Erosion Experiments Research Articles

Chloride ion erosion experiment research in cracked concrete

For the study of chloride ion erosion in cracked concrete, this essay tries to take advantages of relevant trails to build up concrete chloride ion diffusion model based on the Fick’s second law. The parameter of this model is easy to be set, and many factors such as the effect of cracks are taken into consideration in this experiment. The concept of “chloride ion diffusion coefficient of equivalent apparent” is introduced to simplify the calculation. It can help simplify the calculation process, and get a more accurate test result, as well as facilitating the practical application of this parameter.

Meltwater erosion process of frozen soil as affected by thawed depth under concentrated flow in high altitude and cold regions

AbstractChanges in thawed depth of frozen soil caused by diurnal and seasonal temperature fluctuations are commonly found in high altitude and latitude regions of the world. These changes significantly influence hydrologic and erosion processes. Experimental data are necessary to improve the understanding and modeling of the phenomenon. Laboratory experiments were conducted in Beijing to assess the impacts of thawed soil depth, slope gradient, and flow rate on soil erosion by concentrated meltwater flow over an underlying frozen soil layer. Soil samples from watershed were filled in flumes, saturated before being frozen. After the soil was completely frozen, flumes were taken out of storage to thaw the frozen soil from top to the designed depths. Meltwater flow was simulated using a tank filled with water and icecubes at approximately 0°C. The erosion experiments involved four thawed soil depths of 1, 2, 5, and 10 cm; three slope gradients of 5°, 10°, and 15°; and three flow rates of 1, 2, and 4 l/min; and seven rill lengths of 0.5, 1, 2, 3, 4, 5, and 6 m. Sediment‐laden water samples were collected at the lower end of the flume for determination of sediment concentration. The results showed that sediment concentration increased exponentially with rill length to approach a maximum value. The sediment concentrations were closely correlated with thawed soil depth, flow rate, and slope gradient. Shallower thawed depths delivered more sediments than deeper thawed depths. Slope gradient was the primary factor responsible for severe erosion. The effect of flow rate on sediment concentration which decreased with increasing slope gradient, was not as significant as that of slope gradient. Results from these experiments are useful for understanding the effect of thawed soil depth on erosion process in thawed soils subject to freezing and for estimating erosion model parameters. Copyright © 2017 John Wiley & Sons, Ltd.

Modelling of resuspension due to fish activity: Mathematical modeling and annular flume experiments

A spatially averaged numerical model was developed to describe the erosion of cohesive sediment. Together with known empirical relations, the model comprises a new formulation for resuspension due to fish activity. Experiments on erosion of natural sediments in the annular flume at Aachen University are used for model calibration. Empirical coefficients were evaluated with genetic algorithms to achieve the best agreement between the model results and the experimental data. The presented model shows sufficient flexibility to account for various sediment properties, including different sediment sources, natural and artificial contaminants, presence or absence of aquatic organisms, and results in an average coefficient of determination, R2 = 90.5% between the model results and the experimental data. Model validation allows it to be assumed that different contaminants affect bed properties differently. Fish activity plays an essential role in correct resuspension prediction. Further sediment erosion experiments with carefully chosen conditions will allow a more comprehensive model evaluation. The presented model is intended to serve as a building block in the development of a hydraulic-sediment-biota model within the W3-Hydro: Water Quality Event Detection for Urban Water Security and Urban Water Management Based on Hydrotoxicological Investigations project that aims to improve the knowledge concerning bioavailability, transport, fate, and effects of contaminants on the aquatic environment.

