scholarly journals Star–disc alignment in the protoplanetary discs: SPH simulation of the collapse of turbulent molecular cloud cores

2020 ◽  
Vol 492 (4) ◽  
pp. 5641-5654 ◽  
Author(s):  
Daisuke Takaishi ◽  
Yusuke Tsukamoto ◽  
Yasushi Suto
Keyword(s):  
Time Scale ◽  
Molecular Cloud ◽  
Three Dimensional ◽  
Gravitational Energy ◽  
Circumstellar Envelope ◽  
Rotation Axes ◽  
Particle Hydrodynamics ◽  
Disc Rotation ◽  
Cloud Cores ◽  
Sph Simulation

ABSTRACT We perform a series of three-dimensional smoothed particle hydrodynamics (SPH) simulations to study the evolution of the angle between the protostellar spin and the protoplanetary disc rotation axes (the star–disc angle ψsd) in turbulent molecular cloud cores. While ψsd at the protostar formation epoch exhibits broad distribution up to ∼130°, ψsd decreases (≲ 20°) in a time-scale of ∼104 yr. This time-scale of the star–disc alignment, talignment, corresponds basically to the mass doubling time of the central protostar, in which the protostar forgets its initial spin direction due to the mass accretion from the disc. Values of ψsd both at t = 102 yr and t = 105 yr after the protostar formation are independent of the ratios of thermal and turbulent energies to gravitational energy of the initial cloud cores: α = Ethermal/|Egravity| and γturb = Eturbulence/|Egravity|. We also find that a warped disc is possibly formed by the turbulent accretion flow from the circumstellar envelope.

A Three-dimensional SPH Simulation of Iceberg Calving generated Waves

2021 ◽  
Author(s):  
Chao Hu ◽  
Xiao-liang Wang ◽  
Qing-quan Liu
Keyword(s):  
Large Scale ◽  
Three Dimensional ◽  
Particle Hydrodynamics ◽  
Flow Field Characteristics ◽  
Smoothed Particle ◽  
Iceberg Calving ◽  
Simulation Results ◽  
Sph Simulation ◽  
The Waves ◽  
Good Agreement

<p>The calving of large-scale icebergs into the sea can generate a local tsunami that may threaten coastal communities or passing ships. A three-dimensional smoothed particle hydrodynamics model of rigid-body–fluid system is established to simulate the spatial wave generated by calving iceberg. The model is tested with simulated waves induced by a cube iceberg fall into the water body. Good agreement is obtained between simulation results and experimental data. The generation and evolution processes, and the near flow-field characteristics of the waves are analyzed. The simulation results show that waves generated in iceberg calving can generate not only a huge leading wave but also notable tailing waves. The initial propagation direction of the leading wave is determined by iceberg geometry, but as the leading wave propagates away, the water level displacement gradually develops into a semicircle wavefront which is irrelevant to iceberg geometry.</p>

scholarly journals Three-dimensional MHD simulations of molecular cloud fragmentation regulated by gravity, ambipolar diffusion, and turbulence

2008 ◽  
Vol 4 (S259) ◽  
pp. 115-116
Author(s):  
Takahiro Kudoh ◽  
Shantanu Basu
Keyword(s):  
Star Formation ◽  
Magnetic Fields ◽  
Time Scale ◽  
Molecular Cloud ◽  
Molecular Clouds ◽  
Three Dimensional ◽  
Core Formation ◽  
Mhd Simulations ◽  
Dimensional Simulation

AbstractWe find that the star formation is accelerated by the supersonic turbulence in the magnetically dominated (subcritical) clouds. We employ a fully three-dimensional simulation to study the role of magnetic fields and ion-neutral friction in regulating gravitationally driven fragmentation of molecular clouds. The time-scale of collapsing core formation in subcritical clouds is a few ×107 years when starting with small subsonic perturbations. However, it is shortened to approximately several ×106 years by the supersonic flows in the clouds. We confirm that higher-spacial resolution simulations also show the same result.

Coupled FE-SPH Simulation of a High-Speed Grinding Process Using a Multiple-Grain Model

2014 ◽  
Vol 989-994 ◽  
pp. 3248-3251 ◽  
Author(s):  
Rui Dong Shen ◽  
Xiu Mei Wang ◽  
Chun Hui Yang
Keyword(s):  
High Speed ◽  
Three Dimensional ◽  
Grinding Process ◽  
High Speed Cutting ◽  
Particle Hydrodynamics ◽  
High Speed Grinding ◽  
Smoothed Particle ◽  
Armor Steel ◽  
Sph Simulation ◽  
Cutting Model

A multiple-grain cutting model is developed to simulate the grinding process for rolled homogeneous armor steel (RHA) 4043 using a coupled three-dimensional (3-D) finite element (FE) - smoothed-particle hydrodynamics (SPH) approach in the research. The proposed numerical model is then employed to investigate interactions and interferences among the grains at high speed cutting. The numerical results show the cutting forces and pile-ups of chips are greatly influenced by these interactions and interferences during the cutting process.

scholarly journals GIS-Based Three-Dimensional SPH Simulation for the 11 April 2018 Yabakei Landslide at Oita Nakatsu, Japan

