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The development of pier scour in coastal environments severely affects the bridge's stability. Therefore, estimating pier scour around the vertical cylinder is important for the safety of the bridge structure. The estimation of pier scour depth in combined wave-current conditions has become a challenging task for researchers in recent times. The existing empirical formulations that calculate scour in the combined action of current and wave are scarce and may not always provide accurate results. Machine-learning (ML) techniques have become increasingly popular for their prediction capabilities in the fields of hydraulics and coastal engineering in recent years. Therefore, the present study aims to develop Boosting ML techniques (i.e., AdaBoost, XGBoost, CatBoost, and LightGBM) of ML to estimate pier scour in combined wave-current conditions. The non-dimensional parameters, such as Keulegan–Carpenter (KC) number, Relative flow velocity (Ucw), and Absolute Froude number (Fra), are used as input parameters, whereas scour depth (S/D) is the output parameter in Boosting ML models. The sensitivity analysis has been performed to demonstrate the relative importance of the input parameter on S/D. The performance metrics show that the XGBoost model with the input combination of Fra, KC, and Ucw provides the highest accuracy of 92.47% and outperforms SVM, CatBoost, AdaBoost, and LightGBM models. The XGBoost model also outperforms the existing empirical formulations. Therefore, it can be concluded that the XGBoost techniques can be used as a reliable, accurate, and alternative tool to estimate pier scour depth in the combined action of current and wave. [ABSTRACT FROM AUTHOR]

Follett et al. (2020, https://doi.org/10.1029/2020gl089346) demonstrated that a large wood jam can be modeled as a porous obstruction with momentum loss proportional to the number, size, and packing density of the logs and jam length. Poppema and Wüthrich (2024, https://doi.org/10.1029/2023gl106348) incorporated uniform flow Froude number, broadening the scope of our work. Here, we demonstrate that Froude number can be directly introduced to equations in the main body of Follett et al. (2020, https://doi.org/10.1029/2020gl089346), without requiring uniform flow. Based on this, we show that a managed increase in upstream depth is possible for conditions below a critical discharge, in which equilibrium upstream depth over uniformly distributed jams can be adjusted with inter‐jam spacing. This design could retain water in low flow conditions, allowing jams to act independently above critical discharge. Finally, we suggest that log orientation can be included in our model by varying both drag coefficient and frontal area perpendicular to the flow. Plain Language Summary: Logjams can increase upstream water surface elevation, creating an upstream pool with slower, deeper water. We demonstrated that the increase in water depth upstream of a logjam is related to the number, size, and packing density of the logs and the jam length. In this Reply to a Comment by Poppema and Wüthrich (2024, https://doi.org/10.1029/2023gl106348), we clarify that our prediction of upstream water depth does not depend on river steepness and sediment size. We go on to show that a progressive increase in upstream depth is possible under some low flow conditions, if logjams are spaced closely enough so that each logjam is impacted by its downstream neighbor. This arrangement could be used to design nature‐based solutions for water retention during drought. In response to Poppema and Wüthrich (2024, https://doi.org/10.1029/2023gl106348), we clarify the observed agreement between our model and a similar model by Schalko et al. (2018, https://doi.org/10.1061/(asce)hy.1943‐7900.0001501) and suggest that the effect of log orientation can be included in our model by varying the drag coefficient in addition to the frontal area perpendicular to the flow. Key Points: Response to Comment by Poppema and Wüthrich (2024, https://doi.org/10.1029/2023gl106348), which re‐writes backwater rise equations in Follett et al. (2020, https://doi.org/10.1029/2020gl089346) using Froude numberFollett et al. (2020, https://doi.org/10.1029/2020gl089346) does not require river slope & roughness, as implied in Comment. We show use of Froude number with main text equationsA series of jams can generate a progressive increase in water depth, allowing for water storage during low flows below a critical discharge [ABSTRACT FROM AUTHOR]

Follett et al. (2020a, https://doi.org/10.1029/2020gl089346) developed an analytical model to predict backwater rise by log jams, using the size and packing density of logs and the jam length, as well as river slope and bed roughness. We show that the model formulas can be rewritten using the Froude number instead of river slope and roughness, thus improving their applicability in engineering practice. The equation terms and results of Follett et al. (2020a, https://doi.org/10.1029/2020gl089346) are found to be similar to those of the empirically derived formula by Schalko et al. (2018, https://doi.org/10.1061/(asce)hy.1943‐7900.0001501). However, some differences are identified, calling for further study. Most notably, these distinctions pertain to the effect of accumulation porosity, with additional minor differences in the exponent of the Froude number. Lastly, model implications for some broader applications are explored, showing a methodology to calculate the representative log size for log mixtures, and the expected effect of log orientation on backwater rise. Plain Language Summary: Accumulations of wood in rivers (log jams) can block the flow and thereby cause water level rise. Follett et al. (2020a, https://doi.org/10.1029/2020gl089346) developed a theoretical model to predict how this water level rise depends on log jam properties and local river conditions. For the local river conditions, they used the river slope and bottom roughness. In this comment, we show that the Froude number can be used instead, with exactly the same result. The Froude number is a dimensionless number that depends directly on the local river conditions, making the adapted formula easier to apply in practice. The resulting formula shows good agreement with an earlier one based on experimental work by Schalko et al. (2018, https://doi.org/10.1061/(asce)hy.1943‐7900.0001501). Still, some differences were found that raise questions. Most notably, the formulas differ for the effect of accumulation porosity. This becomes especially clear when logs are packed closely together. Next, model implications for slightly different settings than those studied by Follett et al. (2020a, https://doi.org/10.1029/2020gl089346) were explored. This showed how to determine the average log size for a mixture of logs with different sizes, and how the expected water level rise changes with log orientation. Key Points: Follett et al. (2020a, https://doi.org/10.1029/2020gl089346) predicted backwater rise by log jams using river slope and roughness. We show the Froude number can be used insteadBy using the Froude number, the link to the local river conditions becomes stronger, improving formula applicability in engineering practiceThe resulting formula is shown to be similar to earlier empirical work. But differences in jam porosity effects call for further study [ABSTRACT FROM AUTHOR]

