Empirical Erosion Research Articles

Eulerian approach for erosion induced by particle-laden impinging jets

Particle dispersion and erosion play an important role in various engineering applications, particularly in impinging jet flows. This study presents a new Eulerian method for characterizing these phenomena in axisymmetric, laminar, and turbulent jets, impinging and transiently eroding a flat wall. The Eulerian mass and momentum conservation equations are solved assuming a one-way coupling between the flow and the particles. The carrier flow boundary layer velocity profiles in the laminar case are validated with analytical solutions. The particle calculation involves two stages, incident and reflected particles, connected via a restitution model. The reflected particles’ results offer insights into secondary erosion areas but are not used for the main erosion calculations. Subsequently, erosion at the eroded surface is computed using an empirical erosion model, followed by the displacement of computational nodes using the linear-elastic, small-strain deformation equations, all of which are solved transiently. The solutions reveal the spatial particle concentrations and momentum for different Stokes numbers: smaller Stokes particles follow the carrier flow streamlines, medium Stokes particles deviate, forming a W-shaped erosion profile, while the largest Stokes particles create a U-shaped profile. This numerical model offers a computationally efficient framework for CFD-based transient erosion calculation due to its Eulerian implementation.

Empirical Model of Unconsolidated Tephra Erosion: Verification and Application on Micro Catchment

Erosion is an important process that shapes the earth's surface. Given the complexity of the process, efforts to understand it are essential. Over the last 50 years, numerous models of soil particle erosion by surface runoff emerged, some of which share similar forms and parameters. The differences lie in the coefficient values of the parameters, attributed to the characteristics of the soil material such as texture, structure, and organic matter content. However, these erosion models tend to underpredict in the case of new volcanic deposit erosion. The erosion model for unconsolidated tephra, proposed by Yunita, was developed through laboratory experiments using volcanic material from Merapi Volcano, Indonesia. Nevertheless, the model has not been implemented for other cases. Therefore, this study aims to verify the erosion model for volcanic material in other cases, explore the possibility of broader implementation, identify the factors that influence its accuracy, and determine the model’s limitations. To verify the model’s potential for broader application, we applied it to micro-scale catchments in St. Hellens (USA), Sakurajima (Japan), and a laboratory scale plot in Merapi (Indonesia). The verification yielded satisfactory results for all three cases, especially for new tephra deposits. In the case of St. Helens, the extrapolation of model coefficients was proven to still be applicable even for thicker tephra layers. However, the erosion prediction was overestimated for tephra layer deposits older than 1 year, as the erosion rate decreases over time due to the compaction and stabilization of the tephra layer. In the Sakurajima, the model was also suitable for predicting long-term erosion amounts (daily and monthly). Meanwhile, in Merapi, the model provided accurate predictions for slopes of 20º and 25º but was less accurate for 30º slopes, where the measured erosion was due to both erosion and slope failure. These verification results demonstrate the potential of applying the empirical erosion model to micro catchments with relatively homogenous slopes and tephra properties. The sensitivity test revealed that slope, runoff, rainfall intensity, and volcanic ash thickness are strongly influence the erosion rate. This study also simplified the volcanic ash erosion model as a function of slope (S0), runoff (q), and rainfall (i) by assuming the value of (1-τc/τ0) is equal to 1. Further study using GIS tools is required for its application on several catchments with heterogeneous characteristics. Doi: 10.28991/CEJ-2024-010-07-02 Full Text: PDF

Application of Remote Sensing for Identifying Soil Erosion Processes on a Regional Scale: An Innovative Approach to Enhance the Erosion Potential Model

