2,911 research outputs found
Wind tunnel supplementary Mach number minimum section insert
A device is described which changes the Mach number capability of a wind tunnel without permanently altering the existing nozzle of the tunnel. An insert is removably attached to the wall of the existing nozzle expansion area thereby creating a second minimum section upstream of the model test section. The added insert may be removed without complicated and expensive changes to the basic wind tunnel. In one embodiment, a removable insert is disposed within wind tunnel nozzle walls with a portion of the flow boundary layer being bled off from the tunnel via passageway and tunnel exit to reduce the extent of separated flow normally occuring upstream of the insert contraction section
Exploratory wind tunnel tests of a shock-swallowing air data sensor at a Mach number of approximately 1.83
The test probe was designed to measure free-stream Mach number and could be incorporated into a conventional airspeed nose boom installation. Tests were conducted in the Langley 4-by 4-foot supersonic pressure tunnel with an approximate angle of attack test range of -5 deg to 15 deg and an approximate angle of sideslip test range of + or - 4 deg. The probe incorporated a variable exit area which permitted internal flow. The internal flow caused the bow shock to be swallowed. Mach number was determined with a small axially movable internal total pressure tube and a series of fixed internal static pressure orifices. Mach number error was at a minimum when the total pressure tube was close to the probe tip. For four of the five tips tested, the Mach number error derived by averaging two static pressures measured at horizontally opposed positions near the probe entrance were least sensitive to angle of attack changes. The same orifices were also used to derive parameters that gave indications of flow direction
Effect of blockage ratio on drag and pressure distributions for bodies of revolution at transonic speeds
Experimental data were obtained in two wind tunnels for 13 models over a Mach number range from 0.70 to 1.02. Effects of increasing test-section blockage ratio in the transonic region near a Mach number of 1.0 included change in the shape of the drag curves, premature drag creep, delayed drag divergence, and a positive increment of pressures on the model afterbodies. Effects of wall interference were apparent in the data even for a change in blockage ratio from a very low 0.000343 to an even lower 0.000170. Therefore, models having values of blockage ratio of 0.0003 - an order of magnitude below the previously considered safe value of 0.0050 - had significant errors in the drag-coefficient values obtained at speeds near a Mach number of 1.0. Furthermore, the flow relief afforded by slots or perforations in test-section walls - designed according to previously accepted criteria for interference-free subsonic flow - does not appear to be sufficient to avoid significant interference of the walls with the model flow field for Mach numbers very close to 1.0
Effects of geometric variables on the performance of a probe for direct measurement of free-steam stagnation pressure in supersonic flow
An investigation was conducted at Mach numbers of 1.41, 1.83, and 2.20 to determine the effects of parametric variations in the height of the pitot-tube center line from the probe surface and in the radius of the surface curvature on the pressure recovery of a probe designed to measure the free-stream stagnation pressure. The probe consists of a pitot tube mounted on the surface of a curved cylinder of circular cross section. The pitot tube senses the pressure of the stream tube which has been slowed by isentropic compression along the curved surface. Pressure recovery, greater than or equal to 99.8 percent of the free-stream stagnation pressure, was obtained for a wide range both of angle of attack and of yaw for probes satisfying the predetermined optimum design criteria
Drag and stability characteristics of a variety of reefed and unreefed parachute configurations at Mach 1.80 with an empirical correlation for supersonic Mach numbers
An investigation was conducted at Mach 1.80 in the Langley 4-foot supersonic pressure tunnel to determine the effects of variation in reefing ratio and geometric porosity on the drag and stability characteristics of four basic canopy types deployed in the wake of a cone-cylinder forebody. The basic designs included cross, hemisflo, disk-gap-band, and extended-skirt canopies; however, modular cross and standard flat canopies and a ballute were also investigated. An empirical correlation was determined which provides a fair estimation of the drag coefficients in transonic and supersonic flow for parachutes of specified geometric porosity and reefing ratio
Flow-field measurements downstream of two protuberances on a flat plate submerged in a turbulent boundary layer at Mach 2.49 and 4.44
Flow field measurements on flat plate with attached protuberances in supersonic turbulent boundary laye
The Shape of Cas A
Based on optical, IR and X-ray studies of Cas A, we propose a geometry for
the remnant based on a "jet-induced" scenario with significant systematic
departures from axial symmetry. In this model, the main jet axis is oriented in
the direction of strong blue-shifted motion at an angle of 110 - 120 degrees
East of North and about 40 - 50 degrees to the East of the line of sight.
