scholarly journals Parametric instability in a free-evolving warped protoplanetary disc

2020 ◽  
Vol 500 (3) ◽  
pp. 4248-4256
Author(s):  
Hongping Deng ◽  
Gordon I Ogilvie ◽  
Lucio Mayer
Keyword(s):  
Wave Equations ◽  
Hydrodynamic Instability ◽  
Parametric Instability ◽  
Low Viscosity ◽  
Crossing Time ◽  
Particle Hydrodynamics ◽  
Smoothed Particle ◽  
First Time ◽  
Bending Wave ◽  
Grid Based

ABSTRACT Warped accretion discs of low viscosity are prone to hydrodynamic instability due to parametric resonance of inertial waves as confirmed by local simulations. Global simulations of warped discs, using either smoothed particle hydrodynamics or grid-based codes, are ubiquitous but no such instability has been seen. Here, we utilize a hybrid Godunov-type Lagrangian method to study parametric instability in global simulations of warped Keplerian discs at unprecedentedly high resolution (up to 120 million particles). In the global simulations, the propagation of the warp is well described by the linear bending-wave equations before the instability sets in. The ensuing turbulence, captured for the first time in a global simulation, damps relative orbital inclinations and leads to a decrease in the angular momentum deficit. As a result, the warp undergoes significant damping within one bending-wave crossing time. Observed protoplanetary disc warps are likely maintained by companions or aftermath of disc breaking.

scholarly journals SPLASH: An Interactive Visualisation Tool for Smoothed Particle Hydrodynamics Simulations

2007 ◽  
Vol 24 (3) ◽  
pp. 159-173 ◽  
Author(s):  
Daniel J. Price
Keyword(s):  
Smoothed Particle Hydrodynamics ◽  
Three Dimensional ◽  
Two Dimensional ◽  
Mapping Procedure ◽  
Visualisation Tool ◽  
Pixel Array ◽  
Particle Hydrodynamics ◽  
Smoothed Particle ◽  
Interactive Visualisation ◽  
Grid Based

AbstractThis paper presents SPLASH, a publicly available interactive visualisation tool for Smoothed Particle Hydrodynamics (SPH) simulations. Visualisation of SPH data is more complicated than for grid-based codes because the data are defined on a set of irregular points and therefore requires a mapping procedure to a two dimensional pixel array. This means that, in practise, many authors simply produce particle plots which offer a rather crude representation of the simulation output. Here we describe the techniques and algorithms which are utilised in SPLASH in order to provide the user with a fast, interactive and meaningful visualisation of one, two and three dimensional SPH results.

scholarly journals Using synthetic emission maps to constrain the structure of the Milky Way

2013 ◽  
Vol 9 (S298) ◽  
pp. 246-252 ◽  
Author(s):  
Alex R. Pettitt ◽  
Clare L. Dobbs ◽  
David M. Acreman ◽  
Daniel J. Price
Keyword(s):  
Pitch Angle ◽  
Milky Way ◽  
Spiral Arms ◽  
The Earth ◽  
Particle Hydrodynamics ◽  
Smoothed Particle ◽  
Pattern Speeds ◽  
Best Fit ◽  
Grid Based ◽  
Key Questions

AbstractWe present the current standing of an investigation into the structure of the Milky Way. We use smoothed particle hydrodynamics (SPH) to simulate the ISM gas in the Milky Way under the effect of a number of different gravitational potentials representing the spiral arms and nuclear bars, both fixed and time-dependent. The gas is subject to ISM cooling and chemistry, enabling us to track the CO and HI density. We use a 3D grid-based radiative transfer code to simulate the emission from the SPH output, allowing for the construction of synthetic longitude-velocity maps as viewed from the Earth. By comparing these maps with the observed emission in CO and HI from the Milky Way ([Dame et al. 2001, Kalberla et al. 2005]), we can infer the arm/bar geometry that provides a best fit to our Galaxy. By doing so we aim to answer key questions concerning the morphology of the Milky Way such as the number of the spiral arms, the pattern speeds of the bar(s) and arms, the pitch angle of the arms and shape of the bar(s).

scholarly journals 3D Thermal Simulation of a Laser Drilling Process with Meshfree Methods

2020 ◽  
Vol 4 (2) ◽  
pp. 58
Author(s):  
Mohamadreza Afrasiabi ◽  
Konrad Wegener
Keyword(s):  
Heat Transfer ◽  
Laser Drilling ◽  
Meshfree Methods ◽  
Drilling Process ◽  
Particle Hydrodynamics ◽  
Recent Developments ◽  
Smoothed Particle ◽  
Thermal Simulations ◽  
The Laplace Operator ◽  
First Time

Numerical simulation of laser drilling is rapidly gaining interest in academia and industry since this process remains one of the most important and widely-used technologies in modern manufacturing. Meshfree methods such as Smoothed Particle Hydrodynamics (SPH) have proven to be successful as a numerical tool for the computation of the heat transfer and material removal associated with a laser drilling problem. Nonetheless, the vast majority of recent developments incorporate an inconsistent SPH kernel into their thermal simulations. In this paper, several enhanced schemes are implemented to address this problem by solving the heat transfer more accurately. These meshfree schemes can provide a second-order accurate discretization of the Laplace operator and abolish the inconsistency issue of the standard SPH kernels. An efficient approach is additionally suggested to handle the associated boundary conditions, which relies on the idea of the color function and particle label. The implementation is initially validated by a 3D benchmark study and then applied for the first time to a laser drilling problem.

