Erosion Analysis for the Carcass of Unbonded Flexible Pipes

At present, unbonded flexible pipes (UFPs) are widely used in ocean engineering for oil exploitation. In practice, erosion will lead to premature failure of pipelines. There is a lack of researches on the erosion of interlock carcass of UFPs. As the authority in the field of offshore engineering, DET NORSKE VERITAS(DNV) suggested a way to estimate the erosion rate of pipes, however, it does not study the erosion mechanism of UFPs in detail and the relevant parameters are not specified. This paper modifies erosion prediction of UFPs based on a user defined Fortran subroutine. A series of CFD simulations have been conducted, and three widely used erosion models were used for comparative verification. The effect of geometric shape on erosion rate has been carefully studied. and the effect of velocity, particle size, and concentration are also studied to verify the reliability of the improved model.

Study on Parameters of Two Widely Used Cohesive Soils Erosion Models

The erosion rate of cohesive soils was typically modeled with the excess shear stress model and the Wilson model. Several kinds of research have been conducted to determine the erodibility parameters of the two models, but few attempts have been made hitherto to investigate the general trends and range of the erodibility parameter values obtained by the commonly used Erosion Function apparatus. This paper collected a database of 177 erosion function apparatus tests to indicate the variability of all erodibility parameters; the range of erodibility parameters is determined by data statistics and parameter theoretical value derivation. The critical shear stress (τc) and erodibility coefficient (Z0) in the over-shear stress model have a positive proportional relationship when the data samples are sufficient. However, there is no such relationship between the erodibility coefficient (b0) and erodibility coefficient (b1) in the Wilson model. It is necessary to express the soil erosion resistance by considering all erosion parameters in the erosion model. Equations relating erodibility parameters to water content, plasticity index, and median particle size were developed by regression analysis.

Comparison of the Applicability of Different Soil Erosion Models to Predict Soil Erodibility Factor and Event Soil Losses on Loess Slopes in Hungary

Climate change induces more extreme precipitation events, which increase the amount of soil loss. There are continuous requests from the decision-makers in the European Union to provide data on soil loss; the question is, which ones should we use? The paper presents the results of USLE (Universal Soil Loss Equation), RUSLE (Revised USLE), USLE-M (USLE-Modified) and EPIC (Erosion-Productivity Impact Calculator) modelling, based on rainfall simulations performed in the Koppány Valley, Hungary. Soil losses were measured during low-, moderate- and high-intensity rainfalls on cultivated soils formed on loess. The soil erodibility values were calculated by the equations of the applied soil erosion models and ranged from 0.0028 to 0.0087 t ha h ha−1 MJ−1 mm−1 for the USLE-related models. EPIC produced larger values. The coefficient of determination resulted in an acceptable correlation between the measured and calculated values only in the case of USLE-M. Based on other statistical indicators (e.g., NSEI, RMSE, PBIAS and relative error), RUSLE, USLE and USLE-M resulted in the best performance. Overall, regardless of being non-physically based models, USLE-type models seem to produce accurate soil erodibility values, thus modelling outputs.

The Analysis of Erosive Wear Resistance of WC-Co Carbides Obtained by Spark Plasma Sintering Method

WC-Co (tungsten carbide-cobalt) composites are widely used in industry, wear-resistant parts, and cutting tools. As successful tool materials, WC-Co carbides are widely applied in metal cutting, wear applications, chipless forming, stoneworking, wood, and plastic working. These materials are exposed to severe solid particle erosion by sand particles, such as in the wood industry. During the production of furniture with HDF (High Density Fibreboard), MDF (Medium Density Fibreboard), or OSB (Oriented Strand Board), there are observed problems with tool erosion. Contamination, mainly of the HDF by sand, is quite often, which is why all tools used for the machining of such materials are exposed to erosion by sand particles. Although many studies have been performed on the erosion of various metals, and erosion models exist to predict their erosion behavior, the issue is still relevant. The aim of the study was to determine the effect of grain size (submicron, ultrafine) and the manufacturing technology (SPS—Spark Plasma Sintering, conventional) used on the erosive properties of WC-Co sintered carbides. Sinters produced by the SPS method with different sizes of WC grains and commercial samples were used for the tests. Ten two-hour cycles were carried out under medium conditions of quartz sand and quartz sand with 10% SiC added. Used samples were characterised using scanning electron microscopy (SEM) and roughness was determined. Furthermore, erosion studies allowed individuating a wear mechanism as well as the possibility to foresee cutting performance in prospective application.