Improper disposal of wipes results in significant sewer blockages, especially during the COVID-19 pandemic. However, the formation and growth of wipe blockages and their backwater effect in sewers have not been studied. This study employed a vertical rod to simulate sewer obstructions such as tree root intrusion in sewers. Stochastic interactions among wipes, turbulent flow, and the obstruction were experimentally studied in a circular pipe (diameter D = 25 cm), with systematic variations in flow Froude number (Fr), wipe length (L), flow depth (H), submerged rod length (hrod), and rod diameter (drod). It was found that the mean area ratio of wipes (ratio of projected area in water to original surface area of the wipe) ranged from 0.14 to 0.30, indicating the distorted shapes in water. The entrapment probability P (ratio of entrapped to released wipes) for a single wipe was closely correlated with Fr, H/D, L/H, drod/H, and hrod/H, with a maximum value of 0.90. With the increase in the number of wipes released, the influence of the obstruction on wipe accumulation processes became negligible. New equations were developed for characterizing entrapment probability, blockage length, and backwater rise, which can be used to predict the development of wipe blockages and sewage levels. Based on the research findings, policy and management strategies were proposed for wipe blockage reduction in sewers. [ABSTRACT FROM AUTHOR]

Air entrainment is a concern of paramount importance in the process industries, including nuclear power plant, hydraulic machines, water treatment plants, hydrocyclones, and power generation turbines. The ingression of the air into the equipment results in the reduction of the hydraulic efficiency. In the current paper, a combined experimental and numerical investigation has been performed using the commensurate high-speed photography and volume of fluid-based numerical simulations. The mitigation strategies for the reduction of the air ingression include the reduction of the critical height by increasing the number of intakes and changing the intake configuration. The viability of these solutions and the hydrodynamics behind the interfacial evolution leading to the air entrainment have been studied in detail. The air ingression progresses with the establishment of the flow patterns ranging from bubbly flow, slug flow, to the annular flow. The reduction of the critical height can be accomplished by increasing the number of intakes for the same cross-sectional area leading to the reduction in the Froude number F r = V down / g H local < 1 . Further increasing the number of intakes beyond four leads to the minimal reduction in the critical height in the tank. [ABSTRACT FROM AUTHOR]

We propose an asymptotic method to solve the problem of flexural-gravity wave scattering by an ice sheet of variable geometry in the presence of uniform currents. The significance of the article resides in the development of first and second-order solutions via the use of asymptotic expansion and the Fourier transform technique. We consider two different shape functions for the plate geometry, namely, Gaussian and Gaussian oscillatory. For both shape functions, the first and second-order solutions result in a major impact of depth Froude numbers in hydrodynamic coefficients, emphasizing the crucial function of the higher-order solutions in understanding the current responsiveness. We also observe the occurrence of Bragg resonance for the Gaussian oscillatory shape. The depth Froude number alters the frequency of wave components that are most reflected, and wave action conservation causes a rise in the energy of reflected waves. The depth Froude numbers can induce a unique minimum in reflection coefficient, which is close to 0. An examination of plate deflection reveals that the elevation amplitude is substantially higher near the point where there is a peak of elastic plate's shape. The pressure exerted by the plate is also concentrated near this point, highlighting the significance of the elastic plate's shape. The collective numerical observations for both shapes provide insight into resonance phenomena, the role of plate shape, and the intricate relationship between wave characteristics and varying plate properties. The findings from this study could assist geologists and marine engineers in designing and managing ice sheets, ports, and harbor infrastructure. [ABSTRACT FROM AUTHOR]

Raco is a local wind occurring in central Chile where the Maipo River Canyon exits into the Santiago valley. The intensification of the easterly down-canyon flow starts at any time during some cold season nights, accompanied by increases in temperature and drops in humidity. The hypothesis of the raco being a gap wind controlled by the narrowest section in the 12-km canyon exit corridor is tested with data from two events in July 2018 and July 2019. The data are analyzed in the framework of hydraulic theory, and a subcritical-to-supercritical transition is documented to occur at the narrows of the gap where the Froude number is close to unity, confirmed by radiosondes launched in the narrows in 2019. For the raco flow, the sum of potential and kinetic energy is conserved upstream of the narrows, while the acceleration occurring farther downstream loses a large fraction of energy to frictional dissipation. The raco events occur under the influence of regional subsidence, but a differential nocturnal warming of the in-canyon air mass is responsible for a pressure gradient driving the raco. In the 2019 case, a ceilometer mounted on an instrumented pickup truck documented the structure and movement of the interface between the raco air and the cold-air pool (CAP) existing over the valley to the west. Together with a radiosonde launched near the CAP–raco surface front, the observations reveal the intense shear-driven mixing taking place at the interface and the factors supporting the establishment of a stationary front. [ABSTRACT FROM AUTHOR]

The advent of undercuts and humping limits the applicable speed of deep-penetration laser welding. Recent findings additionally show that a significant change of the keyhole's shape is associated with the occurrence of undercuts. Considering that undercuts and humping are melt flow–induced defects, this leads to the question of how the geometry of the keyhole and the melt pool influence the melt flow and vice versa. In this work, the Froude number was used to characterize the melt flow around a keyhole. X-ray images of the keyhole and cross-sections of the weld were therefore used to determine the geometrical boundaries of the melt flow, to estimate the average melt velocity around the keyhole, and finally determine its Froude number. The flow around a cylindrically shaped keyhole was found to always be subcritical, whereas supercritical melt flow was observed around the elongated keyholes that are formed at higher welding speed. The findings may be interpreted in the sense that the elongation of the keyhole is a consequence of a supercritical stream of the melt flowing underneath and around the keyhole. This perception is consistent with the long-known experience that humping may be avoided by reducing the flow speed of the melt by widening the melt pool surrounding the keyhole (e.g., by means of beam shaping) and suggest a new explanation for the elongation of the keyhole at increased welding speed. [ABSTRACT FROM AUTHOR]

Accurate prediction of blockage conditions or the minimum transport boundary is essential for the reliable design and operation of a pneumatic powder conveying system. Many existing empirical models for minimum transport boundary do not consider essential powder properties and operating conditions, such as loose poured bulk density, particle size, and air density. Based on the conveying results of 13 different powders, this paper has developed a new empirical model for the minimum transport boundary. The model includes a Froude number based on particle size and bulk density and a dimensionless gas density term, which makes the model inherently adaptable to variations in powder properties and operating conditions. Results of validation show that the new model provides a significantly improved prediction of minimum Froude Number (in the range of 7 to 13% relative error only) compared to the existing models, which provided relative errors in the range of 19 to 67%. [ABSTRACT FROM AUTHOR]

Physical and flow property tests were carried out on eight pharmaceutical powders. The results obtained from heap analysis and shear cell testing have been compared. A relationship to represent the static angle of repose has been developed using a bulk powder-based Froude number and fine size. The experimental results and predictions for a range of bulk properties have shown that the values of static angle of repose decrease with an increase in the value of bulk powder Froude number, increase in particle shape factor and decrease in the median to fine ratio. Out of all the dimensionless parameter groupings, the particle shape factor strongly influences the static angle of repose, as indicated by its larger absolute value of the exponent in the power function format relationship. The relationship can be used as a techno-economic optimization tool for particle processing/synthesis while maintaining the desired powder flowability. [ABSTRACT FROM AUTHOR]

