15,888 research outputs found
Transonic calculations for a flexible supercritical wing and comparison with experiment
Pressure data measured on the flexible DAST ARW-2 wing are compared with results calculated using the transonic small perturbation code XTRAN3S. A brief description of the analysis is given and a recently-developed grid coordinate transformation is described. Calculations are presented for the rigid and flexible wing for Mach numbers from 0.60 to 0.90 and dynamic pressures from 0 to 1000 psf. Calculated and measured static pressures and wing deflections are compared, and calculated static aeroelastic trends are given. Attempts to calculate the transonic instability boundary of the wing are described
Some recent applications of XTRAN3S
A time marching finite difference code, XTRAN3S that solves the three dimensional transonic small perturbation equation for flow over isolated wings was developed. During initial applications of the program, problems were encountered in the prediction of unsteady forces. The use of a revised grid and force calculation scheme improved those predictions. Comparisons are made between predicted and experimental pressure data for a rectangular supercritical wing. Comparisons of steady and unsteady data at M sub infinity = 0.700 show good agreement between calculated and experimental values. A comparison of steady data at M sub infinity 0.825 shows poor agreement between calculations and experiment. Program difficulties were encountered with swept and tapered configurations
Transverse-Longitudinal Coupling by Space Charge in Cyclotrons
A method is presented that enables to compute the parameters of matched beams
with space charge in cyclotrons with emphasis on the effect of the
transverse-longitudinal coupling. Equations describing the
transverse-longitudinal coupling and corresponding tune-shifts in first order
are derived for the model of an azimuthally symmetric cyclotron. The
eigenellipsoid of the beam is calculated and the transfer matrix is transformed
into block-diagonal form. The influence of the slope of the phase curve on the
transverse-longitudinal coupling is accounted for. The results are generalized
and numerical procedures for the case of an AVF cyclotron are presented. The
algorithm is applied to the PSI Injector II and Ring cyclotron and the results
are compared to TRANSPORT.Comment: 8 pages, 2 figure
An exploratory study of finite difference grids for transonic unsteady aerodynamics
Unsteady aerodynamic forces are calculated by the XTRAN2L finite difference program which solves the complete two dimensional unsteady transonic small perturbation equation. The unsteady forces are obtained using a pulse transfer function technique which assumes the flow field behaves in a locally linear fashion about a mean condition. Forces are calculated for a linear flat plate using the default grids from the LTRAN2-NLR, LTRAN2-HI, and XTRAN3S programs. The forces are compared to the exact theoretical values for flat plate, and grid generated boundary and internal numerical reflections are observed to cause significant errors in the unsteady airloads. Grids are presented that alleviate the reflections while reducing computational time up to fifty-three percent and program size up to twenty-eight percent. Forces are presented for a six percent thick parabolic arc airfoil which demonstrate that the transform technique may be successfully applied to nonlinear transonic flows
THz-range free-electron laser ESR spectroscopy: techniques and applications in high magnetic fields
The successful use of picosecond-pulse free-electron-laser (FEL) radiation
for the continuous-wave THz-range electron spin resonance (ESR) spectroscopy
has been demonstrated. The combination of two linac-based FELs (covering the
wavelength range of 4 - 250 m) with pulsed magnetic fields up to 70 T
allows for multi-frequency ESR spectroscopy in a frequency range of 1.2 - 75
THz with a spectral resolution better than 1%. The performance of the
spectrometer is illustrated with ESR spectra obtained in the
2,2-diphenyl-1-picrylhydrazyl (DPPH) and the low-dimensional organic material
(CHN)CuCl.Comment: 9 pages, 9 figures. Rev. Sci. Instrum., accepte
Beam Dynamics in High Intensity Cyclotrons Including Neighboring Bunch Effects: Model, Implementation and Application
Space charge effects, being one of the most significant collective effects,
play an important role in high intensity cyclotrons. However, for cyclotrons
with small turn separation, other existing effects are of equal importance.
Interactions of radially neighboring bunches are also present, but their
combined effects has not yet been investigated in any great detail. In this
paper, a new particle in cell based self-consistent numerical simulation model
is presented for the first time. The model covers neighboring bunch effects and
is implemented in the three-dimensional object-oriented parallel code
OPAL-cycl, a flavor of the OPAL framework. We discuss this model together with
its implementation and validation. Simulation results are presented from the
PSI 590 MeV Ring Cyclotron in the context of the ongoing high intensity upgrade
program, which aims to provide a beam power of 1.8 MW (CW) at the target
destination
Dynamical Evolution of Boson Stars II: Excited States and Self-Interacting Fields
The dynamical evolution of self-gravitating scalar field configurations in
numerical relativity is studied. The previous analysis on ground state boson
stars of non-interacting fields is extended to excited states and to fields
with self couplings.
Self couplings can significantly change the physical dimensions of boson
stars, making them much more astrophysically interesting (e.g., having mass of
order 0.1 solar mass). The stable () and unstable () branches of
equilibrium configurations of boson stars of self-interacting fields are
studied; their behavior under perturbations and their quasi-normal oscillation
frequencies are determined and compared to the non-interacting case.
Excited states of boson stars with and without self-couplings are studied and
compared. Excited states also have equilibrium configurations with and
branch structures; both branches are intrinsically unstable under a generic
perturbation but have very different instability time scales. We carried out a
detailed study of the instability time scales of these configurations. It is
found that highly excited states spontaneously decay through a cascade of
intermediate states similar to atomic transitions.Comment: 16 pages+ 13 figures . All figures are available at
http://wugrav.wustl.edu/Paper
Towards Quantitative Simulations of High Power Proton Cyclotrons
PSI operates a cyclotron based high intensity proton accelerator routinely at
an average beam power of 1.3MW. With this power the facility is at the
worldwide forefront of high intensity proton accelerators. The beam current is
practically limited by losses at extraction and the resulting activation of
accelerator components. Further intensity upgrades and new projects aiming at
an even higher average beam power, are only possible if the relative losses can
be lowered in proportion, thus keeping absolute losses at a constant level.
Maintaining beam losses at levels allowing hands-on maintenance is a primary
challenge in any high power proton machine design and operation. In
consequence, predicting beam halo at these levels is a great challenge and will
be addressed in this paper. High power hadron driver have being used in many
disciplines of science and, a growing interest in the cyclotron technology for
high power hadron drivers are being observed very recently. This report will
briefly introduce OPAL, a tool for precise beam dynamics simulations including
3D space charge. One of OPAL's flavors (OPAL-cycl) is dedicated to high power
cyclotron modeling and is explained in greater detail. We then explain how to
obtain initial conditions for our PSI Ring cyclotron which still delivers the
world record in beam power of 1.3 MW continuous wave (cw). Several crucial
steps are explained necessary to be able to predict tails at the level of
3\sigma ... 4\sigma in the PSI Ring cyclotron. We compare our results at the
extraction with measurements, obtained with a 1.18 MW cw production beam. Based
on measurement data, we develop a simple linear model to predict beam sizes of
the extracted beam as a function of intensities and confirm the model with
simulations.Comment: Corrections and new figur
Immunodetection of overwintering Oidium mycelium in bud scales of Vitis vinifera
Research NoteAntigens were isolated from the walls of Oidium conidia by a simple extraction method. Polyclonal antiserum was produced against these antigens and an immunofluorescent assay was developed to detect overwintering mycelium of Oidium in dormant buds. The results show that a specific detection of Oidium mycelium is possible without visualizing other fungal mycelia in dormant buds of grapevines
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