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A hydraulic jump forming in the stilling basin at the base of a high-head dam spillway is often characterized by high Froude number and inflow pre-aeration conditions. Although the air entrainment in hydraulic jump has been studied extensively, the effects of the inflow pre-air-entrainment on the downstream air–water flow properties and energy dissipation performance have not been investigated systematically, especially for high-Froude-number cases. This paper presents a comparative study of the pre-aeration effects on the air–water flow characteristics of high-Froude-number hydraulic jumps. Two pre-aeration levels were achieved using a smooth sloping chute and a ramp aerator on the chute. Apart from the change in jump length required for the same amount of energy dissipation, the major impact of the variation in pre-aeration was observed for the void fraction and air entrainment flux within the jet-shear region, whereas the bubble count rate and interfacial velocity were less affected. Differences were also observed from the prediction of previous studies under smaller Froude number and negligible pre-air-entrainment conditions. The pre-air-entrainment was found to affect the scale effects on the bubble counts and the interfacial area between air and water phases. This study may facilitate a bridging between the laboratory findings and the cases closer to the real engineering application of large-scale hydraulic jumps.

On 19 April 2019, a mature squall-line mesoscale convective system (MCS) with the characteristics of a leading convective line and trailing stratiform landed on Taiwan, resulting in strong gust wind and heavy rainfall. This squall-line MCS became asymmetric after landfall on Taiwan. Two sets of idealized numerical simulations (mountain heights and low-level vertical wind shear) using the Weather Research and Forecasting (WRF) model were conducted to examine the impacts of realistic Taiwan topography on a squall-line MCS. Results showed numerous similarities between the idealized simulations and real-case observations. The low-level Froude number which considered the terrain height (Fmt) was calculated to examine the blocking effect of the Taiwan terrain, and the cold pool (determined by − 1.5 K isotherm) was found to be completely blocked by the 500-m height contour. The northeast-southwest orientation of the Snow Mountain Range (SMR), and the north–south orientation of the Central Mountain Range (CMR) led to the upwind side asymmetry. On the other hand, the lee-side asymmetry was associated with different intensities and occurrence locations of the hydraulic jump between the SMR and southern CMR, and the cold-pool Froude number (Fcp) indicated the flow-regime transition from subcritical to supercritical.

In this study, the joint effects of submerged vanes and flow expansion on the hydraulic jump are experimentally investigated. Experiments include four expansions and four vane layouts with the Froude number ranging from 4.60 to 8.56. The results show, abrupt expansion and the vanes that are 5 cm apart are the best in dissipating energy, the energy loss increases about 30%, with respect to classical jump. The sequent depths ratio decreased up to 54% and the length of hydraulic jump decreased up to 45%. On the other hand, shear force coefficient shows a relative increase in the transition length of the hydraulic jump. We conclude that using the combination of the vanes and expansion in proper orientation relative to each other can be cost effective in the construction of the stilling basins.

Scour downstream of smooth and rough rigid aprons under wall jets has been studied experimentally. Effect of apron roughness on scour has been investigated, and quantification of reduction in the scour depth due to rough apron has been performed. Characteristics of velocity and turbulence over smooth and rough aprons as well as within the scour hole have been analyzed to study the behavior of the jet and its interaction with the rough apron. Results show that there is a significant reduction in the equilibrium scour depth due to roughness. A maximum of 82.8% and a minimum of 31.1% reduction in the equilibrium scour depth was observed due to inducing roughness over the rigid apron. Velocity characteristics establish the cause of reduction in the equilibrium scour depth, which is due to reduction in the erosive capacity of the jet as it moves over the rough apron. The potential core of the jet gets consumed at a much lesser length due to roughness over the apron than over a smooth apron, as the boundary layer develops at a smaller distance. Further, it was observed that it takes a smaller length for the flow to get fully developed under the rough apron as compared with the smooth apron. Based on the results of the present analysis, recommendation can be made for use of roughness over the apron to restrict scour due to wall jets.

A numerical study was performed on the embankment weir overflows with various surface roughness and tailwater submergence, to better understand the effects of weir roughness on discharge performances under the free and submerged conditions. The variation of flow regime is captured, from the free overflow, submerged hydraulic jump, to surface flow with increasing tailwater depth. A roughness factor is introduced to reflect the reduction in discharge caused by weir roughness. The roughness factor decreases with the roughness height, and it also depends on the tailwater depth, highlighting various relations of the roughness factor with the roughness height between different flow regimes, which is linear for the free overflow and submerged hydraulic jump while exponential for the surface flow. Accordingly, the effects of weir roughness on overflow discharge appear nonnegligible for the significant roughness height and the surface flow regime occurring under considerable tailwater submergence. The established empirical expressions of discharge coefficient and submergence and roughness factors make it possible to predict the discharge over embankment weirs considering both tailwater submergence and surface roughness.

This paper analyzed the flow pattern around damaged and undamaged bridge piers in a channel with a mild slope. The experiments were carried out on a straight channel with a length of 12 meters and a slope of 0.008. Acoustic Doppler velocimeter (ADV) was employed to collect three-dimensional flow velocity data, and the results were analyzed and compared with particle image velocimetry (PIV) data. Sediment Simulation in Intakes with Multiblock option (SSIIM) was incorporated for the numerical simulation of the flow in this study. Generally, the results obtained from the comparisons referred to the appropriate agreement between the numerical and the experimental data. The results showed that an undular hydraulic jump occurred at a distance of two meters from the channel entrance in every case; the maximum bed shear stress in the sloped channel was 12 times that in a horizontal channel for installing two damaged and undamaged piers. With this position of the piers in the sloped channel, the upstream water level underwent a 72.5% reduction compared to similar conditions in a horizontal channel, while the amount of this water level decrease was equal to 8.3% compared to the other cases in a sloped channel. In addition, with the presence of both piers, the maximum Froude number was 5.7 times that in a horizontal channel.