Normal to this axis would be an expanding torus as predicted by jet-induced
models. In the proposed geometry, iron-peak elements in the main jet-like flow
could appear "beyond" the portions of the remnant rich in silicon by projection
effects, not the effect of mixing. In the context of the proposed geometry, the
displacement of the compact object from the kinematic center of the remnant at
a position angle of ~169 degrees can be accommodated if the motion of the
compact object is near to, but slightly off from, the direction of the main
"jet" axis by of order 30 degrees. In this model, the classical NE "jet," the
SW "counter-jet" and other protrusions, particularly the "hole" in the North,
are non-asymmetric flows approximately in the equatorial plane, e.g., out
through the perimeter of the expanding torus, rather than being associated with
the main jet. We explore the spoke-like flow in the equatorial plane in terms
of Rayleigh-Taylor, Richtmyer-Meshkov and Kelvin-Helmholz instabilities and
illustrate these instabilities with a jet-induced simulation.Comment: 25 pages, 4 figures. Accepted for publication in the Astrophysical
Journa
Inferring Type II-P Supernova Progenitor Masses from Plateau Luminosities
Connecting observations of core-collapse supernova explosions to the
properties of their massive star progenitors is a long-sought, and challenging,
goal of supernova science. Recently, Barker et al. (2022) presented bolometric
light curves for a landscape of progenitors from spherically symmetric
neutrino-driven core-collapse supernova (CCSN) simulations using an effective
model. They find a tight relationship between the plateau luminosity of the
Type II-P CCSN light curve and the terminal iron core mass of the progenitor.
Remarkably, this allows us to constrain progenitor properties with photometry
alone. We analyze a large observational sample of Type II-P CCSN light curves
and estimate a distribution of iron core masses using the relationship of
Barker et al 2022. The inferred distribution matches extremely well with the
distribution of iron core masses from stellar evolutionary models, and namely,
contains high-mass iron cores that suggest contributions from very massive
progenitors in the observational data. We use this distribution of iron core
masses to infer minimum and maximum mass of progenitors in the observational
data. Using Bayesian inference methods to locate optimal initial mass function
parameters, we find M and
M solar masses for the observational data.Comment: Accepted to ApJ Letters. 9 pages, 4 figure
WINGS: a WIde-field Nearby Galaxy-cluster Survey. I - Optical imaging
This is the first paper of a series that will present data and scientific
results from the WINGS project, a wide-field, multiwavelength imaging and
spectroscopic survey of galaxies in 77 nearby clusters. The sample was
extracted from the ROSAT catalogs with constraints on the redshift
(0.0420). The global goal of
the WINGS project is the systematic study of the local cosmic variance of the
cluster population and of the properties of cluster galaxies as a function of
cluster properties and local environment. This data collection will allow to
define a local 'Zero-Point' reference against which to gauge the cosmic
evolution when compared to more distant clusters. The core of the project
consists of wide-field optical imaging of the selected clusters in the B and V
bands. We have also completed a multi-fiber, medium resolution spectroscopic
survey for 51 of the clusters in the master sample. In addition, a NIR (JK)
survey of ~50 clusters and an H_alpha + UV survey of some 10 clusters are
presently ongoing, while a very-wide-field optical survey has also been
programmed. In this paper we briefly outline the global objectives and the main
characteristics of the WINGS project. Moreover, the observing strategy and the
data reduction of the optical imaging survey (WINGS-OPT) are presented. We have
achieved a photometric accuracy of ~0.025mag, reaching completeness to V~23.5.
Field size and resolution (FWHM) span the absolute intervals (1.6-2.7)Mpc and
(0.7-1.7)kpc, respectively, depending on the redshift and on the seeing. This
allows the planned studies to get a valuable description of the local
properties of clusters and galaxies in clusters.Comment: 24 pages, 15 figures, Accepted by Astronomy and Astrophysic
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