scholarly journals Chemical evolution during the formation of a protoplanetary disk

2020 ◽  
Vol 643 ◽  
pp. A108
Author(s):  
A. Coutens ◽  
B. Commerçon ◽  
V. Wakelam
Keyword(s):  
Chemical Composition ◽  
Chemical Evolution ◽  
Adaptive Mesh Refinement ◽  
Chemical Elements ◽  
Adaptive Mesh ◽  
Abundant Species ◽  
Common Species ◽  
Dense Core ◽  
The Impact ◽  
Cold Core

Context. The chemical composition of protoplanetary disks is expected to impact the composition of the forming planets. Characterizing the diversity of chemical composition in disks and the physicochemical factors that lead to this diversity is consequently of high interest. Aims. The aim of this study is to investigate the chemical evolution from the prestellar phase to the formation of the disk, and to determine the impact that the chemical composition of the cold and dense core has on the final composition of the disk. Methods. We performed 3D nonideal magneto-hydrodynamic (MHD) simulations of a dense core collapse using the adaptive-mesh-refinement RAMSES code. For each particle ending in the young rotationally supported disk, we ran chemical simulations with the three-phase gas-grain chemistry code Nautilus. Two different sets of initial abundances, which are characteristic of cold cores, were considered. The final distributions of the abundances of common species were compared to each other, as well as with the initial abundances of the cold core. Results. We find that the spatial distributions of molecules reflect their sensitivity to the temperature distribution. The main carriers of the chemical elements in the disk are usually the same as the ones in the cold core, except for the S-bearing species, where HS is replaced by H2S3, and the P-bearing species, where atomic P leads to the formation of PO, PN, HCP, and CP. However, the abundances of less abundant species change over time. This is especially the case for “large” complex organic molecules (COMs) such as CH3CHO, CH3NH2, CH3OCH3, and HCOOCH3 which see their abundances significantly increase during the collapse. These COMs often present similar abundances in the disk despite significantly different abundances in the cold core. In contrast, the abundances of many radicals decrease with time. A significant number of species still show the same abundances in the cold core and the disk, which indicates efficient formation of these molecules in the cold core. This includes H2O, H2CO, HNCO, and “small” COMs such as CH3OH, CH3CN, and NH2CHO. We computed the MHD resistivities within the disk for the full gas–grain chemical evolution and find results in qualitative agreement with the literature assuming simpler chemical networks. Conclusions. In conclusion, the chemical content of prestellar cores is expected to affect the chemical composition of disks. The impact is more or less important depending on the type of species. Users of stand-alone chemical models of disks should pay special attention to the initial abundances they choose.

scholarly journals The impact of AGN feedback on the 1D power spectra from the Ly α forest using the Horizon-AGN suite of simulations

2020 ◽  
Vol 495 (2) ◽  
pp. 1825-1840 ◽  
Author(s):  
Solène Chabanier ◽  
Frédéric Bournaud ◽  
Yohan Dubois ◽  
Nathalie Palanque-Delabrouille ◽  
Christophe Yèche ◽  
...  
Keyword(s):  
Galaxy Evolution ◽  
Adaptive Mesh Refinement ◽  
Power Spectra ◽  
Adaptive Mesh ◽  
Processing Stage ◽  
Galactic Winds ◽  
Upper Limits ◽  
Feeding Parameters ◽  
Future Work ◽  
The Impact

ABSTRACT The Lyman-α forest is a powerful probe for cosmology, but it is also strongly impacted by galaxy evolution and baryonic processes such as active galactic nucleus (AGN) feedback, which can redistribute mass and energy on large scales. We constrain the signatures of AGN feedback on the 1D power spectrum of the Lyman-α forest using a series of eight hydro-cosmological simulations performed with the adaptive mesh refinement code ramses. This series starts from the Horizon-AGN simulation and varies the subgrid parameters for AGN feeding, feedback, and stochasticity. These simulations cover the whole plausible range of feedback and feeding parameters according to the resulting galaxy properties. AGNs globally suppress the Lyman-α power at all scales. On large scales, the energy injection and ionization dominate over the supply of gas mass from AGN-driven galactic winds, thus suppressing power. On small scales, faster cooling of denser gas mitigates the suppression. This effect increases with decreasing redshift. We provide lower and upper limits of this signature at nine redshifts between z = 4.25 and 2.0, making it possible to account for it at post-processing stage in future work given that running simulations without AGN feedback can save considerable amounts of computing resources. Ignoring AGN feedback in cosmological inference analyses leads to strong biases with 2 per cent shift on σ8 and 1 per cent shift on ns, which represents twice the standards deviation of the current constraints on ns.

