Shock Propagation Dynamics Research Articles

Internal shocks hydrodynamics: the collision of two cold shells in detail

ABSTRACT Emission in many astrophysical transients originates from a shocked fluid. A central engine typically produces an outflow with varying speeds, leading to internal collisions within the outflow at finite distances from the source. Each such collision produces a pair of forward and reverse shocks with the two shocked regions separated by a contact discontinuity (CD). As a useful approximation, we consider the head-on collision between two cold and uniform shells (a slower leading shell and a faster trailing shell) of finite radial width, and study the dynamics of shock propagation in planar geometry. We find significant differences between the forward and reverse shocks, in terms of their strength, internal energy production efficiency, and the time it takes for the shocks to sweep through the respective shells. We consider the subsequent propagation of rarefaction waves in the shocked regions and explore the cases where these waves can catch up with the shock fronts and thereby limit the internal energy dissipation. We demonstrate the importance of energy transfer from the trailing to leading shell through pdV work across the CD. We outline the parameter space regions relevant for models of different transients,e.g. Gamma-ray burst internal shock model, fast radio burst blast wave model, Giant flare due to magnetars, and superluminous supernovae ejecta. We find that the reverse shock likely dominates the internal energy production for many astrophysical transients.

Sensitivity analysis of shock distributions in the world economy.

With the ever increasing interconnectedness among countries and industries, globalization has empowered economies and promoted international trade, capital flow and labor mobility, leading to improved products and services. However, the growing interdependence has also propelled an inherent reliance on joint cooperation which has considerably influenced the complexity of global value chains (GVCs). This plays a significant role in policy decisions, raising questions about trade risks that originate from such interdependence. In this paper, we study the impact of network linkage disturbances on the output supply and input demand of countries. We model the network interconnectedness of countries according to the latest 2016 release of the World Input-Output Database (WIOD) that includes data tables for the period 2000-2014 covering 43 countries as well as a model for the Rest of the World (ROW). We assess the shock distributions across the world economy by quantifying the changes in the network linkages using sensitivity analysis. Our contribution is in the definition of a shock tensor with the purpose of evaluating the impact of link sensitivity. The shock tensor is a straightforward yet comprehensive tool that allows us to obtain ample results at various levels of granularity when combining it with aggregation operators. Our study introduces a novel methodology that enables us to acquire input and output link sensitivities for all country pairings when an economic shock initiates or concludes within a country of interest. This innovative approach also facilitates the analysis of evolving trends in these link sensitivities, providing a comprehensive understanding of the dynamics of shock propagation across the global network. Taking advantage of the time-series nature of the WIOD, our results reveal illustrative visualizations and quantative measures that characterize patterns of shock distribution and relationships among countries throughout the period from 2000 to 2014. Our methodology and results not only uncover valuable trends but also establish a structured approach to better understand the aggregate effects of shock distributions. Thus, this study could be helpful for policy makers to assess trade relationships between countries and obtain quantitative insights for making informed decisions as well as explore the overall state of the globalization as a whole.

The cascade influence of grain trade shocks on countries in the context of the Russia-Ukraine conflict

The Russia-Ukraine conflict has severely impacted global food security. This may increase the risk of supply chain disruption in low-income countries that rely heavily on grain imports. This study used production and trade data for wheat, barley and maize from 1995 to 2021 to construct longitudinal trade networks. On this basis, a cascading failure network model of shock propagation was used to identify the direct or indirect dependence of other countries on grain exported from Russia and Ukraine and the impact caused by trade shocks. The results revealed that the interruption of grain exports from Russia and Ukraine has resulted in an increasing impact on the global grain trade year by year and that the wheat trade is the most vulnerable to shock propagation, but it is also the most resilient. Russia and Ukraine interrupt exports of grain, causing more than 50% reduction in direct imports to 30 countries, including Eritrea, Seychelles, Kazakhstan and Mongolia. A shock propagation model that considers indirect dependence yields divergent results, with lower middle income (LM) countries in North Africa, Southeast Asia and West Asia facing supply shocks from reduced imports because they are unable to fully exploit the trade channels to balance grain supply and demand. Under the COVID-19 pandemic, this indirect dependence on imports is more prominent. It is worth noting that Eastern and Southern European countries often act as intermediaries to spread shocks during cascading failures. In the process of shock propagation, the main suppliers of grain include the United States, Canada, France, Argentina and Brazil. After the outbreak of COVID-19, the import demand faced by Australia increased significantly. We also examined how nodal characteristics relate to shock propagation dynamics and country vulnerability, finding that high import diversity, low import dependence and regional characteristics are effective in buffering countries from supply shocks. This study contributes to our understanding of the external supply risks for grain arising from the Russia-Ukraine conflict in a pandemic context, highlights the issue of accessibility in food security and provides trade policy recommendations to mitigate national vulnerability to food insecurity, thereby creating a resilient food trade system.