Soil erosion represents a complex ecological issue that is present on a global level, with negative consequences for environmental quality, the conservation and availability of natural resources, population safety, and material security, both in rural and urban areas. To mitigate the harmful effects of soil erosion, a soil erosion map can be created. Broadly applied in the Balkan Peninsula region (Serbia, Bosnia and Herzegovina, Croatia, Slovenia, Montenegro, North Macedonia, Romania, Bulgaria, and Greece), the Erosion Potential Method (EPM) is an empirical erosion model that is widely applied in the process of creating soil erosion maps. In this study, an innovation in the process of the identification and mapping of erosion processes was made, creating a coefficient of the types and extent of erosion and slumps (φ), representing one of the most sensitive parameters in the EPM. The process of creating the coefficient (φ) consisted of applying remote sensing methods and satellite images from a Landsat mission. The research area for which the satellite images were obtained and thematic maps of erosion processes (coefficient φ) were created is the area of the Federation of Bosnia and Herzegovina and the Brčko District (situated in Bosnia and Herzegovina). The Google Earth Engine (GEE) platform was employed to process and retrieve Landsat 7 Enhanced Thematic Mapper plus (ETM+) and Landsat 8 Operational Land Imager and Thermal Infrared Sensor (OLI/TIRS) satellite imagery over a period of ten years (from 1 January 2010 to 31 December 2020). The mapping and identification of erosion processes were performed based on the Bare Soil Index (BSI) and by applying the equation for fractional bare soil cover. The spatial–temporal distribution of fractional bare soil cover enabled the definition of coefficient (φ) values in the field. An accuracy assessment was conducted based on 190 reference samples from the field using a confusion matrix, overall accuracy (OA), user accuracy (UA), producer accuracy (PA), and the Kappa statistic. Using the confusion matrix, an OA of 85.79% was obtained, while UA ranged from 33% to 100%, and PA ranged from 50% to 100%. Applying the Kappa statistic, an accuracy of 0.82 was obtained, indicating a high level of accuracy. The availability of a time series of multispectral satellite images for each month is a crucial element in monitoring the occurrence of erosion processes of various types (surface, mixed, and deep) in the field. Additionally, it contributes significantly to decision-making, strategies, and plans in the domain of erosion control work, the development of plans for identifying erosion-prone areas, plans for defense against torrential floods, and the creation of soil erosion maps at local, regional, and national levels.

An assessment of anticipated future changes in water erosion dynamics under climate and land use change scenarios in South Asia

Water erosion has emerged as a significant global environmental challenge, particularly in South Asia, recognized as one of the regions hardest to hit globally by climate change. This study aims to identify the potential erosion hotspots in South Asia and to assess areas under risk in the future due to climate and land use change scenarios. We utilized the Revised Universal Soil Loss Equation (RUSLE), an empirical erosion model, to estimate erosion for both historical and future periods, considering two distinct Shared Socio-economic Pathways (SSP126 and SSP585). The baseline model predicts a mean water erosion rate of 10.6 t. ha−1. year−1 in South Asia, with more than 30 t. ha−1. year−1 recorded for 6.3 % of the total land area. Notably, Bangladesh and Nepal exhibit significantly higher erosion rates than other South Asian countries. Further, our projection indicates an + 10 % increase in erosion rates during the near future (2021–2040) under SSP585 compared to the historical estimates. A substantial rise of approximately + 31 % and + 39 % in water erosion rates in South Asia is anticipated during the far future periods of 2061–2080 and 2081–2100 under SSP585. At the country level, Bangladesh (+42 %), Bhutan (+108 %), and Nepal (+70 %) are expected to experience substantial increases in erosion rates during the 2081–2100 period, with India projecting a + 38 % increase. Additionally, a significant + 35 % expansion in the spatial extent of high erosion areas (>30 t. ha−1. year−1) is foreseen in 2081–2100 under SSP585. Furthermore, under the low climate change scenario (SSP126), the impact on the erosion rates is minimal, while under SSP585, a substantial increase in erosion rates is anticipated. Regions such as Southern India, the arid and semi-arid areas near the India-Pakistan border, and the Himalayan foothills are identified as hotspots for significant changes in erosion rates. Acknowledging a certain level of uncertainty, our study provides valuable insights into erosion risk areas in South Asia and their plausible future impacts due to climate and land use changes. This information can assist policymakers in South Asian countries in developing national-level strategies for soil conservation and climate resilience.

