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The present article is the sixth of a series of seven, all relatives to the energy dissipators that can be used in hydraulic works. The whole group of these articles conform a monograph about the subject that is being prepared by the author, concluding it by the middle of the 2017 year and later on incorporating it into a new edition - in preparation - of the textbook "Spillways and Intake Structures". This sixth article is a detailed presentation about the baffled apron employed with an energy dissipation function and of the riprap frequently placed at the exit (discharge) of the energy disipators. [ABSTRACT FROM AUTHOR]

Detached hydraulic jumps are major features of supercritical open-channel flows interacting with emerging obstacles. Such a flow pattern exhibits strong similarities with shock waves detached in front of bluff bodies in supersonic aerodynamic flows. This paper aims at evaluating the capacities of an analytical model, adapted from supersonic aerodynamics, to predict the hydraulic jump detachment length. The analytical predictions are compared to the measured hydraulic jumps from two experiments: (i) a uniform supercritical open-channel flow that skirts a mounted and emerging obstacle (with a horseshoe vortex) and (ii) a mounted and emerging obstacle moving at constant velocity in water at rest (without a horseshoe vortex). Moreover, numerical calculations of supercritical flow skirting emerging obstacles are undertaken, with a free-slip condition at the bed to remove the horseshoe vortex, while keeping the detached hydraulic jump. The comparison of the detachment lengths of these experimental, analytical, and computed hydraulic jumps reveals that two types of detachment lengths can be defined. The detachment length visible on experiments corresponds to the toe of the hydraulic jump, while the detachment length predicted by the analytical model rather corresponds to the location of flow regime transition from the supercritical to subcritical regime. The present work thus validates the analytical model for predicting the location of flow regime transition (for configurations without a horseshoe vortex) but not for predicting the toe of the hydraulic jump. We finally confirm the strong connections between two distinct phenomena: a hydraulic jump in water flow and a shock wave in gas flow. [ABSTRACT FROM AUTHOR]

The National Taiwan University/Purdue (NTU/PU) nonhydrostatic model is used to study mountain waves, hydraulic jumps, and lee vortices. The NTU/PU model is based on a compressible and three-dimensional system of equations with a terrain-following vertical coordinate. A major advantage of the model is the use of a modified forward-backward integration scheme that retains internal gravity waves but suppresses unwanted sound waves. In flow around an isolated ideal elliptical mountain, the simulated flow from the NTU/PU model spreads broadly in the crosswind direction with a well-defined stagnation point at the windward side of the mountain. Two semi-idealized downslope wind cases were conducted using the real topography at White Sand Missile Range (WSMR), New Mexico, USA. Our simulated flows including hydraulic jumps and vortex shedding in the lee of the Organ Mountains agree very well with observations for the case on 25 January 2004, at 15 UTC, but the discrepancy is somewhat larger for the case on 19 January 2004, at 15 UTC. This paper shows that the model results are sensitive to the detailed numerical schemes, filters, and physics, etc. It also suggests that more observations and improvements are required for a model to realistically simulate the flow over complex terrain. [ABSTRACT FROM AUTHOR]

Highlights • The effect of nozzle-to-surface distance on two-phase jet impingement was investigated. • The Nusselt number attained a maximum value at the lowest nozzle-to-surface distance. • The stagnation Nusselt number is governed by the stagnation pressure. • The normalized Nusselt number is a function of the nozzle-to-surface distance only. Abstract In this study, heat transfer and hydrodynamics of air-assisted free water jet impinging a flat plate surface are experimentally investigated. The effects of the nozzle-to-surface distance (H/d = 0.02–0.51) and volumetric quality (β = 0.3–0.8) on the stagnation Nusselt number, stagnation pressure, and hydraulic jump diameter are considered. The results show that the normalized stagnation Nusselt number and hydraulic jump diameter drastically increase with decreasing the nozzle-to-surface distance, since the stagnation pressure increases due to the jet deflection effect. Based on the experimental results, new correlations for the stagnation Nusselt number and pressure are developed as a function of the nozzle-to-surface distance. [ABSTRACT FROM AUTHOR]

Abstract Kaye et al. (1995) conducted an experimental investigation of the cleaning of thin soil layers by water jets generated from stationary nozzles of diameter 0.25–2 mm and velocities ranging from 6 to 40 m s−1. The soil layers were prepared by drying a commercial cleaning suspension on polymethylmethacrylate plates. Several of their data sets have been re-analysed and are shown to fit the 'strong soil' model for cleaning by peeling reported by Bhagat et al. (2017). The model is demonstrated to be able to explain the trends in cleaning efficiency observed by Kaye et al. quantitatively, including the transition in efficiency observed at longer times. Kaye et al. also investigated the case of cleaning by a moving nozzle for one set of jet conditions, and reported an increase in cleared area with nozzle velocity. This behaviour is not predicted for the 'strong soil' and the model was modified to incorporate a contribution from the milling action of the jet in its impingent zone. This 'very strong soil' result gave good agreement with the data for the area cleared and the shape of the cleared region. Graphical abstract fx1 Highlights • Data from Kaye et al. were re-analysed using newly developed models for peeling. • 'Strong soil' model gives good description of cleaning by static nozzle. • Observed variation in cleaning efficiency is predicted by the model. • Strong soil model extended to cover cleaning by moving nozzle. • Size and shape of area cleared by moving nozzle consistent with new model. [ABSTRACT FROM AUTHOR]

Abstract Hydraulic Jump is a phenomenon that occurs in free surface flows during transition from supercritical to subcritical flow. During the impingement of a vertical fluid jet with a flat surface, a circular hydraulic jump forms, which has been studied by several researchers; but no study has been performed on the effect of convexity of the target surface on the jump radius and its form yet. Therefore, in the present study the hydraulic jump phenomenon on convex surfaces and comparison with the flat surface are presented, experimentally. The tests are performed using 3 nozzles in various volumetric flow rates. The results showed that convex surfaces significantly increased the jump radius up to about 30% compared to flat plates for about 50% increase in convex target plate radius. In addition, an experimental relation for the hydraulic jump radius in the convex target plates is proposed. Highlights • In the present study, the effect of curvature of the target surface on the radius of hydraulic jump is studied for the first time. • In addition, an experimental relation for the hydraulic jump radius in the convex plates is presented. • By using curvature in the target plate, the hydraulic jump radius is increased significantly. [ABSTRACT FROM AUTHOR]

Abstract Hydraulic jumps, transitions from supercritical to subcritical flows, tend to maintain suspended particles in the water column and enhance biological productivity near the surface. Transitions occur from flow adjustments as the flow moves through a cross-section reduction, such as a reef crest. Hydraulic jumps can also inhibit the settlement of coral larvae and bivalve mollusks, but could favor connectivity among reefs by dispersing planktonic organisms to surrounding areas. The Veracruz Reef System (VRS) was chosen as a case study of hydraulic jumps produced over reef crests. This system is located in the southwestern part of the Gulf of Mexico (GoM) and features 50 coral reef structures. The area is influenced by vertical stratification that modifies its dynamics. Hydrographic and yearlong current data collections in the area during 2009 identified fronts and a cyclonic recirculation. On the other hand, the presence of a hydraulic jump weakened the cyclonic recirculation on the leeward side of the reefs. The vertical gradient of the horizontal velocity suggested the influence of vertical eddies at least 35% of the time throughout the entire year. Moreover, the current velocity profiles showed a bidirectional behavior in spring and summer conditions of stratified waters. These bidirectional flows contrasted the unidirectional structure caused by frictional dynamics during northerly winds. [ABSTRACT FROM AUTHOR]

