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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 523 records · Page 29
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Advanced Multi-Dimensional Capacitance Sensors Based Subsea Multiphase Mass Flow Meter to Measure and Monitor Offshore Enhanced Oil

This innovation is based on advanced multi-dimensional extensions of ECVT sensors that involve ECVT, Displacement Current Phase Tomography (DCPT), Maxwell-Wagner-Sillars polarization effect (MWS), and velocimetry which exploit the variation of electric properties between the oil, water, and gas coming out of the well. Capacitance sensors are embedded on the inside of a pipe spool and placed in-line with the subsea oil line piping on the extraction end of the well. The difference in dielectric, dielectric loss, surface polarization, and velocity of each phase are used in the multi-dimensional algorithm to measure the volume fraction, distribution, velocity, mass flow rate, and flow regime of the mixture moving through the pipe.

02 PETROLEUM↗
DOE OSTI2017

Superbubbles in the multiphase ISM and the loading of galactic winds

We use numerical simulations to analyze the evolution and properties of superbubbles (SBs), driven by multiple supernovae (SNe), that propagate into the two-phase (warm/cold), cloudy interstellar medium (ISM). We consider a range of mean background densities n{sub avg}=0.1--10 cm{sup −3} and intervals between SNe Δt{sub SN}=0.01--1 Myr, and follow each SB until the radius reaches ∼(1--2)H, where H is the characteristic ISM disk thickness. Except for embedded dense clouds, each SB is hot until a time t{sub sf,m} when the shocked warm gas at the outer front cools and forms an overdense shell. Subsequently, diffuse gas in the SB interior remains at T{sub h}∼10{sup 6}--10{sup 7} K, with an expansion velocity v{sub h}∼10{sup 2}--10{sup 3} km s{sup −1} (both highest for low Δt{sub SN}). At late times, the warm shell gas velocities are several tens to ∼100 km s{sup −1}. While shell velocities are too low to escape from a massive galaxy, they are high enough to remove substantial mass from dwarfs. Dense clouds are also accelerated, reaching a few to tens of km s{sup −1}. We measure the mass in hot gas per SN, M-hat {sub h}, and the total radial momentum of the bubble per SN, p-hat {sub b}. After t{sub sf,m}, M-hat {sub h}∼10--100 M{sub ⊙} (highest for low n{sub avg}), while p-hat {sub b}∼0.7--3×10{sup 5} M{sub ⊙} km s{sup −1} (highest for high Δt{sub SN}). If galactic winds in massive galaxies are loaded by the hot gas in SBs, we conclude that the mass-loss rates would generally be lower than star formation rates. Only if the SN cadence is much higher than usual in galactic disks, as may occur for nuclear starbursts, can SBs breakout while hot and expel up to 10 times the mass locked up in stars. The momentum injection values, p-hat {sub b}, are consistent with requirements to control star formation rates within galaxies at observed levels.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2017

The Pairing of Accreting Massive Black Holes in Multiphase Circumnuclear Disks: the Interplay Between Radiative Cooling, Star Formation, and Feedback Processes

We study the orbital decay of a pair of massive black holes (BHs) with masses 5×10{sup 5} and 10{sup 7} M{sub ⊙}, using hydrodynamical simulations of circumnuclear disks (CNDs) with the alternating presence of sub-grid physics, such as radiative cooling, star formation, supernova feedback, BH accretion, and BH feedback. In the absence of such processes, the orbit of the secondary BH decays over timescales of ∼10 Myr to the center of the CND, where the primary BH resides. When strong dissipation operates in CNDs, fragmentation into massive objects the size of giant molecular clouds with densities in the range 10{sup 4}–10{sup 7} amu cm{sup −3} occurs, causing stochastic torques and hits that can eject the secondary BH from the midplane. Outside the plane, the low-density medium provides only weak drag, and the BH return is governed by inefficient dynamical friction. In rare cases, clump–BH interactions can lead to a faster decay. Feedback processes lead to outflows, but do not significantly change the overall density of the CND midplane. However, with a spherically distributed BH feedback, a hot bubble is generated behind the secondary, which almost shuts off dynamical friction. We dub this phenomenon “wake evacuation.” It leads to delays in the decay, possibly of ∼0.3 Gyr. We discuss the non-trivial implications on the discovery space of the eLISA telescope. Our results suggest that the largest uncertainty in predicting BH merger rates lies in the potentially wide variety of galaxy host systems, with different degrees of gas dissipation and heating, yielding decay timescales from ∼10 to ∼300 Myr.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2017

Quantifying Supernovae-driven Multiphase Galactic Outflows

Galactic outflows are observed everywhere in star-forming disk galaxies and are critical for galaxy formation. Supernovae (SNe) play the key role in driving the outflows, but there is no consensus as to how much energy, mass, and metal they can launch out of the disk. We perform 3D, high-resolution hydrodynamic simulations to study SNe-driven outflows from stratified media. Assuming the SN rate scales with gas surface density Σ{sub gas} as in the Kennicutt–Schmidt relation, we find that the mass loading factor, η {sub m}, defined as the mass outflow flux divided by the star formation surface density, decreases with increasing Σ{sub gas} as η{sub m}∝Σ{sub gas}{sup −0.61}. Approximately Σ{sub gas} ≲ 50 M {sub ⊙} pc{sup −2} marks when η {sub m} ≳ 1. About 10%–50% of the energy and 40%–80% of the metals produced by SNe end up in the outflows. The tenuous hot phase (T > 3 × 10{sup 5} K), which fills 60%–80% of the volume at the midplane, carries the majority of the energy and metals in the outflows. We discuss how various physical processes, including the vertical distribution of SNe, photoelectric heating, external gravitational field, and SN rate, affect the loading efficiencies. The relative scale height of gas and SNe is a very important factor in determining the loading efficiencies.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2017

Probing the Outflowing Multiphase Gas ∼1 kpc below the Galactic Center

Comparison of interstellar medium (ISM) absorption in the UV spectrum of LS 4825, a B1 Ib−II star d = 21 ± 5 kpc from the Sun toward l = 1.°67 and b = −6.°63, with ISM absorption toward an aligned foreground star at d < 7.0 ± 1.7 kpc, allows us to isolate and study gas associated with the Milky Way nuclear wind. Spectra from the Space Telescope Imaging Spectrograph show low-ionization absorption out to d < 7 kpc (e.g., O i, C ii, Mg ii, Si ii, Fe ii, S ii) only between 0 and 40 km s{sup −1}, while absorption at d > 7 kpc, ∼1 kpc below the Galactic plane, is complex and spans −290 to +94 km s{sup −1}. The intermediate and high ions Si iii, C iv, Si iv, and N v show extremely strong absorption with multiple components from −283 to 107 km s{sup −1}, implying that the ISM ∼1 kpc below the Galactic center has a substantial reservoir of plasma and more gas containing C iv and N v than in the Carina OB1 association at z = 0 kpc. Abundances and physical conditions are presented for many absorption components. The high ion absorption traces cooling transition temperature plasma probably driven by the outflowing hot gas, while the extraordinarily large thermal pressure, p / k ∼ 10{sup 5} cm{sup −3} K{sup −1}, in an absorption component at −114 km s{sup −1} probably arises from the ram pressure of the outflowing hot gas. The observations are consistent with a flow whose ionization structure in the high ions can be understood through a combination of nonequilibrium radiative cooling and turbulent mixing.

79 ASTRONOMY AND ASTROPHYSICS↗