For a traditional stepped spillway, low energy dissipation and cavitation damage may occur when the unit discharge is larger than a limit due to reduced air entrainment in the flow. In the present work, a new type of stepped spillway called hydraulic-jump-stepped spillway (HJSS) was developed, and the air was efficiently entrained into the flow by means of a hydraulic jump in the aeration basin, which was an aeration element of this stepped spillway. Compared with the traditional stepped spillway, various aspects of the hydraulic performance of the HJSS were experimentally investigated, including the flow pattern, energy dissipation, air entrainment characteristics and time-averaged pressure. Physical model results demonstrated that the HJSS achieved a higher energy dissipation, a more favorable air entrainment performance, and a more reasonable pressure distribution. The HJSS successfully increased the unit discharge from 50–60m2/s for a traditional stepped spillway to 101.47 m2/s.

When the Froude number F of a free-surface flow ranges between 0.3 and 3, the flow is unstable and frequently characterised by free surface undulations, with the undular hydraulic jump being a seminal flow in hydro-environmental mechanics. The presence of the free surface undulations significantly affects the flow field, with major velocity and pressure field redistributions between successive crests and troughs. All the current theoretical models to simulate undular hydraulic jumps are limited to two-dimensional flow conditions, ignoring all the relevant three-dimensional flow effects, namely shock-wave drag, turbulent breaking and turbulent stresses. These aspects are critically accounted for in this review article, where a depth-averaged Boussinesq model which approximately accounted for 3D flow effects was presented, constituting the first attempt in this line. The model predictions were compared with experimental results from different sources for F1

The difficulty of the problem of the flow hydraulics in compound channels is due to the implicit interaction between the floodplains and the main channel, characterizing every particular shape of the compound channel. The problem is much more complicated when it comes to an energy dissipator like a hydraulic jump as is the case in the present study. In this paper, the general regression neural network (GRNN) was applied to predict the basic characteristics of hydraulic jumps in a straight rectangular compound channel: (i) the sequent depths ratios, (ii) the relative energy losses, and (iii) the relative lengths. Experiments were carried out with three different values of the ratio between the main channel width and the flood plain one (Wy). The Wy values were: (1/4, 1/3, and 1/2). For each Wy ratio, several values of inflow Froude number were considered according to the five inflow ratio depths’ (Wz) values (0.167, 0.200, 0.253, 0.287, and 0.333) between the first sequent depth and of the main channel one. The predicted values in the testing stages using GRNN followed the experimental ones with a correlation coefficient (R) of 0.990 for the sequent depth’s ratios, 0.982 for relative energy losses, and 0.873 for the relative lengths of hydraulic jumps. The best models have been selected among several input configurations for each of three considered characteristics of the jump.

Partially filled pipes have many applications in hydraulic and environmental engineering; such as sewer and storm water collection pipes and circular culverts. Hydraulic jump can lead to scouring at hydraulic structures and thus excess energy should be dissipated to prevent scour and erosion. Calculation of conjugate depths in circular pipes and culverts is important in hydraulic engineering. The conjugate flow depths are commonly used to estimate the length of the hydraulic jump and the energy loss in the jump. Available relationships to estimate the conjugate depths in circular pipes are not accurate and wide application range. In comparison to easily available numerical solutions, a closed-form solution is a function of all input independent variables; and thus the dependence of the conjugate depth on each input independent variable can be easily interpreted. This study presents explicit solutions for the conjugate depths (pre- and post-jump depths) in partially filled pipes. The proposed solutions are examined over a wide range of the Froude number and geometric conditions, providing satisfactory estimations when compared with the exact solution obtained from the specific force relation. If the prejump flow depth of the hydraulic jump is known, the postjump flow depth can be determined using the proposed solution with a maximum relative error less than 1.4%. Inversely, if postjump flow depth is known, the prejump flow depth can be determined with a maximum relative error less than 2.3%. The proposed direct solutions are general, accurate, simple, and useful for studying the partially filled circular open channels.

A hydraulic jump occurs when the supercritical flow transforms into subcritical nature along with the dissipation of energy. It occurs on a variety of horizontal and inclined channels. In this study, two types of jumps were classified, namely the B types that occur partially in the sloping and partially in the horizontal level of plane sections and the plane types that are typical hydraulic jumps occurring on beds with continuous slopes or horizontal beds. Froude numbers at inlet ranged from 2 to 6 for the study and tests were performed at four different angles for B-type jumps. The profiles of the jumps and streamwise flow velocities at different sections of the jumps were determined. From these data, the nature of the rate of decay of stream wise velocity across the jumps was established for both B and plane jumps. To validate the experimental results, numerical simulation was done for both B and plane jumps using the de-Saint Venant hyperbolic equations as governing equations and an explicit scheme MacCormack technique for the second-order accuracy of time and space. A source code was written in Fortran language using the G-Fortran compiler to numerically determine post-jump profiles. Using the appropriate initial boundary conditions, accurate simulated profiles of the jumps were obtained by it. The numerically simulated jump profiles were compared with experimentally obtained jump profiles in current and previous research studies and were found to be consistent. Based on the accuracy achieved, a combined empirical relation was proposed to determine jump profiles that operate both plane and B jumps.

Sea straits are known for important sites to modify water-mass properties and transport nutrients through vigorous vertical mixing. The first microstructure measurements ever taken in the Tsugaru Strait, between the Sea of Japan and the Northwest Pacific Ocean, showed elevated turbulent mixing. The turbulent energy dissipation rate was especially enhanced to O(10−6 W kg−1) via an internal hydraulic jump when the throughflow passed over an abrupt sill. Beyond the sill, the associated vertical eddy diffusivity reached O(10−2 m2 s−1) and the vertical turbulent nitrate flux below the subsurface chlorophyll-a maximum layer was estimated to reach 1 mmolN m−2 day−1, which could elevate the new production of phytoplankton within the layer. Large vertical velocities exceeding 0.1 m s−1 were also observed near the seafloor of the sill where the flow was hydraulically controlled. A simple advection–diffusion model suggested that the energy dissipation rate of O(10−5 W kg−1) was necessary to reproduce the observed modification of subsurface salinity maximum across the strait. Upwelling and/or vertical straining associated with the internal hydraulic jump is also believed to play an important role in the water-mass modification in the strait and could enhance new primary production for a wide area downstream.