scholarly journals What determines the formation and characteristics of protoplanetary discs?

2020 ◽  
Vol 635 ◽  
pp. A67 ◽  
Author(s):  
Patrick Hennebelle ◽  
Benoit Commerçon ◽  
Yueh-Ning Lee ◽  
Sébastien Charnoz
Keyword(s):  
Adaptive Mesh Refinement ◽  
Initial Conditions ◽  
Adaptive Mesh ◽  
Small Scale ◽  
Initial Structure ◽  
Solar Mass ◽  
Central Object ◽  
The Impact ◽  
Protoplanetary Discs

Context. Planets form in protoplanetary discs. Their masses, distribution, and orbits sensitively depend on the structure of the protoplanetary discs. However, what sets the initial structure of the discs in terms of mass, radius and accretion rate is still unknown. Aims. It is therefore of great importance to understand exactly how protoplanetary discs form and what determines their physical properties. We aim to quantify the role of the initial dense core magnetisation, rotation, turbulence, and misalignment between rotation and magnetic field axis as well as the role of the accretion scheme onto the central object. Methods. We performed non-ideal magnetohydrodynamics numerical simulations using the adaptive mesh refinement code Ramses of a collapsing, one solar mass molecular core to study the disc formation and early, up to 100 kyr, evolution. We paid particular attention to the impact of numerical resolution and accretion scheme. Results. We found that the mass of the central object is almost independent of the numerical parameters such as the resolution and the accretion scheme onto the sink particle. The disc mass and to a lower extent its size, however heavily depend on the accretion scheme, which we found is itself resolution dependent. This implies that the accretion onto the star and through the disc are largely decoupled. For a relatively large domain of initial conditions (except at low magnetisation), we found that the properties of the disc do not change too significantly. In particular both the level of initial rotation and turbulence do not influence the disc properties provide the core is sufficiently magnetised. After a short relaxation phase, the disc settles in a stationary state. It then slowly grows in size but not in mass. The disc itself is weakly magnetised but its immediate surrounding on the contrary is highly magnetised. Conclusions. Our results show that the disc properties directly depend on the inner boundary condition, i.e. the accretion scheme onto the central object. This suggests that the disc mass is eventually controlled by a small-scale accretion process, possibly the star-disc interaction. Because of ambipolar diffusion and its significant resistivity, the disc diversity remains limited and except for low magnetisation, their properties are weakly sensitive to initial conditions such as rotation and turbulence.

Dynamics of internal jets in the merging of two droplets of unequal sizes

2016 ◽  
Vol 795 ◽  
pp. 671-689 ◽  
Author(s):  
Chenglong Tang ◽  
Jiaquan Zhao ◽  
Peng Zhang ◽  
Chung K. Law ◽  
Zuohua Huang
Keyword(s):  
Surface Tension ◽  
Weber Number ◽  
Adaptive Mesh Refinement ◽  
Adaptive Mesh ◽  
Volume Of Fluid Method ◽  
Internal Mixing ◽  
Mixing Dynamics ◽  
Mixing Patterns ◽  
The Impact ◽  
Refinement Algorithm