The Kelvin-Helmholtz Instability in Smoothed-Particle Hydrodynamics

2006 ◽  
Vol 2 (S235) ◽  
pp. 210-210
Author(s):  
Veronika Junk ◽  
Fabian Heitsch ◽  
Thorsten Naab
Keyword(s):  
Surface Tension ◽  
Growth Rate ◽  
Smoothed Particle Hydrodynamics ◽  
Linear Regime ◽  
Helmholtz Instability ◽  
Sph Method ◽  
Viscosity Effects ◽  
Particle Hydrodynamics ◽  
Smoothed Particle ◽  
Grid Based

AbstractSmoothed Particle Hydrodynamics (SPH) simulations are a powerful tool to investigate hydrodynamical processes in astrophysics such as the formation of galactic disks. Dense gas clouds raining on the forming disk are possibly disrupted by Kelvin-Helmholtz-Instabilities (KHI). To understand the evolution of the halo clouds, we have to ascertain the capability of SPH to treat the KHI correctly, since SPH-methods tend to suffer from an innate surface tension and viscosity effects, both of which could dampen the KHI. We analytically derive a growth rate of the KHI including surface tension and viscosity in the linear regime, and compare this growth rate to results of numerical simulations by an SPH method and a grid-based method. We find that SPH in some cases suppresses the KHI (Junk et al., in prep).

scholarly journals Modelling shear flows with smoothed particle hydrodynamics and grid-based methods

2010 ◽  
Vol 407 (3) ◽  
pp. 1933-1945 ◽  
Author(s):  
Veronika Junk ◽  
Stefanie Walch ◽  
Fabian Heitsch ◽  
Andreas Burkert ◽  
Markus Wetzstein ◽  
...  
Keyword(s):  
Smoothed Particle Hydrodynamics ◽  
Shear Flows ◽  
Particle Hydrodynamics ◽  
Smoothed Particle ◽  
Grid Based

scholarly journals Gravitational wave emission from unstable accretion discs in tidal disruption events

2019 ◽  
Vol 489 (1) ◽  
pp. 699-706 ◽  
Author(s):  
Martina Toscani ◽  
Giuseppe Lodato ◽  
Rebecca Nealon
Keyword(s):  
Gravitational Wave ◽  
Hydrodynamic Instability ◽  
Maximum Amplitude ◽  
Accretion Discs ◽  
Tidal Disruption ◽  
Particle Hydrodynamics ◽  
Smoothed Particle ◽  
Solar Type ◽  
Measured Strain ◽  
Mass Quadrupole

Abstract Gravitational waves can be emitted by accretion discs if they undergo instabilities that generate a time varying mass quadrupole. In this work we investigate the gravitational signal generated by a thick accretion disc of 1 M⊙ around a static supermassive black hole of 106 M⊙, assumed to be formed after the tidal disruption of a solar type star. This torus has been shown to be unstable to a global non-axisymmetric hydrodynamic instability, the Papaloizou–Pringle instability, in the case where it is not already accreting and has a weak magnetic field. We start by deriving analytical estimates of the maximum amplitude of the gravitational wave signal, with the aim to establish its detectability by the Laser Interferometer Space Antenna (LISA). Then, we compare these estimates with those obtained through a numerical simulation of the torus, made with a 3D smoothed particle hydrodynamics code. Our numerical analysis shows that the measured strain is two orders of magnitude lower than the maximum value obtained analytically. However, accretion discs affected by the Papaloizou–Pringle instability may still be interesting sources for LISA, if we consider discs generated after deeply penetrating tidal disruptions of main-sequence stars of higher mass.

Hydrodynamic Coefficients for an Extraterrestrial Submarine

2019 ◽  
Author(s):  
Hani AlHasni ◽  
Ona Thornquist ◽  
Shafquat Islam ◽  
Peter Garrison ◽  
Iskender Sahin
Keyword(s):  
Hydrological Cycle ◽  
Particle Method ◽  
Free Surface Flow ◽  
Surface Flow ◽  
Cfd Simulations ◽  
Particle Hydrodynamics ◽  
Smoothed Particle ◽  
Parametric Analyses ◽  
Specific Formulation ◽  
Grid Based

Abstract An autonomous submarine design was proposed as part of NASA’s NIAC program to explore the hydrocarbon seas of Titan, the Saturnian moon, and study its hydrological cycle. The submarine is to be capable of operating at both the surface and in a deeply-submerged mode. This study aims to complement and compare previous CFD simulations with results obtained using the panel code CMARC. The comparison is of interest as the previous studies included a grid-based viscous code and a particle method using smoothed-particle hydrodynamics. The previous approaches encountered difficulties in obtaining agreeable results as each method has flow regimes suitable for a specific formulation, specifically free-surface flow versus a deeply submerged case. The panel formulation presented here is for the deeply submerged configuration and results match well with other approaches and parametric analyses, particularly when appendages are included in the modeling.

Simulation de l'écoulement au cours du procédé de rotomoulage par la méthode Smoothed Particle Hydrodynamics (SPH)

2008 ◽  
Vol 96 (6) ◽  
pp. 263-268 ◽  
Author(s):  
E. Mounif ◽  
V. Bellenger ◽  
A. Ammar ◽  
R. Ata ◽  
P. Mazabraud ◽  
...  
Keyword(s):  
Smoothed Particle Hydrodynamics ◽  
Particle Hydrodynamics ◽  
Smoothed Particle
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