scholarly journals Numerical Simulations of Instability in the Shell of a Supernova Remnant Expanding in a Weakly in Inhomogeneous Interstellar Medium

2020 ◽  
pp. 23-35
Author(s):  
Vitaliy Korolev ◽  
Mikhail Eremin ◽  
Ilya Kovalenko ◽  
Andrey Zankovich
Keyword(s):  
Shock Front ◽  
Numerical Simulations ◽  
Blast Wave ◽  
Supernova Remnants ◽  
Spherical Shape ◽  
Linear Analysis ◽  
External Disturbances ◽  
Small Perturbations ◽  
Adiabatic Flow ◽  
Resonance Character

Astronomical observations show that the supernova remnants, even with a close to spherical shape, usually have multiscale ripple-like distortions. For example 15 bends on the shock front are clearly visible in the remnant 0509-67.5. The global instability of the flow is considered as one of the possible mechanisms for generating such structures. In the frame of linear analysis [26] was shown that this instability has a resonance character. It means that the perturbations with a certain wavelength number should grow faster, therefore ripples in the remnant shell will manifest itself predominantly in a certain range of scales. In this paper we present the results of numerical simulations of the nonlinear stage of this instability, caused by small perturbations in the external environment, depending on their scale and intensity. The unpertubed gas is supposed to has a power-law spartial dependence ρ0(r) ~ r-ω, where ω is a constant. The blast wave generated by a supernova expolosion is descibed by a Sedov type similarity solution. We have developed two-dimensional numerical model of adiabatic flow with a blast wave in a comoving frame of reference based on parallel code AstroChemHydro [1]. It was shown that, according to the predictions of linear analysis, perturbations in the external flow amplify behind the front of the shock wave, which leads to the development of convective instability and the development of turbulence. The results of numerical simulations demonstrated that in shell-type flows (for omega = 2,7 and gamma = 4/3) external disturbances along with the characteristic rearrangement of the shock front and turbulization of the flow behind it, cause the formation of radially elongated filaments with a vortex structure behind the shock, the number of which is determined by the harmonic number of the perturbation l.

Direct numerical simulation of isotropic turbulence interacting with a weak shock wave

1993 ◽  
Vol 251 ◽  
pp. 533-562 ◽  
Author(s):  
Sangsan Lee ◽  
Sanjiva K. Lele ◽  
Parviz Moin
Keyword(s):  
Shock Wave ◽  
Kinetic Energy ◽  
Shock Waves ◽  
Shock Front ◽  
Numerical Simulations ◽  
Turbulent Kinetic Energy ◽  
Isotropic Turbulence ◽  
Weak Shock ◽  
Linear Analysis ◽  
Weak Shock Wave

Interaction of isotropic quasi-incompressible turbulence with a weak shock wave was studied by direct numerical simulations. The effects of the fluctuation Mach number Mt of the upstream turbulence and the shock strength M21 — 1 on the turbulence statistics were investigated. The ranges investigated were 0.0567 ≤ Mt ≤ 0.110 and 1.05 ≤ M1 ≤ 1.20. A linear analysis of the interaction of isotropic turbulence with a normal shock wave was adopted for comparisons with the simulations.Both numerical simulations and the linear analysis of the interaction show that turbulence is enhanced during the interaction with a shock wave. Turbulent kinetic energy and transverse vorticity components are amplified, and turbulent lengthscales are decreased. The predictions of the linear analysis compare favourably with simulation results for flows with M2t < a(M21 — 1) with a ≈ 0.1, which suggests that the amplification mechanism is primarily linear. Simulations also showed a rapid evolution of turbulent kinetic energy just downstream of the shock, a behaviour not reproduced by the linear analysis. Investigation of the budget of the turbulent kinetic energy transport equation shows that this behaviour can be attributed to the pressure transport term.Shock waves were found to be distorted by the upstream turbulence, but still had a well-defined shock front for M2t < a(M21— 1) with a ≈ 0.1). In this regime, the statistics of shock front distortions compare favourably with the linear analysis predictions. For flows with M2t > a(M21— 1 with a ≈ 0.1, shock waves no longer had well-defined fronts: shock wave thickness and strength varied widely along the transverse directions. Multiple compression peaks were found along the mean streamlines at locations where the local shock thickness had increased significantly.