The head-on collision, merging and internal mixing dynamics of two unequal-sized droplets were experimentally studied and interpreted, using water, $n$-decane and $n$-tetradecane to identify the distinguishing effects of surface tension and liquid viscosity on the merging and mixing patterns. It is shown that, upon merging of water and $n$-decane droplets, mushroom-like jets of dissimilar characteristics develop within the merged mass for small and large values of the impact Weber number (We), and that such jets are not developed for intermediate values of We. Furthermore, such jet-like mixing patterns were not observed for droplets of $n$-tetradecane, which has smaller surface tension and larger viscosity as compared to water. A regime nomogram relating the Ohnesorge and symmetric Weber numbers is constructed, providing a unified interpretation of the internal mixing patterns. Numerical simulations based on an improved volume-of-fluid method and an adaptive mesh refinement algorithm provide auxiliary diagnoses of the flow fields and the observed phenomena.

scholarly journals Optimization of chemical composition of steel for gearweels of agricultural industry engineering

2020 ◽  
Vol 11 (4) ◽  
pp. 123-129
Author(s):  
O. Ye. Semenovskyi ◽  
◽  
L. L. Titova ◽  
Keyword(s):  
Heat Treatment ◽  
Chemical Composition ◽  
Mechanical Engineering ◽  
Chemical Elements ◽  
Labor Costs ◽  
Agricultural Industry ◽  
Hardening Process ◽  
Chemical Composition Of Steel ◽  
Processing Optimization ◽  
The Impact

Development of new steels in mechanical engineering to create alloys with predetermined properties that can minimize material and labor costs during their processing. Optimization of the chemical composition of the alloy based on the analysis of the impact of complex alloying on the structure and consequently on the manufacturability of steel. This will reduce the level of internal intensities in the heat treatment process. Based on the analysis of existing trends in mechanical engineering, it is established that the complexity of modern parts of gearweels imposes on the material increasing technological requirements for stamping, machinability, weldability, hardenability, cementation and gouging in the hardening process which explains the need for alloying steel via a certain group of chemical elements. The influence of different compositions of steels for gearweels on the level of internal intensities occurring in parts during heat treatment is studied. The optimal composition of complex-alloyed cementing steel is established.

scholarly journals Effect of chemical composition on the performance of centrifugally cast indefinite chilled cast iron rolls

2019 ◽  
Vol 17 (1) ◽  
pp. 32-36 ◽  
Author(s):  
Radiy Kh. Gimaletdinov ◽  
Andrey A. Gulakov ◽  
Ildar Kh. Tukhvatulin
Keyword(s):  
Cast Iron ◽  
Chemical Composition ◽  
Chemical Element ◽  
Chemical Elements ◽  
Dual Function ◽  
Layer Material ◽  
Working Layer ◽  
Finishing Mill ◽  
The Impact ◽  
Chilled Cast Iron

Problem Statement (Relevance): An urgent task of rolling mill operators includes minimizing the cost of manufactured products while ensuring the required quality. To accomplish the task, measures are being taken to optimize the rolling process aimed at increasing the duration of the rolling campaigns and reducing the number of roll regrinds. The performance of the rolls is influenced by the properties of the working layer material which determine wear resistance, formation and development of fire cracks, as well as resistance to metal sticking. Finishing mill rolls dictate the surface quality of the rolled steel. That is why it is important to make timely regrinds in order to completely remove the fire crack layer. The removal depth and the acceptable duration of the campaigns depend on the properties of the roll working layer material. To improve the properties of the rolls, the roll manufacturers need the actual roll operation data to be able to analyze how the chemical composition and the structure of the roll working layer is related to the roll performance. Such analysis will help improve the structure and properties of the materials used, as well as develop new ones. Objectives: The objective of this research is to understand how the chemical composition of the working layer of indefinite chilled cast iron rolls used in finishing mills dictates the roll performance, to evaluate the effect of each chemical element, and to determine what concentrations of the chemical elements could most effectively benefit the performance of indefinite chilled cast iron rolls. Methods Applied: The methods applied include building a database of the finishing mill indefinite chilled cast iron rolls and using artificial neural networks based on a dual-function algorithm. Originality: The authors built a neuromodel which can help understand the effect of the chemical composition of the roll working layer and predict the performance of indefinite chilled cast iron rolls. The authors studied the effect of carbon, silicon, manganese, chromium, nickel, molybdenum, vanadium, niobium and boron on the performance of indefinite chilled cast iron rolls. Findings: Graphic diagrams were built which demonstrate the effect of each chemical element on the performance of indefinite chilled cast iron rolls at constant concentrations of the remaining elements. The authors looked at the relationship between the chemical elements and the roll performance in terms of the impact of the former on the structure of indefinite chilled cast iron rolls. The effective concentrations of the chemical elements were also determined. Practical Relevance: The authors developed a new chemical composition of indefinite chilled cast iron to be used for the working layer of finishing mill rolls. As a result, a 12–14% increase in the roll performance was achieved.