Abstract A flume study using a surge-type flow produced by quickly lifting a gate was conducted to simulate a tsunami the height of which is larger than level 1 (prevention level) by a hybrid system comprising a forest, an embankment, and a moat while changing the layout of the components. The overflow volume, tsunami arrival time, fluid force, and moment by fluid force were measured, and the tsunami reduction effects in each model were compared. The hybrid defense system in the order of vegetation, a moat, and an embankment (Case V 40 ME) from the sea side showed the highest reduction in overflow volume, moment index, and tsunami delay effect. In terms of the fluid force index, Case V 40 ME performed best up to a certain tsunami height. For higher tsunamis, a hybrid system in the order of vegetation, an embankment, and a moat from the sea side (Case V 40 EM) performed better, although Case V 40 ME had a large advantage in total when there was a space landward of the existing forest. Suitable structures when there is space seaward and on both sides of a forest were also clarified for different wave heights through the mechanism of reflection, hydraulic jump, and vegetation resistance. Highlights • Reduction of tsunami energy by the combination of an embankment, a moat and vegetation was measured. • The effectiveness of the hybrid system was investigated in a flume using a surge-type unsteady flow. • Reflection from the components, backwater rise in front of vegetation and hydraulic jump are the key phenomena. • Delay in tsunami arrival time, reduction of fluid force and moment by fluid force are compared as the indices. • The optimum layout is discussed based on the available space of the existing forest. [ABSTRACT FROM AUTHOR]

In order to design a vegetation structure to mitigate floods resulting from extreme events like tsunamis, vegetation density and thickness (width) are important parameters. Flow passing through vegetation faces great resistance, which results in a backwater rise on upstream (U/S) vegetation, increases the water slope inside the vegetation, and for some cases, forms a hydraulic jump downstream (D/S) of the vegetation, thus transforming a subcritical flow to supercritical [Pasha, G. A. and Tanaka, N. [2017] "Undular hydraulic jump formation and energy loss in a flow through emergent vegetation of varying thickness and density," Ocean Eng.141, 308–325.]. Like the concepts of critical velocity and critical slope, this paper introduces the concept of "critical resistance of vegetation," which is defined as "resistance offered by vegetation that transforms a subcritical flow to supercritical." An analytical approach to find the water depths U/S, inside, and D/S of vegetation is introduced and validated well by laboratory experiments. Critical resistance was determined against vegetation of variable densities (G ∕ d , where G = spacing of each cylinder in the cross-stream direction, d = diameter of the cylinder), thicknesses (dn, where d = diameter of a cylinder and n = number of cylinders in a stream-wise direction per unit of cross-stream width), and the initial Froude number (Fro). A subcritical flow (F r o = ∼ 0. 5 5 − 0. 7 5 , without vegetation) was transformed to a supercritical flow (D/S vegetation) with a range of Froude numbers of 1.6–1.9, 1.1–1.2, and 0.85–0.98 against G ∕ d ratios of 0.25, 1.09, and 2.13, respectively, thus defining G ∕ d = ∼ 1. 0 as the critical resistance. However, altering vegetation thickness did not change the results. [ABSTRACT FROM AUTHOR]

Abstract From the early stages of CFD, the computation of shocks using Finite Volume methods has been a very challenging task as they often prompt the generation of numerical anomalies. Such anomalies lead to an incorrect and unstable representation of the discrete shock profile that may eventually ruin the whole solution. The two most widespread anomalies are the slowly-moving shock anomaly and the carbuncle, which are deeply addressed in the literature in the framework of homogeneous problems, such as Euler equations. In this work, the presence of the aforementioned anomalies is studied in the framework of the 1D and 2D SWE and novel solvers that effectively reduce both anomalies, even in cases where source terms dominate the solution, are presented. Such solvers are based on the augmented Roe (ARoe) family of Riemann solvers, which account for the source term as an extra wave in the eigenstructure of the system. The novel method proposed here is based on the ARoe solver in combination with: (a) an improved flux extrapolation method based on a previous work, which circumvents the slowly-moving shock anomaly and (b) a contact wave smearing technique that avoids the carbuncle. The resulting method is able to eliminate the slowly-moving shock anomaly for 1D steady cases with source term. When dealing with 2D cases, the novel method proves to handle complex shock structures composed of hydraulic jumps over irregular bathymetries, avoiding the presence of the aforementioned anomalies. Highlights • The Carbuncle and the slowly-moving shock anomaly are studied for the 1D and 2D Shallow Water Equations with topography. • A solver that eliminates the spike in the discharge when computing hydraulic jumps is proposed and extended to 2D. • The spike-free method is enhanced with a carbuncle-free approach based on artificial diffusion. • The scheme is well-balanced and avoids the previous anomalies when computing 1D and 2D jumps over complex bathymetries. [ABSTRACT FROM AUTHOR]

The effect of jet length and wall curvature on the flow patterns generated by an impinging water jet were quantified and the effect on cleaning investigated in a brief study. The length of time taken to establish steady flow was characterised. Jet impingement on a flat vertical wall was investigated for jets of diameter 2-4 mm for lengths, L, up to 1 m. The amount of liquid lost to splatter was measured and found to be insensitive to L for short L (<300 mm for these nozzles) and strongly related to L for longer values. The shape of the radial flow zone on flat walls agreed with existing models once the fraction of liquid lost to splatter was accounted for. Tests on horizontal and vertical cylinders with curvatures in the range 6.9 - 20 m-1 showed that the curvature of the impinged wall did not affect the shape of the radial flow zone until higher flow rates (>1.5 dm³ min-1). The cleaning of two viscoplastic model food soils was studied briefly: a hydrophobic petroleum jelly and Carbopol®, a watersoluble gel. The splatter correction was not able to account for all the differences observed in cleaning at different jet lengths. There was no appreciable effect of curvature on cleaning behaviour. Soaking of the Carbopol® increased its cleaning rate. [ABSTRACT FROM AUTHOR]

Tehuantepecers or Tehuanos are extreme winds produced in the Isthmus of Tehuantepec, blowing south through the Chivela pass, the mountain gap across the isthmus, from the Gulf of Mexico into the Pacific Ocean. They are the result of the complex interaction between large-scale meteorological conditions and local orographic forcings around Chivela pass and occur mainly in winter months, due to cold air damming in the wake of cold fronts that reach as far south. They can generate localized extreme events, such as downslope windstorms and hydraulic jumps, strong turbulent flows that have a direct effect on the Pacific side of the isthmus and the Gulf of Tehuantepec. This study focuses on investigating these phenomena using high horizontal and vertical resolution WRF (Weather Research and Forecasting) model simulations. In particular, we employ a four nested grid configuration, with up to 444 m horizontal spacing in the innermost domain and 70 hybrid-sigma vertical levels, 8 of which lie within the first 200 m above ground. We select one 36 hour period in December 2013, when favorable conditions for a strong gap wind situation were observed. The high-resolution WRF experiment reveals a significant fine-scale structure in the strong Tehuano wind flow, beyond the well known gap jet. Depending on the Froude number upstream the topographic barrier, different downslope windstorm conditions and hydraulic jumps with rotor circulations develop simultaneously at different locations east of Chivela pass with varied crest height. A comparison with observations suggests that the model accurately represents the spatially heterogeneous intense downslope windstorm and the formation of mountain wave clouds for several hours, with low errors in wind speed, wind direction, and temperature. [ABSTRACT FROM AUTHOR]