Construction of a monthly dynamic sediment delivery ratio model at the hillslope scale: a case study from a hilly loess region

Introduction: Soil loss is a worldwide environmental problem, and sediment transport is one of its important components. In recent years, a hillslope sediment delivery ratio (SDR) model based on an index of connectivity has been widely used to describe the variation in sediment transport characteristics. However, the hillslope SDR model only considers the structural characteristics of the watershed and ignores the dynamic mechanism of sediment transport, which leads to poor dynamic applicability over short timescales and makes it difficult to reflect changes of sediment yield.Methods: Therefore, we here propose a monthly dynamic SDR model that integrates the hillslope structural connectivity and sediment transport threshold of rainfall event based on the main influencing factors of sediment delivery. We then combine the dynamic SDR model with an empirical erosion model to simulate the hillslope sediment yield in the Mahuyu watershed, and verify the applicability of the coupled model using the Heimutouchuan watershed.Results: The results show that the coupled model can effectively simulate the hillslope sediment yields of the Mahuyu and Heimutouchuan watersheds. The contribution of the rainfall transport threshold factor to sediment delivery and yield is essentially in dynamic stability at the multi-year timescale, but increases the heterogeneity of both inter-month distributions and the spatial distribution of hillslope sediment yield.Discussion: The dynamic SDR model, which considers the rainfall thresholds of transport and re-transport, can effectively improve the simulation accuracy of low and high sediment yield values on hillslopes. Our results can provide a reference for understanding sediment transport processes on hillslopes and optimizing soil and water conservation measures in watersheds.

Determination of the potential soil losses and prioritization of sub-watersheds: Insight from North African highland system

Soil erosion has negative effects on people and property, hinders the sustainable development of natural resources, and poses a threat to the economic growth of territories worldwide, and is particularly acute for African countries. Consequently, identifying and prioritizing areas susceptible to this phenomenon is crucial for the implementation of efficient preventative measures. In this study, the empirical Erosion Potential Method (EPM) was used to quantify soil losses, and two Game Theory (GT) algorithms (Borda and Condorcet) were employed to identify locations prone to soil erosion and prioritize sub-watershed (SW) based on hydromorphometric characteristics in a hydrological system from High Atlas in Morocco. For this purpose, 26 factors were calculated, subsequently, a linear correlation analysis was conducted to assess the relationship between potential soil erosion and various influencing factors. The EPM model findings indicated average loss rates of roughly 3356 m3/km2/year, which are corroborated by 217 inventory points gathered in the most productive sediment locations, with an AUC value of 80 %. The results of prioritization using GT algorithms show that the SW6 and SW8 are classified as areas with high vulnerability to soil erosion, and the sub-watersheds located upstream of the Lakhdar river watershed are the units that deserve prioritization in terms of planning intervention. The validation of results indicates that the Borda algorithm performed better (AUC= 92 %) than the Condorcet algorithm (AUC= 72 %). This innovative approach enhances our understanding of erosive processes within specific spatial units, enabling informed decision-making and making a substantial contribution to the sustainable and efficient management of water resources. This represents a significant advancement compared to previous studies in the region.

Fractal characteristics of a worn wall and the influence on the particle-wall collisions

A new particle-wall collision model is proposed to analyse the random rebound process of particles after collision with a rough wall. The new model includes two parts. First, the wear caused by particle collisions and the self-similarity of the wall microstructure are considered. The topography of a rough wall is constructed using fractal theory combined with an empirical erosion formula. Second, a return-to-subdivision method is used to determine the contact point between the particle and wall. The hard ball model is used to analyse the motion state of the rebound particles. The present model is numerically implemented through the Monte Carlo method and validated by comparison with the experimental data available in the literature. The possible reasons for the deviation between the predicted and measured results are presented. In addition, the compatibility of the present model with classical models is discussed in detail.