An interdisciplinary tillage erosion experiment: establishing a field in grassland with reconstructed ard plough of the Bronze Age-Iron Age

Despite recognising the role of tillage erosion in landforms evolution, little research has documented its effects in prehistoric times. Herein, an interdisciplinary archaeological-geomorphological experiment with reconstructed tillage tools and management was conducted in order to measure tillage erosion when a new field in grasslands was established in the Bronze Age-Iron Age. Three wooden ards were reconstructed based on archaeological findings. They were tested in a cross-tillage experiment, consisting of a tillage pass perpendicular to the primary slope (6.5-9.7%), and a second tillage pass parallel to the primary slope of a convex-convex ridge with mowed grass (0.2 m high, vegetation cover >90%). The standard sole ard proved to be the most effective, with a mean tillage depth of ~0.12 m, a mean tillage speed of 3.8 km h-1, and a mean distance between furrows of 0.20-0.25 m. Only 13% of the 264 tracers placed on 6 transects were displaced, and the mean tracers displacement parallel to the primary slope was 0.04 ± 0.17 m. Contour tillage perpendicular to primary slope created V or U shaped furrows with a mean depth of 0.1-0.12 m, a mean width of 0.05-0.1 m, and incision under the main root zone. Only soil in direct contact with the ard was displaced, with a mean translocation distance of 0.06 ± 0.2 m parallel and 0.06 ± 0.3 m perpendicular to the primary slope. During tillage parallel to slope, soil clods of ~0.20 x 0.25 x 0.10 m were created and slightly disturbed or turned over one another. The tracers moved within the furrows and with the soil clods. Loose soil, resembling a seedbed, was not covered by soil clods. Mean displacement during the second pass was 0.03 ± 0.19 m parallel and 0.00 ± 0.15 m perpendicular to primary slope. The displacement from cross-tillage with a wooden ard in permanent grasslands was lower than many previously measured values of traditional animal-powered metal ploughs in permanent fields. No relationship between mean soil displacement and slope gradient was found. Dense vegetation and root structure influenced ard soil-penetration, its movement within the soil, and the displacement of tracers packed between the roots. Cross-tillage with a wooden ard proved to be insufficient for seedbed preparation. The results suggest that grazing or fire management, followed by repeated tillage with ard or hoe in order to destroy soil clods were necessary to establish a new field in grasslands during the Bronze Age-Iron Age.

Conditional Network Assembly and Targeted Protein Retention via Environmentally Responsive, Engineered β-Roll Peptides.

Stimulus-responsive biomaterials have applications in many areas of biotechnology, such as tissue engineering, drug delivery, and bioelectrocatalysis. The intrinsically disordered repeat-in-toxin (RTX) domain is a conformationally dynamic peptide that gains β-roll secondary structure when bound to calcium ions. A smart hydrogel platform was constructed by genetically fusing two rationally designed mutant RTX domains: first, a mutant peptide with hydrophobic interfaces capable of calcium-dependent network assembly, and second, another mutant that conditionally binds the model target protein lysozyme. In this way, the calcium-induced control over the secondary structure of the β-roll peptide was exploited to regulate both the cross-linking and lysozyme-binding functionalities. The constructed biomaterial exhibited calcium-dependent gelation and target molecule retention, and erosion experiments showed that β-roll peptides with a higher affinity for lysozyme produced more robust hydrogel networks. This work demonstrates the use of RTX domains for introducing two useful features simultaneously, network cross-linking and target protein binding, and that the calcium-dependent regulation of these systems can be useful for controlling bulk self-assembly and controlled release capabilities.

Erosion characteristics and stochastic nature of bed shear stress in underwater mine tailings

The erosion of mine tailings was investigated by examining the physical processes during the initiation of motion of the tailings. Erosion experiments were conducted on mine tailings samples and natural soils in a Plexiglas laboratory annular column under 50 cm water cover. Resuspension was introduced with a Teflon stirrer and the bed shear stress was estimated from the measured near-bed velocity field and the pressure change in the boundary layer. Two modes of initiation of motion of cohesive mine tailings that showed cohesive behaviour was noticed: pitting erosion and line erosion and the modes of initiation of motion changed mainly with percentage of fines. At incipient motion of the tailings that showed cohesive behaviour, the pore water pressure distribution showed a relative sudden peak and a decline when the aggregated tailings burst. A four order of magnitude difference was observed between the undrained shear strength and critical shear stress for surface erosion of the tailings. The stochastic nature of the bed shear stress was explained by the Rayleigh distribution that provides an approach for correcting the critical shear stress estimated from the near-bed velocity. This correction is necessary to achieve a conservative estimate of the critical shear stress for design purposes.

