Measurement of Erosional Parameters Using ASERA, Automated Sediment Erosion Rate Apparatus

This paper presents results of sediment and cavitation erosion through Tunnel 2 and Tunnel 3 of Tarbela Dam in Pakistan. Main bend and main branch of Tunnel 2 and outlet 1 and outlet 3 of Tunnel 3 are concluded to be critical for cavitation and sediment erosion. Studies are also performed for increased sediments flow rate, concluding 5 kg/sec as the critical value for sudden increase in erosion rate density. Erosion rate is concluded to be the function of sediment flow rate and head condition. Particulate mass presently observed is reasonably low, hence presently not affecting the velocity and the flow field.

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The Sediment Erosion Rate Flume (SERF): A New Testing Device for Measuring Soil Erosion Rate and Shear Stress

Geotechnical Testing Journal ◽

10.1520/gtj103814 ◽

2012 ◽

Vol 35 (4) ◽

pp. 103814 ◽

Cited By ~ 9

Author(s):

Raphael W. Crowley ◽

David B. Bloomquist ◽

Falak D. Shah ◽

Courtney M. Holst

Keyword(s):

Shear Stress ◽

Soil Erosion ◽

Erosion Rate ◽

Testing Device ◽

Sediment Erosion ◽

Soil Erosion Rate

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A Case Study: Sediment Erosion in Francis Turbines Operated at the San Francisco Hydropower Plant in Ecuador

Energies ◽

10.3390/en15010008 ◽

2021 ◽

Vol 15 (1) ◽

pp. 8

Author(s):

Cristian Cruzatty ◽

Darwin Jimenez ◽

Esteban Valencia ◽

Ivan Zambrano ◽

Christian Mora ◽

...

Keyword(s):

San Francisco ◽

Erosion Rate ◽

Guide Vane ◽

Flow Simulation ◽

Numerical Approach ◽

Operating Conditions ◽

Hydropower Plant ◽

Two Phase ◽

Sediment Erosion ◽

Main Components

The operation of various types of turbomachines is importantly affected by sediment erosion. Francis turbines used for power generation typically suffer said effects due to the fact that they are used in sediment-laden rivers and are usually operated disregarding the long-term effect of the erosion on turbine performance. This investigation seeks to study the erosion rate for the main components of the turbines located at San Francisco hydropower plant in Pastaza, Ecuador. A sediment characterization study was performed in order to determine the properties of the particles present in Pastaza River and accurately predict their effect on the turbine flow passages. A numerical approach combining liquid–solid two-phase flow simulation and an erosion model was used to analyze the erosion rates at different operating conditions and determine wear patterns in the components. As expected, the results indicated that an increase in the erosion rate was obtained for higher intake flows. However, a dramatic increase in the erosion rate was observed when the turbine was operated at near-full-load conditions, specifically when guide vane opening exceeded a 90% aperture.

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GLACIAL EROSION RATE FOR THE CORDILLERAN ICE SHEET IN SOUTHEAST ALASKA USING COSMOGENIC 10BE CONCENTRATIONS IN BEDROCK AND PERCHED BOULDERS

10.1130/abs/2018ne-310627 ◽

2018 ◽

Author(s):

Christopher Sbarra ◽

◽

Jason P. Briner ◽

Alia J. Lesnek ◽

James F. Baichtal

Keyword(s):

Erosion Rate ◽

Ice Sheet ◽

Glacial Erosion ◽

Southeast Alaska ◽

Cordilleran Ice Sheet ◽

Cosmogenic 10Be

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Effect of Nitrogen Ion Implantation on the Cavitation Erosion Resistance and Cobalt-Based Solid Solution Phase Transformations of HIPed Stellite 6

Materials ◽

10.3390/ma14092324 ◽

2021 ◽

Vol 14 (9) ◽

pp. 2324

Author(s):

Mirosław Szala ◽

Dariusz Chocyk ◽

Anna Skic ◽

Mariusz Kamiński ◽

Wojciech Macek ◽

...

Keyword(s):

Plastic Deformation ◽

Stainless Steel ◽

Ion Implantation ◽

Phase Transformations ◽

Erosion Rate ◽

Cavitation Erosion ◽

Matrix Phase ◽

Nitrogen Ion Implantation ◽

Stellite 6 ◽

Nitrogen Ion

From the wide range of engineering materials traditional Stellite 6 (cobalt alloy) exhibits excellent resistance to cavitation erosion (CE). Nonetheless, the influence of ion implantation of cobalt alloys on the CE behaviour has not been completely clarified by the literature. Thus, this work investigates the effect of nitrogen ion implantation (NII) of HIPed Stellite 6 on the improvement of resistance to CE. Finally, the cobalt-rich matrix phase transformations due to both NII and cavitation load were studied. The CE resistance of stellites ion-implanted by 120 keV N+ ions two fluences: 5 × 1016 cm−2 and 1 × 1017 cm−2 were comparatively analysed with the unimplanted stellite and AISI 304 stainless steel. CE tests were conducted according to ASTM G32 with stationary specimen method. Erosion rate curves and mean depth of erosion confirm that the nitrogen-implanted HIPed Stellite 6 two times exceeds the resistance to CE than unimplanted stellite, and has almost ten times higher CE reference than stainless steel. The X-ray diffraction (XRD) confirms that NII of HIPed Stellite 6 favours transformation of the ε(hcp) to γ(fcc) structure. Unimplanted stellite ε-rich matrix is less prone to plastic deformation than γ and consequently, increase of γ phase effectively holds carbides in cobalt matrix and prevents Cr7C3 debonding. This phenomenon elongates three times the CE incubation stage, slows erosion rate and mitigates the material loss. Metastable γ structure formed by ion implantation consumes the cavitation load for work-hardening and γ → ε martensitic transformation. In further CE stages, phases transform as for unimplanted alloy namely, the cavitation-inducted recovery process, removal of strain, dislocations resulting in increase of γ phase. The CE mechanism was investigated using a surface profilometer, atomic force microscopy, SEM-EDS and XRD. HIPed Stellite 6 wear behaviour relies on the plastic deformation of cobalt matrix, starting at Cr7C3/matrix interfaces. Once the Cr7C3 particles lose from the matrix restrain, they debond from matrix and are removed from the material. Carbides detachment creates cavitation pits which initiate cracks propagation through cobalt matrix, that leads to loss of matrix phase and as a result the CE proceeds with a detachment of massive chunk of materials.