scholarly journals Optimization of the Parameters of RISE Feedback Controller Using Genetic Algorithm

2016 ◽  
Vol 2016 ◽  
pp. 1-9
Author(s):  
Fayiz Abu Khadra ◽  
Jaber Abu Qudeiri ◽  
Mohammed Alkahtani
Keyword(s):  
Genetic Algorithm ◽  
Numerical Simulations ◽  
Control Algorithm ◽  
Chaotic Systems ◽  
Optimization Technique ◽  
Optimization Techniques ◽  
Algorithm Optimization ◽  
External Disturbances ◽  
Van Der Pol ◽  
Control Methodology

A control methodology based on a nonlinear control algorithm and optimization technique is presented in this paper. A controller called “the robust integral of the sign of the error” (in short, RISE) is applied to control chaotic systems. The optimum RISE controller parameters are obtained via genetic algorithm optimization techniques. RISE control methodology is implemented on two chaotic systems, namely, the Duffing-Holms and Van der Pol systems. Numerical simulations showed the good performance of the optimized RISE controller in tracking task and its ability to ensure robustness with respect to bounded external disturbances.

Blast Wave Mitigation from the Straight Tube by Using Water Part II - Numerical Simulation

2018 ◽  
Vol 910 ◽  
pp. 78-83 ◽  
Author(s):  
Yuta Sugiyama ◽  
Tomotaka Homae ◽  
Kunihiko Wakabayashi ◽  
Tomoharu Matsumura ◽  
Yoshio Nakayama
Keyword(s):  
Experimental Data ◽  
Numerical Simulation ◽  
Energy Transfer ◽  
Numerical Simulations ◽  
Blast Wave ◽  
Blast Waves ◽  
Straight Tube ◽  
Water Interface ◽  
Effect Of Water ◽  
Air Water Interface

This paper investigates explosions in a straight square tube in order to understand the mitigation effect of water on blast waves that emerge outside. Numerical simulations are used to assess the effect of water that is put inside the tube. The water reduces the peak overpressure outside, which agrees well with the experimental data. The increases in the kinetic and internal energies of the water are estimated, and the internal energy transfer at the air/water interface is shown to be an important factor in mitigating the blast wave in the present numerical method.

The laboratory simulation of unmagnetized supernova remnants Absence of a blast wave

1984 ◽  
Vol 280 ◽  
pp. 802 ◽  
Author(s):  
J. E. Borovsky ◽  
M. B. Pongratz ◽  
R. A. Roussel-Dupre ◽  
T.-H. Tan
Keyword(s):  
Blast Wave ◽  
Supernova Remnants ◽  
Laboratory Simulation

scholarly journals Access Control Points: Reducing a Possible Blast Impact by Meandering

2018 ◽  
Vol 2018 ◽  
pp. 1-11 ◽  
Author(s):  
Martin Larcher ◽  
Georgios Valsamos ◽  
Vasilis Karlos
Keyword(s):  
Access Control ◽  
Numerical Simulations ◽  
Blast Wave ◽  
Injury Risk ◽  
Terrorist Attack ◽  
Control Points ◽  
The Public ◽  
Terrorist Groups ◽  
Risk Areas ◽  
Wall System