scholarly journals Integrated processing of ferriferous materials in blank production for mechanical engineering facilities

2020 ◽  
Vol 192 ◽  
pp. 02009
Author(s):  
Valery Predein ◽  
Artyom Popov ◽  
Oleg Komarov ◽  
Sergey Zhilin
Keyword(s):  
Chemical Composition ◽  
Mechanical Engineering ◽  
Chemical Elements ◽  
Ferrous Metal ◽  
Metal Product ◽  
Metal Phase ◽  
Exothermic Reactions ◽  
Mill Scale ◽  
Integrated Processing ◽  
The Impact

The paper considers the possibility of reducing the use of crude ore for metal product by using aluminothermy, which facilitates effective integrated processing of metal waste generated by engineering and metallurgy facilities in the form of mill scale, ferrous and non-ferrous metal swarf with simultaneous castings production. The paper studies the impact patterns of thermite components ratios on the parameters of extracting chemical elements from the source components, metal phase output and its chemical composition. The possible applications for experimental alloys resulting from controlled exothermic reactions are determined for supplying castings and melting stock to blank production for mechanical engineering facilities.

scholarly journals Numerical Simulation of Like and Unlike Impinging Jets

2017 ◽  
Author(s):  
Azadeh Kebriaee ◽  
Hamed Dolatkhahi ◽  
Ghader Oliaee
Keyword(s):  
Numerical Simulation ◽  
Adaptive Mesh Refinement ◽  
Adaptive Mesh ◽  
Impinging Jets ◽  
Liquid Sheet ◽  
Impact Behavior ◽  
Injection Speed ◽  
Two Fluids ◽  
Fluid Jets ◽  
The Impact

In the present study, using the open source OpenFOAM code, a numerical simulation is performed taking the adaptive mesh refinement (AMR) technique during solution. Formation of liquid sheet after the impact of two identical cylindrical jets at various conditions is studied. Since the flow pattern depends upon the Reynolds and Weber numbers, numerical tests are conducted at a variety of flow velocities and Reynolds numbers to demonstrate the effect of these parameters on the sheet formation. It is then concluded that at various conditions, different instabilities occur in the flow; hence, different sheet formations a flow patterns happen.In this study, impact of two dissimilar cylindrical fluid jets is successfully simulated for the first time in literature. Actually, water and oil jets are taken into account and their impact behavior is studied. In the presence of the surrounding air, an unstable sheet will form after impact due to the high injection speed of the jets. As depicted in the results, since the inertia and other physical characteristics of the two fluids are dissimilar, different phases are more intensely diffused.DOI: http://dx.doi.org/10.4995/ILASS2017.2017.4865

scholarly journals Chemical composition of soil waters in oil and gas production areas of north of Western Siberia

2020 ◽  
Vol 163 ◽  
pp. 05011
Author(s):  
Marina Opekunova ◽  
Anatoly Opekunov ◽  
Stepan Kukushkin ◽  
Sergey Lisenkov
Keyword(s):  
Chemical Composition ◽  
Western Siberia ◽  
Oil And Gas ◽  
Chemical Elements ◽  
Gas Production ◽  
Anthropogenic Factors ◽  
Oil And Gas Production ◽  
Industrial Facilities ◽  
The North ◽  
The Impact