Highlights • Novel application of four-point phase-detection measurement in highly-aerated open channel flow. • Quantitative characterisation of transverse velocity and velocity fluctuations in quasi-two-dimensional hydraulic jump. • Test of velocity measurements with phase-detection sensors in reversing flow. Abstract The measurement of turbulent velocity in highly aerated flow is difficult because of the presence of air bubbles. The characterisation of three-dimensional velocity field in highly aerated flows is even more challenging using existing phase-detection techniques. This paper presents an attempt on a quantification of transverse velocity and velocity fluctuations in quasi-two-dimensional hydraulic jumps with relatively high Froude and Reynolds numbers. A four-sensor phase-detection probe array was developed to measure the bubble convection in both streamwise and spanwise directions. A characteristic instantaneous transverse velocity component was derived together with a measure of its fluctuations. The transverse velocity component characterised the three-dimensional turbulent structures, although the time-averaged flow pattern was two-dimensional and the average transverse velocity was zero. Both the transverse velocity and velocity fluctuations were smaller than the longitudinal time-averaged velocity and velocity fluctuations in the shear flow, and were quantitatively comparable to those in the free-surface region, revealing different turbulent structures in the lower and upper roller regions. The approximate of Reynolds stresses was discussed together with the limitation of the method. The present work also provided some guidelines for the use of phase-detection probe array and correlation signal processing techniques in complex turbulent two-phase flows. [ABSTRACT FROM AUTHOR]

Hydraulic jumps on a large scale are turbulent, with high Reynolds number. It has been proven difficult to achieve this in previous studies of jumps as two-phase flow. This paper aims to investigate the behaviours of two-phase flow and air entrainment in jumps at relatively high Reynolds numbers. Model predictions of both oscillating and steady jumps at multiple values of Froude number are reported, along with verifications of the predictions using air volume fraction (AVF) measurements, and analytical and empirical solutions for the height of jump, roller length, and free surface. The model captures the macroscopic characters of the two types of jumps and velocity structures. The predicted AVF distributions are consistent with the velocity structures. For steady jumps, AVF profiles are roughly bell-shaped, but are heavier-tailed upward than downward. For oscillating jumps, AVF profiles are even more asymmetrical. The Reynolds number affects air entrainment and transport in two-phase flow. [ABSTRACT FROM AUTHOR]

In the present study, we conducted dual-sonde observations and a numerical simulation when the "Karakkaze", a local wind in Japan, blew. The result showed that the basic features of the Karakkaze coincide closely with the characteristics of convexity wind defined as "strong winds in the leeward region of a convexshaped mountain range". Firstly, we investigated the horizontal distribution of surface winds during the Karakkaze event on 24 January 2019. The results showed that the Karakkaze blows in the downwind plain of the convexity of the mountain range. Secondly, we compared the vertical distribution of the winds inside and outside the Karakkaze region, using the results of dual-sonde observations and a numerical simulation. Our results showed that strong winds blew from near ground level to a height of 1.8 km above mean sea level (AMSL) in the Karakkaze region. In contrast, weaker winds were observed and simulated outside the Karakkaze region. The reason of the weaker winds is that a hydraulic jump occurs on the slope of the mountain range and that the area outside the Karakkaze region is located in a more leeward direction than the hydraulic jump. These features closely match the characteristics of convexity winds. [ABSTRACT FROM AUTHOR]

The goal of the research was to identify the mixing features that distinguish wind forced, medium‐size fjord‐type lakes near the Arctic Circle from systems of similar geometry, but in a temperate climate. Experimental data and the results of 3D numerical hydrodynamic simulations were analyzed for Lake Lagarfljót (27 km long; 2 km wide; 110 m maximum depth; 65°N) during the 5‐month ice‐free period in 2009. The results showed that probably the most distinctive feature of arctic lakes is their low water column stability, one order of magnitude lower than that of mid‐latitude lakes, even in mid‐summer. The second characteristic is the high rate of energy imparted by wind in the Arctic, estimated as one order of magnitude larger than in a temperate climate. Frequent wind events with Lake and Wedderburn numbers below 1 occurred during the ice‐free period, leading to a strong shear at the base of the surface mixed‐layer and the upwelling of deep metalimnetic layers. As a result, nearly continuous density stratification developed in the shallowest 70 m of the water column, and longitudinal temperature gradients may therefore be very significant. On average, 15% of the wind forcing drove large‐scale internal motions. This energy was rapidly dissipated, partly as a result of stronger bottom velocities, nonlinear surges, and hydraulic jumps that repeatedly formed in the lake. The initial V1H1 setup rapidly evolved into spatially complex oscillatory modes, which, given the high latitude, are affected by the Earth's rotation, even in narrow basins. [ABSTRACT FROM AUTHOR]

Hydraulic jumps cause significant flow energy dissipation and generally occur in association with hydraulic structures. Nevertheless, the dissipative mechanisms occurring with this hydraulic phenomenon still require investigation. There are no systematic studies analysing the hydraulic jump energy dissipation for a large range of hydraulic and geometric conditions. To the authors’ knowledge, no studies provide a complete and exhaustive analysis of the dissipative mechanism for rough sloped channels. This study proposes a novel semi-theoretical and general approach to estimate energy dissipation at hydraulic jumps in rough sloped rectangular channels, involving a large range of both hydraulic conditions and bed configurations. Two relationships were derived and their predictive capability has been tested with approximately 500 experimental data points from different studies. [ABSTRACT FROM AUTHOR]

Results from large-eddy simulations and complementary flume experiments of turbulent open channel flows over bed-mounted square bars at intermediate submergence are presented. Scenarios with two bar spacings, corresponding to transitional and k-type roughness, and three flow rates, are investigated. Good agreement is observed between the simulations and the experiments in terms of mean free surface elevations and mean streamwise velocities. Contours of simulated time-averaged streamwise, streamfunction and turbulent kinetic energy are presented and these reveal the effect of the roughness geometry on the water surface response. The analysis of the vertical distribution of the streamwise velocity shows that in the lowest submergence cases no logarithmic layer is present, whereas in the higher submergence cases some evidence of such a layer is observed. For several of the flows moderate to significant water surface deformations are observed, including weak and/or undular hydraulic jumps which affect significantly to the overall streamwise momentum balance. Reynolds shear stress, form-induced stress and form drag are analysed with reference to the momentum balance to assess their contributions to the total hydraulic resistance of these flows. The results show that form-induced stresses are dominant at the water surface and can contribute significantly to the overall drag, but the total resistance in all cases is dominated by form drag due to the presence of the bars. [ABSTRACT FROM AUTHOR]