Towards the Assessment of Soil-Erosion-Related C-Factor on European Scale Using Google Earth Engine and Sentinel-2 Images

Soil erosion is a constant environmental threat for the entirety of Europe. Numerous studies have been published during the last years concerning assessing soil erosion utilising Remote Sensing (RS) and Geographic Information Systems (GIS). Such studies commonly employ empirical erosion models to estimate soil loss on various spatial scales. In this context, empirical models have been highlighted as major approaches to estimate soil loss on various spatial scales. Most of these models analyse environmental factors representing soil-erosion-influencing conditions such as the climate, topography, soil regime, and surface vegetation coverage. In this study, the Google Earth Engine (GEE) cloud computing platform and Sentinel-2 satellite imagery data have been combined to assess the vegetation-coverage-related factor known as cover management factor (C-factor) at a high spatial resolution (10 m) considering a total of 38 European countries. Based on the employment of the RS derivative of the Normalised Difference Vegetation Index (NDVI) for January and December 2019, a C-factor map was generated due to mean annual estimation. National values were then calculated in terms of different types of agricultural land cover classes. Furthermore, the European C-factor (CEUROPE) values concerning the island of Crete (Greece) were compared with relevant values estimated for the island (CCRETE) based on Sentinel-2 images being individually selected at a monthly time-step of 2019 to generate a series of 12 maps for the C-factor in Crete. Our results yielded identical C-factor values for the different approaches. The outcomes denote GEE’s high analytic and processing abilities to analyse massive quantities of data that can provide efficient digital products for soil-erosion-related studies.

Assessing Soil Loss by Water Erosion in a Typical Mediterranean Ecosystem of Northern Greece under Current and Future Rainfall Erosivity

Soil is a non-renewable resource essential for life existence. During the last decades it has been threatened by accelerating erosion with negative consequences for the environment and the economy. The aim of the current study was to assess soil loss changes in a typical Mediterranean ecosystem of Northern Greece, under climate change. To this end, freely available geospatial data was collected and processed using open-source software package. The widespread RUSLE empirical erosion model was applied to estimate soil loss. Current and future rainfall erosivity were derived from a national scale study considering average weather conditions and RCMs outputs for the medium Representative Concentration Pathway scenario (RCP4.5). Results showed that average rainfall erosivity (R-Factor) was 508.85 MJ mm ha h−1 y−1 while the K-factor ranged from 0.0008 to 0.05 t ha h ha−1 MJ−1 mm−1 and LS-factor reached 60.51. Respectively, C-factor ranged from 0.01 to 0.91 and P-factor ranged from 0.42 to 1. The estimated potential soil loss rates will remain stable for the near future period (2021–2050), while an increase of approximately 9% is expected by the end of the 21th century (2071–2100). The results suggest that appropriate erosion mitigation strategies should be applied to reduce erosion risk. Subsequently, appropriate mitigation measures per Land Use/Land Cover (LULC) categories are proposed. It is worth noting that the proposed methodology has a high degree of transferability as it is based on open-source data.

Integrated CO2-H2S corrosion-erosion modeling in gas production tubing and pipeline by considering passive layer activity

Corrosion and erosion are the common pipe-integrity issues that occur when carbon dioxide, hydrogen sulfide and sand exist in the gas stream at the same time. Corrosion is developed by the reaction among carbon dioxide, hydrogen sulfide and iron, while erosion by the physical damage through flowing sand. When it comes to the prediction model which could accommodate both events, complex phenomena related to physics, chemistry and metallurgy should be put into account. In this paper, we develop a new-integrated corrosion-erosion model which can calculate the corrosion-erosion rate by considering the interactions among type of passive layer (mackinawite and siderite), formation and removal rate of passive layer, and surface reaction rate. The integrated model consists of fluid flow in pipes equation, kinetics of reaction, fundamental diffusion law, empirical erosion equation and fundamental Faraday’s law. Corrosion-erosion rate is obtained through iteration scenario after establishing pressure and temperature from fluid flow in pipes equation. Pipe dimension used in the simulation has tubing ID 2.992 in for vertical pipe and flowline ID 2.992 in for horizontal pipe. Simulations were conducted using hypothetic gas field data with variation of hydrogen sulfide and carbon dioxide composition. In constant erosion rate, when the hydrogen sulfide percentage is significantly greater than carbon dioxide, corrosion is more dominant than passive layer formation. However, when the carbon dioxide percentage is greater than that of hydrogen sulfide, the passive layer tends to form, resulting in scaling. These results can be explained by the faster formation rate of siderite than mackinawite. Finally, the proposed model can explain clearly the phenomena of corrosion-erosion and scaling by simplifying the complex phenomena occurred.

