Distribution Of Erosion Research Articles

Estimation of cavitation erosion area in unsteady cavitating flows using a modified approach

Estimation of cavitation erosion area remains a challenging issue. Only an accurate estimation of the erosion-sensitive area can effectively reveal the various mechanisms of cavitation erosion. In this study, large eddy simulation is applied to simulate the unsteady cavitating flows, and an energy approach is developed to estimate cavitation erosion area. This approach is modified by taking into account hydrodynamic efficiency, which is deduced from the perspective of shock wave decays. The numerical estimation is then validated based on an axisymmetric nozzle cavitating flow. The numerical simulation results indicate that the modified approach can reasonably estimate the cavitation erosion area. In addition, various hydrodynamic cavitation erosion mechanisms are numerically analyzed based on the cavitating flow around a NACA0015 hydrofoil. The numerical simulation is able to reproduce the experimentally observed U-shaped cavitation structure. The interaction between cavitation and vortex has an important influence on the distribution of cavitation erosion. The areas in which the U-shaped cavitation pass may be in high erosion risk.

Assessment of erosive wear performance of Pelton turbine injectors using CFD-DEM simulations

The problem of surface erosion due to sediment-laden water in hydropower stations is quite severe, especially in those located in the Himalayan region. It is one of the major causes of reduction in the operational economy for hydropower generation. In Pelton turbines, the injector assembly is subjected to severe erosion, yielding it inoperable in a relatively short period when compared to other parts of the hydropower plant. The present study aims to contribute to an understanding of hydro-abrasive erosion in Pelton turbine injectors due to changes in design and surface material with hard coating. Three different injector designs, conventional design (nozzle and spear angle of 90 o and 50 o , respectively) and two other designs proposed for better hydraulic performance (nozzle and spear angles of 110 o and 70 o , and 150 o and 90 o , respectively) are chosen for the analysis. The simulations are conducted using the CFD coupled discrete element method (DEM). Multi-size sand particles in the range of 75 μm to 300 μm have been selected to conduct the study. The particle-wall collision characteristics are used to estimate the erosion rate using the semi-empirical erosion models calibrated for martensitic steel, high-velocity air fuel (HVAF), and high-velocity oxy-fuel (HVOF) processed WC-CoCr coatings erosion. The erosion distribution on the nozzle and spear for different injector designs with and without coating at different nozzle opening conditions has been studied. The results show that the erosion of the nozzle and spear is asymmetrical. The increase in design angle enhances nozzle erosion while decreasing spear erosion. The erosion resistance of the Pelton injector improves by an order of 100 with a coating of WC–CoCr. Compared to the HVOF technique, coating with the HVAF technique has superior erosive wear performance. The ratio of maximum to minimum erosion ratio reduces with coating. Also, the uniformity in erosion distribution improves for the coated surface compared to the uncoated surface. The results could provide some theoretical assistance for design optimization, coating performance, and maintenance of the Pelton turbine injector for application in sediment-laden water flows. • Comparison of injector designs for hydraulic and erosive wear performance. • Comparison of the erosion of injectors with and without surface coating. • Erosion model for martensitic steel, and HVAF and HVOF processed WC-CoCr coatings. • Identification of zone of higher erosion on nozzle and spear for different designs. • Analysis of particle collision characteristics on nozzle and spear surface.

Temporal and Spatial Variation and Driving Forces of Soil Erosion on the Loess Plateau before and after the Implementation of the Grain-for-Green Project: A Case Study in the Yanhe River Basin, China.

To curb soil erosion, the Grain-for-Green Project has been implemented in the Loess Plateau region, and there have been few quantitative evaluations of the impact of ecological engineering on the spatial distribution of soil erosion on the Loess Plateau. In this paper, we used ArcGIS software, the Revised Universal Soil Loss Equation (RUSLE) model and the Geographic Detector (GeoDetector) model to investigate the changes in the spatial distribution of soil erosion and driving forces before and after the implementation of the Grain-for-Green Project in Yanhe River Basin, a typical area on the Loess Plateau. After the implementation of the Grain-for-Green Project, the soil erosion showed a decreasing trend over time and from local improvement to global optimization in space. The implementation of the Grain-for-Green Project led to changes in the dominant driving force of the spatial distribution of soil erosion, with the dominant driving force changing from the slope factor to the vegetation coverage factor. The main driving force of the two-factor interaction on soil erosion spatial differentiation changed from the slope factor and other factors to the vegetation coverage and other factors. The Grain-for-Green Project mainly influenced soil erosion by increasing the vegetation cover. The effect of the Grain-for-Green Project on the spatial distribution of soil erosion had hysteresis and spatial differences, and the direct and indirect driving forces generated by ecological engineering reached more than 50% on average.