This study describes the changes in the chemical composition of soil waters under the influence of natural and anthropogenic factors in the area of development of oil and gas condensate fields in the north of Western Siberia. The concentration of chemical elements (Na, K, Ca, Cu, Zn, Fe, Pb, Cd, Ni, Co, Cr, Ba, Sr, Cd, and Mn) in soils, ground and soil waters was determined. Pollution of soil water and soil is local in nature and it is characteristic of areas located in the immediate vicinity of industrial facilities. A set of indicators is proposed for assessing the transformation of natural complexes under the influence of oil and gas production. The increased pH values, concentrations of petroleum hydrocarbons, nitrates, chlorides, sodium, potassium, calcium, barium, strontium, iron and manganese, as well as zinc, vanadium, cobalt and nickel are observed. In the impact zones in soil waters and soils. Mechanical disturbances of the soil and vegetation cover lead to an increase in defrost, secondary waterlogging and are accompanied by an increase in the migration of chemical elements in the catenary structure of landscapes.

scholarly journals Vector modes in ΛCDM: the gravitomagnetic potential in dark matter haloes from relativistic N-body simulations

2021 ◽  
Author(s):  
Cristian Barrera-Hinojosa ◽  
Baojiu Li ◽  
Marco Bruni ◽  
Jian-hua He
Keyword(s):  
Dark Matter ◽  
Adaptive Mesh Refinement ◽  
Gravitational Force ◽  
Percent Level ◽  
Adaptive Mesh ◽  
Velocity Fields ◽  
The Core ◽  
Transverse Modes ◽  
General Relativistic ◽  
The Impact

Abstract We investigate the transverse modes of the gravitational and velocity fields in ΛCDM, based on a high-resolution simulation performed using the adaptive-mesh refinement general-relativistic N-body code gramses. We study the generation of vorticity in the dark matter velocity field at low redshift, providing fits to the shape and evolution of its power spectrum over a range of scales. By analysing the gravitomagnetic vector potential, which is absent in Newtonian simulations, in dark matter haloes with masses ranging from ∼1012.5 h−1M⊙ to ∼1015 h−1M⊙, we find that its magnitude correlates with the halo mass, peaking in the inner regions. Nevertheless, on average, its ratio against the scalar gravitational potential remains fairly constant, below percent level, decreasing roughly linearly with redshift and showing a weak dependence on halo mass. Furthermore, we show that the gravitomagnetic acceleration in haloes peaks towards the core and reaches almost 10−10  h cm/s2 in the most massive halo of the simulation. However, regardless of the halo mass, the ratio between the gravitomagnetic force and the standard gravitational force is typically at around the 10−5 level inside the haloes, again without significant radius dependence. This result confirms that the gravitomagnetic effects have negligible impact on structure formation, even for the most massive structures, although its behaviour in low density regions remains to be explored. Likewise, the impact on observations remains to be understood in the future.

scholarly journals The Transition and Adoption to Modern Programming Concepts for Scientific Computing in Fortran

2007 ◽  
Vol 15 (1) ◽  
pp. 27-44 ◽  
Author(s):  
Charles D. Norton ◽  
Viktor K. Decyk ◽  
Boleslaw K. Szymanski ◽  
Henry Gardner
Keyword(s):  
Design Patterns ◽  
Adaptive Mesh Refinement ◽  
Large Scale ◽  
Object Oriented ◽  
Adaptive Mesh ◽  
Particle Simulation ◽  
Programming Techniques ◽  
Early Exploration ◽  
The Impact ◽  
Development Applications

This paper describes our experiences in the early exploration of modern concepts introduced in Fortran90 for large-scale scientific programming. We review our early work in expressing object-oriented concepts based on the new Fortran90 constructs – foreign to most programmers at the time – our experimental work in applying them to various applications, the impact on the WG5/J3 standards committees to consider formalizing object-oriented constructs for later versions of Fortran, and work in exploring how other modern programming techniques such as Design Patterns can and have impacted our software development. Applications will be drawn from plasma particle simulation and finite element adaptive mesh refinement for solid earth crustal deformation modeling.

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