The hydraulic jump phenomenon plays a significant role in dissipating the energy of the upstream current in either natural or artificial waterways. River’s bed roughness is defined as a key parameter that affects the characteristics of the hydraulic jump. In this study, a non-linear regression algorithm was developed to predict the sequent depth ratio of hydraulic jumps over a smooth and rough bed surface using the experimental hydraulic data extracted from the previous studies. Four popular machine learning techniques, known as adaptive network-based fuzzy inference system (ANFIS), ANFIS-Particle Swarm Optimization (ANFIS-PSO), bayesian model averaging (BMA), least absolute shrinkage and selection operator (LASSO), are applied to check the accuracy of the proposed algorithm. The dimensional analysis and Gamma Test model are used to select the effective parameters on the hydraulic jump. In this study, four major parameters named the roughness height (ks), hydraulic radius (R), velocity and Froude number at the upstream of the hydraulic jump control volume were selected as more effective parameters. To compare the performance of the models in prediction of both sequent hydraulic depths, the coefficient of determination, root mean square error (RMSE), mean error, Mean Absolute Error and Nash–Sutcliffe efficiency (NSE) were calculated in both training and testing subsets. It is shown that the proposed model, along with two other non-linear methods, ANFIS and ANFIS-PSO, predicted the hydraulic jump sequent depth ratio more accurately compared to the linear regression techniques, BMA and LASSO. However, the statistical measures show an acceptable accuracy for the linear regression techniques. The results show that the proposed model increases the correlation between observed and predicted values up to 0.987 and decreases the RMSE to 0.324. Simultaneously, the last two linear techniques have RMSE, correlation coefficient 0.333 and 0.98, respectively. Finally, a new non-linear formula addressing the hydraulic jump sequent depth ratio over smooth and rough beds have been proposed. A comparison between the resulted formula of the present study with the previous studies proves the accuracy of the developed equation. Moreover, a dimensionless primary roughness coefficient is presented as a non-linear function of the roughness height (ks) and hydraulic radius (R) parameters.

Hydraulic jump is a phenomenon observed in open channel flow, and studying it has been a challenge for scientific communities. Most of the previous studies on this topic have been devoted to the cases of clear water in rectangular geometry. However, in nature river flows carry sediment loads; meanwhile, trapezoidal stilling basins are proved to be more economical as well. In this paper, the RNG turbulence model has been used to simulate jump characteristics in a symmetrical trapezoidal channel of 45° side slope for clear water flow and three different sediment concentrations of 4%, 8% and 12% and a range of initial Froude number between 1.5 and 12. The results indicate that by increasing the sediment concentration the bed shear stress amounts and energy loss ratio increase while the length of jump ratio decreases. In comparison with the clear water flow, for the case of Fr1 = 7 and sediment concentration of 12%, the length of jump ratio decreases by 18.1%, the sequent depth ratio increases by 17.2% and the energy loss ratio increases by 3.2%. Furthermore, the bed shear stress at the beginning and at the end of the jump is innovatively investigated. The results show that the shear stress at the initial depth section is not dependent on the sediment content, but at the secondary depth of flow, it is highly dependent on the suspended sediment loads content.

The location of a hydraulic jump is a key parameter for analysing the slab stability of the stilling basin in a sluice. A simple method to locate the toe of a hydraulic jump in sloping channels is presented. The essential idea of this method applies the interacting relationship between the sequent depth and jump length to locate a point, satisfying them both simultaneously. The implementation details and the involved sequent depth and jump length equations of this method are discussed, and verification of the method is also presented. The predicted results match well with the published test data, even for a steep sloping channel up to 45°. The method’s application in the failure analysis of a sluice sloping connecting slab is also presented briefly. It is important for the analysis to account for the static hydraulic jump effect. The proposed method can yield a key parameter for such an analysis.

In the recent years, numerical modeling of free surface flows has experienced a rapid and important development. Several programs and software have been used to simulate free surface flows. Transition from supercritical to subcritical flow regime leads to formation of hydraulic jumps. Numerical modeling of hydraulic jumps has taken an important part in this domain. This work aims to assess the efficiency of Iber software in the simulation of hydraulic jump in a rectangular channel. The location and displacement of the hydraulic jump were simulated by 2D Iber software. The data of these simulations were obtained from the experimental tests carried out at the laboratory. The results of the simulated hydraulic jump surface profiles showed a good agreement with those measured experimentally. The velocity distribution is presented in this study. Numerical simulation results satisfactorily predicted the hydraulic jump location, which gives confidence using of Iber software in the simulation of hydraulic jump.

Flows in discharge and energy dissipation buildings generally carry a considerable amount of energy. Therefore, it is important to optimize the discharge and energy dissipation to eliminate the redundant energy as much as possible for the safety of the hydro-junction project and the downstream area. In this paper, a smoothed particle hydrodynamics (SPH) model is applied to optimize the discharge and energy dissipation related to hydraulic jumps for a large-scale real hydro-junction project. The capability of the model in resolving hydraulic jumps is validated by comparing the model results with experimental data. Then, the model is applied to optimize the real hydro-junction project, which requires a sizeable computational effort. The optimization is based on comparisons of the velocity field, the location of the jump toe and the energy dissipation rate between two different schemes for the stilling basin. It is found that the two-stage stilling basin is more effective for energy dissipation than the one-stage stilling basin with the same length. Therefore, two-stage energy dissipation should be adopted for discharge and energy dissipation buildings for similar hydro-junction projects.

Sluice gate has always been used due to their ease of construction, control water level and measure flow discharge. Numerous studies have been carried out on sluice gates. On the other hand, estimating the discharge of flow below sluice gates is a major problem in many water engineering issues. The flow may become supercritical while passing the sluice gate. A bump can be used on the channel bed after the sluice gate in order to accelerate the formation of hydraulic jump phenomenon which converts supercritical flow to subcritical flow, therefore damages and undesirable effects caused by high water pressure in the supercritical flow can be prevented. In this paper, the simultaneous effects of sluice gate and bump in a channel on the formation of the hydraulic jump have been investigated. For this purpose, this phenomenon is modeled in hydraulic laboratory, then, it is simulated by FLOW3D numerical model. The desired conditions are carried out for four different locations of the bump with two different flow rates for each. Also, each experiment conducted on two types of positive and negative channel slope. Finally, a comparison is made between the fine and coarse mesh size on the numerical model to show the sensitivity of hydraulic jump simulation to meshing. The results indicate that as the location of the bump moves downstream of the channel for the positive slope of the channel, the location of the hydraulic jump formation goes downstream, and by decreasing the flow and giving negative slope to the channel, the location of occurrence of hydraulic Jump moves toward upstream of the channel. Also, comparison of different disturbance models indicates the superiority of LES disturbance model in showing jump disturbances compared to other models.