An improved CFD/experimental combined methodology for the calibration of empirical erosion models

A significant source of uncertainty in CFD-based erosion prediction is represented by the erosion model, used to turn the particle-wall impingement characteristics into an estimate of the removal of material. In engineering computations, frequent use is made of empirical erosion models obtained by fitting the experimental results of air-solid jet impingement tests. However, since the applicability conditions of these models are often unknown or unavailable to the users of CFD codes, they are frequently misapplied, producing not only uncertain, but at times also highly inaccurate wear estimates. As part of his PhD thesis defended at the University of Tulsa in 2016, Amir Mansouri proposed a methodology to calibrate the coefficients of an empirical erosion correlation by combining experimental data and CFD results of a slurry jet impingement test. This methodology provided an effective way to overcome the criticisms of using empirical erosion models taken from the literature without facing the complexity and the high computational burden of a multiscale, physically-based approach, in which the micro-scale mechanical interactions between the particles and the target surface are resolved according to the fundamental laws of damage mechanics. This paper presents an improved formulation of Mansouri's methodology, which not only increases the calibration accuracy of the empirical erosion equation, but also enhances the reliability of the CFD-based erosion prediction model as a whole. To this purpose, numerical simulations were supported by in-house slurry jet impingement experiments on an aluminum sample and curved Glass Reinforced Epoxy samples.

Experimental and Numerical Evaluation of the Effect of Particle Size on Slurry Erosion Prediction

AbstractDuring petroleum production, sand particles can be entrained with the transported carrier fluid despite of any sand exclusion process and erode the inner walls of the pipelines. This erosion process may even cause pipe leakage and oil spill. Therefore, investigating the regularities of erosion damage changing with particle size and predicting erosion behavior for different particle sizes are important to pipeline safety. In this study, slurry erosion experiments are conducted using quartz particles with similar shapes and different sizes ranging from 25 μm to 600 μm to investigate the effect of particle size on erosion profiles and provide the database for evaluating available erosion models. Computational fluid dynamics (CFD) is used to simulate the fluid flow and track particles to obtain impact information. Erosion equations then connect the particles’ impact information with erosion rate. Finally, the available mechanistic and empirical equations erosion models are evaluated by comparing predicted erosion profile with experimental data. It was found that the local maximum erosion damage increases with particle size, although the total erosion ratio is not changing significantly. These changes of erosion profiles can be predicted with acceptable accuracy by available empirical erosion models when particle sizes are no less than 75 μm.

Scour Mitigation and Erodibility Improvement Using Microbially Induced Carbonate Precipitation

Enhancing the scour resistance of foundation systems supporting superstructures over waterways is required for the sustainable functionality of the structure. In this article, the use of microbially induced carbonate precipitation (MICP) was investigated for the potential of its use in scour mitigation and erodibility improvement of sand. Testing was performed in a 0.91 by 1.22 by 1.22-m model box, and a double wall delivery system was developed and used to target cementation near the surface. A comparative study was performed on the scour behavior of untreated and treated samples using data from a series of flow tests. Impinging jet testing was used to evaluate the erodibility parameters of treated sand. The results from flow testing indicated that untreated and lightly cemented zones showed similar scour depth, whereas indiscernible scour was observed for the heavily cemented zone. The improvement distribution pattern throughout the media showed an ellipsoidal shape with respect to the injection source. The scour behavior and the cementation pattern indicated less cementation was achieved at the zone near the injection source because of high induced seepage velocity. Based on the impinging jet testing results, an empirical erosion model for MICP-treated sand is proposed as a function of the level of cementation.