Soil Erosion Process Simulation and Factor Analysis of Jihe Basin

Soil erosion is a notable contributor to carbon emissions. Distributed erosion model can be used to study erosion distribution in different land cover, identify the main influential factors, and hence guide soil and water conservation. In this study, Regional Soil Erosion model (RSEM) was used to simulate the soil erosion processes of Jihe Basin in 2015, and the Multiscale Geographically Weighted Regression (MGWR) implementation was applied to compare the erosion regression of Geographically Weighted Regression (GWR) and MGWR as well as study the impact of influential factors on sediment modulus in hillslopes. The results are as follows: (1) MGWR results indicated slope was the dominant factors affecting soil erosion at the catchment scales, where the average coefficients of slope, forest coverage, and grass coverage descended in the value of 0.90, −0.11, and −0.19, and the influences of factors operate over scales; (2) MGWR with the adoptive bandwidths performed well in the goodness of fit, t-test of variables, scales that variables operate, and interactive interpretation of soil erosion; (3) the coupling effects and scales of vegetation and topography factors are an important approach to study soil erosion at a larger scale.

Numerical simulation of particle erosion in the vertical-upward-horizontal elbow under multiphase bubble flow

Pipe erosion is one of the main reasons for oil leakage and safety accidents in many engineering fields. The purpose of this study is to investigate the impact of gas volume fraction, elbow angle and rib installation position on pipe erosion under multiphase bubble flow. The computational fluid dynamics (CFD) simulation approach based on volume of fluid (VOF) model and discrete phase model (DPM) was adopted to analyze the effect of gas-liquid distribution and particle movement on pipe erosion under different gas volume fractions. A good agreement of pipe erosion distribution was observed between the simulation results and measurement values. Furthermore, the CFD simulation results show that the pipe erosion rate increases rapidly as the gas volume fraction increases. The erosion rate also increases as the elbow angle increases from 15° to 90°. The rib at small installation position angles can protect the pipe from the direct impact of particles.

Estimation of annual rate and spatial distribution of soil erosion in the Jamuna basin using RUSLE model: A geospatial approach

Soil erosion poses a serious threat to the western Jamuna sub-basin area in Bangladesh, comprising of 8 districts and 202 unions. The Revised Universal Soil Loss Equation (RUSLE) methodology integrated with Remote Sensing and Geographic Information System (GIS) was applied to compute the annual soil erosion rate for the western Jamuna sub-basin area. Primarily open-source data was utilized in this study to propose a low-cost and rapid soil erosion monitoring framework. Results indicate that a total of 598,232 tons of soil is being lost annually from the study area. Furthermore, the study estimates a potential average soil erosion rate of approximately 29.5 tons/ha/year in the 202 unions. The spatial distribution of soil erosion suggests that the unions of Bogra, Sirajganj and Jamalpur districts undergo higher soil loss compared to the unions of Pabna and Natore districts. The three unions with dominant mean soil erosion rates are the Bhandarbari and the Sariakandi Paurashava of Bogra district, and the Kaoakola union of the Sirajganj district. Heavy rainfall after a prolonged dry season, the presence of steep slopes and the susceptibility of the unions located in proximity to the Bangali river and the Jamuna river leading to higher rates of surface runoff and floods resulted in higher rates of soil erosion. On the contrary, the Atgharia Paurashava and Debottar unions of Pabna district and the Moshinda union of Natore district are the unions with minimal soil erosion rates, which likely be attributed to the presence of flat terrain, low annual rainfall, higher vegetation cover and the predominance of clayey soils. Overall, the study identifies an increasing trend of soil erosion rates from the south-western part of the study area towards the central, north-eastern and south-eastern parts which are close to the Jamuna river. Such quantification of annual soil loss is necessary for the formulation and implementation of effective soil conservation strategies.