Hindered erosion: The biological mediation of noncohesive sediment behavior

AbstractExtracellular polymeric substances (EPS) are ubiquitous on tidal flats but their impact on sediment erosion has not been fully understood. Laboratory‐controlled sediment beds were incubated with Bacillus subtilis for 5, 10, 16, and 22 days before the erosion experiments, to study the temporal and spatial variations in sediment stability caused by the bacterial secreted EPS. We found the biosedimentary systems showed different erosional behavior related to biofilm maturity and EPS distribution. In the first stage (5 days), the biosedimentary bed was more easily eroded than the clean sediment. With increasing growth period, bound EPS became more widely distributed over the vertical profile resulting in bed stabilization. After 22 days, the bound EPS was highly concentrated within a surface biofilm, but a relatively high content also extended to a depth of 5 mm and then decayed sharply with depth. The biofilm increased the critical shear stress of the bed and furthermore, it enabled the bed to withstand threshold conditions for an increased period of time as the biofilm degraded before eroding. After the loss of biofilm protection, the high EPS content in the sublayers continued to stabilize the sediment (hindered erosion) by binding individual grains, as visualized by electron microscopy. Consequently, the bed strength did not immediately revert to the abiotic condition but progressively adjusted, reflecting the depth profile of the EPS. Our experiments highlight the need to treat the EPS‐sediment conditioning as a bed‐age associated and depth‐dependent variable that should be included in the next generation of sediment transport models.

Performance study of erosion resistance on throttle valve of managed pressure drilling

The throttle valve designed for managed pressure drilling (MPD) is a core equipment of MPD technology. Due to the direct contact with drilling fluid at well site, the throttle valve's internal flow passage will be eroded and worn by the drilling fluid with high mobility, which would negatively affect the working performance and service life of the throttle valve. Therefore, based on the working principle and geometric structure of throttle valve, the computational fluid dynamics (CFD) technique is used to establish the three-dimensional fluid numerical model, and the renormalization group k-epsilon (RNG k-ε) model is selected for the turbulence model of liquid-solid two-phase flow in throttle valve of MPD. At the same time, the fluid flow in the wall region is solved by wall function which allows the physical quantity near the wall surface to connect with it in the core turbulence region. In addition, the discrete phase model (DPM) model is selected for the discrete phase model, and the Ahlert erosion model is selected for the erosion model. The finite volume method is used in discrete calculation, and the SIMPLE algorithm is applied in continuity equation, momentum equation, energy equation and turbulent kinetic energy equation when solving the control. The influences of drilling parameters (such as throttle valve opening, drilling fluid flow rate, drilling fluid density, mass flow rate of solid particle) on the erosion characteristics of throttle valve of managed pressure drilling are studied by CFD. The results show that the erosion of the solid particles on the wall of MPD throttle valve mainly occurs at the end of the valve spool. Meanwhile, the drilling fluid flow rate has the greatest impact on the erosion rate of solid particles, which is followed by the solid mass flow. Compared with the above two, the erosion rate of solid particles is less influenced by the throttle pressure difference between inlet and outlet which is caused by the change of throttle opening and drilling fluid density. In addition, the simulation result reaches a good agreement with the laboratory data of throttle valve erosion experiment. This study could give several advices for relevant throttle valve investigation work and operators who attempts to decrease the erosion in valves.

