Journal articles: 'SPH - Coalescence'

1

Wang, Dudou, Hongfu Qiang, and Chao Shi. "A multiphase SPH framework for solving the evaporation and combustion process of droplets." International Journal of Numerical Methods for Heat & Fluid Flow 30, no. 3 (December 12, 2019): 1547–75. http://dx.doi.org/10.1108/hff-08-2019-0666.

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Purpose This paper aims to introduce a two-dimensional smoothed particle hydrodynamics (SPH) framework for simulating the evaporation and combustion process of fuel droplets. Design/methodology/approach To solve the gas–liquid two-phase flow problem, a multiphase SPH method capable of handling high density-ratio problems is established. Based on the Fourier heat conduction equation and Fick’s law of diffusion, the SPH discrete equations are derived. To effectively characterize the phase transition problem, inspired by volume of fluid method, the concept of liquid phase mass fraction of the SPH particles is proposed. The one-step global reaction model of n-hexane is used for the vapor combustion. Findings The evaporation and combustion process of single droplet conforms to the law. The framework works out well when the evaporation of multiple droplets involves coalescence process. Three different kinds of flames are observed in succession in the combustion process of a single droplet at different inflow velocity, which agree well with the results of the experiment. Originality/value To the best of the authors’ knowledge, this is the first computational framework that has the capability to simulate evaporation and combustion with SPH method. Based on the particle nature of SPH method, the framework has natural advantages in interface tracking.

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Xu, Xiaoyang, Tingting Tang, and Peng Yu. "A modified SPH method to model the coalescence of colliding non‐Newtonian liquid droplets." International Journal for Numerical Methods in Fluids 92, no. 5 (May 2020): 372–90. http://dx.doi.org/10.1002/fld.4787.

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Wu, Jun, Xuemei Liu, Haihua Xu, and Hongjian Du. "Simulation on the Self-Compacting Concrete by an Enhanced Lagrangian Particle Method." Advances in Materials Science and Engineering 2016 (2016): 1–11. http://dx.doi.org/10.1155/2016/8070748.

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The industry has embraced self-compacting concrete (SCC) to overcome deficiencies related to consolidation, improve productivity, and enhance safety and quality. Due to the large deformation at the flowing process of SCC, an enhanced Lagrangian particle-based method, Smoothed Particles Hydrodynamics (SPH) method, though first developed to study astrophysics problems, with its exceptional advantages in solving problems involving fragmentation, coalescence, and violent free surface deformation, is developed in this study to simulate the flow of SCC as a non-Newtonian fluid to achieve stable results with satisfactory convergence properties. Navier-Stokes equations and incompressible mass conservation equations are solved as basics. Cross rheological model is used to simulate the shear stress and strain relationship of SCC. Mirror particle method is used for wall boundaries. The improved SPH method is tested by a typical 2D slump flow problem and also applied to L-box test. The capability and results obtained from this method are discussed.

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ESCALA, ANDRES, and LUCIANO DEL VALLE. "GAS-INDUCED MERGER OF MASSIVE BLACK HOLE BINARIES." International Journal of Modern Physics E 20, supp01 (December 2011): 79–84. http://dx.doi.org/10.1142/s0218301311040104.

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We use SPH simulations to investigate the effects of gas on the inspiral and merger of massive black hole binary. This scenario is motivated by the very massive nuclear gas disk observed in the central regions of merging galaxies. We run a variety of models, ranging from simulations with relaty smooth gas to cases in which the gas has a more clumpy spatial distribution. We also vary the Mgas / Mbin ratio identifying the case M bin /M gas = 1 as an important limiting test-case for the analytic formulation of the dynamical process that dominates the binary-disk interaction in the late evolution of the system. We find that gas has an important effect in the evolution of interacting massive black hole binary on merging galaxies and that this interaction can be separate in two principal stages. The coalescence timescale that we find for the MBH binary varies between 5 · 106 yr and 2.5 · 107 yr for typical parameters of ULIRGs galaxies. This results supports scenarios of massive black hole evolution and growth in which hierarchical merging plays an important role. The final coalescence of the black hole leads to gravitational radiation emission that would be detected out to high redshift by LISA.