The one-dimensional shallow water equations were modified for a Venturi contraction and expansion in a rectangular open channel to achieve more accurate results than with the conventional one-dimensional shallow water equations. The wall-reflection pressure–force coming from the contraction and the expansion walls was added as a new term into the conventional shallow water equations. In the contraction region, the wall-reflection pressure–force acts opposite to the flow direction; in the expansion region, it acts with the flow direction. The total variation diminishing scheme and the explicit Runge–Kutta fourth-order method were used for solving the modified shallow water equations. The wall-reflection pressure–force effect was counted in the pure advection term, and it was considered for the calculations in each discretized cell face. The conventional shallow water equations produced an artificial flux due to the bottom width variation in the contraction and expansion regions. The modified shallow water equations can be used for both prismatic and nonprismatic channels. When applied to a prismatic channel, the equations become the conventional shallow water equations. The other advantage of the modified shallow water equations is their simplicity. The simulated results were validated with experimental results and three-dimensional computational fluid dynamics result. The modified shallow water equations well matched the experimental results in both unsteady and steady state. [ABSTRACT FROM AUTHOR]

Abstract In this work, the influence of constant background vorticity on the properties of shock waves in a shallow water system are considered. It is shown that the flow-depth ratio of stationary shocks can be written as a function of two non-dimensional parameters: the Froude number, suitably defined in the presence of the shear flow, and a non-dimensional vorticity. Some properties of these hydraulic jumps are explored, and it is shown that stronger background vorticity has the effect of moderating the strength of the hydraulic jump. [ABSTRACT FROM AUTHOR]

Bora in Novorossiysk (seaport on the Black Sea coast of the Caucasus) is one of the strongest and most prominent downslope windstorms on the territory of Russia. In this paper, we evaluate the applicability of the hydraulic and wave hypotheses, which are widely used for downslope winds around the world, to Novorossiysk bora on the basis of observational data, reanalysis, and mesoscale numerical modeling with WRF-ARW. It is shown that mechanism of formation of Novorossiysk bora is essentially mixed, which is expressed in the simultaneous presence of gravity waves breaking and a hydraulic jump, as well as in the significant variability of the contribution of wave processes to the windstorm dynamics. Effectiveness of each mechanism depends on the elevated inversion intensity and mean state critical level height. Most favorable conditions for both mechanisms working together are moderate or weak inversion and high or absent critical level. [ABSTRACT FROM AUTHOR]

A hydraulic jump mainly serves as an energy dissipator downstream of hydraulic structures. For analysis and design of a hydraulic jump on a corrugated bed, the specific energy curve was used: the maximum possible amount of energy dissipation of the hydraulic jump, the minimum possible value of sequent depth for the hydraulic jump, and efficiency of energy dissipation of a smooth hydraulic jump are theoretically related to the inflow Froude number. A wide range of existing experimental data from hydraulic jumps on smooth and corrugated beds was also used. Results of this study indicate that the energy dissipation of a hydraulic jump on a corrugated bed is mainly influenced by horizontal distance from the sluice gate section to the start point of the corrugated bed. To reach the maximum value of energy dissipation (i.e., minimum value of subcritical sequent depth) and the minimum value of jump length, the corrugated bed should start from the gate opening. [ABSTRACT FROM AUTHOR]

For mitigating tsunamis that overtop an embankment, flume tests were conducted to clarify the energy reduction of a tsunami due to a compound defense system by a combination of a sea embankment and lined vertical piles behind the embankment. The relationship between the flow structure and energy reduction was investigated with changing pile height, spacing, and number of rows. The flow structure was classified into 10 types, and the patterns were classified into two. The energy reduction increased with smaller spacing between lined piles, and the reduction of energy and fluid force behind piles gradually decreased when the piles were submerged. In some cases, energy reduction became very low or energy was locally concentrated because standing waves were generated behind the piles. Two important parameters were proposed, ResP * , consisting of pile spacing, pile diameter, and number of lines of piles in the downstream direction, and Ps * , comprising overflowing water depth, pile height, and embankment height. Ps * discriminates whether the piles are emergent or submerged, and ResP * classifies the change in the flow structure pattern. Recommended design criteria to reduce tsunami energy and to prevent the formation of the standing waves downstream of piles were elucidated by these two parameters. [ABSTRACT FROM AUTHOR]

The present article is the second of a series of seven, all relative to energy dissipators that can be used in hydraulic works. The whole group of these articles conform a monograph about the subject that is being prepared by the author, concluding it by the middle of the 2017 year and later on incorporating it into a new edition - in preparation - of the textbook "Spillways and Intake Structures." This second article is a detailed presentation about two structures of energy dissipation that have a wide universal use. [ABSTRACT FROM AUTHOR]

The present article is the first of a series of seven, all relatives to energy dissipators that can be used in hydraulic works. The whole group of these articles conform a monograph about the subject that is being prepared by the author, concluding it by the middle of the 2017 year and later on incorporating it into a new edition - in preparation - of the textbook "Spillways and Intake Structures." This first article is a detailed presentation about the hydraulic jump employed with the function of energy dissipation. [ABSTRACT FROM AUTHOR]

A disposal system for low- and medium-level nuclear waste in Hungary is being constructed inside the fractured rock body of the Lower Carboniferous Mórágy Granite. Previous studies proved that the granitoid massif is rather heterogeneous in terms of lithological composition, brittle structure and hydrodynamic behaviour. A significant part of the body consists of monzogranite, while other portions are more mafic in composition and are monzonites. As a result of at least three significant brittle deformation events, the area is at present crosscut by wide shear zones that separate intensively fractured zones and poorly deformed domains among them. Due to late mineralization processes, some of these fractured zones are totally sealed and cannot conduct fluids, while others are excellent migration pathways. The spatial distribution of these two types nevertheless does not show any systematics. Hydrodynamic behaviour clearly reflects this heterogeneous picture; in some places, hydraulic jumps as great as 25 m at compartment boundaries can be detected. In this study, the fracture network of the Mórágy Granite body is evaluated from a geometric aspect using datasets measured at a wide range of scales. 2D digitized images of a hand specimen, one large (20 × 60 m) and 12 smaller subvertical wall rocks (outcrops) and 120 images from tunnel faces representing the ground level of the underground repository site were analysed. Moreover, 1D data from 13 wells that all penetrate the granitoid massif were studied. Based on measured geometric data (spatial position, length, orientation, and aperture) fracture networks are simulated to study connectivity relations and for computing the fractured porosity and permeability at different scales. The results prove the scale-invariant geometry of the fracture system. Geostatistical calculations indicate that measurable fracture geometry parameters behave as regionalized variables and so can be extended spatially. Estimated localities of connected subsystems fit very well with fault zones mapped previously. Moreover, the spatial position of regimes of different hydrodynamic behaviours can be explained by connectivity relations both regionally and within wells. [ABSTRACT FROM AUTHOR]