Estimation of small-scale soil erosion in laboratory experiments with Structure from Motion photogrammetry

The quantitative estimation of changes in terrain surfaces caused by water erosion can be carried out from precise descriptions of surfaces given by means of digital elevation models (DEMs). Some stages of water erosion research efforts are conducted in the laboratory using rainfall simulators and soil boxes with areas less than 1m2. Under these conditions, erosive processes can lead to very small surface variations and high precision DEMs are needed to account for differences measured in millimetres. In this paper, we used a photogrammetric Structure from Motion (SfM) technique to build DEMs of a 0.5m2 soil box to monitor several simulated rainfall episodes in the laboratory. The technique of DEM of difference (DoD) was then applied using GIS tools to compute estimates of volumetric changes between each pair of rainfall episodes. The aim was to classify the soil surface into three classes: erosion areas, deposition areas, and unchanged or neutral areas, and quantify the volume of soil that was eroded and deposited. We used a thresholding criterion of changes based on the estimated error of the difference of DEMs, which in turn was obtained from the root mean square error of the individual DEMs. Experimental tests showed that the choice of different threshold values in the DoD can lead to volume differences as large as 60% when compared to the direct volumetric difference. It turns out that the choice of that threshold was a key point in this method. In parallel to photogrammetric work, we collected sediments from each rain episode and obtained a series of corresponding measured sediment yields. The comparison between computed and measured sediment yields was significantly correlated, especially when considering the accumulated value of the five simulations. The computed sediment yield was 13% greater than the measured sediment yield. The procedure presented in this paper proved to be suitable for the determination of sediment yields in rainfall-driven soil erosion experiments conducted in the laboratory.

Abrasion erosion modeling in particulate flow

Solid particle erosion is of great importance to many industries including oil and gas production, drilling, process and transportation of minerals including oil sands. The particles that may cause erosion are of various sizes, shapes and hardnesses. These particles may impact the surface at various speeds and angles, and the influence of these parameters is characterized to some extent in the literature. Experimental and numerical studies have shown that when particles are transported by liquid (e.g. slurry transport in the pipe) or dense gas, the particle impact angles are very low. The impact angles in these cases are sometimes less than the smallest value that can be obtained in a direct impingement erosion test in gas. In this work, the mechanistic erosion equation developed previously is extended to near zero impact angles for sharp particles. The abrasion erosion equation is developed by introducing an initial penetration of the sharp particle in the equation of the motion. This initial penetration may be attributed to the sharp particle rotation and/or turbulent flow fluctuations of the carrier fluid near the wall. The empirical constants are obtained from submerged erosion experiments in liquid. The equation has been implemented in a commercially available Computational Fluid Dynamics (CFD) code (ANSYS FLUENT) to calculate erosion for a submerged impingement jet geometry, and the result is compared with the experiment. It is shown that by neglecting the abrasive term in the erosion equation, the specimen mass loss does not match the experimental measured mass loss. While by including the abrasive term, the total mass loss of the specimen agrees well with the experimental data. Moreover, the erosion pattern becomes closer to the experimentally measured pattern especially farther from the center of the highly eroded area where abrasive wear is expected to dominate.

Cavitation erosion and erosion-corrosion resistance of austenitic stainless steel by plasma transferred arc welding

Abstract 41WC-36Ni7.5CrSiB (Colmonoy75) and NiCrBSiW (Colmonoy88) alloy coatings were synthesized on 316 L stainless steel by plasma transferred arc welding, aiming at improving cavitation erosion and erosion-corrosion resistance. The microstructure, chemical composition, phase constituents and microhardness were determined by using SEM, EDS, XRD and microhardness tester. The cavitation erosion and erosion-corrosion experiments of the coatings were investigated using an ultrasonic vibrator and a jet erosion testing measurement in 3.5 wt% NaCl solution, respectively. Experimental results showed that the coatings with few pores, cracks or other defects could be obtained. The microstructure of the Colmonoy75 and Colmonoy88 coatings exhibited cellular dendrite and irregular blocky phases. The two coatings were composed of γ-Ni solid solution and WC particles, while the formation mechanism of WC was different. In the cavitation erosion and erosion-corrosion tests, the cumulative volume losses of the two coatings were much lower than that of the substrate. Colmonoy88 coating exhibited a better resistance to cavitation erosion and erosion-corrosion than Colmonoy75 coating. The cavitation erosion and erosion-corrosion resistance of the Colmonoy75 coating could reach about 3 times and 8 times that of 316 L substrate, while the Colmonoy88 coating could reach about 12 times and 31 times that of 316 L substrate, respectively. The improvment in the cavitation erosion and erosion-corrosion resistance for Colmonoy88 coating could be attributed to the fact that the in situ synthesized WC particles increased the cavitation erosion and erosion-corrosion resistance by providing an anchoring effect on the solid solutions to hinder the nucleation and propagation of cracks.

