scholarly journals Three-dimensional simulations of the interaction between the nova ejecta, accretion disk, and companion star

2018 ◽  
Vol 613 ◽  
pp. A8 ◽  
Author(s):  
Joana Figueira ◽  
Jordi José ◽  
Enrique García-Berro ◽  
Simon W. Campbell ◽  
Domingo García-Senz ◽  
...  
Keyword(s):  
Accretion Disk ◽  
White Dwarf ◽  
Binary Systems ◽  
Three Dimensional ◽  
Chemical Properties ◽  
Potential Effect ◽  
Model Parameters ◽  
Chemical Contamination ◽  
Particle Hydrodynamics ◽  
The Impact

Context. Classical novae are thermonuclear explosions hosted by accreting white dwarfs in stellar binary systems. Material piles up on top of the white dwarf star under mildly degenerate conditions, driving a thermonuclear runaway. The energy released by the suite of nuclear processes operating at the envelope, mostly proton-capture reactions and β+-decays, heats the material up to peak temperatures ranging from 100 to 400 MK. In these events, about 10−3–10−7 M⊙, enriched in CNO and, sometimes, other intermediate-mass elements (e.g., Ne, Na, Mg, and Al) are ejected into the interstellar medium. Aims. To date, most of the efforts undertaken in the modeling of classical nova outbursts have focused on the early stages of the explosion and ejection, ignoring the interaction of the ejecta, first with the accretion disk orbiting the white dwarf and ultimately with the secondary star. Methods. A suite of 3D, smoothed-particle hydrodynamics (SPH) simulations of the interaction between the nova ejecta, accretion disk, and stellar companion were performed to fill this gap; these simulations were aimed at testing the influence of the model parameters—that is, the mass and velocity of the ejecta, mass and the geometry of the accretion disk—on the dynamical and chemical properties of the system. Results. We discuss the conditions that lead to the disruption of the accretion disk and to mass loss from the binary system. In addition, we discuss the likelihood of chemical contamination of the stellar secondary induced by the impact with the nova ejecta and its potential effect on the next nova cycle.

scholarly journals The interaction of core-collapse supernova ejecta with a stellar companion

2018 ◽  
Vol 14 (S346) ◽  
pp. 55-58
Author(s):  
Zheng-Wei Liu ◽  
T. M. Tauris ◽  
F. K. Röpke ◽  
T. J. Moriya ◽  
M. Kruckow ◽  
...  
Keyword(s):  
Binary Systems ◽  
Main Sequence ◽  
Three Dimensional ◽  
Core Collapse ◽  
Chemical Contamination ◽  
Binary Separation ◽  
Hydrodynamical Simulations ◽  
Many Core ◽  
The Impact

AbstractThe progenitors of many core-collapse supernovae (CCSNe) are expected to be in binary systems. By performing a series of three-dimensional hydrodynamical simulations, we investigate how CCSN explosions affect their binary companion. We find that the amount of removed stellar mass, the resulting impact velocity, and the chemical contamination of the companion that results from the impact of the SN ejecta, strongly increases with decreasing binary separation and increasing explosion energy. Also, it is foud that the impact effects of CCSN ejecta on the structure of main-sequence (MS) companions, and thus their long term post-explosion evolution, are in general not dramatic.

scholarly journals Superoutbursts and Superhumps of SU UMa Stars

1988 ◽  
Vol 108 ◽  
pp. 238-239
Author(s):  
Yoji Osaki ◽  
Masahito Hirose
Keyword(s):  
Accretion Disk ◽  
Orbital Period ◽  
White Dwarf ◽  
Binary Systems ◽  
Roche Lobe ◽  
Light Curves ◽  
Close Binary ◽  
Dwarf Novae ◽  
Dwarf Nova ◽  
Close Binary Systems

SU UMa stars are one of subclasses of dwarf novae. Dwarf novae are semi-detached close binary systems in which a Roche-lobe filling red dwarf secondary loses matter and the white dwarf primary accretes it through the accretion disk. The main characteristics of SU UMa subclass is that they show two kinds of outbursts: normal outbursts and superoutbursts. In addition to the more frequent narrow outbursts of normal dwarf nova, SU UMa stars exhibit “superoutbursts”, in which stars reach about 1 magnitude brighter and stay longer than in normal outburst. Careful photometric studies during superoutburst have almost always revealed the “superhumps”: periodic humps in light curves with a period very close to the orbital period of the system. However, the most curious of all is that this superhump period is not exactly equal to the orbital period, but it is always longer by a few percent than the orbital period.