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Co-variation of silicate, carbonate and sulfide weathering drives CO2 release with erosion

Nature Geoscience ◽

10.1038/s41561-021-00714-3 ◽

2021 ◽

Vol 14 (4) ◽

pp. 211-216

Author(s):

Aaron Bufe ◽

Niels Hovius ◽

Robert Emberson ◽

Jeremy K. C. Rugenstein ◽

Albert Galy ◽

...

Keyword(s):

Erosion Rate ◽

Global Climate ◽

Stream Water ◽

Sulfide Oxidation ◽

Silicate Weathering ◽

Emission Rates ◽

Mountain Ranges ◽

Weathering Rates ◽

Southern Taiwan ◽

Co2 Release

AbstractGlobal climate is thought to be modulated by the supply of minerals to Earth’s surface. Whereas silicate weathering removes carbon dioxide (CO2) from the atmosphere, weathering of accessory carbonate and sulfide minerals is a geologically relevant source of CO2. Although these weathering pathways commonly operate side by side, we lack quantitative constraints on their co-variation across erosion rate gradients. Here we use stream-water chemistry across an erosion rate gradient of three orders of magnitude in shales and sandstones of southern Taiwan, and find that sulfide and carbonate weathering rates rise with increasing erosion, while silicate weathering rates remain steady. As a result, on timescales shorter than marine sulfide compensation (approximately 106–107 years), weathering in rapidly eroding terrain leads to net CO2 emission rates that are at least twice as fast as CO2 sequestration rates in slow-eroding terrain. We propose that these weathering reactions are linked and that sulfuric acid generated from sulfide oxidation boosts carbonate solubility, whereas silicate weathering kinetics remain unaffected, possibly due to efficient buffering of the pH. We expect that these patterns are broadly applicable to many Cenozoic mountain ranges that expose marine metasediments.

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Buoyancy-driven dissolution of inclined blocks: Erosion rate and pattern formation

Physical Review Fluids ◽

10.1103/physrevfluids.5.053802 ◽

2020 ◽

Vol 5 (5) ◽

Author(s):

Caroline Cohen ◽

Michael Berhanu ◽

Julien Derr ◽

Sylvain Courrech du Pont

Keyword(s):

Pattern Formation ◽

Erosion Rate

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Impacts of oak deforestation and rainfed cultivation on soil redistribution processes across hillslopes using 137Cs techniques

Forest Ecosystems ◽

10.1186/s40663-021-00311-1 ◽

2021 ◽

Vol 8 (1) ◽

Author(s):

Shamsollah Ayoubi ◽

Nafiseh Sadeghi ◽

Farideh Abbaszadeh Afshar ◽

Mohammad Reza Abdi ◽

Mojtaba Zeraatpisheh ◽

...

Keyword(s):

Land Use ◽

Magnetic Susceptibility ◽

Soil Erosion ◽

Erosion Rate ◽

Land Use Changes ◽

Soil Samples ◽

Natural Forest ◽

Oak Forests ◽

Erosion Rates ◽

Rainfed Farming

Abstract Background As one of the main components of land-use change, deforestation is considered the greatest threat to global environmental diversity with possible irreversible environmental consequences. Specifically, one example could be the impacts of land-use changes from oak forests into agricultural ecosystems, which may have detrimental impacts on soil mobilization across hillslopes. However, to date, scarce studies are assessing these impacts at different slope positions and soil depths, shedding light on key geomorphological processes. Methods In this research, the Caesium-137 (137Cs) technique was applied to evaluate soil redistribution and soil erosion rates due to the effects of these above-mentioned land-use changes. To achieve this goal, we select a representative area in the Lordegan district, central Iran. 137Cs depth distribution profiles were established in four different hillslope positions after converting natural oak forests to rainfed farming. In each hillslope, soil samples from three depths (0–10, 10–20, and 20–50 cm) and in four different slope positions (summit, shoulder, backslope, and footslope) were taken in three transects of about 20 m away from each other. The activity of 137Cs was determined in all the soil samples (72 soil samples) by a gamma spectrometer. In addition, some physicochemical properties and the magnetic susceptibility (MS) of soil samples were measured. Results Erosion rates reached 51.1 t·ha− 1·yr− 1 in rainfed farming, whereas in the natural forest, the erosion rate was 9.3 t·ha− 1·yr− 1. Magnetic susceptibility was considerably lower in the cultivated land (χhf = 43.5 × 10− 8 m3·kg− 1) than in the natural forest (χhf = 55.1 × 10− 8 m3·kg− 1). The lower soil erosion rate in the natural forest land indicated significantly higher MS in all landform positions except at the summit one, compared to that in the rainfed farming land. The shoulder and summit positions were the most erodible hillslope positions in the natural forest and rainfed farming, respectively. Conclusions We concluded that land-use change and hillslope positions played a key role in eroding the surface soils in this area. Moreover, land management can influence soil erosion intensity and may both mitigate and amplify soil loss.

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