This study experimentally investigates the hydrodynamic forces acting on wood debris accumulations. Tests were performed under steady subcritical flow conditions by letting debris elements accumulate against an obstacle. We analyze the influence of a variety of variables involved in the problem, namely the Froude number, the blockage ratio, the geometric parameters of the dam, its porosity, and the debris type. Resulting forces are expressed through a typical drag coefficient formula, where the coefficient depends on the Froude number and the blockage ratio, but is independent of the geometric characteristics of the debris accumulation. The model is validated against literature data, providing both best-fit and safe-side predictors. Practical Applications: Wood debris can build up on bridge piers and decks, which increase the water's force on these structures. In this paper, we offer a straightforward method to estimate these forces. We have calibrated an empirical model using data from laboratory experiments and checked its accuracy against information from existing studies. With this model, one can input the basic characteristics of the flowing water (such as its depth, width, and speed) and the size of the debris pile facing the flow. The model then provides the drag coefficient, which, in turn, allows determining the drag force acting on the debris pile. [ABSTRACT FROM AUTHOR]

This study conducted experiments to investigate the impact of bottom obstacles, specifically broad-crest weir-type and cylindrical obstacles, on the flow within a sewer pipe. It was observed that these two types of obstacles, when possessing the same cross-sectional area and length, exhibited nearly equivalent hydraulic responses for both supercritical and subcritical flows. The obstacle height was found to be the primary factor responsible for choking and the transition between different flow regimes. The results of the one-dimensional analysis show that the threshold value of obstacle height depends on the approaching flow conditions, including the Froude number and the filling ratio that is defined as the flow depth to the pipe diameter. In the context of a partially blocked sewer, the relationships established by using the one-dimensional model between the size of the bottom obstacle and the inflow characteristics enable the identification of flow regimes, assessment of reduced hydraulic capacity, and evaluation of local energy loss. The findings of this study elucidate the hydraulic behavior of obstructed sewers, contributing to the development of more effective strategies for the identification of obstructions through monitoring data. [ABSTRACT FROM AUTHOR]

Planar wall plumes are gravity-driven flows where a fluid of lower (or higher) density than the ambient rises (or lowers) along a vertical or inclined wall. This study investigates planar wall plumes at five different wall slopes, ranging from a vertical wall (θ = 90 °) to a shallow inclination of θ = 3 ° , using highly resolved direct numerical simulations. The three-dimensional turbulent structure of these supercritical flows is investigated in detail along with the streamwise evolution of the depth-averaged quantities. Simulations were performed in very large domains in order to focus attention on the behavior of the plumes in the near self-similar state, far downstream of the inlet. In the self-similar state, key quantities such as the entrainment rate, the basal drag coefficient, the Richardson number (or equivalently the Froude number), and the shape factors reach constant values, which dependent only on the slope. The present simulations, along with earlier results for subcritical currents at shallower slopes, provide a complete description of this dependency. [ABSTRACT FROM AUTHOR]

This numerical study investigated the influence of the heave plate's diameter on the amplitude of the transitional motions of a marine circular cylinder (MCC) with a low aspect ratio under the marine current and regular waves. Due to the experimental model of the straked MCC, different diameters of the circular heave plate were chosen to be installed at the keel of the 3-straked MCC. In this numerical study, the diameter of the heave plate varied from 1.2 to 1.6 DMCC, while other parameters, such as reduced velocity (VR), Reynolds (Re) number, and Froude number, were kept constant. In this study, the transitional motions, including surge, sway, and heave, were analyzed. The results showed that increasing the heave plate's diameter decreased the amplitude of the transitional motions in both marine current and regular waves. Also, the finding revealed that the heave plate not only reduced the amplitude of the heave motion but also decreased the amplitude of surge and sway motions. Moreover, the outcomes indicated that the heave plate's diameter increased by approximately 20%–40% more than the MCC's diameter. This caused the smaller amplitude of the transitional motions under both marine currents and regular waves. [ABSTRACT FROM AUTHOR]

During mining activities, deep-sea mining vehicles (DSMVs) are highly susceptible to causing massive disturbance to the seafloor sediment, resulting in the formation of plumes due to underlying turbulence and currents. To gain a better understanding of the dispersion mechanism of sediment plumes, both experimental and numerical methods were employed. The numerical model was primarily used to characterize the solidity and liquidity of the sediment plume through volume of fluid and discrete phase model methods, respectively. The experimental data were validated against the numerical results. The plume distribution was studied in physical experiments for three different DSMV parameters. The study findings indicate that the discharge of the plume in the near field occurs in three stages due to a combination of plume release inertial forces, negative buoyancy in the water column, and wall restoring forces. Additionally, the increase in the travel velocity of the DSMV reduces the propagation of the plume in the direction of discharge and instead increases its lateral spread across the bottom surface. As the size of the DSMV decreases in three dimensions, changes in the vertical vortex structure become dominant in the plume distribution. This leads to a reduction in the length of the plume head and a faster sinking of the plume. When the wake Froude number Frw is between 0.7 and 6.8, representing the wake turbulence effect of DSMV on plume discharge, the diffusion width of the plume on the bottom surface is linearly related to Frw. [ABSTRACT FROM AUTHOR]

The impact of pipe inclination angle on oil-water flow regimes transition boundaries is vital in various engineering applications, including pipeline and separator inlet design. Understanding this influence is crucial for identifying alternative and optimal designs. The standard way of presenting oil and water superficial velocities on 2D flow pattern maps doesn't consider how the flow pattern varies with pipe tilt angle. This article aims to clarify how the angle of pipe inclination affects oil-water flow regime transitions. This method uses pipe inclination angle as a direct representation, with the angle shown on the x-axis of a 2D flow pattern map, which has not been done before in literature. The y-axis, or ordinate, is a dimensionless number that accounts for mixture velocity, fluid densities, and pipe diameter. Two dimensionless numbers were utilized. The Froude number based on mixture velocity, Fr M, and the Reynolds number (Re OM) based on mixture velocity and oil properties, are plotted against pipe inclination angle. The evaluation and validation of the proposed methods for the effect of the inclination angle were performed using a database of more than 10,000 points established from studies reported in the literature. The findings show that both the Dispersed (DF) and Semi-Dispersed flow regimes (SDF) exhibit higher Fr M values than smooth stratified regardless of the pipe's incline. Moreover, the spreading area is symmetric around the horizontal line which means that the DF and SDF can be observed at similar Fr M for both positive and negative inclinations. Focusing horizontally, Fr M is highest for ST-MI, lower for SW, and lowest for ST. This paper also presents and demonestrates a case study showcasing a new application for flow pattern maps, illustrating their potential in design purposes. [ABSTRACT FROM AUTHOR]

