DEM/CFD-DEM Modelling of Non-spherical Particulate Systems: Theoretical Developments and Applications

Over the past 25 years, our understanding of the physical processes that drive volcanic eruptions has increased enormously thanks to major advances in computational and analytical facilities, instrumentation, and collection of comprehensive observational, geophysical, geochemical, and petrological data sets associated with recent volcanic activity. Much of this work has been motivated by the recognition that human exposure to volcanic hazard is increasing with both expanding populations and increasing reliance on infrastructure (as illustrated by the disruption to air traffic caused by the 2010 eruption of Eyjafjallajokull volcano in Iceland). Reducing vulnerability to volcanic eruptions requires a thorough understanding of the processes that govern eruptive activity. Here, we provide an overview of our current understanding of how volcanoes work. We focus particularly on the physical processes that modulate magma accumulation in the upper crust, transport magma to the surface, and control eruptive activity.

How volcanoes work: a 25 year perspective

Pyroclastic density currents: state of the art and perspectives

https://research-information.bris.ac.uk/files/76554515/1_s2.0_S221424281500039X_main.pdf

Optimising shape analysis to quantify volcanic ash morphology

Microplastics are ubiquitous pollutants within the marine environment, predominantly (>90%) accumulating in sediments worldwide Despite the increasing global concern regarding these anthropogenic pollutants, research into the remediation of microplastics is lacking Here, we examine those characteristics of microplastics that are essential to adequately evaluate potential remediation techniques such as sedimentation and (air) flotation techniques We analyzed the sinking behavior of typical microplastics originating from real plastic waste samples and identified the best-available drag model to quantitatively describe their sinking behavior Particle shape is confirmed to be an important parameter strongly affecting the sinking behavior of microplastics Various common shape descriptors were experimentally evaluated on their ability to appropriately characterize frequently occurring particle shapes of typical microplastics such as spheres, films, and fibers This study is the first in this field to include film particles in its experimental design, which were found to make up a considerable fraction of marine pollution and are shown to significantly affect the evaluation of shape-dependent drag models Circularity χ and sphericity Φ are found to be appropriate shape descriptors in this context We also investigated the effect of biofouling on the polarity of marine plastics and estimated its potential contribution to the settling motion of initially floating microplastics based on density-modification It is found that biofouling alters the polarity of plastics significantly; this is from (near) hydrophobic (ie, water contact angles from 70 to 100°) to strong hydrophilic (ie, water contact angles from 30 to 40°) surfaces, rendering them more difficult to separate from sediment based on polarity as a primary separation factor Thus, besides providing a better understanding of the fate and behavior of typical marine microplastics, these findings serve as a fundamental stepping-stone to the development of the first large-scale sediment remediation technique for microplastics to address the global microplastic accumulation issue

/pdf/characteristics-and-sinking-behavior-of-typical-1u9re55iwa.pdf

Characteristics and Sinking Behavior of Typical Microplastics Including the Potential Effect of Biofouling: Implications for Remediation.

A new shape dependent drag correlation formula for non-spherical rough particles. Experiments and results

https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1002/2017JB014926

A New One-Equation Model of Fluid Drag for Irregularly Shaped Particles Valid Over a Wide Range of Reynolds Number

The source conditions of volcanic plumes and collapsing fountains are investigated by means of large-scale experiments. In the experiments, gas-particle jets issuing from a cylindrical conduit are forced into the atmosphere at different mass flow rates. Dense jets (high particle volumetric concentration, e.g., C
 0 > 0.01) generate collapsing fountains, whose height scales with the squared exit velocity. This is consistent with Bernoulli’s equation, which is a good approximation if air entrainment is negligible. In this case, kinetic energy is transformed into potential energy without any significant loss by friction with the atmosphere. The dense collapsing fountain, on hitting the ground, generates an intense shear flow similar to a pyroclastic density current. Dilute hot jets (low particle volumetric concentration, e.g., C
 0  3).

https://link.springer.com/content/pdf/10.1007%2Fs00445-014-0834-6.pdf

Volcanic jets, plumes, and collapsing fountains: evidence from large-scale experiments, with particular emphasis on the entrainment rate

Experimental evidence links volcanic particle characteristics to pyroclastic flow hazard

Accepted for publication in (Geophysical Research Letters). Copyright (2009) American Geophysical Union.

https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2009JB006781

Fabio Dioguardi

Papers

A new shape dependent drag correlation formula for non-spherical rough particles. Experiments and results

A New One-Equation Model of Fluid Drag for Irregularly Shaped Particles Valid Over a Wide Range of Reynolds Number

Volcanic jets, plumes, and collapsing fountains: evidence from large-scale experiments, with particular emphasis on the entrainment rate

Experimental evidence links volcanic particle characteristics to pyroclastic flow hazard

Conduit flow experiments help constraining the regime of explosive eruptions