Dental erosion: In vitro model of wine assessor's erosion

The document attached has been archived with permission from the Australian Dental Association. An external link to the publisher’s copy is included.Background: Wine makers and assessors frequently experience severe dental erosion. The objectives of this study were to develop an in vitro model of dental erosion caused by frequent wine contact with teeth, and to use this model to assess the effectiveness of a variety of methods which might protect against this form of erosion. Methods: An initial pilot study found that riesling style wine was more erosive than champagne style, and both more than claret. Wine tasting was simulated by subjecting exposed windows of enamel and root surfaces on 50 intact, extracted human teeth to 1400 one minute exposures to white wine (pH 3.2). A variety of dental materials were applied to the exposed windows on groups of teeth prior to erosive challenge, to assess their protective ability. Results: Protective resin coatings and fluoride varnishes protected both enamel and roots against wine induced erosion. A high degree of protection was provided by APF gel, with less by NaF gel. Conclusions: It was concluded that dentists may be able to help minimise erosion resulting from frequent wine-tasting in their patients by the clinical application of one or a combination of these agents at times prior to prolonged assessment periods.Tong Bee Mok, J McIntyre and D Hun

Model for erosion-deposition patterns

We investigate through computational simulations with a pore network model the formation of patterns caused by erosion-deposition mechanisms. In this model, the geometry of the pore space changes dynamically as a consequence of the coupling between the fluid flow and the movement of particles due to local drag forces. Our results for this irreversible process show that the model is capable to reproduce typical natural patterns caused by well known erosion processes. Moreover, we observe that, within a certain range of porosity values, the grains form clusters that are tilted with respect to the horizontal with a characteristic angle. We compare our results to recent experiments for granular material in flowing water and show that they present a satisfactory agreement.Comment: 8 pages, 12 figures, submitted to Phys. Rev.

A CFD model of erosion-corrosion of Fe at elevated temperatures in aqueous environments

In studies of erosion-corrosion at materials at elevated temperatures, there have been many attempts to model the process. Such models have comprised quasi-static and simulation models. However in many environments, erosion-corrosion occurs in aqueous conditions and can be considerably affected by flowing gases in dry conditions. In such cases, any accurate models of erosion-corrosion must include an algorithm due to flow in addition to the mechanics and chemistry of the tribo-corrosion interactions. In this paper, a CFD model is generated of the tribo-chemical interaction at elevated temperatures. The initial work has concentrated on modeling temperature effects in wet conditions; however, the potential application of the model to dry conditions is also outlined. The results are discussed in relation to existing erosion-corrosion models in the literature at elevated temperatures

Erosion of dust aggregates

Aims: The aim of this work is to gain a deeper insight into how much different aggregate types are affected by erosion. Especially, it is important to study the influence of the velocity of the impacting projectiles. We also want to provide models for dust growth in protoplanetary disks with simple recipes to account for erosion effects. Methods: To study the erosion of dust aggregates we employed a molecular dynamics approach that features a detailed micro-physical model of the interaction of spherical grains. For the first time, the model has been extended by introducing a new visco-elastic damping force which requires a proper calibration. Afterwards, different sample generation methods were used to cover a wide range of aggregate types. Results: The visco-elastic damping force introduced in this work turns out to be crucial to reproduce results obtained from laboratory experiments. After proper calibration, we find that erosion occurs for impact velocities of 5 m/s and above. Though fractal aggregates as formed during the first growth phase are most susceptible to erosion, we observe erosion of aggregates with rather compact surfaces as well. Conclusions: We find that bombarding a larger target aggregate with small projectiles results in erosion for impact velocities as low as a few m/s. More compact aggregates suffer less from erosion. With increasing projectile size the transition from accretion to erosion is shifted to higher velocities. This allows larger bodies to grow through high velocity collisions with smaller aggregates.Comment: accepted for publication in Astronomy & Astrophysic

Numerical modelling of erosion and sedimentation around offshore pipelines

In this paper a numerical model is presented for the description of the erosion and sedimentation near pipelines on the sea bottom. The model is based on the Navier-Stokes equations and the equation of motion and continuity of sediment.\ud \ud The results of the simulations have been compared with the results of tests in a large-scale facility. The agreement between the results of the simulations and the experimental results is good.\ud \ud The applicability of the method is twofold: firstly, the processes of erosion and sedimentation around bodies on the sea bottom can be simulated; secondly, the method can be used for the design of pipelines, including erosion stimulating elements, such as spoilers

A note on threshold velocity criteria for modelling the solid particle erosion of WC/Co MMCs

