112 research outputs found
AFC-Enabled Vertical Tail System Integration Study
This document serves as the final report for the SMAAART AFC-Enabled Vertical Tail System Integration Study. Included are the ground rule assumptions which have gone into the study, layouts of the baseline and AFC-enabled configurations, critical sizing information, system requirements and architectures, and assumed system properties that result in an NPV assessment of the two candidate AFC technologies
Refined AFC-Enabled High-Lift System Integration Study
A prior trade study established the effectiveness of using Active Flow Control (AFC) for reducing the mechanical complexities associated with a modern high-lift system without sacrificing aerodynamic performance at low-speed flight conditions representative of takeoff and landing. The current technical report expands on this prior work in two ways: (1) a refined conventional high-lift system based on the NASA Common Research Model (CRM) is presented that is more representative of modern commercial transport aircraft in terms of stall characteristics and maximum Lift/Drag (L/D) ratios at takeoff and landing-approach flight conditions; and (2) the design trade space for AFC-enabled high-lift systems is expanded to explore a wider range of options for improving their efficiency. The refined conventional high-lift CRM (HL-CRM) concept features leading edge slats and slotted trailing edge flaps with Fowler motion. For the current AFC-enhanced high lift system trade study, the refined conventional high-lift system is simplified by substituting simply-hinged trailing edge flaps for the slotted single-element flaps with Fowler motion. The high-lift performance of these two high-lift CRM variants is established using Computational Fluid Dynamics (CFD) solutions to the Reynolds-Averaged Navier-Stokes (RANS) equations. These CFD assessments identify the high-lift performance that needs to be recovered through AFC to have the CRM variant with the lighter and mechanically simpler high-lift system match the performance of the conventional high-lift system. In parallel to the conventional high-lift concept development, parametric studies using CFD guided the development of an effective and efficient AFC-enabled simplified high-lift system. This included parametric trailing edge flap geometry studies addressing the effects of flap chord length and flap deflection. As for the AFC implementation, scaling effects (i.e., wind-tunnel versus full-scale flight conditions) are addressed, as are AFC architecture aspects such as AFC unit placement, number AFC units, operating pressures, mass flow rates, and steady versus unsteady AFC applications. These efforts led to the development of a novel traversing AFC actuation concept which is efficient in that it reduces the AFC mass flow requirements by as much as an order of magnitude compared to previous AFC technologies, and it is predicted to be effective in driving the aerodynamic performance of a mechanical simplified high-lift system close to that of the reference conventional high-lift system. Conceptual system integration studies were conducted for the AFC-enhanced high-lift concept applied to a NASA Environmentally Responsible Aircraft (ERA) reference configuration, the so-called ERA-0003 concept. The results from these design integration assessments identify overall system performance improvement opportunities over conventional high-lift systems that suggest the viability of further technology maturation efforts for AFC-enabled high lift flap systems. To that end, technical challenges are identified associated with the application of AFC-enabled high-lift systems to modern transonic commercial transports for future technology maturation efforts
Accurate Wavenumbers for Mid-Infrared Fine-Structure Lines
We present accurate new wavenumbers for a set of 13 mid-infrared
fine-structure lines. The wavenumbers were determined from observations of the
planetary nebula NGC 7027 and of the red supergiant Alpha Scorpii. Most of the
new wavenumbers are good to within 0.0025%, or 8 km/s. We provide details on
the measurements and present an analysis of the errors. In addition, we present
the first observations of hyperfine splitting in the [Na IV] 1106 cm-1 line.Comment: 12 pages text, 2 postscript figures, uses AASTeX macros, figures are
gzipped and uuencode
Measurement of Galactic Logarithmic Spiral Arm Pitch Angle Using Two-Dimensional Fast Fourier Transform Decomposition
A logarithmic spiral is a prominent feature appearing in a majority of
observed galaxies. This feature has long been associated with the traditional
Hubble classification scheme, but historical quotes of pitch angle of spiral
galaxies have been almost exclusively qualitative. We have developed a
methodology, utilizing two-dimensional fast Fourier transformations of images
of spiral galaxies, in order to isolate and measure the pitch angles of their
spiral arms. Our technique provides a quantitative way to measure this
morphological feature. This will allow comparison of spiral galaxy pitch angle
to other galactic parameters and test spiral arm genesis theories. In this
work, we detail our image processing and analysis of spiral galaxy images and
discuss the robustness of our analysis techniques.Comment: 23 pages, 22 figures, and 3 Tables; published in ApJS 199, 33
http://iopscience.iop.org/0067-0049/199/2/33/; software available for