The Combined Use of 137Cs Measurements and Zr-Methods for Estimating Soil Erosion and Weathering in Karst Areas of Southwestern China

Soil physical erosion and chemical weathering quantification at the slope scale are important to reveal the material cycle of the ecosystem in the karst region, because of the high heterogeneity due to the complex habitats. The Zr-based mass balance method has been widely used to quantify long-term physical erosion and chemical weathering at the slope scale, but the method is still in the exploratory research stage for quantifying short-term physical erosion and chemical weathering. In this paper, sloping fields (nine sampling sites and two sloping fields) in Zunyi, within the Guizhou karst region, were studied. We attempted to quantify the short-term physical erosion and chemical weathering rates by 137Cs combined with the Zr-based mass balance method, and an ideal distribution curve of the Zr concentration in the soil surface layer of a karst region is proposed. The results showed the following: (1) The average soil erosion rate on the slope of the study area is 580 t/(km2·a), which is equivalent to 14% of the average value of the Wujiang River basin in which it is located. This shows that the spatial distribution of soil erosion in this area varies significantly. (2) The Zr concentration in the erosion profile (EUC (1)) corresponds to 48% of that in the deposition profile (DUC (3)). This indicates that physical erosion in the study area survives chemical weathering, which is also consistent with the relationship model hypothesis. In addition, the vertical distribution characteristics of Zr concentration in all profiles are basically consistent with the ideal hypothesis curve. (3) The chemical weathering rate of the topsoil has been preliminarily estimated to be around 30 t/(km2·a), and the ratio between the physical soil erosion and chemical weathering is 20:1. The results show that the physical erosion is dominant over the chemical weathering of topsoil, and the chemical weathering rate was proportional to the physical erosion. This study provides a new method for quantifying short-term soil erosion and weathering erosion at the slope scale in karst regions, which is important for regional ecological restoration and sustainable development.

Numerical study of solid–liquid two-phase flow and erosion in ball valves with different openings

In the coal chemical industry, petrochemical industry, and other industries, ball valve is a common and important valve due to its reliable structure. The conveying medium has particles that affect the valve surface under the drive of water flow, thereby making the ball valve face the risk of erosion and damage. In this study, the CFD-DEM method was adopted to study the influence of different openings and particle diameters on the two-phase flow and erosion characteristics inside the ball valve. The two-phase flow and particle distribution of the ball valve were analyzed, and the main erosion wall surfaces were determined. The erosion distribution of these walls was obtained. The variation rule of particle number with erosion rate was analyzed, which shows that particle number played a dominant role in erosion degree. Result also showed that in the case of small opening, the erosion decreased with the increase in particle diameter.

A study of sediment erosion of runner seal of a Francis turbine

Abstract Suspended sediment particles included in working fluid of hydro turbines often cause erosion and reduce reliability and lifetime of the hydro turbine. It is important for understanding and suppressing erosion problems to understand characteristics of two-phase-flows of liquid and solid particles. In the present study, experimental and numerical studies were carried out to understand mechanisms of erosion in runner seal of a Francis turbine. The experiments were carried out using small-scale seal models. Flow patterns were visualized using coated mica flakes to understand entire flow patterns and a particle image velocimetry were also carried out to measure velocity field in a meridional cross-section. Accelerated erosion tests were also carried out and it was observed similar erosion distributions to that was observed in the actual hydro-turbine. Numerical flow simulations were also carried out to examine mechanisms of the erosion, contributions of each forces acting on the particles and appropriate parameters to capture characteristics of liquid-solid flows and erosion distribution, which were observed in experiments.

How many grains are needed for quantifying catchment erosion from tracer thermochronology?