Ｔｈｅ ｈｙｄｒａｕｌｉｃ ｊｕｍｐ ｉｎ ｒｅｃｔａｎｇｕｌａｒ， ｈｏｒｉｚｏｎｔａｌ ａｎｄ ａｂｒｕｐｔ ｅｎｌａｒｇｅｍｅｎｔｓ ｃｈａｎｎｅｌｓ ｗａｓ ａｎａｌｙｚｅｄ． Ｂａｓｅｄ ｏｎ ｔｈｅ ｉｎｖｅｓｔｉｇａｔｉｏｎ ｏｆ ｈｙｄｒａｕｌｉｃ ｊｕｍｐｓ ｆｏｒｍａｔｉｏｎ ｍｅｃｈａｎｉｓｍ ｔｈｒｏｕｇｈ ｂｏｔｈ ｅｘｐｅｒｉｍｅｎｔａｌ ａｎｄ ａｎａｌｙｔｉｃａｌ ｍｅｔｈｏｄｓ ｉｎ ａｂｒｕｐｔ ｅｎｌａｒｇｅｍｅｎｔｓ ｃｈａｎｎｅｌｓ， ｔｈｉｓ ｐａｐｅｒ ｆｏｕｎｄ ｏｕｔ ｔｈａｔ ｔｈｅ ｃｈａｎｎｅｌ ｓｉｄｅ ｗａｌｌ ａｖｅｒａｇｅ ｄｅｐｔｈ ｏｆ ｔｈｅ ｒｅ⁃ｃｉｒｃｕｌａｔｉｏｎ ｚｏｎｅ ａｔ ｔｈｅ ｓｕｄｄｅｎ ｅｎｌａｒｇｅｍｅｎｔ ｃｈａｎｎｅｌ ｃｒｏｓｓ ｓｅｃｔｉｏｎ ｗａｓ ｒｅｌａｔｅｄ ｔｏ ｔｈｅ ｉｎｆｌｏｗ ｅｎｅｒｇｙ ｈｅａｄ ａｎｄ ｔｈｅ ｒａｔｉｏ ｏｆ ｕｐｓｔｒｅａｍ ａｎｄ ｄｏｗｎｓｔｒｅａｍ ｃｈａｎｎｅｌ ｗｉｄｔｈｓ， ａｓ ｗｅｌｌ ａｓ ａｓｓｕｍｅｄ ｔｈａｔ ｔｈｅ ａｖｅｒａｇｅ ｄｅｐｔｈ ｅｑｕａｌｅｄ ｔｈｅ ｐｒｏｄｕｃｔ ｏｆ ｔｈｅ ｉｎｆｌｏｗ ｅｎｅｒｇｙ ｈｅａｄ ｔｉｍｅｓ ｔｈｅ ｃｏｒｒｅｃｔｉｏｎ ｃｏｅｆｆｉｃｉｅｎｔ， ｗｈｉｃｈ ｗａｓ ｐｒｅｓｅｎｔｅｄ ｉｎ ｔｅｒｍｓ ｏｆ ｔｈｅ ｉｎｆｌｏｗ Ｆｒｏｕｄｅ ｎｕｍｂｅｒ ａｎｄ ｔｈｅ ｒａｔｉｏ ｏｆ ｕｐｓｔｒｅａｍ ａｎｄ ｄｏｗｎｓｔｒｅａｍ ｃｈａｎｎｅｌ ｗｉｄｔｈｓ ａｃｃｏｒｄｉｎｇ ｔｏ ｓｏｍｅ ｏｂｓｅｒｖａｔｉｏｎ ｄａｔａ ｐｒｅｓｅｎｔｅｄ． Ｔｈｅｎ ｔｈｅ ｓｅｑｕｅｎｔ ｄｅｐｔｈｓ ｆｏｒｍｕｌａ ｗａｓ ａｃｑｕｉｒｅｄ ｂｙ ｐｌｕｇｇｉｎｇ ｔｈｅ ａｖｅｒａｇｅ ｗａｔｅｒ ｄｅｐｔｈ ｉｎｔｏ ｔｈｅ ｅｑｕａｔｉｏｎ ｆｏｒ ｔｈｅ ｓｅｑｕｅｎｔ ｄｅｐｔｈｓ ｒａｔｉｏ． Ａｎｄ ｉｔ ｃｏｕｌｄ ｂｅ ｆｏｕｎｄ ｔｈａｔ ｔｈｅ ｓｅｑｕｅｎｔ ｄｅｐｔｈｓ ｃａｌｃｕｌａｔｅｄ ｂｙ ｔｈｅ ｆｏｒｍｕｌａ ｗｅｒｅ ｉｎ ｇｏｏｄ ａｇｒｅｅｍｅｎｔ ｗｉｔｈ ｔｈｅ ｏｔｈｅｒ ｏｂｓｅｒｖａｔｉｏｎ ｄａｔａ ｐｒｅｓｅｎｔｅｄ， ｗｉｔｈ ｈｉｇｈｅｒ ｃａｌｃｕｌａｔｉｏｎ ａｃｃｕｒａｃｙ ｔｈａｎ ｔｈｅ ｐｒｅｓｅｎｔｅｄ ｆｏｒｍｕｌａ． [ABSTRACT FROM AUTHOR]

Common features of the flow behavior over mountains within the hydraulic jump model are identified based on an analysis of 36 episodes of severe winds in the regions of Novorossiysk, Pevek, and Novaya Zemlya. In all these episodes, the incoming flow is characterized by a strong inversion layer at altitudes of 0.5-1.5 km and, in the case of bora, by a critical level in the wind profile in the middle troposphere, which creates conditions for a weakened dynamic interaction between the low-level air flowing over mountains and the upper layers of the atmosphere. The wind-speed increase on the lee slope is caused by the transition of the incoming flow from the subcritical to supercritical state. In this case, the velocity amplitude increases with increasing inversion intensity. Model estimates of wind-speed increase are in good agreement with observations at lee-side weather stations for episodes with a strong elevated inversion. [ABSTRACT FROM AUTHOR]

The ocean-interior shows omnipresent internal wave motions whose importance becomes more and more acknowledged for deep mixing across the stable vertical density stratification for heat and suspended matter redistribution. To observationally study vertical propagation variations of internal tides away from a steep topographic slope, a >1-km long mooring with 760 high-resolution temperature sensors was deployed at 2380 m depth halfway Mount Josephine NE-Atlantic Ocean for 4 months. In the lower 150 m above the seafloor, internal waves slosh, become highly non-linear and break vigorously, every tidal cycle. After signal separation using semidiurnal band-pass and harmonic filters, the vertical phase propagation shows: 1. Phase differences of 90° are observed in isotherms and cross-slope currents over typically 600 m in the vertical, 2. Non-linearity is already found in harmonic records that describe 300-m large-scale internal tides, 3. Non-uniform thin-layer stratification causes about 50% of the semidiurnal variance in small-scales, 4. Upward internal tide propagation starts at the top of non-linear wave breaking, 5. Downward propagation from above leading to energy-focusing at 700 m above the ocean-floor and about 700 m below the nearest seamount-ridge generates interior hydraulic jumps during spring tide. • High-resolution observations from 760 T-sensors along a >1-km mooring. • Separation of large- and small-scale internal tides above a steep deep-ocean slope. • Internal tide generation at the top of the >100-m tall wave breaker zone. • Internal wave focusing and straining leads to hydraulic jump well above topography. • Phase differences of 90° in isotherms and cross-slope currents over vertical 600 m. [ABSTRACT FROM AUTHOR]

This approach is equal to using Eq. (17) with a head-loss coefficient HT ht . The sole aim of introducing a correction factor like HT ht is to obtain a discharge value, calculated by Eq. (11), equal to the measured one. In such cases, to correctly calculate the momentum correction factor, it is necessary to introduce the lateral nonuniformity as well as the nonuniform velocity distribution in the HT ht -direction. Aminpour et al. do not explain why the variable HT ht is considered as a function of HT ht . [Extracted from the article]

