852 research outputs found
Simulator model specification for the augmentor wing jet STOL research aircraft
The configuration and simulation studies of a C-8A (De Havilland Buffalo) aircraft are described. The modifications to STOL configuration consisted of augmentor-wing jet flaps, blown and drooped ailerons, and leading edge slats. The total simulator model includes a number of component parts for producing realistic visual, aural, tactile, vestibular, and kinesthetic cues for the pilot to assess the predicted behavior of the real airplane
Design evaluation criteria for commercial STOL transports
Handling qualities criteria and operational performance margins have been determined for the landing phase of commercial short-takeoff-and-landing airplanes. The requirements are the result of a literature survey, analysis of areas found to be inadequately covered by current criteria, and a subsequent piloted simulator investigation of critical criteria requiring substantiation. Three complete simulator models were used, each describing the characteristics of a different high-lift system, the externally blown flap, the augmentor flap, and the internally blown flap. The proposed criteria are presented with substantiating discussions from currently available data or directly from the results of this simulation work where it is applicable
Overview and Summary of the Third AIAA High Lift Prediction Workshop
The third AIAA CFD High-Lift Prediction Workshop was held in Denver, Colorado, in June 2017. The goals of the workshop continued in the tradition of the first and second high-lift workshops: to assess the numerical prediction capability of current-generation computational fluid dynamics (CFD) technology for swept, medium/high-aspect-ratio wings in landing/takeoff (high-lift) configurations. This workshop analyzed the flow over two different configurations, a clean high-lift version of the NASA Common Research Model, and the JAXA Standard Model. The former was a CFD-only study, as experimental data were not available prior to the workshop. The latter was a nacelle/pylon installation study that included comparison with experimental wind tunnel data. The workshop also included a 2-D turbulence model verification exercise. Thirty-five participants submitted a total of 79 data sets of CFD results. A variety of grid systems (both structured and unstructured) as well as different flow simulation methodologies (including Reynolds-averaged Navier-Stokes and Lattice-Boltzmann) were used. This paper analyzes the combined results from all workshop participants. A statistical summary of the CFD results is also included
Time-resolved optical/near-IR polarimetry of V404 Cyg during its 2015 outburst
We present optical and near-IR linear polarimetry of V404 Cyg during its 2015
outburst and in quiescence. We obtained time resolved r'-band polarimetry when
the source was in outburst, near-IR polarimetry when the source was near
quiescence and multiple wave-band optical polarimetry later in quiescence. The
optical to near-IR linear polarization spectrum can be described by
interstellar dust and an intrinsic variable component. The intrinsic optical
polarization, detected during the rise of one of the brightest flares of the
outburst, is variable, peaking at 4.5 per cent and decaying to 3.5 per cent. We
present several arguments that favour a synchrotron jet origin to this variable
polarization, with the optical emission originating close to the jet base. The
polarization flare occurs during the initial rise of a major radio flare event
that peaks later, and is consistent with a classically evolving synchrotron
flare from an ejection event. We conclude that the optical polarization flare
represents a jet launching event; the birth of a major ejection. For this event
we measure a rather stable polarization position angle of -9 degrees E of N,
implying that the magnetic field near the base of the jet is approximately
perpendicular to the jet axis. This may be due to the compression of magnetic
field lines in shocks in the accelerated plasma, resulting in a partially
ordered transverse field that have now been seen during the 2015 outburst. We
also find that this ejection occurred at a similar stage in the repetitive
cycles of flares.Comment: 9 pages, 5 figures, accepted for publication by MNRA
Overview and Summary of the Second AIAA High Lift Prediction Workshop
The second AIAA CFD High-Lift Prediction Workshop was held in San Diego, California, in June 2013. The goals of the workshop continued in the tradition of the first high-lift workshop: to assess the numerical prediction capability of current-generation computational fluid dynamics (CFD) technology for swept, medium/high-aspect-ratio wings in landing/takeoff (high-lift) configurations. This workshop analyzed the flow over the DLR-F11 model in landing configuration at two different Reynolds numbers. Twenty-six participants submitted a total of 48 data sets of CFD results. A variety of grid systems (both structured and unstructured) were used. Trends due to grid density and Reynolds number were analyzed, and effects of support brackets were also included. This paper analyzes the combined results from all workshop participants. Comparisons with experimental data are made. A statistical summary of the CFD results is also included
Description of a Website Resource for Turbulence Modeling Verification and Validation