Abstract. Detrital tracer thermochronology utilizes the relationship between bedrock thermochronometric age–elevation profiles and a distribution of detrital grain ages collected from riverine, glacial, or other sediment to study spatial variations in the distribution of catchment erosion. If bedrock ages increase linearly with elevation, spatially uniform erosion is expected to yield a detrital age distribution that mimics the shape of a catchment's hypsometric curve. Alternatively, a mismatch between detrital and hypsometric distributions may indicate spatial variability of sediment production within the source area. For studies seeking to identify the pattern of sediment production, detrital samples rarely exceed 100 grains due to the time and costs related to individual measurements. With sample sizes of this order, detecting the dissimilarity between two detrital age distributions produced by different catchment erosion scenarios can be difficult at a high statistical confidence level. However, there are no established software tools to quantify the uncertainty inherent to detrital tracer thermochronology as a function of sample size and spatial pattern of sediment production. As a result, practitioners are often left wondering “how many grains is enough to detect a certain signal?”. Here, we investigate how sample size affects the uncertainty of detrital age distributions and how such uncertainty affects the ability to infer a pattern of sediment production of the upstream area. We do this using the Kolmogorov–Smirnov statistic as a metric of dissimilarity among distributions. From this, we perform statistical hypothesis testing by means of Monte Carlo sampling. These techniques are implemented in a new tool (ESD_thermotrace) to (i) consistently report the confidence level allowed by the sample size as a function of application-specific variables and given a set of user-defined hypothetical erosion scenarios, (ii) analyze the statistical power to discern each scenario from the uniform erosion hypothesis, and (iii) identify the erosion scenario that is least dissimilar to the observed detrital sample (if available). ESD_thermotrace is made available as a new open-source Python-based script alongside the test data. Testing between different hypothesized erosion scenarios with this tool provides thermochronologists with the minimum sample size (i.e., number of bedrock and detrital grain ages) required to answer their specific scientific question at their desired level of statistical confidence.

Study on Infiltration and Soil Moisture Characteristics of a Sand-Covered Slope

By observing the processes of infiltration, flow generation, water flow characteristics and the spatial distribution of erosion in a designed rainfall test, and analyzing the infiltration, flow generation characteristics, water content change characteristics, soil moisture parameters change characteristics, and changes in the spatial patterns of erosion and sediment yield, this study draws the following conclusions: under different rainfall densities, the initial runoff generation time of sand-covered slope is 1~12 min longer than that of loess slope, the initial soil infiltration velocity of sediment-covered slope is about 1.23 times that of loess slope, and the time to reach stable infiltration of loess slope is shorter than that of sediment-covered slope. Under different rainfall densities, the rising time of the water content curve of sand-covered slope is earlier than that of loess slope. For the same duration of rainfall, the vertical infiltration performance of soil water of sand-covered slope is higher than that of loess slope, and when the rainfall density on the slope increases by 0.5 mm/min, the increase in runoff shear stress of the sediment-covered slope is about 1.5 times that of the loess slope, and the runoff power is about 1.13 times that of the loess slope.

Effects of Different Cropland Reclamation Periods on Soil Particle Size and Nutrients From the Perspective of Wind Erosion in the Mu Us Sandy Land

Land use changes could notably influence the magnitude and distribution of wind erosion. In recent decades, land reclamation flourished in the Mu Us Sandy Land (MUSL) to supplement cultivated lands (CLs) occupied by urbanization. To analyze the effects of land reclamation on wind erosion, the soil texture and soil nutrients in arable and uncultivated lands should be evaluated. In this study, we collected 54 paired soil samples from CLs and nearby uncultivated lands (NULs) in the MUSL considering land use data pertaining to different phases. Then, the soil particle distribution (PSD) and contents of soil organic carbon (SOC) and total nitrogen (TN) were measured in the laboratory. The results indicated that after 1–15 years (Yr) of cultivation, compared to the NULs, particles ranging from 60 to 400 μm obviously decreased. With increasing number of cultivation years, the wind sorting effects accumulated, and the content of erodible particles susceptible to wind erosion decreased. Among the CLs with different cultivation years, new CLs exhibited the highest erodible particle content, and medium CLs exhibited the lowest erodible particle fraction content. The SOC contents in the medium and fine sand groups among the new CLs was significantly influenced by wind erosion, whereas the TN content was primarily controlled by nitrogenous fertilizer application. After cultivation for longer than 40 years, the total SOC and TN contents in the CLs were significantly higher than those in the NULs. Among the CLs, the wind sorting effects and number of cultivation years obviously influenced the SOC content, whereas the TN content in the CLs was mainly influenced by nitrogenous fertilizer utilization. Rapid urbanization of Shaanxi Province, a new round of national ecological policy adjustments and altered wind environments are the main reasons for the development of new CLs, and a superior location and soil physicochemical properties contribute to the occurrence of old CLs. Based on the above analysis, we propose that conservative cultivation is the key to the protection of new CLs from wind erosion hazards.