Interpretation and application of the hydro-abrasive erosion model from IEC 62364 (2013) for Pelton turbines

Abstract An accurate prediction of hydro-abrasive erosion helps in design, planning and operation strategies of a hydropower plant. In the empirical erosion model from the International Electrotechnical Commission (IEC) 62364 standard, various terms such as flow co-efficient (Kf), material factor (Km) and exponent (p) were not provided for Pelton turbines components. The present paper aims to find the values of these terms and to interpret inadequately defined terms like erosion depth (S) and shape factor (Kshape) for application of IEC 62364 (2013)# model. From some field and laboratory data, the values of Kf and p were obtained for Pelton turbine components using multivariate regression analysis. The obtained values of Kf are in the order of 10−6 and 10−12 for various zones of buckets and nozzle assembly respectively whereas p values are in range 1–5. The Km values for 6 different materials, i.e. three types of chrome nickel steels, plasma and high velocity oxygen fuel (HVOF) sprayed coatings and bronze buckets were obtained as 1, 1, 1, 0.6, 0.1 and 2.2, respectively. #IEC 62364 (2013). Hydraulic machines - Guide for dealing with hydro-abrasive erosion in Kaplan, Francis and Pelton turbines. Edition 1.0 (June 2013), International Electro technical Commission, Geneva, Switzerland.

Modeling Deposit Erosion in Internal Turbine Cooling Geometries

Abstract Experiments were performed to study the erosion of deposit structures due to large particle impacts (>5 μm). Cone-shaped dust deposits were created in an oversized (6.35 mm diameter) impingement cooling jet at 811 K with 0–5 μm Arizona road dust (ARD). Subsequently, the deposit cones were eroded with larger particle distributions (5–10, 10–20, 20–40, and 40–80 μm ARD) at various velocities and temperatures. It was found that erosion rate increased with increasing particle size and flow velocity and with decreasing temperature. The dependency on size and velocity occurs through the particle's kinetic energy at impact, while the dependency on temperature is related to the adhesive forces in the deposit structure. Using the experimental data, an empirical erosion model was developed to be added to the Ohio State University (OSU) deposition model. A computational flow simulation combined with mesh morphing is shown to capture key features of the erosion physics.

Erosion modelling: a systematic review of available models and equations

Across the years there was an increased attention drawn by erosion modelling, both as a general approach and also towards pipeline applications (with a concentration on pipe bends). Several authors have studied the phenomena and tried to explain the mechanisms and factors affecting the emergence and magnitude of erosion. Most of the proposed models and equations were developed for ductile materials, with a smaller part looking also at brittle materials. There are several differences observed, starting with the proposed wear mechanism and continuing with the parameters used in the equations as significant factors (for the erodent particles, target material and working conditions). The most important models and equations are analysed and presented in this article and a systematic visual representation is used to ease and simplify the understanding of the erosion modelling evolution across the years (erosion modelling in general conditions, empirical erosion modelling in pipes and bends, CFD erosion modelling in pipes and bends).

Multiscale simulation of erosive wear in a prototype-scale Pelton runner

The technical capacity to predict the erosion process is instrumental for the optimization of the runner designs and operation strategies of hydroelectric plants. A multiscale model of erosion recently formulated by the authors and validated on a laboratory-scale jet impingement case is used to study the erosion of a prototype-scale Pelton runner. The model is shown to provide physically-sound descriptions of the sediment impact condition distributions on the bucket surface; furthermore, the erosion distribution obtained is explained in terms of these underlying impact condition distributions. The model predictions for the erosion depth distribution on the bucket surface are validated with the corresponding experimental data, resulting in an average error of 35% for eight point-wise comparisons, 14% for line-averaged values along four transversal sections, and 4% for the surface-averaged erosion depth, directly linked to the total eroded mass. A careful error propagation analysis of the comparison between simulation and field data yields an uncertainty of ±22%. Based on these considerations, the modeling error is estimated to be 26±22%. The results obtained, namely quantitative predictions of the erosion of industrial-scale hydraulic machines, have no precedent in the literature; they demonstrate the accuracy and transferability of the multiscale model of erosion and suggest an improvement over the state-of-the-art computational fluid dynamics models based on empirical erosion correlations.