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Li, S. L., C. Agnor, and D. N. C. Lin. "Giant impact, planetary merger, and diversity of planetary-core mass." Proceedings of the International Astronomical Union 3, S249 (October 2007): 301–3. http://dx.doi.org/10.1017/s1743921308016736.

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AbstractTransit observations indicate a large dispersion in the internal structure among the known gas giants. This is a big challenge to the conventional sequential planetary formation scenario because the diversity is inconsistent with the expectation of some well defined critical condition for the onset of gas accretion in this scenario. We suggest that giant impacts may lead to the merger of planets or the accretion of planetary embryos and cause the diversity of the core mass. By using an SPH scheme, we show that direct parabolic collisions generally lead to the total coalescence of impinging gas giants whereas, during glancing collisions, the efficiency of core retention is much larger than that of the envelope. We also examine the adjustment of the gaseous envelope with a 1D Lagrangian hydrodynamic scheme. In the proximity of their host stars, the expansion of the planets' envelopes, shortly after sufficiently catastrophic impacts, can lead to a substantial loss of gas through Roche-lobe overflow. We are going to examine the possibility that the accretion of several Earth-mass objects can significantly enlarge the planets' photosphere and elevate the tidal dissipation rate over the time scale of 100 Myr.

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Filloux, Charline, J. A. de Freitas Pacheco, Fabrice Durier, and Joseph Silk. "Evolution of Supermassive Black Holes." Proceedings of the International Astronomical Union 5, S267 (August 2009): 202. http://dx.doi.org/10.1017/s1743921310006228.

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Cosmological simulations describing both the evolution of supermassive black holes and their host galaxies were performed by using the tree PM-SPH code GADGET-2 (Springel 2005). Physical mechanisms affecting the dynamics and the physical conditions of the gas (ionization and cooling processes, local heating by stars, injection of mechanical energy by supernovae, chemical enrichment) were introduced in the present version of the code (Filloux 2009). Black holes in a state of accretion (AGNs) also inject mechanical energy in the surrounding medium, contributing for quenching the star formation activity. In all simulations a ΛCDM cosmology was adopted (h = 0.7, ΩΛ=0.7, Ωm=0.3, Ωb=0.046 and σ8=0.9). Simulations were performed in a volume with a side of 50h−1 Mpc, starting at z = 50 and through the present time (z = 0). For low and intermediate resolution runs, the initial gas mass particles are respectively 5.35× 108M⊙ and 3.09×108M⊙. Black holes (BHs) are represented by collisionless particles and seeds of 100 M⊙ were introduced in density peaks at z = 15, growing either by accretion or coalescence. The accretion rate from the “disk mode” is based on a turbulent viscous thin disk model whereas in the “spherical mode” the rate is given by the Bondi–Hoyle formula. When accreting matter, jets, modeled by conical regions perpendicular to the disk plane, inject kinetic energy into the surrounding medium. Two models were tested: in the first, the injected energy rate is about 10% of the gravitational energy rate released in the accretion process while in the second, the injected energy rate is based on the Blandford & Znajek (1977) mechanism. All simulations give, at z = 0, similar black hole mass function but they overestimate slightly the BH density for masses above ~ 108M⊙. The resulting BH density in this mass range is affected by feedback processes since they control the amount of gas available for accretion. The present simulations are not able to produce very massive BHs (~109M⊙) at z ~ 6. However the evolution of the BH mass density derived from our simulations are in quite good agreement with that derived from the QSO luminosity function. This indicates that our simulations reproduce quite well the average accretion rate history of BHs. Correlations between the BH mass and properties of the host galaxy (velocity dispersion for bulge systems or the stellar mass or the dark halo mass) are also well reproduced. In conclusion, these exploratory simulations reproduce the data at z = 0 quite well. However, the present adopted recipe for the accretion rate in the “disk mode” seems to be inefficient to produce massive BHs as early as z ~ 6. Higher resolution simulations including a new approach for modeling the “disk mode” are presently under way and that particular difficulty is expected to be solved.

