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Vegetation significantly affects the soil properties and runoff processes of gully head systems, thereby affecting their development. However, the mechanisms underlying the effects of vegetation on gully headcut erosion remain unclear. To explore these mechanisms, a series of simulation experiments were carried out on plots with four types of vegetation and bare land (BL). The results revealed that vegetation reduces the runoff velocity in the upstream area (Vup), gully head brink (Vbrink), and gully bed (Vbed) areas by 15%–70%, 3%–54%, and 1%–30%, respectively, and that vegetation type impacts Vup, with no obvious impacts on Vbrink, the jet flow velocity (Vjet) or Vbed. Vegetation reduced the jet flow shear stress (τjet) under low inflow discharge, but under high inflow discharge, it increased τjet. Different vegetation types exhibited different effects on the increase in the Darcy–Weisbach friction factor (f) and Manning roughness coefficient (n) in the upstream area, whereas the effect of vegetation on the f and n value of the gully bed was not obvious. Vegetation reduced the gully head retreat length. Compared with BL, vegetation reduced the rate of soil loss by 31%–95%. Vegetation significantly and directly affects soil characteristics, hydrodynamic parameters, and gully head morphology. The gully head morphology significantly and directly influences the soil loss rate, which ultimately affected the length of gully head retreat. These findings contribute to a deeper understanding of the role of vegetation in gully headcut erosion, offering a scientific foundation for the implementation of preventive measures against such erosion. Key Points Vegetation reduced the jet flow shear stress (τjet) under low inflow discharge, but under high inflow discharge, it increased τjet Vegetation significantly and directly affects soil characteristics, hydrodynamic parameters and gully head morphology The gully head morphology directly affects the soil loss rate, and the soil loss rate ultimately affects the length of gully head retreat

Accurate and precise values of hydrodynamic parameters are needed for groundwater modeling and management. Pumping test in the aquifer is the standard method to estimate the transmissivity, hydraulic conductivity, and storage coefficient as the key hydrodynamic parameters. Analytical solutions with curve matching and numerical modeling are two methods to estimate these parameters in the aquifer. Graphical analyses are commonly applied to time-drawdown/water table data which are time-consuming and approximate. Graphical type-curve methods as promising tools are used extensively in water resources studies, while applying these methods is still new in pumping test analysis. In the current study, the first effort based on our knowledge, we have reviewed the literature type-curve graphical methods in pumping test analysis. To achieve this goal, we reviewed and compared the journal articles regarding the characteristics and capabilities of the modeling process from 2000 to 2022. We have clustered the reviewed papers into graphical, modeling, and hybrid categories. Then, a comprehensive review of the selected papers was presented to delineate the highlight of every paper. This review could guide researchers in pumping test analysis. Also, we have presented various recommendations for future research to improve the quality of hydrodynamic parameter estimation.

Although intensified flotation cells have been introduced as fast-kinetic and plug-flow-type flotation machines, there is limited empirical verification and information about their fluid flow patterns and dispersion regimes. The present communication paper investigates this for an Imhoflot[sup.TM] G-06 cell operated in an open-circuit mode using an impulse method to measure and model the residence time of a liquid–gas system. For experimental measurements, a concentrated KCl solution was employed, and water conductivity was monitored for 20 min. By fitting several relevant models, such as large and small tanks in series (LSTS), Weller, N-Mixer, and perfect mixer, to the experimental data, it was revealed that the N-Mixer represented the dispersion pattern the best (N = 1.3–1.6). Further, the obtained practical mean retention time (MRT) of 4.11 ± 0.16 min was somewhat aligned with the theoretical value, i.e., 5.0 min per pass, indicating a back-calculated gas hold-up magnitude of 18%–22% in the separator. These results provide an in-depth perception of scale-up procedures and requirements for cell modification.