Characterizing Low-Z erosion and deposition in the DIII-D divertor using aluminum

We present measurements and modeling of aluminum erosion and redeposition experiments in separate helium and deuterium low power, low density L-mode plasmas at the outer divertor strike point of DIII-D to provide a low-Z material benchmark dataset for tokamak erosion-deposition modeling codes. Coatings of Al ∼100nm thick were applied to ideal (smooth) and realistic (rough) surfaces and exposed to repeat plasma discharges using the DiMES probe. Redeposition in all cases was primarily in the downstream toroidal field direction, evident from both in-situ spectroscopic and post-mortem non-spectroscopic measurements. The gross Al erosion yield was estimated from film thickness change measurements of small area samples, and was found to be ∼40–70% of the expected erosion yield based on theoretical physical sputtering yields after including sputtering by a 1–3% carbon impurity. The multi-step redeposition and re-erosion process, and hence the measured net erosion yield and material migration patterns, were found to be influenced by the surface roughness and/or porosity. A time-dependent model of material migration accounting for deposit accumulation in hidden areas was developed to reproduce the measurements in these experiments and determine a redeposition probability distribution function for sputtered atoms.

Effect of Erodent Impact Angle on the Erosion Behaviour of Plasma Sprayed Cr2O3 coating on Martensitic steel

In the present work, solid particle erosion behavior of plasma sprayed Cr2O3 coatings on Ni/Cr coated AISI 410 martensitic steel was determined using air jet erosion test rig at room temperature as per ASTM G-76 standard. Ni/Cr powder particles were deposited as a bond coat for good fastening. Erosion experiments were conducted by using silica of average particle size 312µm at impact angles of 300,450,600,750,900. Vickers micro hardness test was performed on coated and un-coated substrates to measure the hardness value. Eroded surface morphologies were observed using scanning electron microscope to understand the erosion mechanism. The presence of elements of chromium and oxide were confirmed in the EDX analysis. Experimental results indicate that Cr2O3 coated substrates exhibit better erosion resistance, increased hardness and reduced porosity as compared to un-coated steel substrates. The test results also reveal that erosion at the impact angles of 600 and 750 is many times higher than at the impact angles of 300,450,900

FRP のレインエロージョン挙動に関する研究

Erosion damage have been a serious prob1em in many industries, then there are many reports for homogeneous materia1s but not for composites. Wind power, as an alternative to burning fossil fuels, is plentiful, renewable, clean, and produces no greenhouse gas emissions during operation. On the blade of wind power, the damage of the impact of particles, sand erosion, was found. So, in the case of off-shore wind power, rain erosion is considered to be occurred on the blade of off-shore wind power plant. So in this study, the rain erosion tester was made to examine the rain erosion behavior of FRP. In many cases, for the improvement of erosion resistance, the coating film was performed on the blade of wind power plant. So, in this study, test pieces with coating film were made and erosion resistance of coating paint film was investigated by performing a rain erosion experiment. After experiments, damaged surfaces were observed and erosion resistance of coating paint film was discussed.