How turbulent convective fluctuations organize to form larger-scale structures in planetary atmospheres remains a question that eludes quantitative answers. The assumption that this process is the result of an inverse cascade was suggested half a century ago in two-dimensional fluids, but its applicability to atmospheric and oceanic flows remains heavily debated, hampering our understanding of the energy balance in planetary systems. We show using direct numerical simulations with spatial resolutions of 122882 × 384 points that rotating and stratified flows can support a bidirectional cascade of energy, in three dimensions, with a ratio of Rossby to Froude numbers comparable to that of Earth's atmosphere. Our results establish that, in dry atmospheres, spontaneous order can arise through an inverse cascade to the largest spatial scales. [ABSTRACT FROM AUTHOR]

Sills and baffles are appurtenances used to stabilize hydraulic jump in a stilling basin. The force acting on these appurtenances are characterized by the drag coefficient (CD). This paper describes experimental methods carried out in a rectangular channel to analyze the drag characteristics of sill and baffles in free (unsubmerged) and submerged hydraulic jumps. The sills and baffles were designed as per the USBR type III stilling basin guidelines. A calibrated loadcell connected to an Arduino board was used to measure the drag force. Errors in measurements are limited to 1%. The drag co-efficient was obtained for different Froude numbers (F1=U1/√gy1) pertaining to strong jump (4.5–9) for different relative position of sills (xS/y2) and baffles (xb/y2) from the nozzle of the sluice gate. Both forced (unsubmerged) and submerged jumps were investigated. It is seen that the drag coefficient of appurtenances in submerged jumps were lower than those in free jumps. This may be attributed to the reduction in wake size in submerged jumps. Comparisons of the experimental results of the sill with the previous theoretical studies are reasonable. [ABSTRACT FROM AUTHOR]

Dissolved oxygen (DO) is an important parameter in assessing water quality. The reduction in DO concentration is the result of eutrophication, which degrades the quality of water. Aeration is the best way to enhance the DO concentration. In the current study, the aeration efficiency (E20) of various numbers of circular jets in an open channel was experimentally investigated for different channel angle of inclination (θ), discharge (Q), number of jets (Jn), Froude number (Fr), and hydraulic radius of each jet (HRJn). The statistical results show that jets from 8 to 64 significantly provide aeration in the open channel. The aeration efficiency and input parameters are modelled into a linear relationship. Additionally, utilizing WEKA software, three soft computing models for predicting aeration efficiency were created with Artificial Neural Network (ANN), M5P, and Random Forest (RF). Performance evaluation results and box plot have shown that ANN is the outperforming model with correlation coefficient (CC) = 0.9823, mean absolute error (MAE) = 0.0098, and root mean square error (RMSE) = 0.0123 during the testing stage. In order to assess the influence of different input factors on the E20 of jets, a sensitivity analysis was conducted using the most effective model, i.e., ANN. The sensitivity analysis results indicate that the angle of inclination is the most influential input variable in predicting E20, followed by discharge and the number of jets. [ABSTRACT FROM AUTHOR]

Understanding the drivers of distribution and assemblage composition of aquatic organisms is an important aspect of management and conservation, especially in freshwater systems that are inordinately facing increasing anthropogenic pressures and decreasing biodiversity. For stream organisms, habitat conditions during high flows may be impossible to measure in the field, but can be an important factor for their distribution, especially for less mobile organisms like freshwater mussels. Hence, the objective of this study was to use a two dimensional HEC-RAS model to simulate hydraulic conditions during high and baseline flows (flows approx. 10–600 x and 0.7 x median daily flows respectively) in a 20 km segment in the San Saba River, Texas in combination with existing mussel survey data from 200 sites (collected every 100m) to 1) examine whether hydraulic conditions differed between areas of increased mussel richness and diversity (referred to as hotspots) and other sites, and 2) understand how well site occupancy and species abundance could be explained by hydraulic conditions occurring under different flow conditions. The results showed that richness and diversity hotspots occurred in deeper areas with lower shear stress, stream power, and Froude number during both high and low flows. Occupancy could be predicted with 67–79% accuracy at the site scale and 60–70% accuracy at the mesohabitat scale (∼20 to 1200 m long). In addition, hydraulic conditions across flow scenarios explained up to 55% of variation in species abundances, but predictions were less successful for species often observed to occupy micro-scale flow refuges such as bedrock crevices. The results indicate that pools may serve as important refuge for all species during both high and low flow events, which may be relatively unique to bedrock-dominated systems. Understanding hydraulic conditions that occur at extreme flows such as these is important given that the frequency and magnitude of such events are increasing due to climate change. [ABSTRACT FROM AUTHOR]

Periodic shock waves of roll waves may cause the flow to jump over the canal bank, increase soil erosion, and enhance the destructive power of debris flow. This paper focuses on the spatiotemporal changes in waveform, velocity, discharge, shear stress, and Froude number during the development process of roll waves, taking the non-uniform flow as the initial condition. This work studied numerically the influence mechanism of different variables on the development process of roll waves based on steep slope shallow water equations. The roll wave is unstable when the disturbance amplitude is too large. By reducing the inlet velocity, increasing the disturbance wavelength, and reducing the roughness coefficient, it can make the roll wave stable. Reducing the inlet velocity not only reduces the frequency of the shock wave but also keeps the wave crest from rising. Under different boundary conditions of disturbance amplitude, the crest growth rate (crest water depth difference/crest distance difference) of the roll wave development segment at a certain time is almost consistent. For different initial water depths, there is overlap in the roll wave development segment at a certain time. Under the initial condition of non-uniform flow, the congestion at the inlet means that the initial water depth is less than the normal water depth, and the decline of the water depth at the inlet means that the initial water depth is greater than the uniform water depth. [ABSTRACT FROM AUTHOR]

This paper comprehensively investigates the non-axisymmetric cavity dynamics of a vertically entering sphere under the influence of nearby side-walls through experimental, numerical, and theoretical analyses. Initially, we explore the characteristics of cavity evolutions with the sidewall effect. The emergence of a twin-vortex during cavity pinch-off is observed, and detailed numerical simulations provide insights into its underlying mechanisms. Both the dimensionless distance (λ) and the Froude number Fr significantly influence the pinch-off type. A phase diagram in the λ − F r parameter space is presented, revealing the interplay between these variables. Moreover, we investigate the sidewall effect on the pinch-off time and location at low Froude numbers. The findings indicate that as λ decreases, both the pinch-off time and depth of the cavity increase. Generally, the wall effect is relatively weak when λ exceeds 4. Additionally, the pinch-off time can be described by τ = k r / g , with the constant k determined by λ. Utilizing 2D cavity theory, we estimate the pinch-off time of the water entry cavity with the sidewall effect, revealing a consistent collapse behavior with the mechanics of a two-dimensional cavity. [ABSTRACT FROM AUTHOR]

