Engineering topics
Miller, Jonah Maxwell
Publications and source records attributed to Miller, Jonah Maxwell.
Singularity-EOS: Performance Portable Equations of State and Mixed Cell Closures
We present Singularity-EOS, a new performance-portable library for equations of state and related capabilities. Singularity-EOS provides a large set of analytic equations of state, such as the Gruneisen equation of state, and tabulated equation of state data under a unified interface. It also provides support capabilities around these equations of state, such as Python wrappers, solvers for finding pressure-temperature equilibrium between multiple equations of state, and a unique modifier framework, allowing the user to transform a base equation of state, for example by shifting or scaling the specific internal energy. All capabilities are performance portable, meaning they compile and run on both CPU and GPU for a wide variety of architectures.
The Dependence of Gamma-Ray Burst Jet Collimation on Black Hole Spin
Gamma-ray bursts (GRBs) are the most luminous events in the Universe and are excellent laboratories to study extreme physical phenomena in the cosmos. Despite a long trajectory of progress in understanding these highly energetic events, there are still many observed features that are yet to be fully explained. Observations of the jet opening angle of long gamma-ray bursts (LGRBs) suggest that LGRB jets are narrower for those GRBs at higher redshift. This phenomenon has been explained in the context of collimation by the stellar envelope, with denser (lower metallicity) stars at higher redshifts able to collimate the jet more effectively. However, until now, the dependence of the jet opening angle on the properties of the central engine has not been explored. We investigate the effect of black hole spin on the jet collimation angle for a magnetically launched jet, using the general relativistic radiation magnetohydrodynamical code ν bhlight . We present 3D results for a range of spin values. The simulations show that higher-spinning black holes tend to create narrower jets. If indeed LGRB progenitors in the early Universe are able to produce black hole central engines with higher spin, this could account for at least some of the observed jet opening angle-redshift correlation.
w22_bhmergers FY23 Highlights Viewgraph [Slides]
Observed heavyweight stellar mass black holes require an unknown formation channel; LANL investigating growth inside supermassive black hole accretion disks.
Emergent Nucleosynthesis from a 1.2 s Long Simulation of a Black Hole Accretion Disk
We simulate a black hole accretion disk system with full-transport general relativistic neutrino radiation magnetohydrodynamics for 1.2 s. This system is likely to form after the merger of two compact objects and is thought to be a robust site of r-process nucleosynthesis. We consider the case of a black hole accretion disk arising from the merger of two neutron stars. Our simulation time coincides with the nucleosynthesis timescale of the r-process (~1 s). Because these simulations are time-consuming, it is common practice to run for a “short” duration of approximately 0.1–0.3 s. We analyze the nucleosynthetic outflow from this system and compare the results of stopping at 0.12 and 1.2 s. We find that the addition of mass ejected in the longer simulation as well as more favorable thermodynamic conditions from emergent viscous ejecta greatly impacts the nucleosynthetic outcome. We quantify the error in nucleosynthetic outcomes between short and long cuts.
The Effect of the Velocity Distribution on Kilonova Emission
The electromagnetic emission from the nonrelativistic ejecta launched in neutron star mergers (either dynamically or through a disk wind) has the potential to probe both the total mass and composition of this ejecta. These observations are crucial in understanding the role of these mergers in the production of r-process elements in the Universe. However, many properties of the ejecta can alter the light curves and we must both identify which properties play a role in shaping this emission and understand the effects these properties have on the emission before we can use observations to place strong constraints on the amount of r-process elements produced in the merger. This paper focuses on understanding the effect of the velocity distribution (amount of mass moving at different velocities) for lanthanide-rich ejecta on the light curves and spectra. The simulations use distributions guided by recent calculations of disk outflows and compare the velocity-distribution effects to those of ejecta mass, velocity, and composition. Our comparisons show that uncertainties in the velocity distribution can lead to a factor of 2–4 uncertainties in the inferred ejecta mass based on peak infrared luminosities. We also show that early-time UV or optical observations may be able to constrain the velocity distribution, reducing the uncertainty in the ejecta mass.
Parthenon: Adaptive Mesh Refinement for Exascale Astrophysics
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Predicting Which Massive Stars Explode
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Predicting which massive stars explode
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State of the Art and Future Prospects of Modeling Neutrinos in NS Mergers
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Performance Portability is (Sort of) a Lie
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Parthenon - A Performance Portable Block-Structured Adaptive Mesh Refinement Framework
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On the prospects for r-process nucleosysnthesis in collapsars
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When Light Pushes Back: Radiation-Dominated Accretion
Density of gas orbiting and falling into a black hole for three models with varying accretion rates. The leftmost disk is lowest accretion rate, and the rightmost the highest. All three models are of so-called radiation-supported disks, where the gas is glowing so brightly that the glow of the light emitted pushes the gas away from the black hole, puffing up the accretion disk. Simulations run by Benjamin Ryan.
The Aftermath of a Black Hole Eating a Neutron Star [Slide]
Density and electron fraction of neutron star stuff leftover after a black hole eats the neutron star. Events like this one are believed to power gamma ray bursts, some of the most energetic events in the universe, and be the source of heavy elements like gold and platinum.
The Force Explosion Condition Accurately Predicts Explodability of Core-Collapse Supernova Simulations [Slides]
We are testing the FEC with CCSN Simulations. We will continue to develop the theory. We will continue to develop the Multi-D Simulations.
Singularity-EOS XCAP Report
Solving the Euler equations is a fundamental component of simulating many physical phenomena ranging from high explosives to astrophysics. An equation of state (EOS) is a required piece that relates any two thermodynamic quantities to all other thermodynamic values. The presence of multiple materials within a control volume further complicates the solution requiring additional equations to describe the interaction of materials at a sub-grid level. Equations of state themselves can also come in many forms ranging from simple algebraic relations to more complicated differential equation models that describe material interactions over a broad range of physical conditions. In the latter case, the EOS is often pre-computed at a given set of grid points and provided in a tabular form where additional properties can be derived from the interpolation functions.