Soil Erosion and Deposition in a Taiwanese Watershed Using USPED

Soil erosion is a global problem that has been exacerbated in recent decades by global warming and the increased frequency of extreme weather events. It is also a global issue addressed by the United Nations’ Sustainable Development Goal #15 that seeks to recover degraded land and create a world free of land degradation by 2030. In this study, we used the Unit Stream Power-based Erosion Deposition (USPED) model to investigate the distribution of soil erosion and deposition in an important reservoir watershed in Taiwan, which is known to have a high risk of sediment hazard. We found the average soil erosion rate to be 136.4 Mg/ha/year using the model’s recommended m = 1.3 and n = 1.2 empirical coefficients for a combined occurrence of sheet and rill erosion. Additionally, we selected the Sule sub-watershed and the Kala area as examples to illustrate the pattern of soil erosion and deposition and their relationship to rivers, roadways, and anthropogenic activity, and 3D terrain was employed to further enhance visualization of the model output. It was estimated that 12.6% of eroded soil was deposited with a 200 m buffer of the rivers in the watershed and might be swept into the river system by the next typhoon, torrential rain, landslide, or earthquake. In comparison to previous USLE- and RUSLE-based soil erosion modeling in the same research area, our USPED modeling is unique in that it included the amount and distribution of soil deposition. This successful implementation of USPED in Taiwan establishes a new modeling alternative in addition to the widely used USLE and RUSLE models. The findings can be used to direct future erosion pin placement in the research area, allowing for improved monitoring of sediment movement and avoiding sediment hazards.

Analysis of soil erosion characteristics in small watershed of the loess tableland Plateau of China

Soil is an essentially limited natural resource that natural and human-induced processes have both generated and damaged. Soil degradation has become one of the most crucial socio-economic and environmental problems since it produces deterioration in productivity and quality of soil resources. Soil erosion, a natural phenomenon that causes degradation of soil and, curves the soil surface away from natural physical forces. To reveal the main factors influencing the spatial distribution of soil erosion in the small watershed of the Loess Plateau, the present study has investigated the synergistic as well as the independent influence of land use, vegetation coverage, and slope on the spatial distribution characteristics of soil erosion in the Wangdonggou watershed in 2015. Soil samples have been collected and analyzed in the laboratory together with high-resolution satellite imagery and meteorological data and derived data from digital elevation model (DEM). The results have shown that soil erosion in Wangdonggou watershed in 2015 has been characterized by a slight erosion, highlighting a gradually increased intensity from North to South. Among different land-uses, woodland and grassland have caused more than 50% soil erosion in the study area, and the areas with vegetation coverage of ≥ 50% have been the main source of soil erosion, and they have been all affected by slope. Furthermore, the practice of expanding vegetation presence on the lower coverage of woodland and grassland, particularly where the slope is between 15°∼45°, and converting sloping woodland and grassland to the terrace have seemed to be effective strategies for controlling soil erosion in the Wangdonggou watershed. Finally, the current study has revealed that the RUSLE-GIS integrated model could be a useful tool to quantitatively and spatially map soil erosion at the watershed scale in the Loess Plateau, taking into account the provision of landscape services.

Paths of soil erosion controlled by typical soil and water conservation practices based on the SIMWE model: A case study of the Tongshuang watershed.

Due to the basic topographical characteristics of the gentle and long slope lengths in the Mollisol region of Northeast China, severe soil erosion is easily aggravated by the concentration of surface flow. The spatial distribution of water depth and hydrological connectivity index were introduced to evaluate the effects of typical soil and water conservation practices on the overland flow path and hydrological connectivity based on the GIS and SIMWE (SIMulated Water Erosion) model. We analyzed the effects of different soil and water conservation practices on the hydrological connectivity, water flow path, and spatial distribution of soil erosion and sediment yield by quantifying the variations of soil infiltration rate and surface manning roughness, as well as by constructing an artificial terrain digital elevation model (DEM). The results showed that: 1) terraces could effectively affect the hydrological connectivity of the slope and regulate flow path, with significant differences between the responses of hydrological connectivity and flow path under different forms of terraced fields and ridges. The characteristics of spatial distribution of soil erosion and sediment yield varied with changes in water flow path, which would eventually lead to the intensification of local erosion; 2) practices of vegetated buffer strips and contour tillage presented limited effectiveness on runoff path controlling, though they played a significant role in sediment retention; and 3) conservation tillage could reduce the hydrological connectivity and improve the retention capacity of runoff by increasing surface roughness. This study quantified the effects of different soil and water conservation practices on the hydrological connectivity, flow path, and spatial distribution of soil erosion and sediment yield, and could provide a theoretical reference for scientific layout of soil and water conservation practices in black soil region.