This paper presents the jig operating properties of the selected final parameters of the hard coal concentrate. The quality parameters of the product, such as the yield and ash content, were evaluated in terms of the technical and hydrodynamic parameters of the jig’s operation. The research program included a series of experiments in which the efficiency and the amount of hutch water were changed. The variables selected and analyzed were divided into two categories, i.e., one related to the characteristics of the concentrate produced, and the other to the characteristics of the jig operation. Models were built for narrowed particle size fractions based on concentrate yield and ash content in the concentrate. In addition, a multidimensional analysis was performed, considering variables such as machine throughput, which was determined by the flow rate of the material, the amount of hutch water, the quality of the concentrate, and the amount of concentrate, as well as the accuracy of the jig operation expressed by the imperfection. Two main parameters were taken into account for modeling the operation to examine their significance of influence on the final responses in terms of the possibility of adjusting the value of independent settings of the jig operation. The presented approach to modeling the operation of the jig can be extended by considering the impact of other parameters, taking into account the variability of the final effect, as long as it is allowed under the industrial conditions of machine operation and the assumed production requirements. The approach presented in this paper is a new technique, which was not found in the literature.

This manuscript presents a fully detailed methodology in order to identify the hydrodynamic parameters of a mini autonomous underwater vehicle (mini-AUV) and evaluate its performance using different controllers. The methodology consists of close-to-reality simulation using a Computed Fluid Dynamics (CFD) module of the ANSYS™ Workbench software, the processing of the data, obtained by simulation, with a set of Savistky–Golay filters; and, the application of the Least Square Method in order to estimate the hydrodynamic parameters of the mini-AUV. Finally, these parameters are considered to design the three different controllers that are based on the robot manipulators theory. Numerical simulations are carried out to evaluate the performance of the controllers.

The variations in hydrodynamic parameters at different polysaccharides rates and the relationships between sheet erosion modulus and hydrodynamic parameters were analyzed to reveal the hydrodynamic mechanism of sheet erosion on loessial slopes. Artificially simulated rainfall experiments were carried out under three slope gradients (10°, 15°, and 20°), three rainfall intensities (1.0, 1.5, and 2.0 mm·min −1 ), and four dry-spreading rates of polysaccharides (0, 1, 3, and 5 g·m −2 ). The results showed that (1) four hydrodynamic parameters (flow velocity, shear stress, stream power, and unit stream power) all increased with both rainfall intensities and slope gradients at four rates of polysaccharides. (2) Polysaccharides could effectively reduce hydrodynamic parameters. In contrast to the bare slope, the average flow velocity, shear stress, stream power, and unit stream power diminished by 27.11~41.18%, 9.53~18.67%, 31.82~50.24%, and 27.11~41.18%, respectively. (3) Polysaccharides could effectively reduce the growth rate of the sheet erosion modulus with hydrodynamic parameters, and there were few differences among the different rates (1, 3, and 5 g·m −2 ). The increasing rates of the sheet erosion modulus with flow velocity, shear stress, stream power, and unit stream power were 14.0~65.7%, 14.8~33.9%, 7.8~23.7%, and 9.7~29.5%, respectively. (4) At different polysaccharides rates, the relationships between sheet erosion modulus and hydrodynamic parameters were all in logarithmic functions. Moreover, flow velocity ( R 2  ≥ 0.920) and stream power ( R 2  ≥ 0.876) were better hydrodynamic parameters than shear stress ( R 2  ≥ 0.598) or unit stream power ( R 2  ≥ 0.537). Polysaccharides decreased the hydrodynamic parameters and the response rates of sheet erosion to hydrodynamics.

Ships navigating in the water need to consider their safety first, and the abnormal sinking amount of the ship will be a great threat to the navigation safety of the ship. In this paper, the relationship between hydrodynamic parameters and ship sinking amount is studied in order to realize the reasonable control of the ship by setting different hydrodynamic parameters so as to ensure the safety of ship navigation. Through Taylor’s formula to calculate the hydrodynamic parameters of the ship navigation, and through the combination of potential flow theory and boundary conditions, finally using Green’s function method in the surface element method, it is calculated that the sinking amount of the ship from hydrodynamic parameter 35000 to hydrodynamic parameter 3200000 is a gently increasing trend, and in the case of h/d=2.5, the ship’s speed Fn=0.25, the ship’s sinking amount appears to be oscillating changes.