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Fu, Ming, Vincent Chi Hang Lui, Mai Har Sham, Vassilis Pachnis, and Paul Kwong Hang Tam. "Sonic hedgehog regulates the proliferation, differentiation, and migration of enteric neural crest cells in gut." Journal of Cell Biology 166, no. 5 (August 30, 2004): 673–84. http://dx.doi.org/10.1083/jcb.200401077.

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Enteric neural crest cells (NCCs) migrate and colonize the entire gut and proliferate and differentiate into neurons and glia of the enteric nervous system in vertebrate embryos. We have investigated the mitogenic and morphogenic functions of Sonic hedgehog (Shh) on enteric NCCs in cell and organ culture. Enteric NCCs expressed Shh receptor Patched and transcripts encoding the Shh signal transducer (Gli1). Shh promoted the proliferation and inhibited the differentiation of NCCs. The pro-neurogenic effect of glial cell line–derived neurotrophic factor (GDNF) on NCCs was abolished by Shh. In gut explants, NCCs migrated from the explants onto the adjacent substratum if GDNF was added, whereas addition of Shh abolished this migration. Neuronal differentiation and coalescence of neural crest–derived cells into myenteric plexuses in explants was repressed by the addition of Shh. Our data suggest that Shh controls the proliferation and differentiation of NCCs and modulates the responsiveness of NCCs toward GDNF inductions.

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Petzke, Martin. "The Global “Bookkeeping” of Souls: Quantification and Nineteenth-Century Evangelical Missions." Social Science History 42, no. 2 (2018): 183–211. http://dx.doi.org/10.1017/ssh.2017.50.

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This article combines perspectives of the sociology of quantification and field theory in analyzing the emergence of a field of global evangelical missions. Drawing analogies to Werner Sombart's thesis on the relationship of double-entry bookkeeping and the genesis of capitalism, it shows how the introduction of statistical methods and accounting techniques into the realm of missions in the nineteenth century constructed a visibility of a global distribution of religious adherents that spurred, oriented, and perpetuated an interorganizational sphere geared toward the conversion of the world to Christianity. The article identifies the soteriological and eschatological prerequisites that led to the coalescence of demographic notions and missionary perspectives and draws attention to the extensive reporting system of missionary societies that further consolidated logics of “bookkeeping” in missions. It argues that this ongoing evangelical missionary enterprise is an instance of a more general mechanism of quantification spawning a social field dedicated to the maintenance or alteration of particular “quantities.”

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Ma, Tian-Bao, Yuan-Zhong Hu, and Hui Wang. "Formation and coalescence of linear chains in growth of nanostructured sp–sp2 amorphous carbon films." Chemical Physics Letters 462, no. 1-3 (September 2008): 104–8. http://dx.doi.org/10.1016/j.cplett.2008.07.088.

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Mahulikar, Shripad P., and Pallavi Rastogi. "Study of black hole as dissipative structure using negentropy." Canadian Journal of Physics 94, no. 10 (October 2016): 960–66. http://dx.doi.org/10.1139/cjp-2016-0388.

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The area of the event horizon of a black hole (Aeh) is so far linked only with its entropy (SBH). In this theoretical investigation, it is shown that relating Aeh only to SBH is inadequate, because Aeh is linked to the black hole’s negentropy, which encompasses its entropy. Increasing Aeh of black holes that grow now follows from the negentropy theorem (NET) and also from the well-known area theorem. The decreasing Aeh of black holes that decay follows from the converse to NET and is not a violation of the area theorem. The corollary to NET is proved for the case when two dissipative structures merge, which is the basis for the coalescence of black holes. The converse of corollary to NET explains negentropy loss due to splitting of a dissipative structure. When applied to black hole explosion (i.e., splitting into an infinite number of parts), converse of corollary to NET reduces to converse of NET. The entropy/energy ratio of the exported Hawking radiance from black holes contributes to the entropy increase of the universe. These aspects justify the consideration of black holes as thermodynamic dissipative structures.