In plunging jets and at hydraulic jumps, large amounts of air bubbles are entrained at the impingement of the liquid jet into the receiving body. Air is entrapped and advected into a turbulent shear layer with strong interactions between the air bubble advection process and momentum shear flow. In this new physical study, air–water flow measurements were systematically repeated with identical inflow length, inflow depth and inflow velocity in a vertical supported jet (PJ) and a horizontal hydraulic jump (HJ). Detailed measurements were conducted with the same instrumentation. Both similarities and differences were observed between the two multiphase gas–liquid shear flows. Visual observations showed a key difference in the outer region, with a buoyancy-driven flow in the plunging jet with negligible void fraction, versus a strong recirculation motion with uncontrolled interfacial aeration in the hydraulic jump. Differences were also observed at the impingement perimeter, in terms of fluctuation frequencies and amplitudes, for identical inflow conditions. Both flow conditions yielded intense local singular air entrainment and close results were observed in terms of void fraction, bubble count rate, bubble chord sizes and interfacial area in the shear layer, in both the plunging jet and hydraulic jump. The transfer of momentum between impinging jet and receiving water, as well as the effect of buoyancy, were however affected by the flow geometry.

Pressure fluctuations are among the favorite topics for hydraulic engineers due to their critical role in the design and safe operation of hydraulic structures. In this study, three explicit data-driven models, including Classification and Regression Trees (CART), Gene Expression Programming (GEP), and Multivariate Adaptive Regression Splines (MARS), are used. These methods are applied to predict the pressure fluctuation intensity $$(C_{P}^{'} )$$ , which occurs beneath a hydraulic jump on sloping channels using reliable experimental observations. The main features of the suggested data-driven models are their capability to provide practical formulas for prediction of $$C_{P}^{'}$$ based on the dimensionless form of the effective parameters. The application of these models leads to the extraction of knowledge from data in the form of predictive formulas. In addition, to evaluate the accuracy and performance of the proposed models, some statistical indices and several validation criteria are employed. The obtained results confirm that MARS predicts $$C_{P}^{'}$$ better than CART and GEP. Based on the effective independent variables, MARS presents a simple predictive formula for the computation of $$C_{P}^{'}$$ . GEP-based equations use mathematical trigonometric functions that cause a more complicated and time-consuming process to predict $$C_{P}^{'}$$ . However, the application of simple rules generated by CART enables hydraulic engineers to predict $$C_{P}^{'}$$ , easily and quickly.

River plumes are an important component of estuarine circulation and have a vital role in the transport of estuarine material and momentum balance. However, little information is available on the influence of mouth bars on estuarine plumes. To address this, momentum balance analysis was carried out using the ocean numerical model, to analyze the dynamic characteristics of the Pearl River plumes. The results show that the Pearl River plumes may be divided into three dynamic regions: near-, mid-, and far-field region. In the near-field region are dominated by pressure gradient force, bottom pressure forcing, and horizontal advection, which are obviously affected by river mouth bar. The mid-field momentum balance indicates seasonal differences, while the Coriolis force, pressure gradient force, and horizontal advection have great contribution to momentums in flood season, and in the dry season, momentum is balanced by the Coriolis force, pressure gradient force, and bottom pressure forcing. The momentum balance in the far-field region is determined by the Coriolis force, pressure gradient force, and surface pressure forcing. The internal hydraulic jump can be detected around the mouth bar when the hydrodynamic condition transitions from supercritical to subcritical, which has a close relationship with the local topographic structures. Internal estuarine waves may be further generated with interaction of tide and stratified flows around the river mouth bar.

Three-dimensional stepped spillway problems are simulated numerically using smoothed particle hydrodynamics (SPH) to visualize the flow of water along the steps and its flow dynamics. In particular, two distinct scaled-down stepped spillway models were studied with each having barrier heights of 10 mm and 25 mm, respectively. The impact of varying the height of the barrier in the design of the stepped spillway is studied in terms of it flow pattern, flow dynamics, aeration efficiency and oxygenation performances. State-of-the-art particle image velocimetry (PIV) experiment was carried out to affirm the validity of SPH findings and it turns out that both the water flow patterns attained in the SPH and PIV are quantitatively comparable. Further quantitative analysis revealed that the flow velocities in both methodologies are in great consensus. Conclusively, this has demonstrated that the capability and reliability of SPH to precisely approximate the water using finite set of particles to model the flow along the stepped spillway. Both stepped spillway configurations show nappe flow regime as the water descends down the steps. Nonetheless, vigorous hydraulic jump phenomena that is associates with the formation of turbulence and vortices is prominently observed in the configuration with larger barrier height. Decisive SPH data obtained concluded that as the barrier height increases from 10 mm to 25 mm, the water flows down the steps faster at lower pressure value and the overall aeration efficiency is improved from 1.1% to 1.2%. The usage of the higher barrier would promote the occurrence of substantial air entrainment during water swirling that will increase the power dissipation in flow. Subsequently, this while lower the power drawn to achieve the desired aeration effect. Ultimately, this study has justified the critical influence of barrier height dimension on the stepped spillway flow behavior and aeration performance.

The present paper analyses the advantages and limitations of using numerical modelling to simulate hydraulic jumps at high Froude numbers. Two hydraulic jumps of the same Froude number (7.5) but different Reynolds numbers were simulated using Improved Delayed Detached Eddy Simulation. The free surface was captured using the Volume of Fluid multiphase model with a High-Resolution Interface-Capturing technique. Flow properties including velocity, total pressure and air concentration profiles were compared with experimental results at different streamwise locations. It was observed that while the simulations were able to accurately capture the velocity and pressure fields, the air concentration values were over predicted, although the air concentration distribution was successfully reproduced. Since the simulations capture the complete three-dimensional flow field, further analysis of different physical mechanisms contributing to air entrainment are also carried out. The turbulent kinetic energy and the vorticity field were examined to understand the air–water flow dynamics. The coherent structures responsible for air entrainment were identified using vortex identification techniques. The influence of these structures on the air-entrainment mechanisms is presented with pertinent discussions.