In response to the heightened terror threat in recent years, there is an increasing interest in the introduction of access control zones at sites that are characterized by an increased likelihood of being the target of a terrorist attack, as latest data reveal that unprotected areas of mass congregation of people have become attractive to terrorist groups. Such control zones could be located within the building that has to be protected or attached to it. The elevated security needs for these areas call for a design that will consider the risk of internal explosive events. The purpose of this article is to outline a strategy for limiting the consequences of an internal blast, while guaranteeing that the produced blast wave does not propagate into vulnerable areas. In particular, the focus is on the introduction of a protective wall system in the form of a meander that allows unobstructed access of the public and at the same time reduces the possible blast inflow to the building's interior. The performed numerical simulations show that the proposed strategy yields much smaller injury risk areas compared to a design without the addition of protective walls and is recommended for upgrading the security of buildings.

scholarly journals Modeling the mixed-morphology supernova remnant IC 443

2021 ◽  
Vol 649 ◽  
pp. A14 ◽  
Author(s):  
S. Ustamujic ◽  
S. Orlando ◽  
E. Greco ◽  
M. Miceli ◽  
F. Bocchino ◽  
...  
Keyword(s):  
Blast Wave ◽  
Parameter Space ◽  
Supernova Remnants ◽  
Ambient Medium ◽  
Complex Structure ◽  
Main Property ◽  
Asymmetric Distribution ◽  
Complex Environment ◽  
X Ray ◽  
Multi Wavelength

Context. The morphology and the distribution of material observed in supernova remnants (SNRs) reflect the interaction of the supernova (SN) blast wave with the ambient environment, the physical processes associated with the SN explosion, and the internal structure of the progenitor star. IC 443 is a mixed-morphology (MM) SNR located in a quite complex environment: it interacts with a molecular cloud in the northwestern and southeastern areas and with an atomic cloud in the northeast. Aims. In this work, we aim to investigate the origin of the complex morphology and multi-thermal X-ray emission observed in SNR IC 443 through the study of the effect of the inhomogeneous ambient medium in shaping its observed structure and an exploration of the main parameters characterizing the remnant. Methods. We developed a 3D hydrodynamic (HD) model for IC 443, which describes the interaction of the SNR with the environment, parametrized in agreement with the results of the multi-wavelength data analysis. We performed an ample exploration of the parameter space describing the initial blast wave and the environment, including the mass of the ejecta, the energy and position of the explosion, as well as the density, structure, and geometry of the surrounding clouds. From the simulations, we synthesized the X-ray emission maps and spectra and compared them with actual X-ray data collected by XMM-Newton. Results. Our model explains the origin of the complex X-ray morphology of SNR IC 443 in a natural way, with the ability to reproduce, for the first time, most of the observed features, including the centrally-peaked X-ray morphology (characteristic of MM SNRs) when considering the origin of the explosion at the position where the pulsar wind nebula CXOU J061705.3+222127 was at the time of the explosion. In the model that best reproduces the observations, the mass of the ejecta and the energy of the explosion are ~7 M⊙ and ~1 × 1051 erg, respectively. From the exploration of the parameter space, we find that the density of the clouds is n > 300 cm−3 and that the age of SNR IC 443 is ~8000 yr. Conclusions. The observed inhomogeneous ambient medium is the main property responsible for the complex structure and the X-ray morphology of SNR IC 443, resulting in a very asymmetric distribution of the ejecta due to the off-centered location of the explosion inside the cavity formed by the clouds. It can be argued that the centrally peaked morphology (typical of MM SNRs) is a natural consequence of the interaction with the complex environment. A combination of high resolution X-ray observations and accurate 3D HD modeling is needed to confirm whether this scenario is applicable to other MM SNRs.

scholarly journals Numerical Investigation on a Packed-Bed LHTES System Integrated into a Micro Electrical and Thermal Grid

Energies ◽  
2020 ◽  
Vol 13 (8) ◽  
pp. 2018
Author(s):  
Vittorio Tola ◽  
Simone Arena ◽  
Mario Cascetta ◽  
Giorgio Cau
Keyword(s):  
Energy Storage ◽  
Numerical Simulations ◽  
Thermal Energy ◽  
Supply And Demand ◽  
Spherical Shape ◽  
Packed Bed ◽  
Pv System ◽  
Transient Model ◽  
Auxiliary Component ◽  
Self Sufficiency