This paper delves into the dynamics of a sphere entering flowing water at varying impact velocities and flow speeds. Using a high-speed photography system and image processing, we track the cavity evolution and trajectory. Flowing water is observed to tilt the cavity and postpone its detachment from the free surface. Beyond surface sealing, we identify a flowing-induced pinch-off phenomenon during water entry, marking a transition in closure regimes. This transition establishes a threshold impacting cavity tilt angle and pull-away length. By mapping the phase diagram of flow Reynolds number (Rew) against impact Froude number (Fr), we classify partial surface seal, pinch-off, and surface seal into distinct regimes. The Fr1/3 law effectively predicts the rising trend of cavity depth (H) and pinch-off depth (Hp) in flowing water. However, the Hp/H ratio differs from that reported in existing literature. [ABSTRACT FROM AUTHOR]

Planetary boundary layer (PBL) flow over complex terrain during a cold surge event was investigated using 3-hourly radiosonde measurements in upwind, near ridge, and downwind locations of mountains in the northeastern part of Republic of Korea and using a high-resolution (333-m) numerical simulation. A cold surge occurred on 23 January 2018 and lasted for 4 days. We analyzed onset day of the cold surge when air temperature dropped rapidly. Analysis of the radiosonde data shows that the PBL was characterized by an adiabatic layer with strong capping inversion in early morning and evening as well as during daytime in the upwind and near-ridge sites. The PBL flow at the near-ridge site was strongest among three sites except at 0600 local standard time (LST) when the PBL flow in the lee was strongest. We performed high-resolution (333-m) numerical simulations using the Weather Research and Forecasting (WRF) model. The adiabatic PBL in the upwind site at 0600 LST was simulated, although its depth was underestimated. The model reproduced the strong low-level wind at 0600 LST and large wind shear during the daytime in the lee, but it did not capture the exact timing of the large wind shear. The model showed overall good performance in simulating the vertical profile of the virtual potential temperature and wind below 2 km above ground level at the three sites, with a high index of agreement (IOA) except for the wind at 1200 and 1500 LST in the lee. To examine the cause for the different behavior of PBL flow in the lee of mountains between 0600 LST and the daytime, we calculated the Froude number for PBL flow using radiosonde measurements based on reduced gravity shallow water (RGSW) theory. At 0600 LST, the upwind Froude number F0 was close to 1, while during the daytime, it was much lower than 1. The observed lee flow behavior was consistent with the flow regime change of a single layer over an obstacle with changing F0; the flow with a propagating lee jump changes into that with a stationary lee jump with decreasing F0. Numerical simulation shows that the steepening of streamlines of lee-wave field leads to a jump-like structure in the lee of mountains during the daytime. [ABSTRACT FROM AUTHOR]

This work presents an experimental study of the fluctuating properties of hydraulic jump rollers for high-Froude-number and pre-aerated inflow conditions, to investigate the validity of empirical relationships in the literature that are derived typically from experiments for smaller Froude numbers and clear-water approach flows. The jump roller fluctuations are evaluated in terms of the dimensions of the roller surface profile, the fluctuation magnitudes and frequencies of the instantaneous jump toe positions and water elevations, including at the tailwater surface, and the formation frequency and advection velocity of internal vortices in the shear layer. The effects of pre-aeration are found primarily in the length-scale properties such as jump length and surface fluctuation magnitudes, while the time-scale properties such as characteristic frequencies of the unsteady motions are not affected. Extrapolation of existing quantitative prediction of jump roller dynamic properties to high-Froude-number flow conditions should be performed carefully. An assessment of the fluctuating bubble counts within fixed time intervals yields close frequencies between the bubble grouping motions in the shear layer and the jump toe and tailwater wave motions, thus implying possible correlations between the roller surface deformations and air entrainment. [ABSTRACT FROM AUTHOR]

Over the past decades, a variety of ice control structures (ICSs) have been designed and built, but to date, there has been no systematic evaluation of the effectiveness of these structures. To achieve this objective, first an understanding of the interaction between different ice processes and the ICSs must be established. For this purpose, a total of four ICSs located in the province of Québec were monitored during the 2021–2022 winter. The results showed that the ice jam holding time could vary from 1.5 to 68.5 h. The release of the jam was mechanically driven when the ratio of release to initiation Froude number was higher than one and was thermally driven when this ratio was lower than one, and the water temperature increased between initiation and release. Also, as the ratio of the total pier spacing to upstream river width increased, the holding time decreased. [ABSTRACT FROM AUTHOR]

Effects of bed material and downstream flow depth on bed evolution in a right-angled channel confluence were studied through laboratory experiments. Velocity field, water surface elevation, and bed profile were measured intermittently until the flow attained equilibrium. Sediment discharges at various locations of the confluence were estimated from bed levels. Six prominent bedforms were identified, and their characteristics were quantified. The sediment discharges from different channels were initially high but decreased to approximately zero as the flow attained equilibrium. Downstream flow depth influenced overall sediment transport in the system, including the main features of bed morphology. Overall erosion in the confluence reduced as the particle size of the bed material increased. In addition, the maximum scour depth occurred at the confluence edge, and, due to the sharp corner of the confluence, its location did not change with time. Results from the present experimental study can help validate numerical models and assist in the design of a right-angled confluence. This study is related to the hydraulics of man-made confluences with mobile beds and can be useful in the following practical applications. More accurate numerical models to predict maximum scour, bed morphodynamics, and sediment transport in man-made confluences can be developed using the detailed bed profile measurements at different time instants presented in this study. Note that available numerical models use sediment discharge formulas (e.g., Meyer-Peter-Muller, Van Rijn), which are for sediment flows in straight channels. The interplay between the three-dimensional flow field, developed bed shear stress, and sediment discharge can be explored. In addition, A man-made confluence with the mobile bed can be designed with findings from the present study. The bedforms corresponding to equilibrium flow depend on discharge ratio, confluence angle, flow conditions at the exit channel, and bed material characteristics. The major bedforms can be incorporated into the confluence geometry. [ABSTRACT FROM AUTHOR]