Land use/land cover dynamics and soil erosion in the Umzintlava catchment (T32E), Eastern Cape, South Africa

Land use/land cover (LULC) change is often recognised as one of the most sensitive indicators of the interaction between humans and the natural environment contributing to soil erosion. Assessing the impact of LULC dynamics on soil erosion is imperative for soil conservation planning. Against this background, the primary aim of this paper is to assess the impact of LULC change on soil erosion in the Umzintlava catchment during the period 1989–2017. To achieve this, multi-temporal Landsat data, together with the Revised Universal Soil Loss Equation (RUSLE) were used. Six LULC classes – water bodies, badlands, bare soil and built-up area, agriculture, grassland, and forest – were derived for the years 1989, 2001, and 2017, based on the Normalised Difference Vegetation Index (NDVI) classification. A post-classification change detection analysis showed that water bodies, agriculture, and grassland decreased by 0.038%, 1.796%, and 13.417%, respectively, whereas the areas covered by forest, badlands, and bare soil and built-up area increased by 9.741%, 3.7338%, and 1.778%, respectively. Results further showed that all other LULC classes, except badlands, experienced increased rates of soil loss. The proportion of the catchment area experiencing moderate (12–25t ha-1year-1) to extremely high (>150t ha-1year-1) erosion risk consistently increased. This study provides relevant information on the relationship between LULC dynamics and soil erosion risk, highlighting the necessity and importance of integrating remote sensing and empirical erosion models in spatio-temporal soil erosion assessment at the catchment level.

Fusion Analysis of Optical Satellite Images and Digital Elevation Model for Quantifying Volume in Debris Flow Disaster

Rapid identification of affected areas and volumes in a large-scale debris flow disaster is important for early-stage recovery and debris management planning. This study introduces a methodology for fusion analysis of optical satellite images and digital elevation model (DEM) for simplified quantification of volumes in a debris flow event. The LiDAR data, the pre- and post-event Sentinel-2 images and the pre-event DEM in Hiroshima, Japan affected by the debris flow disaster on July 2018 are analyzed in this study. Erosion depth by the debris flows is empirically modeled from the pre- and post-event LiDAR-derived DEMs. Erosion areas are detected from the change detection of the satellite images and the DEM-based debris flow propagation analysis by providing predefined sources. The volumes and their pattern are estimated from the detected erosion areas by multiplying the empirical erosion depth. The result of the volume estimations show good agreement with the LiDAR-derived volumes.

Erosive wear behaviour of aluminium alloys: a comparison between slurry and dry erosion

The erosive wear performance of AA5083 and AA1050 has been investigated under dry and slurry erosion condition. The current work insights the erosive wear behaviour of Al alloys by changing the impact velocity and impingement angle. AA5083 exhibited remarkable erosion resistance compared to AA1050 by a factor of 2.5 to 3 in both the tests. The surface roughness of the eroded surface for impingement angle 15, 60° was an average of 450, 170 μm respectively for dry and slurry erosion test. Hardness of the eroded surface after the erosion test was measured to be 128.6 and 111.5 Hv for AA5083 and 63.9 and 52.9 Hv for AA1050 respectively for dry and slurry erosion. Wear surface studies reveals that cutting as well as abrasion grooves were dominant at lower impingement angle for both the tests. As the impingement angle increased, the material removal process was tuned by ploughing and formation of a crater in dry erosion and cracking in slurry erosion was witnessed. The subsurface study reveals that the affected region beneath the wear surface was an average of 40 and 25 μm for AA1050 and AA5083. Erosion data was correlated with the published empirical erosion model to analyse the dependence of the impingement angle.