5,578 research outputs found
Wall jet analysis for circulation control aerodynamics. Part 2: Zonal modeling concepts for wall jet/potential flow coupling
Work currently in progress to update an existing transonic circulation control airfoil analysis method is described. Existing methods suffer from two dificiencies: the inability to predict the shock structure of the underexpanded supersonic jets; and the insensitivity of the calculation to small changes in the Coanda surface geometry. A method developed for the analysis of jet exhaust plumes in supersonic flow is being modified for the case of the underexpanded wall jet. In the subsonic case, the same wall jet model was modified to include the calculation of the normal pressure gradient. This model is currently being coupled with the transonic circulation control airfoil analysis
Detecting circumbinary planets using eclipse timing of binary stars - numerical simulations
The presence of a body in an orbit around a close eclipsing binary star
manifests itself through the light time effect influencing the observed times
of eclipses as the close binary and the circumbinary companion both move around
the common centre of mass. This fact combined with the periodicity with which
the eclipses occur can be used to detect the companion. Given a sufficient
precision of the times of eclipses, the eclipse timing can be employed to
detect substellar or even planetary mass companions.
The main goal of the paper is to investigate the potential of the photometry
based eclipse timing of binary stars as a method of detecting circumbinary
planets. In the models we assume that the companion orbits a binary star in a
circular Keplerian orbit. We analyze both the space and ground based photometry
cases. In particular, we study the usefulness of the on-going COROT and Kepler
missions in detecting circumbinary planets. We also explore the relations
binding the planet discovery space with the physical parameters of the binaries
and the geometrical parameters of their light curves. We carry out detailed
numerical simulations of the eclipse timing by employing a relatively realistic
model of the light curves of eclipsing binary stars. We study the influence of
the white and red photometric noises on the timing precision. We determine the
sensitivity of the eclipse timing technique to circumbinary planets for the
ground and space based photometric observations. We provide suggestions for the
best targets, observing strategies and instruments for the eclipse timing
method. Finally, we compare the eclipse timing as a planet detection method
with the radial velocities and astrometry.Comment: 9 pages, 15 figures, accepted for publication in MNRA
Kilohertz laser ablation for doping helium nanodroplets
A new setup for doping helium nanodroplets by means of laser ablation at
kilohertz repetition rate is presented. The doping process is characterized and
two distinct regimes of laser ablation are identified. The setup is shown to be
efficient and stable enough to be used for spectroscopy, as demonstrated on
beam-depletion spectra of lithium atoms attached to helium nanodroplets. For
the first time, helium droplets are doped with high temperature refractory
materials such as titanium and tantalum. Doping with the non-volatile DNA basis
Guanine is found to be efficient and a number of oligomers are detected
2-1 Arc and Plasma Spraying Today and in the 90th(Session 2 : Surface Modification,SIMAP'88 Proceedings of International Symposium on Strategy of Innovation in Materials Processing-New Challenge for the 21st Century-)
The pulsation spectrum of VX Hydrae
We present the results of a two-year, multisite observing campaign
investigating the high-amplitude delta Scuti star VX Hydrae during the 2006 and
2007 observing seasons. The final data set consists of nearly 8500 V-band
observations spanning HJD 2453763.6 to 2454212.7 (2006 January 28 to 2007 April
22). Separate analyses of the two individual seasons of data yield 25
confidently-detected frequencies common to both data sets, of which two are
pulsation modes, and the remaining 23 are Fourier harmonics or beat frequencies
of these two modes. The 2006 data set had five additional frequencies with
amplitudes less than 1.5 mmag, and the 2007 data had one additional frequency.
Analysis of the full 2006-2007 data set yields 22 of the 25 frequencies found
in the individual seasons of data. There are no significant peaks in the
spectrum other than these between 0 and 60 c/d. The frequencies of the two main
pulsation modes derived from the 2006 and 2007 observing seasons individually
do not differ at the level of 3-sigma, and thus we find no conclusive evidence
for period change over the span of these observations. However, the amplitude
of f(1) = 5.7898 c/d changed significantly between the two seasons, while the
amplitude of f(0) = 4.4765 c/d remained constant; amplitudes of the Fourier
harmonics and beat frequencies of f(1) also changed. Similar behavior was seen
in the 1950s, and it is clear that VX Hydrae undergoes significant amplitude
changes over time.Comment: 14 pages, 5 figures, published in Publications of the Astronomical
Society of the Pacific, v.121, p.1076 (October 2009
Spectroscopy of PTCDA attached to rare gas samples: clusters vs. bulk matrices. I. Absorption spectroscopy
The interaction between PTCDA (3,4,9,10-perylene-tetracarboxylic-dianhydride)
and rare gas or para-hydrogen samples is studied by means of laser-induced
fluorescence excitation spectroscopy. The comparison between spectra of PTCDA
embedded in a neon matrix and spectra attached to large neon clusters shows
that these large organic molecules reside on the surface of the clusters when
doped by the pick-up technique. PTCDA molecules can adopt different
conformations when attached to argon, neon and para-hydrogen clusters which
implies that the surface of such clusters has a well-defined structure and has
not liquid or fluxional properties. Moreover, a precise analysis of the doping
process of these clusters reveals that the mobility of large molecules on the
cluster surface is quenched, preventing agglomeration and complex formation
Wall jet analysis for circulation control aerodynamics. Part 1: Fundamental CFD and turbulence modeling concepts
An overview of parabolic and PNS (Parabolized Navier-Stokes) methodology developed to treat highly curved sub and supersonic wall jets is presented. The fundamental data base to which these models were applied is discussed in detail. The analysis of strong curvature effects was found to require a semi-elliptic extension of the parabolic modeling to account for turbulent contributions to the normal pressure variations, as well as an extension to the turbulence models utilized, to account for the highly enhanced mixing rates observed in situations with large convex curvature. A noniterative, pressure split procedure is shown to extend parabolic models to account for such normal pressure variations in an efficient manner, requiring minimal additional run time over a standard parabolic approach. A new PNS methodology is presented to solve this problem which extends parabolic methodology via the addition of a characteristic base wave solver. Applications of this approach to analyze the interaction of wave and turbulence processes in wall jets is presented
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