Currently, energy storage systems are considered a key solution when mismatch occurs between energy supply and demand, allowing a more efficient energy deployment and use. The present paper is focused on the study of a latent heat thermal energy storage (LHTES) system based on a packed bed of encapsulated phase change material (PCM) of spherical shape, conceived as an auxiliary component of a micro-grid to be built in a Research Center located in southwestern Sardinia (Italy). The main purpose of this work was to perform numerical simulations for predicting the performance of the TES system, designed to store the surplus thermal energy produced during the weekend by a heat pump fed by a photovoltaic (PV) plant. The stored energy would then be utilized during the weekdays to integrate the air-conditioning system supply. The numerical simulations were based on a one-dimensional (1-D) two-equation transient model, able to return the thermocline profile of the water and the PCM separately. The behavior of the LHTES device during charge and discharge phases was reproduced, as well as during the standby periods. Finally, two characteristic indexes of the PV system were evaluated, to investigate the effect of TES on grid interchanges, self-consumption, and self-sufficiency.

scholarly journals Mathematical Theory of One-dimensional Isothermal Blast Waves in a Magnetic Field

1979 ◽  
Vol 32 (5) ◽  
pp. 491 ◽  
Author(s):  
I Lerche
Keyword(s):  
Magnetic Field ◽  
Fluid Flow ◽  
Critical Point ◽  
Blast Wave ◽  
Supernova Remnants ◽  
Magnetic Energy ◽  
Flow Speed ◽  
Blast Waves ◽  
One Dimensional ◽  
Self Similar

An investigation is made of the self-similar flow behind a one-dimensional blast wave from a planar explosion (situated on z = 0) in a medium whose density and magnetic field vary with distance as Z-W ahead of the blast front, with the assumption that the flow is isothermal. It is found that; if OJ OJ > 0 the governing equation possesses a set of movable critical points. For a weak, but nonzero, magnetic field it is shown that the value of the smallest critical point does not lie in the physical domain z > O. The post-shock fluid flow then cannot intersect the critical point, and is smoothly continuous. It is shown that to be physically acceptable, the fluid flow speed must pass through the origin. It is also shown that OJ must be less than t for the magnetic energy swept up by the blast wave to remain finite. The overall conclusion from the investigation is that the behaviour of isothermal blast waves in the presence of an ambient magnetic field differs substantially from the behaviour calculated for no magnetic field. These results point to the inadequacy of previous attempts to apply the theory of self-similar flows to evolving supernova remnants without making any allowance for the dynamical influence of magnetic field pressure.

scholarly journals Robust Synchronization of Hyperchaotic Systems with Uncertainties and External Disturbances

2014 ◽  
Vol 2014 ◽  
pp. 1-8 ◽  
Author(s):  
Qing Wang ◽  
Yongguang Yu ◽  
Hu Wang
Keyword(s):  
Numerical Simulations ◽  
Lyapunov Stability ◽  
Stability Theory ◽  
Lyapunov Stability Theory ◽  
Convergence Speed ◽  
External Disturbances ◽  
Adaptive Controllers ◽  
Robust Synchronization ◽  
Hyperchaotic Systems

The robust synchronization of hyperchaotic systems with uncertainties and external disturbances is investigated. Based on the Lyapunov stability theory, the appropriate adaptive controllers and parameter update laws are designed to achieve the synchronization of uncertain hyperchaotic systems. The robust synchronization of two hyperchaotic Chen systems is taken as an example to verify the feasibility of the presented schemes. The size of the subcontroller gain’s influences on the convergence speed is discussed. Finally, numerical simulations are given to demonstrate the effectiveness of the proposed synchronization schemes.

Sign in / Sign up

Export Citation Format

Share Document