An air pocket is very likely to be trapped in a downward-sloping pipe (DSP) when water fills an undulating pipeline consisting of a series of inclined U-shaped pipes. To investigate the entrainment and evolution behavior of the entrapped air pocket, a series of experiments was carried out using a self-built inclined U-shaped device. The results show that at the junction between the DSP and the upward-sloping pipe (USP), the water phase forms a liquid accumulation. In addition to the agreed mechanism of liquid film jet shear and turbulent pulsation, the initiation of air entrainment is promoted further by the unique entraining effect of the reverse upward movement of the liquid accumulation in the DSP. Based on this, the flow patterns in the DSP are classified into four categories, namely single long slug flow (SLSF), unsteady transitional flow (UTF), quasi-slug flow (QSF), and plug flow (PF). Among them, UTF identified in this paper is a new and unique flow pattern for U-shaped pipe. Due to the development of UTF, the additional head loss of the air pocket and the critical Froude number required to completely remove the air pocket are increased. The effects of pipe inflow Froude number, liquid film Reynolds number, and upward-inclination angle on flow pattern transition, bubble movement, and air removal are explained and discussed. [ABSTRACT FROM AUTHOR]

This document discusses the article "Estimating Particle Froude Number of Sewer Pipes by Boosting Machine-Learning Models" by Deepti Shakya, Mayank Agarwal, Vishal Deshpande, and Bimlesh Kumar. The authors conducted a study to determine the effectiveness of different boosting machine-learning models in estimating the minimum velocity required to prevent sedimentation in sewer pipe beds. They found that the boosting models performed better than existing ones, but the discussers point out some important considerations to improve the results, including errors in the equations used for comparison. The document also discusses the use of machine learning models to predict the particle Froude number in sewer systems and suggests incorporating more recent data for improved accuracy. [Extracted from the article]

The present research used a combination of experimental and numerical methods to investigate energy dissipation blocks of different heights placed downstream of a sluice gate in an open channel flow. Numerical model simulations were performed using a 3D computational fluid dynamics (CFD) technique, using the Reynolds-averaged Navier-Stokes (RANS) equations with the volume of fluid (VOF) and k-ε turbulence models. The accuracy of the numerical model and the grid sensitivity was assessed according to a recommended procedure in the literature. Different hydraulic and geometry conditions were investigated to understand the energy dissipation behaviour of the blocks. The hydrodynamic effects of different block spacings, heights and configurations were analysed by means of CFD simulations. The results show that the variable size blocks have a high energy dissipation efficiency in sluice gate flows, particularly at high Froude numbers. The energy dissipation efficiency of the blocks downstream of a sluice gate can reach up to 55% for high discharges (Q = 35 L/s). Interestingly, the energy dissipation performance of small gate openings exceeds that of large gate openings, reaching a peak efficiency of 40% for the same discharge. In addition, the block spacing has a minimal effect on the energy dissipation, while smaller block spacing results in a smoother water surface profile. [ABSTRACT FROM AUTHOR]

The gas-liquid flow regimes transition mechanism and bubble behavior in gas-liquid two-phase impinging jet reactor are studied by numerical method. The liquid phase velocity, gas-liquid flow regimes, bubble behavior in the impinging reactor under different gas and liquid velocities are analyzed to explore. The vortex in flow field changes periodically, and the period is 7.5 s. According to the dispersion mode of bubbles in the reactor, the gas-liquid flow regimes can be divided into three regimes: cluster upflow, gradual dispersion and complete dispersion. The critical condition equations of flow regimes transition are established combination of Flow number (Fl) and Froude number (Fr). The distribution range of bubble diameter in the reactor increases with the increase of gas velocity and decreases with the increase of liquid velocity. The turbulent kinetic energy, turbulent dissipation rate and the velocity in the flow field are gradually weakens from the impact center to the radial direction. Based on dimensionless analysis, the mathematical model of bubble Sauter diameter is established to predict bubble Sauter diameter accurately. This research provides a theoretical basis for the amplification and optimization of reactors. [Display omitted] • The gas-liquid two-phase impinging jet reactor was designed by combining bubbly jet and impinging stream. • Flow regimes in gas-liquid two-phase impinging jet reactor were divided by the bubbly jet motion behavior. • The critical condition equations of flow regimes transition were established combination of Flow number and Froude number. • The dimensionless model was provided to predict bubble Sauter diameter. [ABSTRACT FROM AUTHOR]

Steep creek hazards are characterised according to their solid fraction, νs, which governs the flow dynamics. To arrest these hazards, rigid multiple barriers are installed along a channel. However, existing design guidelines are deficient because the fundamental overflow and landing mechanisms are not well understood. In this study, experiments were conducted using a 5 m long flume to model the impact of flows with different νs values on a rigid barrier. By varying the νs of sand–water mixtures, the dynamics of different steep creek hazards were modelled. The barrier height was varied to obtain barrier Froude numbers Frb (ratio of flow inertia to potential energy related to barrier height) from 0·7 to 3·4. Results show that barriers should be designed so that Frb < 1, which leads to downward overflow with reduced landing distances. In addition, the landing distance for the watery flows (νs = 0 to 0·1) is up to 87% longer than that of dry granular flows. This implies that the design spacing between barriers should cater for different types of steep creek hazards and Frb. An existing framework for multiple barriers is modified to provide guidance on the selection of the barrier height using the Frb. [ABSTRACT FROM AUTHOR]

In this study, the critical submergence of deep well pumps is analyzed. The critical submergence, which is an important parameter for centrifugal pumps and water intakes that usually have a certain diameter, is determined using dimensionless quantities. The innovative aspect of this study is that three different water inlet opening models are created for two shaft pumps with different nominal diameters, these models are related to the water inlet diameters and the critical submergence is defined using dimensionless quantities. The critical submergence of the pumps was determined using a vacuum measurement method and the critical submergence of each model at different flow rates was compared with Froude number dependent submergence equations developed by other researchers. The aim of this study is to determine the critical submergence of the pumps and to use the flow models developed at these depths with the aid of mathematical equations to ensure the operation of the pumps in the reliable zone (vortex-free). The physical models were found to be effective for vortex formation depth and vortex shape. The physical models found Fcr (critical Froude number) ≤1.40 for pump P1 and Fcr ≤1.44 for pump P2, these values can also be used to determine the suction lift of the pumps. The critical Weber and Reynolds numbers decrease as the water suction area of the pumps increases. Considering the depth of vortex formation, it would be appropriate to use the original (D0) physical models for both pumps. As a result, dimensionless quantities can be used to determine the critical submergence of deep well pumps. [ABSTRACT FROM AUTHOR]

