also discusses the research results on pressure fluctuations, velocity field, turbulence characteristics, and air–water properties in a hydraulic jump. Investigating previous studies shows that most of the relationships presented for different characteristics of the hydraulic jump such as velocity or air concentration are dependent on other variables which are not available without measurements. The length of the stilling basin is considered equal to the length of the jump. Various definitions are given for the jump length. The results show that using the decay rate of pressure fluctuation, the stilling basin length could be calculated by less than 5% difference compared to the defined USBR I standard stilling basin length. [ABSTRACT FROM AUTHOR]

In the present study, series of laboratory experiments were conducted to investigate the effectiveness of perforated screens as energy dissipators in mixed triple wall mode in the case of small hydraulic structures. The shapes of openings for each layer of screens were either circular, square or triangular. Every layer of the screen had a porosity of 45% per unit depth of the screen. The experiments were conducted to dissipate the energy for supercritical flows of Froude number F1 ranging from 3.2 to 19.3. The screens were placed vertically with the first screen 1.5 m from the sluice gate and consecutive screen at a gap of 25 mm. The experiments showed that the energy of the supercritical flows can be dissipated effectively by using perforated screens. The difference in energy dissipation between the upstream and downstream of the screen was more significant than the energy dissipation caused by classical hydraulic jumps. Comparing the results of the present study with the previous researchers it is found that the energy loss in case of present study more than the previous researchers. The relative energy loss in the present study was found to be varying from 74 to 94%. The value of the Froude number downstream of the screen, F2, was varying from 1.1 to 1.81, with an average value of 1.35. Tailwater deficit parameter, D, if found to be varying from 0.66 to 0.90. [ABSTRACT FROM AUTHOR]

Stilling basins with sudden expansions are one of the energy dissipation structures. In the hydraulic jump, pressure fluctuations cause significant damages in stilling basins by cavity formation, erosion, and vibration. Roughness can also lead to changes of the behavior of stream lines and vortices. Despite the large number of works on the topic, the role of roughness in spatial hydraulic jumps is not yet fully understood. Present research aimed to study the influence of rough bed on pressure fluctuations of S-jump in abrupt expanding stilling basin. Experiments were conducted in a 0.8 m width and 12 m length flume. Channel expansions ratios were 0.33, 0.5, 0.67, and 1 within the range of Froude numbers, 2 to 9.5. The results showed that roughness decreases intensity of pressure fluctuations in an abrupt expansion stilling basin. Additionally, in sudden expanding sections, the energy loss increases, and the intensity of pressure fluctuations decrease due to the formation of lateral vortices. The reduction rate of maximum pressure fluctuation was 27%, 46%, and 58% for expansion ratio of 0.67, 0.5, and 0.33, respectively. The results revealed the clear dependence of these variables on the Froude number and the distance to the hydraulic jump toe. The maximum values of extreme pressure fluctuations occur in the range 0.609 < X < 3.385, where X is dimensionless distance from the toe of the hydraulic jump, which makes it highly advisable to reinforce the bed of stilling basins in this range. [ABSTRACT FROM AUTHOR]

Here, the effect of sill application on hydraulic jump parameters has been investigated. The model of sills is made of polyethylene in various dimensions. The sills were investigated in different positions relative to the gate in single, double, and triple arrangements. In a certain opening, the sill leads to more energy dissipation. By increasing the ratio of initial depth to sequent depth, the ΔEAB/yA decreases. It occurs due to the convergence of initial and sequent depths. In the under gate suppressed sill state, the ΔEAB/EA is 11.05% more than the upstream tangential position, while it's 14.56% for downstream specific energy. The results showed that the energy dissipation decreases with increasing the opening by at most 34.88%. In the same opening of no-sill and with sill cases, the use of suppressed sill leads to a decrease in the sequent depth compared to the nosill one. The application of the sill causes an increase in the initial depth and accordingly the initial specific energy decreases; therefore, the sill leads to the reduction of the specific energy in the flow conjugate depths. The regression nonlinear polynomial equations were proposed to estimate the relative energy dissipation. Statistical indicators Relative Error (RE), Root Mean Square Error (RMSE), and Kling Gupta Efficiency (KGE) have been used to check the accuracy of presented equations. The mean RE% and RMSE for presented equation of ΔEAB/EA are 0.78%, and 0.004, respectively. These values are 0.87%, and 0.009 for ΔEAB/EB, respectively. The KGE is in very good range for equations. [ABSTRACT FROM AUTHOR]