Spatial and temporal evolution of the Sinian and its implications on petroleum exploration in the Sichuan Basin, China

In recent years, there have been significant discoveries of hydrocarbon resources with commercial value in the Dengying Formation of the central Sichuan Basin. However, the impact of tectonic evolution on hydrocarbon accumulation has not been appropriately documented. In this study, we employed multiple methods, including seismic interpretation, balanced cross-section restoration, deformation quantification, erosion calculation, and paleo-highs/lows reconstruction, to investigate the tectonic kinematics, erosion distribution, paleo-highs/lows evolution of the Sichuan Basin. The quantification of deformation reveals that the Sichuan Basin has experienced a complicated tectonic evolution, with two rounds of transition from tension to contraction since the Sinian. In the Late Ordovician, contraction caused by the Caledonian Orogeny resulted in a foreland basin being developed in the Sichuan Basin. Since the Late Triassic, the Sichuan Basin has experienced intense contraction, resulting in the development of its current structural pattern. By integrating the erosion distribution, the reconstructed paleo-highs/lows maps of Sinian strata indicate the development of inherited paleo-uplifts in the central and southwestern Sichuan Basin from the Early Cambrian to the present. The evolution of paleo-highs/lows plays a critical control on the hydrocarbon accumulation of the Weiyuan and Anyue gas fields, indicating there could be high potential for hydrocarbon exploration in areas with high slope gradients in the paleo-uplifts.

Short-Term Sedimentation Dynamics of Temperate Mangroves in Western Port Bay, Victoria

The promotion of sedimentation by mangrove ecosystems with adequate sediment supply has been well documented. However, predicting the amount of accretion or erosion at a specific point, is difficult due to the inherent stochasticity of sediment movement and deposition. Forcings which have been thought to influence short-term sedimentation rates, such as the amount of suspended matter in the incoming water, the wave regime at the site, elevation above sea level, distance from the low tide mark, and vegetation density, were investigated using large arrays of erosion pins at five sites around Western Port, Victoria over the course of one and a half years. We analyzed large scale/short-term and small-scale/longer-term vertical displacement within and between sites, and quantified small-scale intra-site variability. Results show, that while all study sites within Western Port were accreting sediment, they were not doing so at the same rate, and both intra-site and inter-site variability is high. Short-term large-scale or site wide analysis shows that total suspended matter and significant wave height (SWH) did not significantly affect vertical displacement rates. Surprisingly, neither distance from water nor vegetation density significantly affected vertical displacement or explain the spatial distribution of accretion and erosion within the sites. The coefficient of variation at each pin shows that there is high temporal variability in vertical displacement at each location, with individual pins alternating between erosion and accretion over time. Our study finds that while large scale (1 km2) patterns of sedimentation are temporally consistent, small scale patterns (< 100 m2) are difficult to predict. This small-scale stochasticity therefore compounds management of mangrove ecosystems, especially as it relates to predicting the response to sea level rise. Thus, investment in small scale management of vegetation density, or microtopography, is perhaps not required for overall shoreline stability with sea level rise and blue carbon accumulation, making ecosystem restoration more feasible where resources are limited. However, at larger, forest-wide, spatial scales a higher level of predictability exists such as the overall response of the coastal tract to prevalent wave energy and sediment supply.