The threshold velocity for erosion of a ductile material is considered as the velocity required for initiation of plastic deformation in the substrate. For a brittle material, it defines the velocity required to nucleate a median crack in the elastic/plastic interface beneath the indentation. By invoking models for the solid particle erosion of ductile and brittle materials from the literature, together with a set of criteria based on threshold velocity calculations for erosion of the individual components, various predictions of erosion behaviour of WC/Co MMCs have been made. Qualitative agreement was found between the model predictions and various trends of the solid particle erosion behaviour of WC/Co cermets in the literature. The implications of the findings in addressing some of the puzzling trends of the solid particle erosion of MMCs in the literature, and how such insights may result in a reconsideration of some "classical" solid particle erosion relationships, are addressed in this paper

Estimating potential soil erosion for environmental services in a sugarcane growing area using multisource remote sensing data

Characterization of landscapes is crucial in modelling potential soil erosion to ascertain environmental services that are provided by the main land use in the ecosystem. Remote sensing techniques have proved successful in characterization of landscapes. In this study area of a rain-fed Kibos-Miwani sugar zone of Kenya, we used Normalized Difference Vegetation Index (NDVI) data extracted from satellite imagery to characterize the spatial and temporal heterogeneity of the vegetation conditions, and to model potential soil erosion. Data used included Moderate Resolution Imaging Spectroradiometer (MODIS) 250 m NDVI acquired in the period 2000 to 2012; 30 m Landsat5 time series images acquired between November 2010 and June 2011; a 30 m digital elevation model (DEM); and ground observations (land cover and soil characteristics). Ground observations were cross tabulated and analysed under ISO 17025 laboratory procedures. Temporal NDVI was extracted directly from MODIS 250 m images to study the changes in seasonal vegetation at the region scale, while spatial NDVI was extracted by analysing Landsat 5 images at the field scale. NDVI extracted from Landsat images for a specific date, represented vegetation conditions for that simulation period. To compute potential soil erosion, we ran three simulations using the spatially explicit Fuzzy-based dynamic soil erosion model (FuDSEM) based on identified vegetative conditions, thanks to MODIS data. Input datasets included Landsat 5 NDVI, the slope, aspect, curvature and soil physical properties. Results of land cover presented sugarcane as the main land use, occupying 76% of the land scape. Results of NDVI analysis were consistent with crop management practices, illustrating a spatially heterogeneous land scape with varied vegetation conditions throughout the year. Results of the simulations were not significantly different for the different periods of the year. Out of simulations, we noted a homogeneous low erosion risk in areas with natural land cover with a global mean of 0.42. Medium to intense erosion risk in cropped areas was evident, with erosion risk varying from one pixel to the other. Simulation results suggest that crop management practices (planting and harvesting processes) are the drivers of erosion in sugar cane cultivated areas. (résumé d'auteur

ENVIRONMENTAL AND ECONOMIC IMPACTS OF SOIL EROSION AND FERTILITY MINING IN NORTHERN TANZANIA

This paper develops a soil conservation model that is relevant to smallholder farmers who apply little or no fertilizer. Empirical results drawn from northern Tanzania imply that, ignoring fertility mining problem in model specification leads to overestimation of profits for farms that apply little or no fertilizer. The model also shows that, the impact of output price on soil conservation efforts depends on the curvature of the soil erosion function.Soil erosion, Fertility mining, Soil conservation, Price policy, Soil erosion function, Sub-Saharan Africa, Tanzania., Environmental Economics and Policy, Land Economics/Use,

CFD modelling of erosion-corrosion of steel in aqueous environments : particle concentration effects on the regime boundaries

In this study, a new methodology is used to model the effects of particle concentration on the inner surfaces of a circular pipe 90º bend, assuming applied potential controlled aqueous slurry flow at room temperature. This enables the regimes of the component to be mapped according to the intensity of erosion and corrosion contributions. The results show that for a constant inlet particle concentration, it is shown how transitions between erosion-corrosion regimes are observed around the pipe. For increases in particle concentration, significant variation of the erosion-corrosion regimes are observed, with a reduction of the corrosion dominated regime. The results are interpreted in the terms of the changes in local erosion conditions along the component in the flowing environments. Typical results from the model are shown illustrating how this new mapping method can be used effectively to optimize process conditions and materials in such environments

Long-term predictive capability of erosion models

A brief overview of long-term cavitation and liquid impingement erosion and modeling methods proposed by different investigators, including the curve-fit approach is presented. A table was prepared to highlight the number of variables necessary for each model in order to compute the erosion-versus-time curves. A power law relation based on the average erosion rate is suggested which may solve several modeling problems