On characterization of shock propagation and radiative preheating in x-ray driven high-density carbon foils

Recently, much effort has been dedicated to the high-density carbon ablator coated fuel capsule in indirect drive inertial confinement fusion experiments due to its higher density compared to other ablators. By using detailed radiation hydrodynamic simulations over a broad range of drive and target parameters, a thorough analysis is performed on shock speed, shock breakout, and maximum preheating temperature in pure and tungsten doped high density carbon foils. The ablators are irradiated by a non-equilibrium x-ray temperature drive consisting of the usual Planckian plus an additionally imposed Gaussian distribution lying in the high frequency M-band region of the incident spectrum. All variables have shown a complex interdependence on strength of the drive, its spectral distribution, and the thickness of the target. Maximum preheating temperature, an important parameter in designing experiments, reduces up to 34% for thicker high-density carbon (HDC) foils, whereas a mere 0.44% doping of tungsten in pure HDC is able to reduce preheating up to 17% for extreme drive conditions. The results are explained on the basis of variation of average albedo/wall loss behavior in foils, an outcome of the interplay between total extinction coefficient and spectral intensity variation with photon energy. For a better understanding and comparison among different types of ablators, multi-parameter scaling relations are proposed for above-mentioned variables, which govern the dynamics of shock propagation and preheating phenomena in HDC based foils.

Dynamics of shock propagation and nucleosynthesis conditions in O-Ne-Mg core supernovae

It has been recently proposed that the shocked surface layer s of exploding O-Ne-Mg cores provide the conditions for r-process nucleosynthesis, because their rapid expansion and high entropies enable heavy r-process isotopes to form even in an environment with very low initial neutron excess of the matter. We show here that the most sophisticated available hydrodynamic simulations (in spherical and axial symmetry) do not support this new r-process scenario because they fail to provide the necessary conditions of temperature, entropy, and expansion timescale by significa nt factors. This suggests that, either the formation of r-pr ocess elements works differently than suggested by Ning et al. (2007, NQM07), or that some essential core properties with influence on the explosio n dynamics might be different from those predicted by Nomoto’s progenitor model.

The role of the equation of state in the 'prompt' phase of type II supernovae

view Abstract Citations (86) References (30) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The Role of the Equation of State in the ``Prompt'' Phase of Type II Supernovae Swesty, F. Douglas ; Lattimer, James M. ; Myra, Eric S. Abstract We examine the role of the equation of state (EOS) of hot, dense matter in the prompt phase of stellar collapse. In order to achieve this goal, we have carried out radiation hydrodynamic simulations using an adjustable EOS that is consistent with constraints placed on the EOS by neutron star observations, nuclear systematics, and laboratory experiments. Our simulations of stellar collapse show that these constraints restrict the role that the EOS can play in determining the dynamics of shock propagation. We find that certain nuclear force parameters do not substantially affect the dynamics of collapse as strongly as previously believed. In particular, we find that the shock stall radius is practically independent of the compression modulus and symmetry energy when other constraints on the EOS are satisfied. In contrast, the nuclear symmetry energies have more profound effects on the collapse via electron capture, and these effects may be detectable by means of the neutrino signature of a nearby supernova. Publication: The Astrophysical Journal Pub Date: April 1994 DOI: 10.1086/173974 Bibcode: 1994ApJ...425..195S Keywords: Collapse; Computational Astrophysics; Computerized Simulation; Equations Of State; Hydrodynamics; Shock Wave Propagation; Supernovae; Electron Capture; Free Energy; Helmholtz Equations; Interstellar Matter; Shock Waves; Stellar Models; Astrophysics; DENSE MATTER; EQUATION OF STATE; SHOCK WAVES; STARS: NEUTRON; STARS: SUPERNOVAE: GENERAL full text sources ADS | data products SIMBAD (1)

The development of surface discontinuities (edges) during sputtering induced erosion of solids

In previous conferences in this series we have discussed the development of surface topography resulting from ion bombardment induced sputtering erosion. A general approach, based upon wavefront evolution theory, has been used to predict the dynamic change in the topography of continuous surfaces and the conditions for discontinuity initiation (e.g. edges and points) determined. It had not been possible to predict the subsequent motion of such discontinuities but now we have, for the first time, been able to mathematically predict such trajectories by considering the dynamics of shock propagation. This new development is described and conditions for linear and curved edge trajectory motion are discussed. Comparison is made with both computer simulation of topography development and experimental studies of cone evolution.

Interplanetary shock waves in the post solar maximum year period (January – July, 1981)

The paper discusses 15 interplanetary shocks recorded by the Prognoz-8 satellite. An analysis is made of shock propagation dynamics and energetics, change of plasma kinetic parameters at the front, and large-scale structure of plasma flow behind the front. The electrostatic potential barrier at the shock front depending on the Alfvenic Mach number is estimated.

Theoretical studies of shock-initiated detonations

The dynamics of shock propagation have been studied theoretically for a variety of two-dimensional lattices. The approach used is based on molecular dynamics and hinges on the exact numerical solution by computer of the equations of motion for the individual atoms or molecules in each lattice. Shocks have been launched into the lattices under study by methods designed to simulate flyer-plate impact. Two different interatomic potentials have been used, one endothermic and one net-exothermic. For both types of potential, a shock launched at one side of the lattice will spall a group of atoms off the other side. However, the subsequent behavior of the two types of lattice is very different. For endothermic potentials, after the initial atomic spall, the residual lattice is quiescent with little further activity. For net-exothermic potentials, the initial atomic spall injects additional energy into the system in such a manner that subsequently further spall occurs at both sides. Once this new spall is initiated, it leads rapidly to further bond breaking and explosive disintegration of the system.