Side weirs are widely used for flow control and diversion. Although many studies on sub- and supercritical flows along these weirs have been conducted, only a few research studies have considered the generation of a hydraulic jump along the side weir. Spatially varied flow including a hydraulic jump along the rectangular side weir is studied in this paper. Experimental data for different weir geometries and hydraulic conditions are analysed. Based on the experimental results, new equations for estimating the jump length, the ratio of the conjugate depths and the discharge coefficient are presented. Also, the head loss due to the presence of a hydraulic jump is studied. Furthermore, a numerical model is developed for coupling the water surface profile with a hydraulic jump along the side weir. In this model the lateral outflow momentum is considered, which has been mostly ignored in previous works. The model predicts the location of the hydraulic jump. A comparison of the numerical and experimental results indicates good agreement. [ABSTRACT FROM AUTHOR]

A shallow water model was applied to study the hydraulic jump and Bernoulli equation across the jump. On a flat terrain, when a supercritical flow plunges into a subcritical flow, discontinuity develops on velocity and Bernoulli function across the jump. The shock generated by the obstacle may propagate downstream and upstream. The latter reflected from the inflow boundary, moves downstream and leaves the domain. Before the reflected wave reaching the obstacle, the short-term integration (i.e., quasi-steady) simulations agree with Houghton and Kasahara’s results, which may have unphysical complex solutions. The quasi-steady flow is quickly disturbed by the reflected wave, finally, flow reaches steady and becomes critical without complex solutions. The results also indicate that Bernoulli function is discontinuous but the potential of mass flux remains constant across the jump. The latter can be used to predict velocity/height in a steady flow. [ABSTRACT FROM AUTHOR]

Hydraulic jump is a useful means of dissipating excess energy of a supercritical flow so that objectionable scour downstream is minimized. The present study applies gene expression programming (GEP) to estimate hydraulic jump characteristics in sudden expanding channels. Three types of expanding channels were considered: channels without appurtenances, with a central sill, and with a negative step. 1,000 experimental data were considered as input data to develop models. The results proved the capability of GEP in predicting hydraulic jump characteristics in expanding channels. It was found that the developed models for channel with a central sill performed better than other channels. In the jump length prediction, the model with input parameters Fr1 and (y2-y1)/y1, and in the sequent depth ratio and relative energy dissipation prediction the model with input parameters Fr1 and y1/B led to more accurate outcomes (Fr1, y1, y2, and B are Froude number, sequent depth of upstream and downstream, and expansion ratio, respectively). Sensitivity analysis showed that Fr1 had the key role in modeling. The GEP models were compared with existing empirical equations and it was found that the GEP models yielded better results. It was also observed that channel and appurtenances geometry affected the modeling. [ABSTRACT FROM AUTHOR]

Hydraulic jumps are a complex hydraulic phenomenon characterised by a water surface discontinuity from supercritical to subcritical flows. Along the jump roller, high turbulence, flow aeration and three-dimensional motions are key characteristics which are associated with jump toe oscillations and free-surface fluctuations. Previous studies have provided significant insights into the characterisation of the free-surface and jump toe characteristics in hydraulic jumps. However, a continuous observation of the time-varying free-surface has been so far limited to fixed data points along the hydraulic jump. Herein, novel experiments were conducted with a LIDAR measuring the continuous free-surface profiles in aerated hydraulic jumps providing detailed spatial and temporal free-surface characteristics of aerated hydraulic jumps. The free-surface observations provided basic statistics of the free-surface including mean profiles and standard deviations of the free-surface fluctuations as well as their characteristic frequencies. The effect of the jump toe oscillations on the free-surface properties was analysed for two conditions using a free moving jump toe and a fixed jump toe position. The results showed a strong effect of the jump toe oscillations on the free-surface features close to the jump toe. Based upon the characteristic frequencies, three characteristic regions in hydraulic jumps were identified. Overall the comparison with previous studies showed good agreement highlighting that a LIDAR is a suitable instrument to measure the free-surface characteristics in aerated hydraulic jumps. [ABSTRACT FROM AUTHOR]

Middle Pleistocene Gilbert-type delta in the Gulf of Corinth, Greece, has been investigated combining field methods and photo acquisition by drone to generate a high-resolution 3D model. This study case can be used to document four different dynamics in Gilbert-type bottomset deposits, each one of which is characterized by a specific range of facies, facies associations and geometries: (1) the sandy-gravelly bottomset, (2) the erosional-bypass stage, (3) the fine-grained bottomset and (4) the massive-sandy bottomset. By comparing the typologies of the bottomset, we propose a conceptual model that predicts the occurrence of these four different bottomset stage dynamics depending on the stratigraphic context. During highstand normal regression, the gravelly bottomset develops under subcritical flow. The supercritical flow undergoes a stationary hydraulic jump in the toeset due to the slope break. As a result, a low-relief channel-levees system is formed in the bottomset. The channels are filled/reworked by backstepping conglomeratic lenses interbedded with silty concave-up and concave-down levees. During normal regression, the foreset beds are steeper than during previous stage and scoured in the upper part. In the bottomset, significant erosion recording sediment bypass downstream toward the pro-delta can be observed. During lowstand normal regression, a starved fine silt to shale bottomset onlaps onto the major erosional surface. The bulk of the coarse-grained sediments is stored in the delta topset and foreset. During the transgressive to highstand stage, the former topset and foreset are eroded by high-density turbidity currents and massive-sandy turbidites are deposited in the bottomset, which onlap onto the foreset beds and form a slope apron geometry in the delta toe. The stratigraphic model improves the prediction for the sand distribution within the various parts of the bottomset. This approach is particularly relevant for clastic depositional systems with high sediment discharge and a high accommodation rate. [ABSTRACT FROM AUTHOR]

The purpose of this study was to evaluate two perforated sills in the stilling basin and their impact on characteristics of the hydraulic jump, such as the length of the roller of hydraulic jump, decrease in the secondary depth of the hydraulic jump, and the required tailwater depth. Also, the optimal distance of two perforated sills from the beginning of the stilling basin with a fixed height for the perforated sill and ratios of the opening of holes equal to 50% were determined. The experiments were carried out in the form of 48 tests for different discharges in the range of 47 to 145 lit/s and for Froude numbers in range of 3.6 to 11.2. The results of the experiments on two perforated sills showed that they could only reduce the length of the roller of the hydraulic jump to an acceptable level, with the distance between them providing the conditions to create a stable jump; also, the length of roller of jump was not decreased by reducing the distance between the sills. Also, they decreased the secondary depth of the forced hydraulic jump up to 27.8%, which was less than the secondary depth of the free hydraulic jump; the length of roller was up to 76.9 % less than the length of the roller of the free hydraulic jump for the Froude number of 11.2. [ABSTRACT FROM AUTHOR]

Hydraulic jumps can occur downstream of hydraulic structures, such as normal weirs, gates and ogee spillways. The roller length is one of the most important parameters of hydraulic jumps in open channels. In this study, the roller length of a hydraulic jump on a rough bed is predicted using a hybrid of adaptive neuro-fuzzy inference systems and the firefly algorithm (ANFIS-FA). First, the effect of parameters including the Froude number (Fr), sequent depth (h2/h1) and relative roughness (ks/h1) upstream of a hydraulic jump is studied. Following the modeling result analysis, ANFIS-FA is introduced as the superior model for estimating the roller length of a hydraulic jump on a rough bed according to Fr, h2/h1 and ks/h1. The calculated MAPE, RMSE and correlation coefficient values for the superior model are 7.606, 1.771 and 0.970, respectively. ANFIS-FA predicted approximately 40 % of the results with less than 5 % error, and only 36 % of data had more than 10 % error. [ABSTRACT FROM AUTHOR]