ABSTRACT Turbulent flow is responsible for a significant portion of damages and failures in dams. This paper sought to introduce novel approaches to the estimation of typical parameters used in the design of stilling basins. The standard deviations of pressure samples of 24 hydraulic jumps were analysed throughout the stilling basin longitudinal centreline, and the positions of maximum pressure fluctuation were identified. Next, mean and extreme pressures occurring at this position were calculated. Finally, these parameters were plotted against the inflow Froude number and curves were adjusted to the data. The position where maximum turbulence of undular, weak and oscillating jumps occurs varies according to the Froude number. Steady and strong jumps are more likely to induce negative pressures on the stilling basin. The findings of this paper broaden the knowledge on which regions of the stilling basin must receive special attention, and on how to minimize the chances of damages.

The scope of the paper is to analyse the different similarities of air entrainment among the hydraulic jumps, plunging jets, and plunging breaking waves and to discuss current practices. The measured data are reexamined and scrutinised to investigate the gas exchange phenomena through an air-water interface. In particular, oxygen transfer efficiency and penetration depth by air bubbles are discussed. The calculated results highlight that the oxygen transfer efficiency is decreased with the increase of energy dissipation rate both in plunging jets and breaking waves. In contrast, it is shifted almost parallel in the case of hydraulic jumps. In addition, the aeration lengths in the hydraulic jumps and penetration depths both in plunging jets and plunging breaking waves were dependent on the jet impact velocity. HIGHLIGHTS Air bubble entrainments through hydraulic jumps, plunging jets, and plunging breaking waves are studied.; Aeration lengths in the hydraulic jump and penetration depths in the plunging jets and plunging breaking waves were determined.; Dissolved oxygen, as well as oxygen transfer efficiency, were measured and compared among the phenomena.; Scale effects were observed among the phenomena in terms of the oxygenation.;

North–South‐oriented mountains (known as "The Western Ghats [WG]") running parallel to the west coast of peninsular India separate the Maharashtra state (lying on the northwest of peninsular India) into two meteorological subdivisions (a) Konkan lying on the windward side of WG receiving high monsoon rainfall (2,390 mm) and (b) Madhya Maharashtra (MM) lying on the leeward side receiving low monsoon rainfall (579 mm). The state of Maharashtra has two more subdivisions on the leeward side of WG, viz. Marathwada and Vidarbha, which however do not lie on the immediate leeward side of WG. In this study, a subdivision of MM is further subdivided into (a) north–south strip of 80 km width on the immediate lee side (ILS) from the crest of WG and (b) area extending eastwards from ILS to 280 km, referred to as "distant lee side (DLS)." DLS contains some parts of the Marathwada subdivision also. The study indicates that the mean monsoon rainfall over ILS region is higher than DLS region (proportion is 1.4:1). Higher rainfall over ILS region has been shown due to the occurrence of the "hydraulic jump (HJ)." The dynamics of HJ are explained using Froude number and vertical velocities. The climatological high rainfall over ILS remained an unnoticed feature in the spatial monsoon variability over peninsular India. The study focuses on the unnoticed high rainfall in the ILS region and attributes it to HJ. The incorporation of HJ has the potential to impact on forecasting of monsoon rainfall over the region by numerical models. [ABSTRACT FROM AUTHOR]