In order to understand the effect of porous media on hydraulic jumps, a smoothed particle hydrodynamics (SPH) model is applied to investigate the characteristics of hydraulic jumps interacting with porous media. Various porosities including cases without an obstacle or with a solid obstacle or porous media are considered. The opening of a gate was altered to adjust the hydraulic jump. The conjugate depth ratio, bottom shear stress distribution, and energy dissipation are reported. In the present study, validations are in a good agreement with previous studies. Overall, the result showed that the average error between numerical and experimental data was less than 7.2%. Energy dissipation is compared among cases with three porosities, with and without a solid obstacle. The porosity of 0.68 is found to dissipate more energy than do other porosities. Thus, porous media can be used to enhance energy dissipation of hydraulic jumps in an open channel. In conclusion, the proposed SPH model can simulate the effect of porous media on hydraulic jump characteristics.

A spilling breaker model (SBM) is implemented in an existing two-dimensional (2D) numerical wave tank (NWT), based on fully nonlinear potential flow (FNPF) theory and the boundary element method (BEM), in which an absorbing surface pressure is specified over the crest of impending breaking waves (detected based on a maximum front slope criterion) to simulate the power dissipated during breaking. The latter is calibrated to match that of a hydraulic jump of parameters identical to local wave properties (height, celerity, $$\ldots $$ ). Although this model is not aimed at being fully physical in the surfzone, it allows more accurately simulating properties of fully nonlinear shoaling waves than standard empirical absorbing beaches (AB). After assessing the convergence with the discretization of 2D-NWT results for strongly nonlinear shoaling waves, simulations are first validated based on laboratory experiments for non-breaking and breaking waves, shoaling up a mild slope; a good agreement is found between both. The NWT is then used to compute fully nonlinear local (height, celerity, asymmetry) and integral (mean-water-level, radiation stress) properties of periodic waves shoaling over mild slopes. Discrepancies with standard results of wave theories are discussed in light of fully nonlinear effects modeled in the NWT. While only periodic waves are considered here, the SBM could be applied to shoaling irregular waves, for which the breaking point location will constantly vary, which would be advantageous compared to an AB fixed in space. For such cases, besides its more physical energy absorption, the SBM would allow better preventing wave overturning that may occur far from shore due to nonlinear wave–wave interactions and otherwise interrupt the FNPF–NWT simulations.

Doubtlessly hydraulic jump is a useful phenomenon in open channel flow such as rivers and spillways. As the most important characteristics of hydraulic jump, length, and sequent depth ratio play a key role in designing of hydraulic structures. The hydraulic jump length is one of the most important parameters, which cannot be calculated by mathematical analyses directly. In this context, several relations have been proposed to estimate the length and sequent depth ratio of the hydraulic jumps, but the results of the mentioned equations are not general and acceptable due to the uncertainty of the functions. Achievements of this study follows three aims; firstly to develop and examine support vector machine (SVM) for estimating characteristics of five types of free and submerged hydraulic jumps; secondly to compare the results of SVM models with analytical and semi-empirical equations; and finally to perform a sensitivity analysis to investigate the effect of each input parameter on the output in terms of root mean square error (RMSE), correlation coefficient (R) and Nash-Sutcliffe or determination coefficient (NS or DC). The meteorological data sets used herein to develop the models are obtained from previous credible researches. Performance of the models appoints dominant parameters for predicting the characteristics of the different types of hydraulic jumps As Also based on the comparisons among the SVM models, analytical and semi-empirical equations, it can be seen that, SVM models depict better results than those equations.

In this paper, the hydraulic structure of flood flow on a four-branch urban road intersection with two adjacent input streets and two output streets was investigated theoretically. Not only were previous flow patterns investigated theoretically, but also two new flow patterns were introduced and discussed in this study: Flow Pattern Type 1, when the flows approaching the junction in the street were in subcritical condition and return to subcritical in output streets downstream of the junction; Flow Pattern Type 1 Sub-regime 1, when the flows approaching in the input streets were in supercritical condition and return to supercritical in output streets downstream of the junction. The deflection of supercritical flows was formulated and solved numerically through writing MATLAB codes and was investigated graphically. Nomo-graphs were generated for the case that two oblique hydraulic jumps formed in the junction, which can be used to predict the characteristics of flow downstream of the junction. For example, the jumps angle can be predicted from the known parameters of incoming flows by applying the Angle Model formulas.

Liquid film generated by a jet slit injector on a wall was analyzed experimentally. Liquid film characteristics were investigated by measuring the liquid film thickness distribution for various experimental conditions. At first, the distributions were qualitatively analyzed using backlight imaging. Furthermore, quantitative measurements were performed using a liquid film thickness sensor based on the electric conductance method, which was applied to the high-speed wire-mesh method. The injection angle (15, 30, 45 °), jet velocity (7, 10.5, 13.5 m/s), and injection distance (45, 55, 65 mm) were varied, and the responses of the liquid film were observed. Having increased the injection angle, the main stream thickness decreased and the position of the maximum film thickness moved upstream. A faster jet velocity corresponded to a wider liquid film area and larger perturbation of the liquid film. The injection distance did not affect the characteristics of the liquid film considerably. A hydraulic jump effect was also observed, and a large hydraulic jump affected the film thickness distribution of the main stream. The results of this study can be applied to the development of liquid rocket engines or thrusters using the film-cooling method.

Broad-crested weirs are defined as structures where the streamlines are parallel to each other and the pressure is hydrostatic over the horizontal crest. The water surface profile for submerged flow over weir was estimated through flume experimentation and compared with numerical model results. The numerical model was developed using ANSYS FLUENT version 15 in three dimensions (3D) with a standard k–e turbulent model. The Volume of Fluid (VOF) method was used to estimate the water level in each cell and includes tail water influence acting on a broad-crested weir. The agreement between the FLUENT model and the experimental results for water depth was good. Such conditions are often difficult to predict, particularly at onset of the hydraulic jump. The numerically derived pressure and velocity distributions over the weir are simulated in 3D. Good agreement was achieved between numerical and experimental discharge with a relative error of 6.6%. The relative error between the numerical and experimental coefficient of discharge was 7.7%.