The activities of the Turbulence Model Benchmarking Working Group - which is a subcommittee of the American Institute of Aeronautics and Astronautics (AIAA) Fluid Dynamics Technical Committee - are described. The group s main purpose is to establish a web-based repository for Reynolds-averaged Navier-Stokes turbulence model documentation, including verification and validation cases. This turbulence modeling resource has been established based on feedback from a survey on what is needed to achieve consistency and repeatability in turbulence model implementation and usage, and to document and disseminate information on new turbulence models or improvements to existing models. The various components of the website are described in detail: description of turbulence models, turbulence model readiness rating system, verification cases, validation cases, validation databases, and turbulence manufactured solutions. An outline of future plans of the working group is also provided
A close-pair binary in a distant triple supermassive black-hole system
Galaxies are believed to evolve through merging, which should lead to
multiple supermassive black holes in some. There are four known triple black
hole systems, with the closest pair being 2.4 kiloparsecs apart (the third
component is more distant at 3 kiloparsecs), which is far from the
gravitational sphere of influence of a black hole with mass 10
M (about 100 parsecs). Previous searches for compact black hole systems
concluded that they were rare, with the tightest binary system having a
separation of 7 parsecs. Here we report observations of a triple black hole
system at redshift z=0.39, with the closest pair separated by 140
parsecs. The presence of the tight pair is imprinted onto the properties of the
large-scale radio jets, as a rotationally-symmetric helical modulation, which
provides a useful way to search for other tight pairs without needing extremely
high resolution observations. As we found this tight pair after searching only
six galaxies, we conclude that tight pairs are more common than hitherto
believed, which is an important observational constraint for low-frequency
gravitational wave experiments.Comment: 21 pages, 6 figures. Published online by Nature on 25 June 2014.
Extremely minor differences with published version exis
Skeletal Muscle PGC-1β Signaling is Sufficient to Drive an Endurance Exercise Phenotype and to Counteract Components of Detraining in Mice
Peroxisome proliferator-activated receptor-γ coactivator (PGC)-1α and -1β serve as master transcriptional regulators of muscle mitochondrial functional capacity and are capable of enhancing muscle endurance when overexpressed in mice. We sought to determine whether muscle-specific transgenic overexpression of PGC-1β affects the detraining response following endurance training. First, we established and validated a mouse exercise-training-detraining protocol. Second, using multiple physiological and gene expression end points, we found that PGC-1β overexpression in skeletal muscle of sedentary mice fully recapitulated the training response. Lastly, PGC-1β overexpression during the detraining period resulted in partial prevention of the detraining response. Specifically, an increase in the plateau at which O2 uptake (V̇o2) did not change from baseline with increasing treadmill speed [peak V̇o2 (ΔV̇o2max)] was maintained in trained mice with PGC-1β overexpression in muscle 6 wk after cessation of training. However, other detraining responses, including changes in running performance and in situ half relaxation time (a measure of contractility), were not affected by PGC-1β overexpression. We conclude that while activation of muscle PGC-1β is sufficient to drive the complete endurance phenotype in sedentary mice, it only partially prevents the detraining response following exercise training, suggesting that the process of endurance detraining involves mechanisms beyond the reversal of muscle autonomous mechanisms involved in endurance fitness. In addition, the protocol described here should be useful for assessing early-stage proof-of-concept interventions in preclinical models of muscle disuse atrophy
Numerical Study of the Effect of Mean Three-Dimensionality on Turbulence in Adverse-Pressure-Gradient Boundary Layers
Direct numerical simulation (DNS) is used to isolate the influence of sweep on a separating turbulent boundary layer. Attention here is limited to the behavior of the turbulence within the adverse-pressure-gradient (APG) region upstream of separation. Other regions and quantities are considered in Coleman, Rumsey & Spalart. The mean three-dimensionality and outer-layer inviscid skewing have only a slight effect upon the structure of the turbulence (measured by the relationship of the components of the Reynolds-stress tensor and the efficiency of the turbulence energy transfer) compared with that of the adverse pressure gradient, which dominates both the skewed and unskewed layers
Finite Element Flow Simulations of the EUROLIFT DLR-F11 High Lift Configuration
This paper presents flow simulation results of the EUROLIFT DLR-F11
multi-element wing configuration, obtained with a highly scalable finite
element solver, PHASTA. This work was accomplished as a part of the 2nd high
lift prediction workshop. In-house meshes were constructed with increasing mesh
density for analysis. A solution adaptive approach was used as an alternative
and its effectiveness was studied by comparing its results with the ones
obtained with other meshes. Comparisons between the numerical solution obtained
with unsteady RANS turbulence model and available experimental results are
provided for verification and discussion. Based on the observations, future
direction for adaptive research and simulations with higher fidelity turbulence
models is outlined.Comment: 52nd Aerospace Sciences Meetin
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