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1. The origin and micromechanics of the preferential orientation of crystals in mush

   Carrara, AC ; Bergantz, G ( July 2023 , Gochemical Society)

   none (Ed.)

   An obstacle to developing a general mechanical framework for magma mush is the emergence and complexity of a crystal fabric. To illuminate the conditions that produce a crystal fabric we performed time-dependent numerical simulations using a Computational-Fluid-Dynamics and Discrete-Element-Method (CFD-DEM) model in three dimensions. The specific focus was on the role of shear strain in the creation of a preferential orientation of crystals in mush. CFD-DEM method allows for the simultaneous coupling and frictional interactions of melt and crystals undergoing shear strain. The crystal shapes are represented using spheroids (either oblate or prolate). Simulations consist in imposing a compression stress (pressure) and a simple shear to a dense suspension of crystals in a viscous liquid, and monitoring the evolution of the orientation and strength of the shape fabrics. We ran a series of simulations by varying the size and aspect ratio of the particles. We considered samples in which all the solids have the same volume and shape, and cases including size and aspect ratio distributions. Results show that the strength of the shape fabric and the angle between the crystal preferential orientation and the compression plane both increase with the shear strain up to steady state values, which are primarily controlled by the aspect ratio of the particles. The stronger the aspect ratio, the greater the magnitude of the preferential orientation and the lower its angle relative to the compression plane. When introducing a distribution in the size of the crystals, we observed a decrease in the strength of the shape fabric and an increase in the angle between the preferential orientation of the crystals and the compression plane compared with samples composed of crystals having the same shape and size. Similarly, the distribution in the aspect ratio further decreases the strength of the shape fabric and increases the angle between the preferential orientation of the solids and the compression plane. Finally, we employed an alternative approach to quantify the amount of foliation and lineation and show that the samples always display a stronger foliation than lineation, although the shear strain increases both the foliation and the lineation. 

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2. The first decade of scientific insights from the Deepwater Horizon oil release

   Kujawinski, E.B ; Reddy, C.M. ; Rodgers, R.P. ; Thrash, J.C. ; Valentine, D.L. ; White, H.K. ( April 2020 , Nature reviews)

   null (Ed.)

   The 2010 Deepwater Horizon disaster remains the largest single accidental release of oil and gas into the ocean. During the 87- day release, scientists used oceanographic tools to collect wellhead oil and gas samples, interrogate microbial community shifts and activities, and track the chemical composition of dissolved oil in the ocean’s interior. In the decade since the disaster, field and laboratory investigations studied the physics and chemistry of irrupted oil and gas at high pressure and low temperature, the role of chemical dispersants in oil composition and microbial hydrocarbon degradation, and the impact of combined oil, gas and dispersants on the flora and fauna of coastal and deep- sea environments. The multi- faceted, multidisciplinary scientific response to the released oil, gas and dispersants culminated in a better understanding of the environmental factors that influence the short- term and long- term fate and transport of oil in marine settings. In this Review , we summarize the unique aspects of the Deepwater Horizon release and highlight the advances in oil chemistry and microbiology that resulted from novel applications of emerging technologies. We end with an outlook on the applicability of these findings to possible oil releases in future deep- sea drilling locations and newly- opened high- latitude shipping lanes. 

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3. The first decade of scientific insights from the Deepwater Horizon oil release

   Kujawinski, E.B ; Reddy, C.M. ; Rodgers, R.P. ; Thrash, J.C. ; Valentine, D.L. ; White, H.K ( April 2020 , Nature reviews)

   null (Ed.)

   The 2010 Deepwater Horizon disaster remains the largest single accidental release of oil and gas into the ocean. During the 87-day release, scientists used oceanographic tools to collect wellhead oil and gas samples, interrogate microbial community shifts and activities, and track the chemical composition of dissolved oil in the ocean’s interior. In the decade since the disaster, field and laboratory investigations studied the physics and chemistry of irrupted oil and gas at high pressure and low temperature, the role of chemical dispersants in oil composition and microbial hydrocarbon degradation, and the impact of combined oil, gas and dispersants on the flora and fauna of coastal and deep-sea environments. The multi-faceted, multidisciplinary scientific response to the released oil, gas and dispersants culminated in a better understanding of the environmental factors that influence the short-term and long-term fate and transport of oil in marine settings. In this Review, we summarize the unique aspects of the Deepwater Horizon release and highlight the advances in oil chemistry and microbiology that resulted from novel applications of emerging technologies. We end with an outlook on the applicability of these findings to possible oil releases in future deep-sea drilling locations and newly-opened high-latitude shipping lanes. 

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4. Dynamical evolution of multiple-population globular clusters

   https://doi.org/10.1093/mnras/stab223  

   Vesperini, Enrico ; Hong, Jongsuk ; Giersz, Mirek ; Hypki, Arkadiusz ( February 2021 , Monthly Notices of the Royal Astronomical Society)

   null (Ed.)

   ABSTRACT We have carried out a set of Monte Carlo simulations to study a number of fundamental aspects of the dynamical evolution of multiple stellar populations in globular clusters with different initial masses, fractions of second generation (2G) stars, and structural properties. Our simulations explore and elucidate: (1) the role of early and long-term dynamical processes and stellar escape in the evolution of the fraction of 2G stars and the link between the evolution of the fraction of 2G stars and various dynamical parameters; (2) the link between the fraction of 2G stars inside the cluster and in the population of escaping stars during a cluster’s dynamical evolution; (3) the dynamics of the spatial mixing of the first-generation (1G) and 2G stars and the details of the structural properties of the two populations as they evolve toward mixing; (4) the implications of the initial differences between the spatial distribution of 1G and 2G stars for the evolution of the anisotropy in the velocity distribution and the expected radial profile of the 1G and 2G anisotropy for clusters at different stages of their dynamical history; and (5) the variation of the degree of energy equipartition of the 1G and the 2G populations as a function of the distance from the cluster’s centre and the cluster’s evolutionary phase. 

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5. Lagrangian investigation of the correlation of helicity with coherent flow characteristics for turbulent transport

   https://doi.org/10.1063/5.0180949  

   Pham, Oanh L ; Papavassiliou, Dimitrios V ( January 2024 , Physics of Fluids)

   The correlation between helicity and turbulent transport in turbulent flows is probed with the use of direct numerical simulation and Lagrangian scalar tracking. Channel flow and plane Couette flow at friction Reynolds number 300 and Lagrangian data along the trajectories of fluid particles and passive particles with Schmidt numbers 0.7 and 6 are used. The goal is to identify characteristics of the flow that enhance turbulent transport from the wall, and how flow regions that exhibit these characteristics are related to helicity. The relationship between vorticity and relative helicity along particle trajectories is probed, and the relationship between the distribution of helicity conditioned on Reynolds stress quadrants is also evaluated. More importantly, the correlation between relative helicity density and the alignment of vorticity with velocity vectors and eigenvectors of the rate of strain tensor is presented. Separate computations for particles that disperse the farthest into the flow field and those that disperse the least are conducted to determine the flow structures that contribute to turbulent dispersion. The joint distribution of helicity and vertical velocity, and helicity and vertical vorticity depends on the location of particle release and the Schmidt number. The trajectories of particles that disperse the least are characterized by a correlation between the absolute value of the relative helicity density and the absolute value of the cosine between the vorticity vector and the eigenvectors of the rate of strain tensor, while the value of this correlation approaches zero for the particles that disperse the most.

    

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