Role of Through Silicon Via in 3D Integration: Impact on Delay and Power

2020 ◽  
pp. 2150051
Author(s):  
Shivangi Chandrakar ◽  
Deepika Gupta ◽  
Manoj Kumar Majumder
Keyword(s):  
Power Dissipation ◽  
Three Dimensional ◽  
Propagation Delay ◽  
Model Parameters ◽  
3D Integration ◽  
Coupling Behavior ◽  
Power Delay Product ◽  
Silicon Vias ◽  
The Impact

The metal–semiconductor (MES)-based through silicon vias (TSV) has provided attractive solutions over conventional metal–insulator–semiconductor (MIS) TSVs in recent three-dimensional (3D) integration. This paper aims a comprehensive performance analysis of MIS and MES structures considering different TSV shapes such as cylindrical, tapered, annular, and square. At 32[Formula: see text]nm technology, a CMOS-based coupled driver-via-load (DVL) setup is introduced wherein each via is represented an equivalent RLGC model of MIS- and MES-based TSV shapes. The proposed electrical model accurately considers the impact of micro bump and inter-metal dielectric (IMD) effects at 32[Formula: see text]nm technology as per the fabrication house. A 3D electromagnetic (EM) structural wave simulation is performed to validate the RLGC model parameters of different TSV structures for an operating frequency of up to 20[Formula: see text]GHz. The proposed DVL setup is used to analyze the propagation delay, power dissipation, and dynamic crosstalk for different MIS- and MES-based TSV shapes. A significant improvement in the cross-coupling behavior can be obtained using the MES-based tapered TSV compared to the other MIS structures. Additionally, the power delay product (PDP) of the tapered MES is reduced by 92.4% compared to the conventional MIS-based cylindrical TSV.

Analyzing the Impact of Using Biodiesel in the Parameters of a 30 kW Micro-Turbine Control Model

2006 ◽  
Author(s):  
Manuel A. Rendo´n ◽  
Marco A. R. Do Nascimento ◽  
Pedro P. C. Mendes
Keyword(s):  
Electrical Power ◽  
Chemical Properties ◽  
Control Model ◽  
Model Parameters ◽  
Proposed Model ◽  
Complete Study ◽  
Micro Turbine ◽  
Turbine Speed ◽  
Physical And Chemical ◽  
The Impact

This work presents the modifications in a 30 kW gas micro-turbine speed control model, when it was supplied with castor bean biodiesel in several proportions. The concern about using biodiesel as an alternative fuel is increasing in the Brazilian distributed generation market. For this analytics, a complete study was developed considering the effects of using this new fuel. Characteristics like chemical composition, physical and chemical properties of the different mixtures were analyzed, especially focusing on the kinematic viscosity of the fuel. The tests results performed with the micro-turbine, originally projected for diesel, are shown. Mixtures of 5, 10, 15, 20, 25, 30, 50 e 100% of biodesel were used, and several variables were measured in the whole range of power. The influence of the biodiesel characteristics in the model parameters are commented in the conclusions. The possible application of the proposed model in studies of electrical power network is suggested in the end of the article.

Rogue Wave Impact on a Semi-Submersible Offshore Platform

2008 ◽  
Author(s):  
Murray Rudman ◽  
Paul Cleary ◽  
Justin Leontini ◽  
Matthew Sinnott ◽  
Mahesh Prakash
Keyword(s):  
Rogue Wave ◽  
Three Dimensional ◽  
Breaking Waves ◽  
Attractive Alternative ◽  
Wave Impact ◽  
Particle Hydrodynamics ◽  
Smoothed Particle ◽  
Dimensional Simulation ◽  
The Impact ◽  
Structural Motion

Full three-dimensional simulation of the impact of a rogue wave on a semi-submersible platform is undertaken using the Smoothed Particle Hydrodynamics (SPH) technique. Two different mooring configurations are considered: A Tension Leg Platform (TLP) system and a Taut Spread Mooring (TSM) system. It is seen that for a wave impact normal to the platform side, the heave and surge responses of the platform are significantly different for the two mooring systems. The TLP system undergoes large surge but comparatively smaller heave motions than the TSM system. The degree of pitch is very similar. The total tension in the mooring cables is approximately four times higher in the TSM system and exceeds the strength of the cables used in the simulation. SPH is seen to be an attractive alternative to standard methods for simulating the coupled interaction of highly non-linear breaking waves and structural motion.