As a specific near surface hydrological condition, soil saturation can significantly affect the critical hydrodynamic characteristic and soil erosion rate of rill formation, leading to severe rill erosion. Nevertheless, few studies have investigated the characteristics of critical hydrodynamic parameters and their relationships with rill erosion rate under critical hydrodynamic conditions of rill formation on saturated soil slopes. Consequently, the quantification of critical hydrodynamic parameters and their effects on rill erosion rate under critical hydrodynamic conditions of rill formation on saturated soil slopes is of great significance for understanding the dynamic mechanism of rill formation and evolution and for predicting and controlling soil loss. In this study, indoor simulated rainfall experiments were performed and a new analytical model (Vc(NAM)) was applied to calculate the aforementioned critical parameters under a wide range of hydraulic conditions comprising five slope gradients (SG) (2°, 5°, 10°, 15°, and 20°) and three rainfall intensities (RI) (30, 60, and 90 mm/h). The results indicated that the new analytical model (Vc(NAM)) was suitable for estimating critical hydrodynamic parameters on saturated soil slopes. The critical flow velocity (Vc), the critical shear stress (τc), and the critical stream power (ωc) apparently increased, whereas the critical rill length (Lc) decreased with the increase of slope gradients and rainfall intensities. Moreover, the erosion rate at the critical condition increased with decreasing Lc and increasing Vc, τc, and ωc. Pearson correlation analysis indicated that τc and ωc were significantly positively correlated, whereas Lc was negatively correlated with erosion rate under the critical conditions. Stepwise regression analysis revealed that the erosion rate under critical hydrodynamic conditions of rill formation could be well predicted by τc (R2 = 0.83) with the linear model. The results provide an accurate model for evaluating critical conditions of rill formation and a basis for further understanding the intrinsic dynamic mechanism of rill formation on saturated soil slopes. •A new analytical model Vc(NAM) was built to estimate critical hydrodynamic parameters on saturated soil slopes.•The critical hydrodynamic of rill formation on saturated soil slopes was explored.•Shear stress was optimal hydrodynamic parameter to predicting erosion rates of rill initiation.

In recent decades, due to the population growth and low precipitation, the overexploitation of ground water resources has become an important issue. To ensure a sustainable scheme for these resources, understanding the behavior of the aquifers is a key step. This study takes a numerical modeling approach to investigate the behavior of an unconfined aquifer in an arid area located in the east of Iran. A novel hybrid model is proposed that couples the numerical modeling to a data assimilation model to remove the uncertainty in the hydrodynamic parameters of the aquifer including the hydraulic conductivity coefficients and specific yields. The uncertainty that exists in these parameters results in unreliability of the head values acquired from the models. Meshless local Petrov-Galerkin (MLPG) is used as the numerical model, and particle filter (PF) is our data assimilation model. These models are implemented in the MATLAB software. We have calibrated and validated our PF-MLPG model by the observation head data from the piezometers. The RMSE in head values for our model and other commonly used numerical models in the literature including the finite difference method and MPLG are calculated as 0.166, 1.197 and 0.757 m, respectively. This fact shows the necessity of using this method in each aquifer.

The presence of understory vegetation not only influences slope-scale soil and water conservation but also exerts a profound effect on hydrodynamic characteristics and the processes of runoff and sediment production. Therefore, in this study, different vegetation types and vegetation coverages (bare land, 30%, 60%, and 90%) were set up by simulating rainfall (45, 60, 90, and 120 mm·h−1) to evaluate the runoff-sediment process and the response characteristics of hydrodynamic parameters. The results showed that increasing vegetation cover significantly reduced soil erosion on forest slopes (p < 0.05). When the vegetation cover ranged from 60% to 90%, vegetation pattern C and pattern D were the most effective in suppressing erosion, where increased cover improved runoff stability. Under low-cover conditions, overland flow tended toward turbulent and rapid regimes, whereas under high cover conditions, flow was primarily laminar and slow. Patterns C and D significantly reduced flow velocity and water depth (p < 0.05). Structural equation patterning revealed that, under different vegetation patterns, the runoff power (ω), Reynolds number (Re), and resistance coefficient (f) more effectively characterized the erosion process. Among these, the Reynolds number and runoff power were the dominant factors driving erosion on red soil slopes. By contrast, runoff shear stress was significantly reduced under high-cover conditions and showed weak correlation with sediment yield, suggesting that it was unsuitable as an indicator of slope erosion. Segmental vegetation arrangements and increasing vegetation cover near runoff outlets—especially at 60–90% coverage—effectively reduced soil erosion. These findings provide scientific insight into the hydrodynamic mechanisms of vegetation cover on slopes and offer theoretical support for optimizing soil and water conservation strategies on hilly terrain.