Erosion Experiment of Non-impingement Surface by Cavitating Jet

Erosion Experiment of Non-impingement Surface by Cavitating Jet

Modeling WEPP erodibility parameters in calcareous soils in northwest Iran

Modeling soil detachment rates at the regional scale is important for better understanding of the processes of erosion and the development of erosion models. Soil erodibility is an important factor for predicting soil loss, but its direct measurement at the watershed scale is difficult, time-consuming and costly. This study used stepwise multiple-linear regression (MLR) and artificial neural networks (ANNs) to model Water Erosion Prediction Project (WEPP) soil erodibility parameters, including the baseline inter-rill erodibility (Kib), baseline rill erodibility (Krb) and critical shear stress (τcb) of cropland conditions in calcareous soils of northwest Iran. Simulated inter-rill and rill erosion experiments were conducted at 100 locations with three replications. Kib, Krb and τcb and basic soil properties were measured at each location. Auxiliary variables related to soil erodibility were derived from a Landsat 7 satellite image and a 30m×30m digital elevation model (DEM). MLR and ANN models were employed to predict Kib, Krb and τcb using two groups of input variables: i) more easily measurable basic soil properties (pedo-transfer functions (PTFs)) and ii) more easily measurable basic soil properties and auxiliary data (soil spatial prediction functions (SSPFs)). The results indicated that the WEPP models performed poorly in comparison to the derived models. PTFs and SSPFs generated from ANN models provided more reliable predictions than the MLR models. ANN-based SSPF models yielded the best results (with the highest R2 and lowest RMSE values) for predicting Kib and Krb. ANN-based PTF model performed reasonably well for predicting τcb. These results show that information from terrain attributes and remote sensing data are potential auxiliary variables for improving prediction of soil erodibility parameters.

The role of grain-size ratio in the mobility of mixed granular beds

The main goal of the study was to understand the effects of grain-size distribution on the stability of beds in the sand-silt range, which is a critical subject for the understanding of geomorphological processes in aquatic environments. Although theoretical models can explain the mobilization of a mixed bed, there is a clear lack in knowledge regarding the stabilizing effect of non-cohesive fine material. To connect existing findings, we analysed bed stability in relation to grain-size distribution in laboratory experiments. Erosion experiments in an annular flume were conducted using beds of different size compositions of spherical glass beads, i.e. a) the grain-size ratio RD=D50,coarse/D50,fine (the relative size of coarse and fine grains; D50=39–367μm) and b) the amount of fines. Several glass-bead combinations with unimodal and bimodal grain-size distributions (RD=3.9, 5.8, and 9.4) and varying fine fractions (10–40% dry weight) were subjected to increasing flow speeds (0.01–0.19ms−1). Using acoustic Doppler velocimetry (ADV) and optical backscatter, the flow profile in the vicinity of the bed surface, the changes in bed morphology, and the suspended sediment concentration (SSC) were measured. A new method was developed to evaluate the bed-level changes detected by the ADV as a proxy for the bed mobility. We found different modes of bed mobility depending on the grain-size ratio. For low grain-size ratios, an increase in the fine fraction (to 40%) led to increased bed-level changes during the experiment and the mobilization of the mixed bed at the highest flow speed. For high ratios an increase in fine fraction (to 40%) led to a decrease of bed-level changes and the beds remained stable, i.e. no bed forms developed even at the highest flow speed. Therefore, increasing the amount of fine particles can lead to different modes of behaviour depending on the grain-size ratio. For a bimodal sediment bed with spherical grains under unidirectional flow conditions, the grain-size ratio can be used to estimate the bed mobility, i.e. to evaluate if a bed is likely to mobilize at flow speeds of up to 0.19ms−1. Hence, for the stability of a non-cohesive, mixed bed in the sand-silt range, the grain-size ratio plays a fundamental role, while the amount of fine grains is a secondary factor.