scholarly journals Impact of Pile Punching on Adjacent Piles: Insights from a 3D Coupled SPH-FEM Analysis

2020 ◽  
Vol 1 (1) ◽  
pp. 47-58
Author(s):  
Laddu Bhagya Jayasinghe ◽  
Daniele Waldmann ◽  
Junlong Shang
Keyword(s):  
Three Dimensional ◽  
Fem Analysis ◽  
Field Measurements ◽  
Lateral Loads ◽  
Fem Model ◽  
Soft Clays ◽  
Stiff Clays ◽  
Particle Hydrodynamics ◽  
Smoothed Particle ◽  
The Impact

Pile punching (or driving) affects the surrounding area where piles and adjacent piles can be displaced out of their original positions, due to horizontal loads, thereby leading to hazardous outcomes. This paper presents a three-dimensional (3D) coupled Smoothed Particle Hydrodynamics and Finite Element Method (SPH-FEM) model, which was established to investigate pile punching and its impact on adjacent piles subjected to lateral loads. This approach handles the large distortions by avoiding mesh tangling and remeshing, contributing greatly high computational efficiency. The SPH-FEM model was validated against field measurements. The results of this study indicated that the soil type in which piles were embedded affected the interaction between piles during the pile punching. A comprehensive parametric study was carried out to evaluate the impact of soil properties on the displacement of piles due to the punching of an adjacent pile. It was found that the interaction between piles was comparatively weak when the piles were driven in stiff clays; while the pile-soil interactions were much more significant in sandy soils and soft clays.

scholarly journals Evolution of Rotating White Dwarfs in Close Binaries and Diversity of Type Ia Supernovae

2003 ◽  
Vol 208 ◽  
pp. 459-460
Author(s):  
Tatsuhiro Uenishi ◽  
Ken'ichi Nomoto ◽  
Izumi Hachisu
Keyword(s):  
Angular Momentum ◽  
Accretion Disk ◽  
White Dwarf ◽  
Binary Systems ◽  
Close Binary ◽  
Close Binaries ◽  
Type Ia Supernovae ◽  
Rapid Rotation ◽  
Type Ia ◽  
Ia Supernovae

Type Ia supernovae are very good, but not perfect, standard candles, because their observed brightness shows a little diversity. The origin of this dibersity needs to be understood for the application to cosmology.In close binary systems, a white dwarf must be rotating faster and faster as it gains angular momentum from the accretion disk. Its rapid rotation affects its final mass and strucure just before a supernova expolosion. Brightness of supernovae can be changed if mass of their progenitors have some diversity.

scholarly journals Impact of convection and resistivity on angular momentum transport in dwarf novae

2018 ◽  
Vol 609 ◽  
pp. A77 ◽  
Author(s):  
N. Scepi ◽  
G. Lesur ◽  
G. Dubus ◽  
M. Flock
Keyword(s):  
Angular Momentum ◽  
Accretion Disk ◽  
White Dwarf ◽  
Momentum Transport ◽  
Simple Relationship ◽  
Dwarf Novae ◽  
Angular Momentum Transport ◽  
Viscous Instability ◽  
S Curve ◽  
The Impact

The eruptive cycles of dwarf novae are thought to be due to a thermal-viscous instability in the accretion disk surrounding the white dwarf. This model has long been known to imply enhanced angular momentum transport in the accretion disk during outburst. This is measured by the stress to pressure ratio α, with α ≈ 0.1 required in outburst compared to α ≈ 0.01 in quiescence. Such an enhancement in α has recently been observed in simulations of turbulent transport driven by the magneto-rotational instability (MRI) when convection is present, without requiring a net magnetic flux. We independently recover this result by carrying out PLUTO magnetohydrodynamic (MHD) simulations of vertically stratified, radiative, shearing boxes with the thermodynamics and opacities appropriate to dwarf novae. The results are robust against the choice of vertical boundary conditions. The thermal equilibrium solutions found by the simulations trace the well-known S-curve in the density-temperature plane that constitutes the core of the disk thermal-viscous instability model. We confirm that the high values of α ≈ 0.1 occur near the tip of the hot branch of the S-curve, where convection is active. However, we also present thermally stable simulations at lower temperatures that have standard values of α ≈ 0.03 despite the presence of vigorous convection. We find no simple relationship between α and the strength of the convection, as measured by the ratio of convective to radiative flux. The cold branch is only very weakly ionized so, in the second part of this work, we studied the impact of non-ideal MHD effects on transport. Ohmic dissipation is the dominant effect in the conditions of quiescent dwarf novae. We include resistivity in the simulations and find that the MRI-driven transport is quenched (α ≈ 0) below the critical density at which the magnetic Reynolds number Rm ≤ 104. This is problematic because the X-ray emission observed in quiescent systems requires ongoing accretion onto the white dwarf. We verify that these X-rays cannot self-sustain MRI-driven turbulence by photo-ionizing the disk and discuss possible solutions to the issue of accretion in quiescence.