Hydraulic jump phenomenon occurring in the circular pipes is a complex issue which has been paid studious attentions by hydraulic engineers. Several experimental and numerical studies were performed so as to characterize hydraulic jump in circular pipes. There are few comprehensive equations to predict the conjugate depth in circular pipes. In this investigation, three numerical models on the basis of evolutionary computing as gene-expression programming (GEP), model tree (MT), and evolutionary polynomial regression (EPR) have been utilized to evaluate the conjugate depths of the hydraulic jump in the circular pipes. Two non-dimensional parameters were yielded from conceptions of specific force to determine a functional relationship between the input and output variables. The performances of proposed approaches were compared with those obtained using conventional methods. The performance of MT indicated an accurate prediction of conjugate depths (R = 0.995 and RMSE = 0.023) in comparison with those other artificial intelligence (AI) models and empirical equations. The uncertainties prediction of the improved models were quantified and compared with those of existing models. The results of the proposed models demonstrated that linear equations provided by MT had more convenient application than empirical equations extracted from experimental investigations.

In order to avoid the cavitation damage and the decrease of the energy dissipation of the stepped spillways with a large unit discharge, the air entrainments of the hydraulic jump aeration basin (HJAB) are theoretically and experimentally investigated for the hydraulic-jump-stepped spillway developed by the authors. It is shown that the submerged degree of the hydraulic jump and the air concentration in the measuring section are all functions of the dimensionless discharge, the length and the end sill height of the HJAB. The submerged degree σ decreases with the increase of the dimensionless discharge or the dimensionless length of the HJAB, but increases with the increase of the dimensionless height of the end sill of the HJAB. The flow regimes near the critical hydraulic jump, namely, at σ = 1.0, have the best effect of the air entrainment for the flow at the measuring section and then that of the stepped spillway.

Liquid jet impingement is used in industries for cleaning or cooling the surfaces, since this process is characterized by high heat or mass transport rates. The impinging jet spreads radially outwards and creates a wall film flow, which is bounded by a hydraulic jump. The existing models describing the extent of the radial flow zone and the position of hydraulic jump are only applicable for small nozzle-to-target distances and low flow rates. In this work, the model is extended to include the effect of splattering liquid, which may reduce the extent of the radial flow zone considerably. The splattering in combination with the hydraulic jump position is investigated experimentally for a liquid jet impinging horizontally onto a vertical wall. In addition, the high-speed images of the jet and of the impingement region provide further insight into the splattering mechanisms. It is found that for large nozzle-to-target distances the splattered mass fraction is determined only by the jet Weber number. The hydraulic jump position can be predicted using the extended model with deviations of less than 20% in this region.

A three-dimensional thermal lattice Boltzmann model (TLBM) using multi-relaxation time method was used to simulate stratified atmospheric flows over a ridge. The main objective was to study the efficacy of this method for turbulent flows in the atmospheric boundary layer, complex terrain flows in particular. The simulation results were compared with results obtained using a traditional finite difference method based on the Navier–Stokes equations and with previous laboratory results on stably stratified flows over an isolated ridge. The initial density profile is neutral stratification in the boundary layer, topped with a stable cap and stable stratification aloft. The TLBM simulations produced waves, rotors, and hydraulic jumps in the lee side of the ridge for stably stratified flows, depending on the governing stability parameters. The Smagorinsky turbulence parameterization produced typical turbulence spectra for the velocity components at the lee side of the ridge, and the turbulent flow characteristics of varied stratifications were also analyzed. The comparison of TLBM simulations with other numerical simulations and laboratory studies indicated that TLBM is a viable method for numerical modeling of stratified atmospheric flows. To our knowledge, this is the first TLBM simulation of stratified atmospheric flow over a ridge. The details of the TLBM, its implementation of complex boundaries and the subgrid turbulence parameterizations used in this study are also described in this article.

The energy dissipation is a key index in the evaluation of energy dissipation elements. In the present work, a flip bucket with a slot, called the slot-type flip bucket, is theoretically and experimentally investigated by the method of estimating the energy dissipation. The theoretical analysis shows that, in order to have the energy dissipation, it is necessary to determine the sequent flow depth h1 and the flow speed V1 at the corresponding position through the flow depth h2 after the hydraulic jump. The relative flow depth h2 / ho is a function of the approach flow Froude number Fro, the relative slot width b/Bo, and the relative slot angle θ/β. The expression for estimating the energy dissipation is developed, and the maximum error is not larger than 9.21%.

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.

In this study, energy dissipation and downstream flow regime of labyrinth weirs are investigated. For comparison of results, equation of maximum possible amount of energy dissipation ΔE max on labyrinth weirs is obtained by using the specific energy curve. Experimental results supported by dimensional analysis indicated that relative energy dissipation on labyrinth weir ΔE/E 0 is linearly decreased with increasing relative critical depth y c/E 0, where E 0 is the total upstream energy. Collision of oblique supercritical flows at the base of nappes created a hydraulic jump on downstream of labyrinth weir. This hydraulic jump stabilized the subcritical flow regime on downstream of weir. Total dissipated energy on labyrinth weir is approximately equal to the maximum possible amount of energy dissipation. Therefore, energy dissipation structures are not required on downstream of the weir. Collision of nappes, circulating flow in created pool behind the nappes, and placing a hydraulic jump on weir downstream face are the main reasons of large energy dissipation on labyrinth weirs.

In the present work, oscillating characteristics and cyclic mechanisms in hydraulic jumps are investigated and reproduced using a weakly-compressible XSPH scheme which includes both an algebraic mixing-length model and a two-equation turbulence model to represent turbulent stresses. The numerical model is applied to analyze oscillations of different hydraulic jump types based on the laboratory experiments. The comparison between SPH and experimental results shows an influence of different turbulence models on the amplitude spectrum and peak amplitude of the time-dependent surface elevation upstream and downstream of the hydraulic jump. By analyzing a single cycle of the oscillating phenomena of a hydraulic jump it is possible to indicate their correlation with the vortex structures of the roller. Furthermore, analysis of the oscillating phenomena indicates a correlation among the surface profile elevations, velocity components and pressure fluctuations. This observation leads to conclude that oscillations phenomena are particularly important for analysis of the turbulence characteristics.