Hydraulic jumps are characterized by strong flow turbulence, flow aeration, and three-dimensional flow motions. Whereas comprehensive research into hydraulic jumps on smooth bed has improved the understanding of flow aeration and turbulence, limited research has been done of hydraulic jumps on rough beds. Herein novel experiments were conducted in hydraulic jumps on uniformly-distributed bed macroroughness. Both air-water flow patterns and basic air-water flow properties were investigated. The hydraulic jumps on the rough bed exhibited some remarkable differences compared with smooth bed jumps including some preaeration of the flow upstream of the jump, an upwards shift of the jump roller and a clear water-flow region underneath the jump. Air-water flow measurements were conducted with a phase-detection probe, showing similar distributions of air-water flow properties for the rough and smooth bed jumps. Comparative analyses highlighted some distinctive effects of the bed roughness including an upwards shift of the hydraulic jump and an increase in bubble count rate and void fractions in the region close to the jump toe. In the second half of the hydraulic jumps, the rough bed led to a clear-water region with large-scale vortices which were advected downstream. The present study highlighted the potential that improved and nonstandard invert designs may have for flow manipulations and design enhancements. [ABSTRACT FROM AUTHOR]

Typhoon Khanun caused over 226 mm of accumulated rainfall for 6 h (0700 to 1300 UTC), localized around the summit of Mt. Halla (height 1950 m), with a slanted rainfall pattern to the northeast. In this study, we investigated the enhancement mechanism for precipitation near the mountains as the typhoon passed over Jeju Island via dual-Doppler radar analysis and simple trajectory of passive tracers using a retrieved wind field. The analysis of vertical profiles of the mountain region show marked features matching the geophysical conditions. In the central mountain region, a strong wind (≥ 7 m s − 1 ) helps to lift low-level air up the mountain. The time taken for lifting is longer than the theoretical time required for raindrop growth via condensation. The falling particles (seeder) from the upper cloud were also one of the reasons for an increase in rainfall via the accretion process from uplifted cloud water (feeder). The lifted air and falling particles both contributed to the heavy rainfall in the central region. In contrast, on the leeward side, the seeder-feeder mechanism was important in the formation of strong radar reflectivity. The snow particles (above 5 km) were accelerated by strong downward winds (≤−6 m s − 1 ). Meanwhile, the nonlinear jumping flow (hydraulic jump) raised feeders (shifted from the windward side) to the upper level where particles fall. To support these development processes, a numerical simulation using cloud-resolving model theoretically carried out. The accreting of hydrometeors may be one of the key reasons why the lee side has strong radar reflectivity, and a lee side weighted rainfall pattern even though lee side includes no strong upward air motion. [ABSTRACT FROM AUTHOR]

The length of the hydraulic jump on the basis of physical and numerical modeling. The outcomes of physical and numerical modeling of the sluice gate outflow are presented. The measured velocity distributions in verticals of a physical model were compared with results of numerical modeling, obtained using ANSYS Fluent software. The research goal was verification of suitability of the computational fluid dynamic (CFD) approach in determination of the hydraulic jump length at the outflow of the flow control structure. Studies were performed for the model of the sluice gate and stilling basin with two setups of baffle blocks: in one and two rows. The jump lengths were estimated by an analysis of vertical velocity profiles at the outflow. Two rows of baffle blocks in the stilling basin allowed to reduce the length of the hydraulic jump by 5-10%, comparing to the length with the single row of blocks. The computational fluid dynamic approach underestimated the length of the hydraulic jump by 4-7%, comparing to the physical model. [ABSTRACT FROM AUTHOR]

Hydraulic jumps are induced in hydraulic facilities for the purposes of energy dissipation or flow aeration. Presently there is no means for a simple estimate of void fraction distribution and air entrainment flux, without detailed physical modelling. This paper presents a semi-theoretical model to simulate the void fraction and velocity distributions in hydraulic jumps characterized by partially-developed inflow conditions. Relationships were established between the inflow Froude number, jump roller length and key parameters that determine the full expression of void fraction and velocity profiles. The proposed model enables accurate prediction of void fraction, longitudinal velocity, and air flux using the inflow Froude number. The results indicated considerable air flux contribution of free-surface aeration, in addition to the singular air entrainment at the jump toe, for moderate to large Froude numbers. A Froude number between 8 and 9 tended to achieve highest aeration rate with maximum total air flux in the roller. [ABSTRACT FROM AUTHOR]

The aim of this paper is to study flow regime changes of Newtonian fluid flow in an open Venturi channel. The simulations are based on the volume of fluid method with interface tracking. ANSYS Fluent 16.2 (commercial code) is used as the simulation tool. The simulation results are validated with experimental results. The experiments were conducted in an open Venturi channel with water at atmospheric condition. The inlet water flow rate was 400 kg/min. The flow depth was measured by using ultrasonic level sensors. Both experiment and simulation were done for the channel inclination angles 0°, −0.7°, and −1.5°. The agreement between computed and experimental results is satisfactory. At horizontal condition, flow in the channel is supercritical until contraction and subcritical after the contraction. There is a hydraulic jump separating the supercritical and subcritical flow. The position of the hydraulic jump oscillates within a region of about 100 mm. Hydraulic jumps coming from the contraction walls to the upstream flow are the main reasons for the conversion of supercritical flow into subcritical flow. An “oblique jump” can be seen where there is a supercritical flow in the contraction. There is a triple point in this oblique jump: the triple point consists of two hydraulic jumps coming from the contraction walls and the resultant wave. The highest flow depth and the lowest velocity in the triple point are found at the oblique jump. [ABSTRACT FROM AUTHOR]

In a natural estuary, a tidal bore may progress on a small sloping bed from the downstream to the upstream. In this study, a simple analytical solution for tidal bore formed in a small slope channel was developed using the finite control volume analysis. New unsteady experiments were conducted to verify the theoretical model. The model predictions generally agree with the observations. A general relation is obtained for the conjugate depth ratio as a function of the Froude number and the channel slope from the experimental data. The results indicate that the conjugate depth ratio increases with an increasing Froude number as well as with a decrease in channel slope. On a negative slope, the Froude number increases as the bore propagates along the channel, and decreases for a positive slope. The theoretically based model is accurate and simple to estimate the celerity of the tidal bore progressing along a small slope channel. [ABSTRACT FROM AUTHOR]

As part of the Precision Atmospheric Marine Boundary Layer Experiment, the University of Wyoming King Air sampled an atmospheric environment conducive to the formation of a hydraulic jump on 24 May 2012 off the coast of California. Strong, northwesterly flow rounded the Point Arguello-Point Conception complex and encountered the remnants of an eddy circulation in the Santa Barbara Channel. The aircraft flew an east-west vertical sawtooth pattern that captured a sharp thinning of the marine boundary layer and the downstream development of a hydraulic jump. In situ observations show a dramatic rise in isentropes and a coincident sudden decrease in wind speeds. Imagery from the Wyoming Cloud Lidar clearly depicts the jump feature via copolarization and depolarization returns. Estimations of MBL depth are used to calculate the upstream Froude number from hydraulic theory. Simulations using the Weather Research and Forecasting Model produced results in agreement with the observations. The innermost domain uses a 900-m horizontal grid spacing and encompasses the transition from supercritical to subcritical flow south of Point Conception. Upstream Froude number estimations from the model compare well to observations. A strongly divergent wind field, consistent with expansion fan dynamics, is present upwind of the hydraulic jump. The model accurately resolves details of the marine boundary layer collapse into the jump. Results from large-eddy simulations show a large increase in the turbulent kinetic energy field coincident with the hydraulic jump. [ABSTRACT FROM AUTHOR]

