1,644 research outputs found
Buffet characteristics of the F-8 supercritical wing airplane
The buffet characteristics of the F-8 supercritical wing airplane were investigated. Wing structural response was used to determine the buffet characteristics of the wing and these characteristics are compared with wind tunnel model data and the wing flow characteristics at transonic speeds. The wingtip accelerometer was used to determine the buffet onset boundary and to measure the buffet intensity characteristics of the airplane. The effects of moderate trailing edge flap deflections on the buffet onset boundary are presented. The supercritical wing flow characteristics were determined from wind tunnel and flight static pressure measurements and from a dynamic pressure sensor mounted on the flight test airplane in the vicinity of the shock wave that formed on the upper surface of the wing at transonic speeds. The comparison of the airplane's structural response data to the supercritical flow characteristics includes the effects of a leading edge vortex generator
SPH Simulations of Counterrotating Disk Formation in Spiral Galaxies
We present the results of Smoothed Particle Hydrodynamics (SPH) simulations
of the formation of a massive counterrotating disk in a spiral galaxy. The
current study revisits and extends (with SPH) previous work carried out with
sticky particle gas dynamics, in which adiabatic gas infall and a retrograde
gas-rich dwarf merger were tested as the two most likely processes for
producing such a counterrotating disk. We report on experiments with a cold
primary similar to our Galaxy, as well as a hot, compact primary modeled after
NGC 4138. We have also conducted numerical experiments with varying amounts of
prograde gas in the primary disk, and an alternative infall model (a spherical
shell with retrograde angular momentum). The structure of the resulting
counterrotating disks is dramatically different with SPH. The disks we produce
are considerably thinner than the primary disks and those produced with sticky
particles. The time-scales for counterrotating disk formation are shorter with
SPH because the gas loses kinetic energy and angular momentum more rapidly.
Spiral structure is evident in most of the disks, but an exponential radial
profile is not a natural byproduct of these processes. The infalling gas shells
that we tested produce counterrotating bulges and rings rather than disks. The
presence of a considerable amount of preexisting prograde gas in the primary
causes, at least in the absence of star formation, a rapid inflow of gas to the
center and a subsequent hole in the counterrotating disk. In general, our SPH
experiments yield stronger evidence to suggest that the accretion of massive
counterrotating disks drives the evolution of the host galaxies towards earlier
(S0/Sa) Hubble types.Comment: To appear in ApJ. 20 pages LaTex 2-column with 3 tables, 23 figures
(GIF) available at this site. Complete gzipped postscript preprint with
embedded figures available from http://tarkus.pha.jhu.edu/~thakar/cr3.html (3
Mb
UK Geoenergy Observatories Glasgow : express data release, mine water and environmental baseline monitoring boreholes at Cuningar Loop (updated June 2020)
Drilling of six mine water and five environmental baseline monitoring boreholes at Cuningar Loop was completed in December 2019 at the UK Geoenergy Observatory in Glasgow. This document and accompanying files provide an initial overview of the ‘as-built’ borehole infrastructure available for research and innovation
Mesh-free simulation of complex LCD geometries
We use a novel mesh-free simulation approach to study the post aligned bistable nematic (PABN) cell. By employing the Qian-Sheng formalism for liquid crystals along with a smooth representation of the surface posts, we have been able to identify two distinct stable configurations. The three-dimensional order field configurations of these states and their elastic free energies are consistent with both experimental results and previous simulation attempts. However, alternative states suggested in previous studies do not appear to remain stable when finite post curvature is considered.</p
Maximum gravitational-wave energy emissible in magnetar flares
Recent searches of gravitational-wave (GW) data raise the question of what
maximum GW energies could be emitted during gamma-ray flares of highly
magnetized neutron stars (magnetars). The highest energies (\sim 10^{49} erg)
predicted so far come from a model [K. Ioka, Mon. Not. Roy. Astron. Soc. 327,
639 (2001)] in which the internal magnetic field of a magnetar experiences a
global reconfiguration, changing the hydromagnetic equilibrium structure of the
star and tapping the gravitational potential energy without changing the
magnetic potential energy. The largest energies in this model assume very
special conditions, including a large change in moment of inertia (which was
observed in at most one flare), a very high internal magnetic field, and a very
soft equation of state. Here we show that energies of 10^{48}-10^{49} erg are
possible under more generic conditions by tapping the magnetic energy, and we
note that similar energies may also be available through cracking of exotic
solid cores. Current observational limits on gravitational waves from magnetar
fundamental modes are just reaching these energies and will beat them in the
era of advanced interferometers.Comment: 16 pages, 5 figures, 1 tabl
Equilibrium Configurations of Strongly Magnetized Neutron Stars with Realistic Equations of State
We investigate equilibrium sequences of magnetized rotating stars with four
kinds of realistic equations of state (EOSs) of SLy (Douchin et al.), FPS
(Pandharipande et al.), Shen (Shen et al.), and LS (Lattimer & Swesty).