In the present study, the effect of inlet flow condition of a stilling basin on the hydrodynamic parameters of flow as well as velocity and pressure distributions, vorticities, pressure fluctuations, turbulence intensities, and hydrodynamic loads were investigated. To do so, two practical and usual cases of flow at the downstream of a bottom outlet and downstream of a chute spillway were simulated and analyzed. To verify the numerical simulations, a scaled physical model was employed. Large eddy simulation and volume of fluid models were used to simulate the turbulence and free surface, respectively. Results showed that when moving the place of the formed hydraulic jump at the first 25% length of the stilling basin, pressure fluctuations were on average 42.6% more at downstream of the chute spillway in comparison with bottom outlet. However, in the middle of the stilling basin length due to the impact of the jet at the downstream of the bottom outlet model, the pressure fluctuations were on average 47.3% more than the pressure fluctuations at the downstream of the spillway model. The maximum values of vorticity and turbulence intensity occurred in the section of hydraulic jump formation in the stilling basin.

Motivated by need to study supercritical overbank flows on floodplain, we experimentally investigate if initially supercritical flow in a rectangular flume would maintain its state throughout. Varying upstream gate opening, flow rate and angle of the slope, a total of 37 experimental cases were carried out. The experimental results are compared to two existing theories: an inviscid theory based on nonlinear shallow water equations and jump conditions and a hydraulic theory that takes friction into account. The experimental data are consistent with the two theories. Flows on downward slope were stable, while those on upward slope had unstable hydraulic jump and transformed into subcritical flow. The reported results should serve well in designing a laboratory flume with the supercritical inflow and in conducting hydraulic model experiments on overbank flows.

Hydraulic jumps generally occur subsequent to structures such as ogee spillways, control gates, and weirs. The jump roller length is considered one of the main hydraulic jump parameters. In this study, the roller length of a hydraulic jump on a rough channel bed is predicted using a novel, evolutionary, generalized structure design of a group method of data handling (GS-GMDH)-type neural network. The topology of GMDH is designed with a genetic algorithm . Initially, the three most important non-dimensional parameters affecting hydraulic jump roller length, including the Froude number upstream of a hydraulic jump $$\left( {Fr} \right) $$ , the ratio of sequent depths $$\left( {{h_2 }/{h_1 }} \right) $$ , and the relative roughness $$\left( {{ks}/{h_1 }} \right) $$ were used to generate four different GS-GMDH models, and the most accurate model is identified. The best new GS-GMDH model prediction statistics, including RMSE, MARE, and correlation coefficient are 1.816, 0.081, and 0.966, respectively, while the scatter index and BIAS values are 0.084 and 1.45, respectively. A partial derivative sensitivity analysis of the input parameters for the new model is also performed. The new model predictions are then compared with predictions of a number of other models. The superior performance of the new GS-GMDH over these existing models is illustrated.

Hydraulic jumps have complex flow structures, characterised by strong turbulence and large air contents. It is difficult to numerically predict the flows. It is necessary to bolster the existing computer models to emphasise the gas phase in hydraulic jumps, and avoid the pitfall of treating the phenomenon as a single-phase water flow. This paper aims to improve predictions of hydraulic jumps as bubbly two-phase flow. We allow for airflow above the free surface and air mass entrained across it. We use the Reynolds-averaged Navier–Stokes equations to describe fluid motion, the volume of fluid method to track the interface, and the k–e model for turbulence closure. A shear layer is shown to form between the bottom jet flow and the upper recirculation flow. The key to success in predicting the jet flow lies in formulating appropriate bottom boundary conditions. The majority of entrained air bubbles are advected downstream through the shear layer. Predictions of the recirculation region’s length and air volume fraction within the layer are validated by available measurements. The predictions show a linear growth of the shear layer. There is strong turbulence at the impingement, and the bulk of the turbulence kinetic energy is advected to the recirculation region via the shear layer. The predicted bottom-shear-stress distribution, with a peak value upstream of the toe of the jump and a decaying trend downstream, is realistic. This paper reveals a significant transient bottom shear stress associated with temporal fluctuations of mainly flow velocity in the jump. The prediction method discussed is useful for modelling hydraulic jumps and advancing the understanding of the complex flow phenomenon.

The information content of the classic equations describing the problem of forced hydraulic jumps in open channels is the subject of this paper. The forcing refers to designed structural composites to transform incoming supercritical flows into outgoing subcritical flows through hydraulic jumps. The complete flow history through such systems is described by two stable flow profiles, which are interlocked and one can jump to the other. The interlocked profiles underpin a hydraulic effect known as hysteresis with the prime feature of the dependence of flows on their past history. The paper develops an algorithm by using classic hydraulic equations alone to identify hysteresis by building on tacit knowledge already published. The algorithm reproduces the effects of catastrophe theory and shows that hysteresis has predictable configurations. It is validated for geometries with step-rises by using published experimental data; as well as a flume with abrupt contractions by authors’ experimental data.

Despite many deaths annually worldwide due to floods, no strategy exists to mechanistically map hydraulic hazards people face when entrained in a river. Previous work determined water depth–velocity product thresholds for human instability from standing or walking positions. Because whitewater rivers attract diverse recreation that risks entraining people into hazardous flow, this study takes the next step by predicting the hazard pattern facing people swept away. The study site was the 12.2-km bedrock–alluvial upper South Yuba River in the Sierra Nevada Mountains. A novel algorithm was developed and applied to two-dimensional hydrodynamic model outputs to delineate three hydraulic hazard categories associated with conditions for which people may be unable to save themselves: emergent unsavable and steep emergent surfaces, submerged unsavable surfaces, and hydraulic jumps. Model results were used to quantify exposure of both an upright and supine entrained person to collision and body entrapment hazards. Hazard exposure was expressed with two metrics: passage proximity (how closely a body approached a hazard) and reaction time (time available to respond to and avoid a hazard). Hazard exposure maps were produced for multiple discharges, and the areal distributions of exposure were synthesized for the river segment. Analyses revealed that the maximum hazard exposure occurred at an intermediate discharge. Additionally, longitudinal profiles of the results indicated both discharge-dependent and discharge-independent hazards. Relative to the upright body, the supine body was overall exposed to less dangerous channel regions in passage down the river, but experienced more abrupt encounters with the danger that did occur.