The underwater vehicle is subjected to complex hydrodynamic loads during water-exit process, which seriously affect the structural strength and water-exit stability of the vehicle. This paper investigates the effect of high-pressure venting conditions on the dynamic evolution characteristics of the cavity during the completely free water-exit of a vehicle based on self-designed experiments. Some novel phenomena are found in the experiment, and the hypothesis of constant acceleration is established to explain the formation mechanism. The results reveal that the reentrant jet is the main factor influencing the pattern of cavity development and causes great differences between the partial and supercavity states. The balance between the initial cavity volume increase and the gas leakage rate results in the fact that increasing the launch Froude number in the partial cavity state does not cause significant changes in the cavity size. There is a stable interval between 0.0038 and 0.03 for the effect of gas entrainment coefficient on the development of the cavity. The influence of the launch Froude number on the cavity morphology varies within different gas entrainment coefficient ranges. Besides, six patterns of cavity closure are found for free water-exit conditions. The coupling closure pattern of reentrant jet and interaction vortex tube is the most stable during the water-exit process. The stable development intervals of cavity closure pattern and cavity morphology are roughly the same. The present study aims to provide a reference for the active venting flow control of the vehicle during water-exit. [ABSTRACT FROM AUTHOR]

The lateral confinement effect significantly influences wave amplitude at the generation and propagation stage. A series of physical experiments and numerical simulations considering different parameters was conducted to study the effect of lateral confinement on waves, and the enlargement percentage from lateral confinement on the maximum wave amplitude has been estimated and validated. Results indicate that sliding mass is the most significant factor influencing the wave amplitude on wave generation, with an average influence ratio of 19.0%, and there is a lower influence ratio of 12.3% for particle size parameter. The enlargement percentage induced by lateral confinement decreases from 55.0% to 31.1% on wave generation location as the slide Froude number increases. On the location of wave propagation, the enlargement percentage increases as the slide Froude number increases, ranging from 17.4% to 47.7%. Equations of the enlargement percentage are presented in this study to align the maximum wave amplitude when physical experiments are influenced by lateral confinement. [ABSTRACT FROM AUTHOR]

In the present study, a one-dimensional governing equation with a vertical acceleration term is used to analyse the free surface profile of various types of jumps. Initially, the surface profile of various types of jumps are reproduced analytically by using a suitable eddy diffusivity term. The approximations of the surface profile for various jumps are then verified numerically. Based on the comparisons, an empirical relationship between the Froude number and the turbulent diffusivity coefficient is established. The proposed empirical relationship is used in the governing equation to compute the various jumps, where an implicit two dimensional flow is assumed. The obtained results are compared with the experimental data to assure the transition of flow from undular jump to breaking jump. The comparisons of numerical results of wave profiles, pressure distribution, wave length and wave amplitude with the existing experimental data for various Froude numbers indicated the suitability of the proposed empirical relationship. Finally, the transitions of flow from undular jump to breaking hydraulic jump are discussed. [ABSTRACT FROM AUTHOR]

Submarine channels parallel river channels in their ability to transport sediment. However, in contrast to rivers, sediment transport and bed-form development in submarine channels are less well understood. Many steep (>1°), sandy submarine channels are dominated by upstream-migrating bed forms. The flow conditions required to form these upstream-migrating bed forms remain debated because the interactions between turbidity currents and active bed forms are difficult to measure directly. Consequently, we used a depth-resolved numerical model to test the role of flow parameters that are hypothesized to control the formation of upstream-migrating bed forms in submarine channels. While our modeling results confirmed the importance of previously identified flow parameters (e.g., densiometric Froude number), we found that basal sediment concentration in turbidity currents is the strongest predictor of upstream-migrating bed-form formation. Our model shows how locally steep gradients enable high sediment concentrations (average >5 vol%) in the basal parts of flows, which allow the development of cyclic step instabilities and their associated bed forms. This new insight explains the previously puzzling observation that upstream-migrating bed forms are abundant in proximal, steep, sandy reaches of submarine channels, while their occurrence becomes more intermittent downslope. [ABSTRACT FROM AUTHOR]

The free surface and pycnocline wake characteristics of SUBOFF were studied by simulations and experiments in a two-layer ocean. The experimental results showed that the simulation method accurately calculated the wake characteristics of the scaling model, and the simulation method was expanded to full-scale prototypes. When typical Froude numbers of flow is from 0.05 to 2.7, the submerged body velocity can influence the wake characteristics of the free surface and pycnocline interface. The wake system of the free surface would transform into a Kelvin wake, and the angles of the V-shaped divergent waves of the pycnocline interface would be reduced with the increasing Froude number. [ABSTRACT FROM AUTHOR]

Building a chute aerator is an efficient way of protecting the chute bottom from cavitation damage in large flood-discharging hydraulic structures, but it sometimes fails to provide sufficient protection to the side-walls. In this study, basic air–water flow properties were investigated for discharge flows over an offset chute aerator model, with particular focus on the near-bottom and near-wall regions, for a range of discharge velocities over the offset brink (3.58 m/s < V < 8.02 m/s), Froude numbers (4.8 < Fr < 12.0) and Reynolds numbers (8.0 × 104 < Re < 9.2 × 105). The results indicated little transverse variations in air–water flow properties except near the jet impact perimeter. The bottom air concentration and bubble frequency decreased at different rates downstream of the impact point; the influence of Reynolds number on the bubble size and density should not be ignored. The shape of the clear-water core between the upper and lower aeration layers was identified with the aid of high-speed imaging and air concentration calibration against the wall. A formula to predict narrowing of the jet core until its end position was developed. [ABSTRACT FROM AUTHOR]

Contraction ratio is an important parameter for the type selection of water measuring flume. At present, there is no effective solution to determine the contraction ratio. The empirical equations of Froude number and backwater height were fitted based on dimensional analysis, and the determination method of contraction ratio was explored. In order to define the range of contraction ratio and determine the suitable contraction ratio, five types of contraction ratios and ten body types of triangular flumes were selected on two types and four slopes of U-shaped channels for field experiments. The study result shows that the accuracy of the empirical formula is higher, the average relative error of Froude number is 2.21% and the average absolute error of backwater height is 0.76 cm. The quantitative relationship between Froude number, backwater height and throat width, channel slope, channel discharge and channel bottom arc diameter established based on empirical formulas can be used to determine the contraction ratio. Based on the empirical formula, the upper and lower limits of the contraction ratio are obtained by using the Froude number equal to 0.5 and the backwater height equal to the channel freeboard, which defines the range of the contraction ratio. The suitable contraction ratio can take the middle value of the upper and lower limits of the contraction ratio. [ABSTRACT FROM AUTHOR]