download at http://dafix.uark.edu/~ages/downloads.html and
http://astro.host.ualr.edu/2DFFT
RC J0311+0507: A Candidate for Superpowerful Radio Galaxies in the Early Universe at Redshift z=4.514
A strong emission line at 6703A has been detected in the optical spectrum for
the host galaxy (R=23.1) of the radio source RC J0311+0507 (4C+04.11). This
radio galaxy, with a spectral index of 1.31 in the frequency range 365-4850
MHz, is one of the ultrasteep spectrum objects from the deep survey of a sky
strip conducted with RATAN-600 in 1980-1981. We present arguments in favor of
the identification of this line with Ly\alpha at redshift z=4.514. In this
case, the object belongs to the group of extremely distant radio galaxies of
ultrahigh radio luminosity (P_{1400}=1.3 x 10^{29}W Hz^{-1}). Such power can be
provided only by a fairly massive black hole (~10^9M_\sun}) that formed in a
time less than the age of the Universe at the observed z(1.3 Gyr) or had a
primordial origin.Comment: 8 pages, 3 figure
Reverberation Mapping of the Kepler-Field AGN KA1858+4850
KA1858+4850 is a narrow-line Seyfert 1 galaxy at redshift 0.078 and is among
the brightest active galaxies monitored by the Kepler mission. We have carried
out a reverberation mapping campaign designed to measure the broad-line region
size and estimate the mass of the black hole in this galaxy. We obtained 74
epochs of spectroscopic data using the Kast Spectrograph at the Lick 3-m
telescope from February to November of 2012, and obtained complementary V-band
images from five other ground-based telescopes. We measured the H-beta light
curve lag with respect to the V-band continuum light curve using both
cross-correlation techniques (CCF) and continuum light curve variability
modeling with the JAVELIN method, and found rest-frame lags of lag_CCF = 13.53
(+2.03, -2.32) days and lag_JAVELIN = 13.15 (+1.08, -1.00) days. The H-beta
root-mean-square line profile has a width of sigma_line = 770 +/- 49 km/s.
Combining these two results and assuming a virial scale factor of f = 5.13, we
obtained a virial estimate of M_BH = 8.06 (+1.59, -1.72) x 10^6 M_sun for the
mass of the central black hole and an Eddington ratio of L/L_Edd ~ 0.2. We also
obtained consistent but slightly shorter emission-line lags with respect to the
Kepler light curve. Thanks to the Kepler mission, the light curve of
KA1858+4850 has among the highest cadences and signal-to-noise ratios ever
measured for an active galactic nucleus; thus, our black hole mass measurement
will serve as a reference point for relations between black hole mass and
continuum variability characteristics in active galactic nuclei
CO emission and associated HI absorption from a massive gas reservoir surrounding the z=3 radio galaxy B3 J2330+3927
We present results of a comprehensive multi-frequency study of the radio
galaxy B3 J2330+3927. The 1.9" wide radio source, consisting of 3 components,
is bracketed by 2 objects in our Keck K-band image. Optical and near-IR Keck
spectroscopy of these two objects yield z=3.087+-0.004. The brightest (K=18.8)
object has a standard type II AGN spectrum, and is the most likely location of
the AGN, which implies a one-sided jet radio morphology. Deep 113 GHz
observations with the IRAM Plateau de Bure Interferometer reveal CO J=4-3
emission, which peaks at the position of the AGN. The CO line is offset by 500
km/s from the systemic redshift of the AGN, but corresponds very closely to the
velocity shift of an associated HI absorber seen in Lya. This strongly suggests
that both originate from the same gas reservoir surrounding the AGN host
galaxy. Simultaneous 230 GHz interferometer observations find a ~3x lower
integrated flux density when compared to single dish 250 GHz observations with
MAMBO at the IRAM 30m telescope. This can be interpreted as spatially resolved
thermal dust emission at scales of 0.5" to 6". Finally, we present a tau <1.3%
limit to the HI 21 cm absorption against the radio source, which represents the
seventh non-detection out of 8 z>2 radio galaxies observed to date with the
WSRT. We present mass estimates for the atomic, neutral, and ionized hydrogen,
and for the dust, ranging from M(HI)=2x10^7 M_Sun derived from the associated
HI absorber in Lya up to M(H_2)=7x10^{10} M_Sun derived from the CO emission.
This indicates that the host galaxy is surrounded by a massive reservoir of gas
and dust. The K-band companion objects may be concentrations within this
reservoir, which will eventually merge with the central galaxy hosting the AGN.Comment: 16 Pages, including 11 PostScript figures. Accepted for publication
in Astronomy & Astrophysic
Circumstellar discs: What will be next?
This prospective chapter gives our view on the evolution of the study of
circumstellar discs within the next 20 years from both observational and
theoretical sides. We first present the expected improvements in our knowledge
of protoplanetary discs as for their masses, sizes, chemistry, the presence of
planets as well as the evolutionary processes shaping these discs. We then
explore the older debris disc stage and explain what will be learnt concerning
their birth, the intrinsic links between these discs and planets, the hot dust
and the gas detected around main sequence stars as well as discs around white
dwarfs.Comment: invited review; comments welcome (32 pages
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