Stilling basins and hydraulic jumps are designers’ favorable choice for energy dissipation downstream of spillways and outlets. A properly designed stilling basin can ensure considerable energy dissipation in the short distance of a basin. In this study, experiments have been conducted to evaluate effects of a perforated sill and its position on the length of a favorable B-type hydraulic jump in a stilling basin. Perforated sills with different heights and ratio of openings were placed in different positions of the stilling basin. Tests were carried out for three tail water depths to assess the sensitivity of the jump to tail water. The hydraulic characteristics of the jump were measured and compared with continuous sill-controlled and free hydraulic jumps. Results of the experiments confirmed significant effect of the perforated sill on dissipation of energy and development of the jump in a shorter distance. Results are also presented in the form of mathematical models for estimation of the sill height, sill position, and basin length with the inflow measurable parameters of depth and velocity.

A hydraulic jump is the rapid transition from a supercritical to subcritical flow. This transition is characterized by large-scale turbulence and energy dissipation. Despite the importance of understanding the hydraulic jump to design hydraulic structures, few studies have aimed on hydraulic jumps in U-shaped channels. In this paper, the 3D pattern of hydraulic jumps in U-shaped channels is studied numerically. The variations of the flow free surface are predicted using the volume of fluid scheme. Also, the flow field turbulence is simulated using the standard $$k-\varepsilon $$ and RNG $$k-\varepsilon $$ turbulence models. According to the numerical modeling results, the standard $$k-\varepsilon $$ turbulence model estimates the flow characteristics with more accuracy. A comparison between the laboratory and numerical results shows that the numerical model simulates the flow field characteristics with good accuracy. For example, in the hydraulic jump model with a relative discharge $$({q=Q/{\sqrt{( {gD^{5}})}}})$$ equal to 0.321 and a Froude number $$({{F}_1})$$ equal to 4.85, the values of MAPE, RMSE and $${R}^{2}$$ are calculated 7.617, 0.022 and 0.989, respectively. Next, 45 numerical models are simulated in different hydraulic conditions and some relationships are provided for calculating the sequent depth $$({{h_2 }/{h_1 }})$$ , hydraulic length $$({{L_\mathrm{j}}/{h_1}})$$ and roller length $$({{L_\mathrm{r} }/{h_1}})$$ ratios by analyzing their results.

This technical note studies the supercritical junction flow occurring at the right-angled confluence of four equal-width channels in which two upstream channels carry flow towards the junction. The note seeks to investigate, firstly, the pertinence of a 2D shallow water equation model to reproduce the typical flow structures at the junction. The second objective is to build a computationally efficient model with more resolution applied at critical point i.e. junction and less in areas where the flow is primarily 1D i.e. channels and compare such model, named, ‘sparse’ with a uniformly meshed model regarding solution accuracy and computational efficiency. The results indicate that the sparse model is able to reproduce typical flow structures appearing at the channel junction in an adequate manner. The discharge distribution is fairly well predicted. The jump angles are almost the same in the two models as well as the location and size of the recirculation zones and the flow depth super-elevation areas. However, the two models diverge in the prediction of very small depths in the recirculation zone where the sparse model overestimates the depths. As regards, computational efficiency, the sparse model is found to be 61% more efficient than the uniform mesh model.

The large deformations associated with air and water interactions are critical factors that affect the hydrodynamic characteristics of hydraulic structures. As a type of Lagrange meshless particle method, smoothed particle hydrodynamics (SPH) has been shown to have many advantages when modeling the interface flow and tracing the free surface because the particles inherit the velocity, mass, and density properties. Significant theoretical and numerical studies have been performed recently in this area. In the present study, a two-phase SPH framework was developed based on these previous studies and we explored its capacity to capture the main features of large density ratio aerated flows. The cohesive pressure was included only in the momentum equation of the air phase for additional amendments to ensure the stability and accuracy of the two-phase SPH model. Three case studies were performed to test the performance of the two-phase SPH model. A convergence study demonstrated the need to balance the CPU time consumption and the real-time requirements. A dam-break simulation based on pressure variation in the air pocket showed the superior analytical performance of the two-phase model compared with the single-phase model. The results of a hydraulic jump simulation were compared with the theoretical results in order to understand the collision between the solid and liquid using the SPH method more clearly. Thus, the consistency between the simulation and the theoretical and experimental results demonstrated the feasibility and stability of the two-phase SPH framework.

Mountainous torrents often carry large amounts of loose materials into the rivers, thus causing strong sediment transport. Experimentally it was found for the first time that when the intensive sediment motion occurs downstream over a gentle slope, the siltation of the riverbed is induced and the sediment particles can move upstream rapidly in the form of a retrograde sand wave, resulting in a higher water level along the river. To further study the complex mechanisms of this problem, a sediment mass model in the framework of the Smoothed Particle Hydrodynamics (SPH) method was presented to simulate the riverbed evolution, sediment particle motion, and the generation and development of dynamic hydraulic jump under the condition of sufficient sediment supply over a steep slope with varying angles. Because the sediment is not a continuous medium, the marker particle tracking approach was proposed to represent a piece of sediment with a marked sediment particle. The two-phase SPH model realizes the interaction between the sediment and fluid by moving the bed boundary particles up and down, so it can reasonably treat the fluid-sediment interfaces with high CPU efficiency. The critical triggering condition of sediment motion, the propagation of the hydraulic jump and the initial siltation position were all systematically studied. The experimental and numerical results revealed the extra disastrous sediment effect in a mountainous flood. The findings will be useful references to the disaster prevention and mitigation in mountainous rivers.

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 (h 2/h 1) and relative roughness (ks/h 1) 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, h 2/h 1 and ks/h 1. 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.

The flow structure in the aerated region of the roller generated by breaking waves remains a great challenge to study, with large quantities of entrained air and turbulence interactions making it very difficult to investigate in details. A number of analogies were proposed between breaking waves in deep or shallow water, tidal bores and hydraulic jumps. Many numerical models used to simulate waves in the surf zone do not implicitly simulate the breaking process of the waves, but are required to parameterise the wave-breaking effects, thus relying on experimental data. Analogies are also assumed to quantify the roller dynamics and the energy dissipation. The scope of this paper is to review the different analogies proposed in the literature and to discuss current practices. A thorough survey is offered and a discussion is developed an aimed at improving the use of possible breaking proxies. The most recent data are revisited and scrutinised for the use of most advanced numerical models to educe the surf zone hydrodynamics. In particular, the roller dynamics and geometrical characteristics are discussed. An open discussion is proposed to explore the actual practices and propose perspectives based on the most appropriate analogy, namely the tidal bore.