Recent flood hazards occurring in mountainous areas are often characterized by numerous amounts of sediment and large wood supplied from upstream, which often exacerbate flood disasters in downstream areas. This paper proposes a method for describing large-wood behavior in terms of the convection and storage equations, together with the governing equations for describing flood flows and channel changes associated with active sediment erosion and deposition. The proposed method is tested for its validity by simulating the phenomena occurring in an open channel with an erodible bed and flood flow with numerous amounts of sediment and large wood in the Akatani River flood disaster. As a result of calculations reproducing the open channel experiment, the applicability of the method is indicated as the percentage of wood pieces captured in the sediment deposition areas in the channel is within the range of the experimental results. The results of 2-D flood flow calculations with sediment and large wood in the Akatani River flood disaster suggested that large-wood deposition is reproduced where bed deformation is well reproduced. Overall, since the proposed method makes it possible to simulate the behavior of various amounts of large wood, it can be applied to the management of hazards in mountainous rivers such as the Akatani River. [ABSTRACT FROM AUTHOR]

The flow around an elongated smooth contour under the free surface of a fluid is considered. The fluid is perfect, incompressible, and heavy. The critical flow branching and flow shedding points are located on the contour. The depth of the contour immersion and its length are given. It is assumed that the velocity magnitude on the free surface is close to its value in the undisturbed flow. A nonlinear approximation of the Bernoulli integral on the free surface associated with logarithm is used. Two auxiliary planes in which the flow domain is a half-plane with an excluded circle and an annular region are used. The complex potential is determined in the first parametric plane using a conformal mapping onto the annular region. A system of equations is derived for finding the defining parameters. This system is solved using the minimization of a functional and an iteration method over two sets of parameters. An algorithm and computer program for solving this system are developed. The hydrodynamic characteristics of a specific hydrofoil are computed. Results for the coefficients of wave drag, lift force, moment, and position of the contour center are analyzed depending on the Froude number and circulation of different signs. Examples of computations of nonlinear waves formed on the free surface at significant Froude numbers are given. [ABSTRACT FROM AUTHOR]

The purpose of the present study is to examine the influence of baffles presence at downstream system on weir gate hydraulic response. Two baffles configuration (triangle and angle shapes) are installed in bed flume. Two different spacing are used between the baffles and two different directions for baffles are also adopted. The study tries to investigate the variation in upstream Froude number, downstream Froude number, Reynolds number, actual discharge, discharge coefficient, downstream average water depth and the hydraulic system efficiency which is expressed as function of downstream water depth. It has been shown that the number of baffles has a direct and significant impact on flow hydraulic characteristics of weir-gate structure regardless of the spacing between baffles and the direction of baffles related to flow. Baffles number and spacing have essential impact on the water flow velocity of system and this impact leads to increase the flow resistance. The results clarify that the upstream Froude number, downstream Froude number, Reynolds number, actual discharge and discharge coefficient are decreased with the increase in baffles number except the average downstream water depth which increases with increase in baffles number. The efficiency of hydraulic system gives a good indicator for using baffles with weir-gate structure. At the end this paper shows a fruitful result of efficiency. This experiment run condense on the baffle’s numbers and directions with respect to the water flow direction at the downstream regime. So, the rises in the water level relies on the numbers and directions of the baffles as compare to the case without using baffles at the flume downstream region. The actual discharge and weir-gate discharge coefficient are more sensitive to the increase in the baffles’ numbers and the baffles direction with respect to the water flow direction. [ABSTRACT FROM AUTHOR]

The influence of the ablation velocity Va on the evolution of single-mode ablative Rayleigh–Taylor instability from the linear to the deeply nonlinear phases is investigated via two-dimensional numerical simulations. Linear growth rates from simulations agree well with the asymptotic theory except for larger discrepancies in the intermediate Froude number regime. The weakly nonlinear growth behavior of the bubble amplitude is found dependent on a critical perturbation wavenumber in a broad Froude number regime. For a linearly stable mode, its nonlinear excitation threshold is higher for larger Va and thus harder to be exceeded. For short-wavelength modes taking significant ablation effects, the bubble penetration velocity is found to reaccelerate after the first saturation and eventually saturate at a larger value with larger Va, due to stronger vortex-acceleration effects and more significant increase in g. [ABSTRACT FROM AUTHOR]

Understanding the optimal values and interactions of parameters within each process is of highest importance. This study is dedicated to exploring the influence of various parameters and their interactions on ventilation supercavitation phenomena through interpretable machine learning (ML) models. In this study, the characteristics of supercavitation on a disk cavitator with enhanced ventilation at different Froude numbers have been examined through both experimental and numerical means. Subsequently, the data generated from the experimental and numerical methods have been employed to create the optimized ML model. Then, to investigate the behavior of important parameters, their interactions with each other, and the resulting impact of these interactions on conditioned cavitation, interpretable machine learning techniques, such as shapley additive explanations, partial dependence plots, and individual conditional expectations, were employed within an optimized ML model. The findings highlight that the ventilation coefficient is the most crucial parameter affecting the characteristics of supercavitation. Ventilation coefficient exhibits a non-linear behavior and performs effectively within the range of 0.06–0.12. Additionally, the water speed parameter and the ratio of the back-body's diameter significantly influence the cavity length and cavitation number. These parameters exhibit complex interactions, shaping the characteristics of blowing supercavitation. [ABSTRACT FROM AUTHOR]

The work at hand studies thin-film flow instabilities in a non-Newtonian second-grade fluid moving over a stretching sheet. The analysis considers the free surface evolution equation of the thin second-grade viscoelastic fluid model based on the long-wave approximation method. We undertook a linear stability analysis using a normal mode approach and obtained expressions for the linear time growth rate, linear phase speed, and critical wavenumber, which illustrates the linear stability structure of the flow system. Furthermore, the multi-scale analysis of the fluid's weakly non-linear stability characteristics reveals the presence of subcritical instability in the linear stability zone. The study shows that the varying flow parameters affect the threshold amplitude, which influences the stable and unstable zones in the subcritical region. The outcomes show a stabilizing effect spanning the range of non-dimensional parameters, such as the second-grade parameter ranging from 0 to 100 in values, the surface tension parameter ranging from 0 to 100 in values, and the modified Froude number from 0 to 100 in values. [ABSTRACT FROM AUTHOR]

We consider a general compressible viscous and heat conducting fluid confined between two parallel plates and heated from the bottom. The time evolution of the fluid is described by the Navier–Stokes–Fourier system considered in the regime of low Mach and Froude numbers suitably interrelated. Surprisingly and differently to the case of Neumann boundary conditions for the temperature, the asymptotic limit is identified as the Oberbeck–Boussinesq system supplemented with non-local boundary conditions for the temperature deviation. [ABSTRACT FROM AUTHOR]