Largest Grains Dominate River Bedrock Erosion Rates

The heavy clinopyroxene mineral pigeonite forms a glacial indicator dispersal train originating from diabase intrusions in the Nipigon region of northwestern Ontario. Analysis and interpretation of the pigeonite dispersal pattern adjacent to the up-ice portion of the diabase provides a number of insights into the nature of glacial erosion of bedrock and the generation of heavy-mineral dispersal trains. Bedrock erosion and entrainment rates at the time of pigeonite dispersal train formation were high (314 mm·a1), suggesting that bedrock erosion was rapid yet spatially and temporally restricted. Contrasting erosion rates between the diabase and surrounding greenstone lithologies suggests that modern shield topography is not an assemblage of equilibrium bedforms with respect to the ice sheet. This agrees with hypothesized low total erosion of shield bedrock during the Pleistocene. Pigeonite grain size coarsens over the diabase source, indicating that most of the pigeonite was quarried from outcrops as coarse diabase fragments. Down-ice of the diabase source the mean particle size of pigeonite recovered from till decreases, suggesting most of the pigeonite was liberated from bedrock by the comminution of coarse diabase clasts during glacial transport. While the conclusions drawn from this study may not necessarily apply to all heavy-mineral dispersal trains, the interpretive framework provides a foundation for comparative studies.

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Experimental Study of the Effect of Particle Size on Erosion of Elbows in Series for Annular Gas-Liquid Flows

10.1115/fedsm2021-64375 ◽

2021 ◽

Author(s):

Mazen Othayq ◽

Ghulam Haider ◽

Ronald E. Vieira ◽

Siamack A. Shirazi

Keyword(s):

Particle Size ◽

Curvature Radius ◽

Particle Sizes ◽

Flow Loop ◽

Erosion Rates ◽

Complex Process ◽

In Series ◽

Effect Of Particle Size ◽

Liquid Flows ◽

Paint Removal

Abstract Erosion is a complex process, especially with the presence of small particles and in complex geometries such as elbows in series. Erosion due to the solid particle is affected by different parameters such as material properties, particle material, shape and size, superficial gas and liquid velocities, flow regime and geometry. The main objective of this work is to investigate the effect of particle size in two 3-inch (76.2 mm) diameter elbows in series with curvature radius to pipe diameter ratio (r/D) equal to 1.5. A test section was constructed in a flow loop with a distance between the elbows equal to 12D. Paint removal experiments were conducted to determine the erosion patterns and hot spots of erosion using acrylic elbows. Additionally, erosion experiments were conducted with 300, 75, and 25 μm particle sizes in gas-liquid-sand annular flow in stainless steel elbows. The wall thickness loss of the elbows has been measured using state of the art non-destructive fix-mounted, temperature compensated, ultrasonic transducers. Experimental results showed that higher erosion was obtained with 300 μm particle size where the erosion in the second elbow is lower than the first elbow with the 12D distance. With respect to the maximum erosion ratio of the second elbow to the first elbow, the results showed that the ratio of erosion rates in two elbows (second to first) decreases with increasing the particle size. A higher ratio of the two elbows was obtained with 25 μm compared to 300 and 75 μm particle sizes. However, in the first elbow, the erosion rates decrease with decreasing particle sizes.

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