Water ◽  
2021 ◽  
Vol 13 (21) ◽  
pp. 3012
Author(s):  
Zheng Han ◽  
Fan Yang ◽  
Yange Li ◽  
Jie Dou ◽  
Ningsheng Chen ◽  
...  
Keyword(s):  
Dynamic Process ◽  
Residential Buildings ◽  
Three Dimensional ◽  
Field Investigation ◽  
Sph Method ◽  
Landslide Event ◽  
Gis Data ◽  
Particle Hydrodynamics ◽  
Sph Simulation ◽  
Event Based

Landslides are usually triggered by strong earthquakes, heavy rainfalls, or intensive human activities in common wisdom. However, an unexpected landslide occurred in the Yabakei area, Nakatsu, Oita, Japan, at the pre-dawn hour 3:50 a.m. on 11 April 2018, without any accompanying rainfall and earthquake records during the event. This catastrophic landslide was 200 m in width, 110 m in height, and 60,000 m3 in mass volume, damaging four residential buildings with fatalities of six residents at the landslide toe. Field investigation was conducted immediately to identify geological setting, hydrological condition, and landslide geomorphological characteristics. Key findings speculate that infiltration of groundwater stored in the internal fractures led to the swelling and breaking of illite and askanite in the weathered sediment rocks, resulting in the failure of the Yabakei landslide. To reproduce and explore the dynamic process of this landslide event, based on spatial GIS data, we applied the proposed three-dimensional, Herschel-Bulkley-Papanastasiou rheology model-based smooth particle hydrodynamics (HBP-SPH) method to simulate the landslide dynamic process. Buildings in the landslide area are covered by a set of surfaced cells (SC) to analyze the mass impact on the residential buildings. Results showed good accordance between observation and simulation by the proposed SC-HBP-SPH method. The landslide impact force to the residential buildings could be up to 4224.89 kN, as indicated by the simulation.

scholarly journals THE ANGULAR MOMENTUM OF MAGNETIZED MOLECULAR CLOUD CORES: A TWO-DIMENSIONAL-THREE-DIMENSIONAL COMPARISON

2010 ◽  
Vol 723 (1) ◽  
pp. 425-439 ◽  
Author(s):  
Sami Dib ◽  
Patrick Hennebelle ◽  
Jaime E. Pineda ◽  
Timea Csengeri ◽  
Sylvain Bontemps ◽  
...  
Keyword(s):  
Angular Momentum ◽  
Molecular Cloud ◽  
Three Dimensional ◽  
Two Dimensional ◽  
Cloud Cores

scholarly journals Multi-Resolution SPH Simulation of a Laser Powder Bed Fusion Additive Manufacturing Process

2021 ◽  
Vol 11 (7) ◽  
pp. 2962
Author(s):  
Mohamadreza Afrasiabi ◽  
Christof Lüthi ◽  
Markus Bambach ◽  
Konrad Wegener
Keyword(s):  
Search Algorithm ◽  
Computational Effort ◽  
Powder Bed Fusion ◽  
Laser Powder Bed Fusion ◽  
Powder Bed ◽  
Neighbor Search ◽  
Particle Hydrodynamics ◽  
Sph Simulation ◽  
Particle Refinement ◽  
Search Approach

This paper presents an efficient mesoscale simulation of a Laser Powder Bed Fusion (LPBF) process using the Smoothed Particle Hydrodynamics (SPH) method. The efficiency lies in reducing the computational effort via spatial adaptivity, for which a dynamic particle refinement pattern with an optimized neighbor-search algorithm is used. The melt pool dynamics is modeled by resolving the thermal, mechanical, and material fields in a single laser track application. After validating the solver by two benchmark tests where analytical and experimental data are available, we simulate a single-track LPBF process by adopting SPH in multi resolutions. The LPBF simulation results show that the proposed adaptive refinement with and without an optimized neighbor-search approach saves almost 50% and 35% of the SPH calculation time, respectively. This achievement enables several opportunities for parametric studies and running high-resolution models with less computational effort.

scholarly journals Aperture synthesis CS and 98 GHz continuum observations of protostellar IRAS sources in Taurus

1991 ◽  
Vol 147 ◽  
pp. 353-356
Author(s):  
N. Ohashi ◽  
R. Kawabe ◽  
M. Hayashi ◽  
M. Ishiguro
Keyword(s):  
Molecular Cloud ◽  
Total Mass ◽  
T Tauri Stars ◽  
Continuum Emission ◽  
Beam Size ◽  
Dust Grains ◽  
Dynamical Mass ◽  
T Tauri ◽  
Cloud Cores ◽  
The Continuum

The CS (J = 2 — 1) line and 98 GHz continuum emission have been observed for 11 protostellar IRAS sources in the Taurus molecular cloud with resolutions of 2.6″−8.8″ (360 AU—1200 AU) using the Nobeyama Millimeter Array (NMA). The CS emission is detected only toward embedded sources, while the continuum emission from dust grains is detected only toward visible T Tauri stars except for one embedded source, L1551-IRS5. This suggests that the dust grains around the embedded sources do not centrally concentrate enough to be detected with our sensitivity (∼4 m Jy r.m.s), while dust grains in disks around the T Tauri stars have enough total mass to be detected with the NMA. The molecular cloud cores around the embedded sources are moderately extended and dense enough to be detected in CS, while gas disks around the T Tauri are not detected because the radius of such gas disks may be smaller than 70 (50 K/Tex) AU. These results imply that the total amount of matter within the NMA beam size must increase when the central objects evolve into T Tauri stars from embedded sources, suggesting that the compact and highly dense disks around T Tauri stars are formed by the dynamical mass accretion during the embedded protostar phase.

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