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Knorr, Rudolf, Monika Knittl, and Eva C. Rossmann. "Microsolvation and sp2-stereoinversion of monomeric α-(2,6-di-tert-butylphenyl)vinyllithium as measured by NMR." Beilstein Journal of Organic Chemistry 10 (October 29, 2014): 2521–30. http://dx.doi.org/10.3762/bjoc.10.263.

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The β-unsubstituted title compound dissolves in THF as a uniformly trisolvated monomer, whereas it forms exclusively disolvated monomers in tert-butyl methyl ether, Et2O, TMEDA, or toluene with TMEDA (1.4 equiv). This was established at low temperatures through the observation of separated NMR signals for free and lithium-coordinated ligands and/or through the patterns and magnitudes of 13C,6Li NMR coupling constants. An aggregated form was observed only with Et2O (2 equiv) in toluene as the solvent. The olefinic geminal interproton coupling constants of the H2C= part can be used as a secondary criterion to differentiate between these differently solvated ground-states (3, 2, or <2 coordinated ligands per Li). Due to a kinetic trisolvation privilege of THF, the cis/trans sp2-stereoinversion rates could be measured through analyses of 1H NMR line broadening and coalescence only in THF as the solvent: The pseudomonomolecular (because THF-catalyzed), ionic mechanism is initialized by a C–Li bond heterolysis with the transient immobilization of one additional THF ligand, followed by stereoinversion of the quasi-sp2-hybridized carbanionic center in cooperation with a “conducted tour” migration of Li+(THF)4 along the α-aryl group within the solvent-separated ion pair.

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Přibylová, Eva, and Miroslav Holík. "Determination of the Accurate Values of the Rate Constant and Thermodynamic Parameters for the Rotation About the C(sp2)-C(aryl) Bond; Adamantan-1-yl 3-Bromo-2,4,6-trimethylphenyl Ketone." Collection of Czechoslovak Chemical Communications 63, no. 7 (1998): 955–66. http://dx.doi.org/10.1135/cccc19980955.

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Four programs for the 1H NMR line shape analysis: two commercial - Winkubo (Bruker) and DNMR5 (QCPE 165) and two written in our laboratory - Newton (in Microsoft Excel) and Simtex (in Matlab) have been tested in order to get highly accurate rate constants of the hindered rotation about a single bond. For this purpose four testing criteria were used, two of them were also developed by us. As supplementary determinations the rate constants obtained for the coalescence temperature and for the thermal racemization of chromatographically separated enantiomers were used which fitted well the temperature dependence of the rate constants determined by the line shape analysis. As a test compound adamantan-1-yl 3-bromo-2,4,6-trimethylphenyl ketone was prepared and studied. It was shown that supermodified simplex method used in our algorithm (Simtex), though time consuming, gives the most accurate values of the rate constants and consequently the calculated thermodynamic parameters Ea, ∆H≠, and ∆S≠ lay in relatively narrow confidence intervals.

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Becker, Marvin, Tom De Vuyst, Marina Seidl, and Miriam Schulte. "Comparative Study on High Strain Rate Fracture Modelling Using the Application of Explosively Driven Cylinder Rings." Materials 14, no. 15 (July 29, 2021): 4235. http://dx.doi.org/10.3390/ma14154235.