scholarly journals Role of baffle shape on debris flow impact in step-pools channel: an SPH study

2021 ◽  
Author(s):  
Shuai Li ◽  
Chong ◽  
Wei Wu ◽  
shun wang ◽  
Xiaoqing Chen ◽  
...  
Keyword(s):  
Debris Flow ◽  
Empirical Relation ◽  
Three Dimensional ◽  
Numerical Results ◽  
Impact Pressure ◽  
Jet Flows ◽  
Flow Density ◽  
Particle Hydrodynamics ◽  
Pool System ◽  
The Impact

Drainage channels with step-pool system are widely used to control debris flow. The blocking of debris flow often gives rise to local damage at the steps and ba?es. Hence, the estimation of impact force of debris flow is crucial for designing step-pools channel. Existing empirical models for impact pressure prediction cannot consider the influence of baffle shape. In this work, a three-dimensional smoothed particle hydrodynamics (SPH) study on the impact behaviour of debris flows in step-pool systems is presented, where debris material is modelled using the regularizedBingham model. The SPH method is first checked using the results from two laboratory tests. Then it is used to investigate the influence of bafflee shape and flow density. Numerical results show that the impact pressure at the first ba?e highly depends on the ba?e shape; however, the largest impact pressure usually occurs at subsequent baffles due to the violent impact induced by jet flows. The peak impact pressure at the first ba?e initially grows with increasing flow density; however, it starts to drop as density is beyond a threshold. Based on the numerical results, an empirical relation considering the influence of ba?e shape is proposed for better prediction of debris impact pressure.

scholarly journals On the impact of modelling assumptions in multi-scale, subject-specific models of aortic haemodynamics

2016 ◽  
Vol 13 (119) ◽  
pp. 20160073 ◽  
Author(s):  
Jordi Alastruey ◽  
Nan Xiao ◽  
Henry Fok ◽  
Tobias Schaeffter ◽  
C. Alberto Figueroa
Keyword(s):  
Boundary Conditions ◽  
Three Dimensional ◽  
Small Region ◽  
Model Parameters ◽  
Simulation Framework ◽  
Non Invasive ◽  
Subject Specific ◽  
Modelling Assumptions ◽  
The Impact

Simulation of haemodynamics has become increasingly popular within the research community. Irrespective of the modelling approach (zero-dimensional (0D), one-dimensional (1D) or three-dimensional (3D)), in vivo measurements are required to personalize the arterial geometry, material properties and boundary conditions of the computational model. Limitations in in vivo data acquisition often result in insufficient information to determine all model parameters and, hence, arbitrary modelling assumptions. Our goal was to minimize and understand the impact of modelling assumptions on the simulated blood pressure, flow and luminal area waveforms by studying a small region of the systemic vasculature—the upper aorta—and acquiring a rich array of non-invasive magnetic resonance imaging and tonometry data from a young healthy volunteer. We first investigated the effect of different modelling assumptions for boundary conditions and material parameters in a 1D/0D simulation framework. Strategies were implemented to mitigate the impact of inconsistencies in the in vivo data. Average relative errors smaller than 7% were achieved between simulated and in vivo waveforms. Similar results were obtained in a 3D/0D simulation framework using the same inflow and outflow boundary conditions and consistent geometrical and mechanical properties. We demonstrated that accurate subject-specific 1D/0D and 3D/0D models of aortic haemodynamics can be obtained using non-invasive clinical data while minimizing the number of arbitrary modelling decisions.

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