Application of the KINEROS 2 Model to Natural Basin for Estimation of Erosion

This study compares different methods to calculate erosion and sedimentation processes in the Aviar Basin, a natural peri-urban basin located in Comúd’Encamp (Andorra).The basin area is small, covering less than one square kilometer. Currently, increased densities of houses and buildings under natural basins can cause drainage problems. This is due to the heavy accumulation of eroded solid material in the sewer systems. Therefore, for a given basin condition, accurate estimation of erosion and sedimentation amounts is important. The development of erosion models aims to facilitate the estimation of eroded solid material and the design of possible protective measures to prevent soil losses. Both empirical and physically based erosion models were used to study the Aviar Basin for these purposes. Empirical models include USLE (Universal Soil Loss Equation), RUSLE (Revised USLE) and MUSLE (Modified USLE), while one physically based model, KINEROS 2, was used. The volumes of solid materials produced in the Aviar Basin during the year 2012 were determined using these four different erosion models and then compared between them. The results of this study show that the estimation of soil loss using KINEROS 2 is useful in practice because the results obtained are close to those obtained from the empirical models.

Can the models keep up with the data? Possibilities of soil and soil surface assessment techniques in the context of process based soil erosion models – A Review

Climate change, accompanied by intensified extreme weather events, results in changes in intensity, frequency and magnitude of soil erosion. These unclear future developments make adaption and improvement of soil erosion modelling approaches all the more important. Hypothesizing that models cannot keep up with the data, this review gives an overview of 44 process based soil erosion models, their strengths and weaknesses and discusses their potential for further development with respect to new and improved soil and soil erosion assessment techniques. We found valuable tools in areas, as remote sensing, tracing or machine learning, to gain temporal and spatial distributed high resolution parameterization and process descriptions which could lead to a more holistic modelling approach. Most process based models are so far not capable to implement cross-scale erosional processes or profit from the available resolution on a temporal and spatial scale. We conclude that models need further development regarding their process understanding, adaptability in respect to scale as well as their parameterization and calibration. The challenge is the development of models which are able to simulate soil erosion processes as close to reality as possible, as user-friendly as possible and as complex as it needs to be.

Uncertainty Estimation in CFD Simulations of Erosion for Elbows

Computational Fluid Dynamics (CFD) is used extensively in the industry and academia for analyzing the motion of solid particles and the associated solid particle erosion that may occur in various pipe components. However, CFD simulations always carry levels of inherent uncertainties due to the numerical approximations of governing equations, generated grid, and turbulence models. Also, because of the complex nature of solid particle erosion, additional uncertainties are added to erosion prediction simulations. Aspects such as particle size, number of impacts, particles’ initial condition, near-wall mesh effects, forces considered in particle tracking procedures, particle-particle interaction, and near-wall particle-fluid interactions are all possible sources of uncertainties associated with erosion prediction in CFD. Furthermore, unique problems that accompany discrete phase handling and erosion calculation needed for the industrial applications magnify the importance of uncertainty estimation in erosion calculations. Commercially available CFD codes are used with user-developed subroutines to investigate particle erosion prediction uncertainties, numerically in elbows, by considering gas and liquid flow for several pipe sizes. Moreover, different particle sizes, inlet flow velocities, turbulence models, wall functions, and erosion models are examined. According to the ASME’s Verification and Validation (V&V) standard, uncertainties are divided into 3 categories; input, numeric, and modeling. Thus, it is possible to utilize the ASME’s standard as guidance to predict uncertainty for erosion simulations. Furthermore, an extra parameter was considered for uncertainties to account for the uncertainties induced by different simulation procedures and erosion models. The current investigations resulted in developing a framework for estimating uncertainties of erosion simulation. For each simulation result, two bounds (upper and lower) were predicted for erosion. The results show that the Reynolds Stress turbulence model (RSM) and Arabnejad’s erosion model usually predict results corresponding to the lowest uncertainties.

Erosive investigation of various erosion models for vibro cleaner developed based on ultrasonic technique using COMSOL multiphysics

The ability of ultrasound to produce highly controlled erosion phenomenon was investigated and various erosion models have been compared by considering various parameters. In cleaning industry, Vibro Cleaner (VC) has been used to remove contaminations from the surface of metal components. This process is most preferable to out of reach or critical surface of the objects. The novelty of this research is to compare various erosion models and to identify appropriate model for ultrasonic cleaning application to get meaningful results of metal removal rate. The computational model of Vibro Cleaner has been developed using pressure acoustic transient in COMSOL Multiphysics software. Acoustic and Computational Fluid Dynamics (CFD) modules have been coupled together to investigate erosion rate. In acoustic approach, acoustic pressure and sound pressure level have been studied by means of piezoelectric transducer through tank wall transience. In CFD approach, Bubbly fluid flow has been applied to get turbulence in acoustic streaming. Also, particle tracing has been coupled to understand the particle trajectories and motion of fluid flow. Erosion terms are also introduced at a surface of metal parts which need to be clean. The Erosion rate has been evaluated by using cavitation erosion phenomenon in which cavitation bubbles strike and implode over the metal surface and clean the dirt, dust, oil and other contaminations. Various Erosion models like Finnie, E/CRC, Oka and Det Norske Veritas (DNV) have been studied and results have been compared to identify appropriate erosion model towards the ultrasonic cleaning application by considering 28 kHz frequency and PZT-4 piezoelectric transducer. Comparative study leads to conclude that the Finnie erosion model have given stringent results as compare to other erosion model.