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The effect of different constitutive modelling choices is crucial under a high strain rate as encountered in ballistic applications. Natural fragmentation of explosively driven cylinder rings is chosen as a simplified example to describe the ability of numerical simulations to describe fractures. The main research interests are the importance of (i) material imperfections, (ii) the accuracy of fracture models vs. damage models, (iii) the plasticity algorithm (stress update), (iv) the introduction of a triaxiality cutoff criterion to the damage models, and (v) different constitutive models (plasticity and damage). Due to the complexity of the propagation and coalescense of multiple cracks in classical methods, smoothed-particle hydrodynamics (SPH) is used as a tailor-made method to discretise the model. An elasto-plasticity model, a damage model and an equation of state describe the material behaviour. The required material parameters are determined based on stress–strain curves from quasi-static and dynamic tests. The Johnson–Cook model, with and without a modification of the strain rate term, and the Rusinek–Klepaczko model are used to describe plasticity. These plasticity models are combined either with the Johnson–Cook, the Lemaitre, or the Dolinski–Rittel damage model and the Mie–Grüneisen equation of state. The numerical results show that (i) a random distribution of initial damage increases irregularity of cracks, and gives more realistic fragment shapes, (ii) a coupling of plasticity model and fracture criterion has only a small effect on the fracture behaviour, (iii) using an iterative plasticity solver has a positive effect on the fracture behaviour, although this effect is marginal, (iv) adding a triaxiality cutoff criterion to the damage models improves the predicted fragment masses in the numerical simulations significantly, and (v) good accordance between experiments and numerical simulations are found for the Dolinski–Rittel and Lemaitre damage model with both plasticity models.

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Cortijo-Ferrero, C., R. M. González Delgado, E. Pérez, R. Cid Fernandes, R. García-Benito, P. Di Matteo, S. F. Sánchez, et al. "The spatially resolved star formation history of mergers." Astronomy & Astrophysics 607 (November 2017): A70. http://dx.doi.org/10.1051/0004-6361/201731217.

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This paper presents the spatially resolved star formation history (2D-SFH) of a small sample of four local mergers: the early-stage mergers IC 1623, NGC 6090, and the Mice, and the more advanced merger NGC 2623, by analyzing IFS data from the CALIFA survey and PMAS in LArr mode. Full spectral fitting techniques are applied to the datacubes to obtain the spatially resolved mass growth histories, the time evolution of the star formation rate intensity (ΣSFR), and the local specific star formation rate (sSFR), over three different time scales (30 Myr, 300 Myr, and 1 Gyr). The results are compared with non-interacting Sbc–Sc galaxies, to quantify if there is an enhancement of the star formation and to trace its time scale and spatial extent. Our results for the three LIRGs (IC 1623 W, NGC 6090, and NGC 2623) show that a major phase of star formation is occurring in time scales of 107 yr to few 108 yr, with global SFR enhancements of between approximately two and six with respect to main-sequence star forming (MSSF) galaxies. In the two early-stage mergers IC 1623 W and NGC 6090, which are between first pericentre passage and coalescence, the most remarkable increase of the SFR with respect to non-interacting spirals occurred in the last 30 Myr, and it is spatially extended, with enhancements of factors between two and seven both in the centres (r < 0.5 half light radius, HLR), and in the disks (r > 1 HLR). In the more advanced merger NGC 2623 an extended phase of star formation occurred on a longer time scale of ~1 Gyr, with a SFR enhancement of a factor of approximately two-to-three larger than the one in Sbc–Sc MSSF galaxies over the same period, probably relic of the first pericentre passage epoch. A SFR enhancement in the last 30 Myr is also present, but only in NGC 2623 centre, by a factor of three. In general, the spatially resolved SFHs of the LIRG-mergers are consistent with the predictions from high spatial resolution simulations. In contrast, the star formation in the Mice, specially in Mice B, is not enhanced but inhibited with respect to Sbc–Sc MSSF galaxies. The fact that the gas fraction of Mice B is smaller than in most non-interacting spirals, and that the Mice are close to a prograde orbit, represents a new challenge for the models, which must cover a larger space of parameters in terms of the availability of gas and the orbital characteristics.

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Faber, Joshua A., and Frederic A. Rasio. "Post-Newtonian SPH calculations of binary neutron star coalescence: Method and first results." Physical Review D 62, no. 6 (August 8, 2000). http://dx.doi.org/10.1103/physrevd.62.064012.

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Faber, Joshua A., and Frederic A. Rasio. "Post-Newtonian SPH calculations of binary neutron star coalescence. III. Irrotational systems and gravitational wave spectra." Physical Review D 65, no. 8 (April 9, 2002). http://dx.doi.org/10.1103/physrevd.65.084042.

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Journal articles on the topic 'SPH - Coalescence'

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