Quantifying spatial distribution of interrill and rill erosion in a loess at different slopes using structure from motion (SfM) photogrammetry

The spatial distribution of interrill and rill erosion is essential for unravelling soil erosion principles and the application of soil and water conservation practices. To quantify interrill and rill erosion and their spatial development, four 30-min rainfalls at 90 mm h−1 intensity were consecutively simulated on runoff plots packed with a loess at six slopes of 10°, 15°, 20°, 25°, 30° and 35°. The soil surface was measured using the structure from motion (SfM) photogrammetry upon each simulation run, and the runoff and sediment samples were collected and measured at every 10 min. Rills did not develop until the third simulation run. During the initial two runs, the lower third section was more severely eroded than the upper and middle thirds along the slope direction, yet the interrill erosion was statistically uniform from left to right. Rills tended to emerge by both sidewalls and in the lower portion in the third run. The corresponding rill erosion increased with slope from 10° to 20° and then decreased for the slopes steeper, which was consistent with the slope trend of the sediment yield directly measured. The rills expanded substantially primarily via head retreat and to a lesser extent via sideward erosion after receiving another 30-min rainfall. Rill erosion contributed 69.3% of the total erosion loss, and shifted the critical slope corresponding to the maximum loss from 20° to 25°. These findings demonstrate the significance of rill erosion not only in total soil loss but also in its relation to slope, as well as the effectiveness of SfM photogrammetry in quantifying interrill and rill erosion.

Spatiotemporal analysis of the quantitative attribution of soil water erosion in the upper reaches of the Yellow River Basin based on the RUSLE-TLSD model

Soil erosion leads to land fertility reduction and land degradation, which threaten food and ecological security. Therefore, it is fundamental for soil erosion risk control to accurately assess the dynamics of water soil erosion and reveal its driving mechanism. This paper aims to integrate and calibrate the transport limited sediment delivery (TLSD) function with the revised universal soil loss equation (RUSLE) model, and then to simulate the long-term soil erosion by water in the upper reaches of the Yellow River Basin (UYRB) and estimate the influence of each factor on soil loss using the GeoDetector method. The results reveal that the water erosion dynamics in the UYRB were reliably simulated by the RUSLE-TLSD model (with the Nash-Sutcliffe efficiency coefficient surpassing 0.809). From 1982 to 2019, the net soil loss rates ranged from 1.63 to 5.41 t⋅ha−1⋅a−1 in the UYRB, with the most intense erosion occurring from June to August. Steep hillside grasslands, especially in the canyon zone with fragmented topography, suffered from intense erosion, while river valleys and the feet of steep slopes experienced sediment deposition. Major factors that impact the distribution of water erosion in the UYRB include the slope followed by vegetation (soil erosion risk should be monitored on steep grasslands with slopes greater than 15°), and the combination of the two represents the core interaction factor, which explained at least 46% of the water erosion distribution. The annual net water erosion in the UYRB showed a slight increasing trend from 1982 to 2000, which was mainly affected by natural factors, but significantly decreased after 2000, which was mainly caused by vegetation restoration. In the UYRB, the implementation of the “Grain to Green Program” has had significant benefits in terms of water and soil conservation, and forests have a greater ability to control erosion than grasslands.

Particulate flow and erosion modeling of a Pelton turbine injector using CFD-DEM simulations

Hydro-abrasive erosion of the injector assembly is a critical issue that affects the operational economy and efficiency of Pelton turbines operating in sediment-laden water. The current study focuses on determining the critical zones of erosion for the Pelton turbine injector. Computational fluid dynamics coupled discrete element method (CFD-DEM) simulations have been adopted to model the sediment-laden flows. The effects of particle rotation and collisions between the particles have been considered while modeling the particle motion. Multi-size particles in the range 75 μm to 350 μm have been considered for the simulation. A semi-empirical erosion model has been developed to predict the erosion of the injector, which includes the effect of particle size on the erosion of the target material. The developed erosion model is calibrated with the available experimental data for the target material, namely turbine steel (CA6NM). The simulated results discuss the physical processes underlying particulate flow and hydro-abrasive erosion. It has been found that the erosion of injector parts namely, nozzle and spear, is asymmetrical. The variation in particle size in the flow is one of the major sources of asymmetrical erosion distribution. The erosion distribution in the nozzle is similar for different nozzle opening conditions. However, the nozzle opening conditions have a significant impact on the erosion distribution and the location of maximum erosion on the spear. At full nozzle opening the tip of the spear is having relatively higher erosion. The present work provides important engineering insights to control the erosion and the problem of jet breakage for the Pelton turbine injector.