Drainage channels with step-pool configurations, one type of debris-flow drainage system used in gullies with steep gradients, have good application potential because of their high-performance control effect and engineering value. In this study, a pool depth design method is proposed based on the hydraulic jump theory. The dynamic behavior of debris flows in drainage channels with step-pool configurations is explored via a series of specially made flume experiments, where the debris-flow bulk density and the scale and depth of the step-pool configuration are the main controlling factors. The debris-flow pattern and flow depth are investigated along with the material-interchange phenomenon. There is a dramatic difference in the dynamic behaviors of different types of debris flows. Because of the associated intense turbulence and particle collision, the observed material-interchange phenomenon was greatest when the debris flow with a bulk density of 1700 kg/m3 passed through the drainage channel. The analysis indicated that, when a debris flow passes through a step-pool configuration, the flow depth increases significantly as a result of the hydraulic jump. However, a step-pool configuration with an overly large depth traps sediment, which is detrimental to transporting sediment. In addition, modified coefficients of the proposed design method were determined based on an analysis of the experimental results. The analysis further indicated that the coefficients significantly depend on the debris-flow viscosity and turbulence. Our results can be used to improve understanding of step-pool configurations and provide a reference for practical engineering design. [ABSTRACT FROM AUTHOR]

Using an idealized channel representative of a coastal plain estuary, we conducted numerical simulations to investigate the generation of internal lee waves by lateral circulation. It is shown that the lee waves can be generated across all salinity regimes in an estuary. Since the lateral currents are usually subcritical with respect to the lowest mode, mode-2 lee waves are most prevalent but a hydraulic jump may develop during the transition to subcritical flows in the deep channel, producing high energy dissipation and strong mixing. Unlike flows over a sill, stratified water in the deep channel may become stagnant such that a mode-1 depression wave can form higher up in the water column. With the lee wave Froude number above 1 and the intrinsic wave frequency between the inertial and buoyancy frequency, the lee waves generated in coastal plain estuaries are nonlinear waves with the wave amplitude Δh scaling approximately with V / N ¯ , where V is the maximum lateral flow velocity and N ¯ is the buoyancy frequency. The model results are summarized using the estuarine classification diagram based on the freshwater Froude number Frf and the mixing parameter M. The Δh decreases with increasing Frf as stronger stratification suppresses waves, and no internal waves are generated at large Frf. The Δh initially increases with increasing M as the lateral flows become stronger with stronger tidal currents, but decreases or saturates to a certain amplitude as M further increases. This modeling study suggests that lee waves can be generated over a wide range of estuarine conditions. [ABSTRACT FROM AUTHOR]

Most dams include bottom outlets consisting of tunnels or pipes to control water discharge by using valves or slide gates to regulate water level in reservoirs for service operation or during an emergency. When the gates are partially open, subatmospheric pressure can develop on the downstream side of the gates, leading to possible damage by cavitation and vibration. In order to avoid the latter, an aeration system is usually installed downstream of the gates to keep the local pressure above the vapor pressure for preventing cavitation. The present study aims to estimate the air concentration profiles for a series of hydraulic jumps that occur on the downstream side of a partially open gate of a bottom outlet using a flow visualization technique, known as Image Processing Procedure (IPP), which consists of the Image Editing and the Pixel Intensity Matrix algorithms. This technique uses a high-speed camera and is based on the hypothesis that air concentration profiles can be estimated from the pixel intensity of each photograph, and also offers the possibility to obtain such profiles in any point along the hydraulic jump without disturbing the flow. The results obtained after applying the IPP to the photographs of the experimental study have very good agreement with the profiles obtained with a conductivity probe, indicating that the IPP can be a powerful tool to complement intrusive probe measurements. In addition, to evaluate the capability of the proposed IPP the experimental data were compared with a two-dimensional diffusion equation. Comparisons between predicted and measured results show good correlation demonstrating the potential of the proposed methodology. [ABSTRACT FROM AUTHOR]

The bed elevation of the stilling basins is most often located below the river bed in order to provide the required tail water depth. Both basins located in alignment with the erodible bed or below it are studied. To this end, the scoured hole dimensions under various circumstances and the sediment transport process within the scour hole were thoroughly examined. Results revealed that the upstream slopes of the dimensionless scour profiles are approximately identical at different times. According to the results, the basin located below the erodible bed was of a greater maximum scour depth and a lower scour depth at the beginning of the erodible bed. Moreover, a simple generalized equation correlating the temporal development of the maximum scour depth and the scour depth at the beginning of the erodible bed at equilibrium time was derived for the USBR Type I basin aligned with or below the erodible bed. [ABSTRACT FROM AUTHOR]