Sudden diverging channels are one of the energy dissipaters which can dissipate most of the kinetic energy of the flow through a hydraulic jump. An accurate prediction of hydraulic jump characteristics is an important step in designing hydraulic structures. This paper focuses on the capability of the support vector machine (SVM) as a meta-model approach for predicting hydraulic jump characteristics in different sudden diverging stilling basins (i.e. basins with and without appurtenances). In this regard, different models were developed and tested using 1,018 experimental data. The obtained results proved the capability of the SVM technique in predicting hydraulic jump characteristics and it was found that the developed models for a channel with a central block performed more successfully than models for channels without appurtenances or with a negative step. The superior performance for the length of hydraulic jump was obtained for the model with parameters F1 (Froude number) and (h2--h1)/h1 (h1 and h2 are sequent depth of upstream and downstream respectively). Concerning the relative energy dissipation and sequent depth ratio, the model with parameters F1 and h1/B (B is expansion ratio) led to the best results. According to the outcome of sensitivity analysis, Froude number had the most significant effect on the modeling. Also comparison between SVM and empirical equations indicated the great performance of the SVM. [ABSTRACT FROM AUTHOR]

Two-phase gas-liquid slug flow is the prevailing flow regime in many processes in the petroleum and chemical industries. This flow regime is the result of the growth of wavelike instabilities at the gas-liquid interface. The main characteristic of slug flow is the presence of liquid slugs that span the entire pipe diameter separated by gas bubbles. The rear end of these gas pockets can exhibit a staircase shape (also known as plug flow) or a hydraulic jump that reaches the top of the pipe when the flow rate is increased. In this paper, an experimental investigation of the statistical properties of slug flow is presented for flow initiation. A gas-liquid circuit made of acrylic tubes with a 26 mm ID was used to make these measurements. The test facility was composed of two sections: the first corresponded to a downward flow of −3 degree inclination where the prevalent flow regime was stratified flow, and the second was a horizontal section where the prevalent flow regime was slug flow. Resistive sensors located at three different positions in the horizontal section were used to acquire the liquid holdup, and the time series were processed and analyzed. Statistics for slug initiation position, slug and bubble lengths, bubble velocity, slug and unit-cell frequencies are presented. Further, the length and probability of occurrence of the bubble tail were also analyzed in the cases where the bubbles exhibited a staircase shape. Ultimately, data are provided for the validation and development of mathematical models and numerical codes for the simulation of two-phase slug flow. [ABSTRACT FROM AUTHOR]

Inferred supercritical structures and bedforms, including sediment waves and backset-bedded sets, are identified as components of coarse-grained siliciclastic and bioclastic, high-gradient clinoform wedges (Plio-Pleistocene of southern Italy) and canyon head infills (Tortonian of Venetian pre-Alps), showing evidence of having been built out in a setting influenced by shallow-marine hydrodynamics. The facies identified are dominated by a range of traction carpets, formed after segregation of coarser particles in the lower part of bipartite density underflows. The generation of backset-bedded sets is thought to imply scouring due to impact of a submerged hydraulic jump on the bed, and upstream migration of the jump, concomitant with the deposition of backset beds on the stoss side of the developing bedform. Submerged hydraulic jumps apparently formed spontaneously and in any position on the foreset and toeset, without requiring any precursor bed defect. The mostly solitary, non-cyclical character of the bedforms prevents their attribution to cyclic steps. The sets of backset beds are locally underlain by chaotic infills of deep, steep-sided scours attributed to vigorous erosion at the hydraulic jump, accompanied by instantaneous loss in transport capacity which results in rapid plugging of the scour (hydraulic jump facies of Postma et al., 2014). Gravel waves have a distinct internal stratigraphy, and their length to amplitude ratios show lower mean values and higher variability when compared to sediment waves consisting of sand. The presence of supercritical bedforms on steep foreset slopes of the studied clinoform systems, even in proximity to the topset-foreset rollover, is believed to reflect high inefficiency of mud-poor and short run-out bipartite underflows episodically transporting relatively small volumes of coarse-grained sediment. This may also account for common solitary, non-cyclical bedforms. It is proposed that during intense oceanographic events, such as coastal storms, seaward sediment entrainment, assisted by gravity, was very effective on the gently sloping subaqueous topset, and that, beyond the topset-foreset rollover, the flows evolved to high-concentration turbidity underflows with supercritical Froude numbers. The flows are inferred to have been sustained, probably lasting for the duration of the meteorological events, and to have commonly been unsteady in discharge, fluctuating in concentration and size of transported sediments, and subject to peaks in velocity. The characteristics of the structures are regarded as typical of the systems fed by oceanographic processes, and may fall into the class of coarse-grained “small sediment waves with mixed relief” of Symons et al. (2016), formed from a combination of erosion and deposition, and by the action of stratified flows depositing from denser basal layers, and typically restricted to small-scale shallow-marine slope systems. [ABSTRACT FROM AUTHOR]

Cyclic steps are ubiquitous in modern sedimentary environments, yet their recognition remains sparse in the rock record. Here, we interpret three sets of undulating backsets (1 to 3) recognized in the late Miocene-early Pliocene Latrania Formation in the Anza-Borrego Desert, the Fish Creek-Vallecito Basin, southern California, USA as the first cm- to dm-scale outcrop record of cyclic steps, based on asymmetrical cross-sections, upstream migration, and inversely graded laminae. Upstream migration and asymmetrical cross-sections of backsets and concomitant backset laminae are attributed to supercritical-to-subcritical flow transitions through weak hydraulic jumps, which are composed of: (i) thin (tens of centimetres) and slower (reported as flow velocities ( Ū ) of 0.45 to 1.45 m s − 1 , with mean value of Ū = 0.89 m s − 1 ) subcritical (represented by internal Froude numbers ( Fr ) of 0.67 to 0.99, with mean value of Fr = 0.84) turbidity currents on the stoss sides, and (ii) thin (tens of centimetres) and faster (reported as Ū of 0.99 to 4.03 m s − 1 , with mean value of Ū = 2.24 m s − 1 ) supercritical (represented by Fr of 1.84 to 3.07, with mean value of Fr = 2.42) turbidity flows on the lee sides. The inversely graded laminae in the troughs of backsets are 2 to 5 cm thick, and consist of two discrete divisions: (i) 1 to 2 cm thick, lower finer-grained divisions made up of parallel laminated siltstones, overlain by very fine- to fine-grained sandstones, and (ii) 2 to 3 cm thick, upper divisions composed of medium- to coarse-grained sandstones, with sporadic occurrence of subrounded pebbles. These inversely graded laminae are related to stratified, collisional and/or frictional traction carpets under conditions of high fall-out rates. Due to the poor preservation potential of cyclic steps, the rock record of cyclic steps is generally considered to be rare. The present outcrop-based study presents a detailed analysis of sedimentary facies, growth patterns, and flow dynamics of marine cyclic steps, thereby contributing to better understand architectural styles and lithological properties of cyclic steps in the geological record. [ABSTRACT FROM AUTHOR]