Mechanical and corrosion behavior of thick and soft DLC coatings

The DLC coatings are chemically inert, have low friction coefficient and good wear resistance. Depending on H content and sp3 bonds, they can be classified in “soft” or “hard” films. In this work, the corrosion and mechanical behavior, as well as the adhesion of thick DLC coatings are studied. The coatings, which are in fact silicon containing amorphous hydrogenated carbon films, were deposited by PACVD on nitrided austenitic stainless steel (duplex sample) and non-nitrided austenitic stainless steel (coated sample). The films were characterized by EDS and Raman spectroscopy, hardness was assessed by nanoindentation and microstructure was analysed by OM and SEM. To evaluate sliding wear behavior and friction, pin on disk tests were performed. The abrasive wear resistance was tested using the ASTM G65-95 Dry Sand/Rubber Wheel test. Erosion tests were conducted in water and sand flux. The corrosion resistance was evaluated by the Salt Spray Fog Test and electrochemical tests. The adhesion was tested using Scratch Test. The purpose was to systematically characterize the defects present in these thick DLC coatings relating them to adhesion, wear and corrosion resistance.The thickness of the DLC coating was about 37μm, and its hardness was 12GPa. The coatings presented a low friction coefficient, about 0.09. In the abrasive tests, the mass loss was negligible and in erosion experiments, the mass loss was reduced to 30%. Regarding the corrosion performance, the behavior in the Salt Spray Fog Test was good only in the duplex samples. In potentiostatic tests in 3.5% NaCl using steps, the current density increased at higher potentials for the duplex sample. Concerning the film adhesion, the critical load was also higher in theses samples than in the coated ones. The nitrided layer was a good interface for reducing the stresses and improving the adhesion, which is relevant for the decrease of the propagation rate of corrosion, when traversing defects are formed in the coating.

Research on erosion wear of high-pressure pipes during hydraulic fracturing slurry flow

The frequent erosion of high-pressure pipelines (HPP) is one of the most serious problems in petroleum industry. Since HPP is designed for hydraulic fracturing operations, the tubing wall is prone to be affected by non-uniform erosions caused by slurries with high rates. The erosion in multiphase flow is not widely understood and previous work has mostly focused on single phase. This paper studied the slurry erosion of HPP during hydraulic fracturing slurry flow. Through failure analysis of high-pressure elbows based on its macroscopic features and scanning electron microscope (SEM), the failure cause and failure mechanism are obtained. Depending on the failure analysis, an erosion wear test rig and experiment approach is developed to extract the main parameters influencing on erosion wear. As a result of the erosion wear experiment, the erosion model in ANSYS-FLUENT software is established. The wear distribution of pipes under different connections are obtained by CFD numerical simulation method, the experiment validates the consistency of the erosion wear results from CFD method and the field inspection. The study may provide references to carry out the optimization design, installation strategy and detection scheme for HPP and make sure the safety of the whole technological process.

Comparative study of erosion processes of thawed and non-frozen soil by concentrated meltwater flow

Investigating the erosion processes of freeze–thaw-affected soils caused by concentrated snow/glacier meltwater flow can be challenging. Experimental data can help improve our understanding and modeling of the phenomenon. Laboratory experiments were conducted to assess the effects of slope gradient and flow rate on soil erosion by concentrated meltwater flow over thawed and non-frozen soil surfaces. Flumes were filled with the silty–sandy soil materials collected from a watershed delta formed by deposited sediments before being saturated and stored in a freezer to freeze the soil. After the soil was completely frozen, the flumes were taken out of the freezer and placed in the experimental hall to thaw the soil for a period of sufficient length until all the soil materials were thawed. Similarly, flumes which were filled with the same soil in the same procedures without undergoing the freezing and thawing process were used for the comparative experiments. Meltwater was simulated with a tank filled with ice water mixture to supply water flow at a temperature of 0°C. The erosion experiments involved four slope gradients of 5°, 10°, 15°, and 20° and three flow rates of 1, 2, and 4L/min, with seven rill lengths of 0.5, 1.0, 2.0, 3.0, 4.0, 5.0, and 6.0m, as determined by the distance between the water inlets and exit sill. Sediment concentrations at the seven locations formed a rill erosion process, which increased exponentially with rill length to approach a limiting value. The sediment concentrations were positively correlated with flow rate and slope gradient. However, the effect of flow rate on sediment concentration was not as significant as that of slope gradient. The effect of flow rate on sediment concentration decreased with the increase in slope gradient. The maximum sediment concentrations in water flow over thawed slopes were higher than those over non-frozen slopes. Results from these experiments will be useful for estimating erosion model parameters for predicting erosion by meltwater.