12,780 research outputs found
3D Radio and X-Ray Modeling and Data Analysis Software: Revealing Flare Complexity
We have undertaken a major enhancement of our IDL-based simulation tools
developed earlier for modeling microwave and X-ray emission. The object-based
architecture provides an interactive graphical user interface that allows the
user to import photospheric magnetic field maps and perform magnetic field
extrapolations to almost instantly generate 3D magnetic field models, to
investigate the magnetic topology of these models by interactively creating
magnetic field lines and associated magnetic flux tubes, to populate the flux
tubes with user-defined nonuniform thermal plasma and anisotropic, nonuniform,
nonthermal electron distributions; to investigate the spatial and spectral
properties of radio and X-ray emission calculated from the model, and to
compare the model-derived images and spectra with observational data. The
application integrates shared-object libraries containing fast gyrosynchrotron
emission codes developed in FORTRAN and C++, soft and hard X-ray codes
developed in IDL, a FORTRAN-based potential-field extrapolation routine and an
IDL-based linear force free field extrapolation routine. The interactive
interface allows users to add any user-defined radiation code that adheres to
our interface standards, as well as user-defined magnetic field extrapolation
routines. Here we use this tool to analyze a simple single-loop flare and use
the model to constrain the 3D structure of the magnetic flaring loop and 3D
spatial distribution of the fast electrons inside this loop. We iteratively
compute multi-frequency microwave and multi-energy X-ray images from realistic
magnetic fluxtubes obtained from an extrapolation of a magnetogram taken prior
to the flare, and compare them with imaging data obtained by SDO, NoRH, and
RHESSI instruments. We use this event to illustrate use of the tool for general
interpretation of solar flares to address disparate problems in solar physics.Comment: 12 pages, 11 figures, ApJ accepte
The effect of non-uniform damping on flutter in axial flow and energy harvesting strategies
The problem of energy harvesting from flutter instabilities in flexible
slender structures in axial flows is considered. In a recent study, we used a
reduced order theoretical model of such a system to demonstrate the feasibility
for harvesting energy from these structures. Following this preliminary study,
we now consider a continuous fluid-structure system. Energy harvesting is
modelled as strain-based damping and the slender structure under investigation
lies in a moderate fluid loading range, for which {the flexible structure} may
be destabilised by damping. The key goal of this work is to {analyse the effect
of damping distribution and intensity on the amount of energy harvested by the
system}. The numerical results {indeed} suggest that non-uniform damping
distributions may significantly improve the power harvesting capacity of the
system. For low damping levels, clustered dampers at the position of peak
curvature are shown to be optimal. Conversely for higher damping, harvesters
distributed over the whole structure are more effective.Comment: 12 pages, 10 figures, to appear in Proc. R. Soc.
The UTRC wind energy conversion system performance analysis for horizontal axis wind turbines (WECSPER)
The theory for the UTRC Energy Conversion System Performance Analysis (WECSPER) for the prediction of horizontal axis wind turbine performance is presented. Major features of the analysis are the ability to: (1) treat the wind turbine blades as lifting lines with a prescribed wake model; (2) solve for the wake-induced inflow and blade circulation using real nonlinear airfoil data; and (3) iterate internally to obtain a compatible wake transport velocity and blade loading solution. This analysis also provides an approximate treatment of wake distortions due to tower shadow or wind shear profiles. Finally, selected results of internal UTRC application of the analysis to existing wind turbines and correlation with limited test data are described
An Integrated Approach for Characterizing Aerosol Climate Impacts and Environmental Interactions
Aerosols exert myriad influences on the earth's environment and climate, and on human health. The complexity of aerosol-related processes requires that information gathered to improve our understanding of climate change must originate from multiple sources, and that effective strategies for data integration need to be established. While a vast array of observed and modeled data are becoming available, the aerosol research community currently lacks the necessary tools and infrastructure to reap maximum scientific benefit from these data. Spatial and temporal sampling differences among a diverse set of sensors, nonuniform data qualities, aerosol mesoscale variabilities, and difficulties in separating cloud effects are some of the challenges that need to be addressed. Maximizing the long-term benefit from these data also requires maintaining consistently well-understood accuracies as measurement approaches evolve and improve. Achieving a comprehensive understanding of how aerosol physical, chemical, and radiative processes impact the earth system can be achieved only through a multidisciplinary, inter-agency, and international initiative capable of dealing with these issues. A systematic approach, capitalizing on modern measurement and modeling techniques, geospatial statistics methodologies, and high-performance information technologies, can provide the necessary machinery to support this objective. We outline a framework for integrating and interpreting observations and models, and establishing an accurate, consistent, and cohesive long-term record, following a strategy whereby information and tools of progressively greater sophistication are incorporated as problems of increasing complexity are tackled. This concept is named the Progressive Aerosol Retrieval and Assimilation Global Observing Network (PARAGON). To encompass the breadth of the effort required, we present a set of recommendations dealing with data interoperability; measurement and model integration; multisensor synergy; data summarization and mining; model evaluation; calibration and validation; augmentation of surface and in situ measurements; advances in passive and active remote sensing; and design of satellite missions. Without an initiative of this nature, the scientific and policy communities will continue to struggle with understanding the quantitative impact of complex aerosol processes on regional and global climate change and air quality
Subsonic finite elements for wing body combinations
Capabilities, limitations, and applications of various theories for the prediction of wing-body aerodynamics are reviewed. The methods range from approximate planar representations applicable in preliminary design to surface singularity approaches applicable in the later stages of detail design. The available methods for three-dimensional configurations are limited as inviscid solutions with viscous effects included on an empirical or strip basis
Surface temperature distribution along a thin liquid layer due to thermocapillary convection
The surface temperature distributions due to thermocapillary convections in a thin liquid layer with heat fluxes imposed on the free surface were investigated. The nondimensional analysis predicts that, when convection is important, the characteristics length scale in the flow direction L, and the characteristic temperature difference delta T sub o can be represented by L and delta T sub o approx. (A2Ma)/1/4 delta T sub R, respectively, where L sub R and delta sub R are the reference scales used in the conduction dominant situations with A denoting the aspect ratio and Ma the Marangoni number. Having L and delta sub o defined, the global surface temperature gradient delta sub o/L, the global thermocapillary driving force, and other interesting features can be determined. Numerical calculations involving a Gaussian heat flux distribution are presented to justify these two relations
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