Employing the Tomimura-Eriguchi scheme to construct the equilibrium
configurations. we study the basic physical properties of the sequences in the
framework of Newton gravity. In addition we newly take into account a general
relativistic effect to the magnetized rotating configurations. With these
computations, we find that the properties of the Newtonian magnetized stars,
e.g., structure of magnetic field, highly depends on the EOSs.
The toroidal magnetic fields concentrate rather near the surface for Shen and
LS EOSs than those for SLy and FPS EOSs. The poloidal fields are also affected
by the toroidal configurations. Paying attention to the stiffness of the EOSs,
we analyze this tendency in detail. In the general relativistic stars, we find
that the difference due to the EOSs becomes small because all the employed EOSs
become sufficiently stiff for the large maximum density, typically greater than
. The maximum baryon mass of the magnetized stars
with axis ratio increases about up to twenty percents for that of
spherical stars. We furthermore compute equilibrium sequences at finite
temperature, which should serve as an initial condition for the hydrodynamic
study of newly-born magnetars. Our results suggest that we may obtain
information about the EOSs from the observation of the masses of magnetars.Comment: submitted to MNRA
Velocity Structure Diagnostics of Simulated Galaxy Clusters
Gas motions in the hot intracluster medium of galaxy clusters have an
important effect on the mass determination of the clusters through X-ray
observations. The corresponding dynamical pressure has to be accounted for in
addition to the hydrostatic pressure support to achieve a precise mass
measurement. An analysis of the velocity structure of the ICM for simulated
cluster-size haloes, especially focusing on rotational patterns, has been
performed, demonstrating them to be an intermittent phenomenon, strongly
related to the internal dynamics of substructures. We find that the expected
build-up of rotation due to mass assembly gets easily destroyed by passages of
gas-rich substructures close to the central region. Though, if a typical
rotation pattern is established, the corresponding mass contribution is
estimated to be up to ~17% of the total mass in the innermost region, and one
has to account for it. Extending the analysis to a larger sample of simulated
haloes we statistically observe that (i) the distribution of the rotational
component of the gas velocity in the innermost region has typical values of
~200-300 km/s; (ii) except for few outliers, there is no monotonic increase of
the rotational velocity with decreasing redshift, as we would expect from
approaching a relaxed configuration. Therefore, the hypothesis that the
build-up of rotation is strongly influenced by internal dynamics is confirmed,
and minor events like gas-rich substructures passing close to the equatorial
plane can easily destroy any ordered rotational pattern.Comment: 13 pages, 10 figures; Accepted for publication in MNRA
Mine water characterisation and monitoring borehole GGA05, UK Geoenergy Observatory, Glasgow
This report and accompanying data release describe the ‘as-built’ borehole GGA05 at the UK Geoenergy Observatory in Glasgow, as well as summarising hydrogeological testing and an initial geological interpretation.
Mine water borehole GGA05 at the UK Geoenergy Observatory in Glasgow is screened across the Glasgow Main mine working void and overlying sandstone roof. The mine working is a water-filled void and initial hydrogeological indications from the test pumping are of a very high yielding borehole. Borehole GGA05 has ERT and DTS cables installed between the borehole casing and the rock wall and has a hydrogeological data logger installed within the borehole
Mine water characterisation and monitoring borehole GGA01, UK Geoenergy Observatory, Glasgow.
This report and accompanying data release describe the ‘as-built’ borehole GGA01 at the UK Geoenergy Observatory in Glasgow, as well as summarising hydrogeological testing and an initial geological interpretation.
Mine water borehole GGA01 at the UK Geoenergy Observatory in Glasgow is screened across the Glasgow Upper mine working and overlying sandstone roof. The mine working is interpreted to be filled with a loosely packed mine waste. Hydrogeological evidence from test pumping indicates that the borehole is very high yielding. Borehole GGA01 has ERT and DTS cables installed between the borehole casing and the rock wall and has a hydrogeological data logger installed within the borehole
Mine water characterisation and monitoring borehole GGA04, UK Geoenergy Observatory, Glasgow
This report and accompanying data release describe the ‘as-built’ borehole GGA04 at the UK Geoenergy Observatory in Glasgow, as well as summarising hydrogeological testing and an initial geological interpretation.
Mine water borehole GGA04 at the UK Geoenergy Observatory in Glasgow is screened across the Glasgow Upper coal and overlying sandstone roof. The borehole was drilled within an area of stoop (pillar) and room mine workings and is interpreted to have hit a coal pillar or partially collapsed pillar and a possibly fractured sandstone roof. It can be used for characterising and monitoring a fractured rock mass within a mine working area. Initial hydrogeological indications from the test pumping indicate that borehole GGA04 is high yielding. Borehole GGA04 has ERT and DTS cables installed between the borehole casing and the rock wall and has a hydrogeological data logger installed within the borehole
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