scholarly journals Improving Weather Simulations Through Increased Generality

Eos ◽  
2021 ◽  
Vol 102 ◽  
Author(s):  
Morgan Rehnberg
Keyword(s):  
Velocity Fields ◽  
Variable Velocity ◽  
Physical Phenomena ◽  
Simulation Package

By adding support for spatially variable velocity fields and anisotropy, the CoSMoS simulation package can more accurately reproduce physical phenomena.

The Interpretation of Line Profiles

1977 ◽  
Vol 36 ◽  
pp. 191-215
Author(s):  
G.B. Rybicki
Keyword(s):  
Magnetic Fields ◽  
Atomic Physics ◽  
Velocity Fields ◽  
Spectral Lines ◽  
Inhomogeneous Structure ◽  
The Sun ◽  
Line Profiles ◽  
Physical Phenomena

Observations of the shapes and intensities of spectral lines provide a bounty of information about the outer layers of the sun. In order to utilize this information, however, one is faced with a seemingly monumental task. The sun’s chromosphere and corona are extremely complex, and the underlying physical phenomena are far from being understood. Velocity fields, magnetic fields, Inhomogeneous structure, hydromagnetic phenomena – these are some of the complications that must be faced. Other uncertainties involve the atomic physics upon which all of the deductions depend.

Investigation of Combustion in a Dump Combustor Using Different Combustion and Turbulence Models

2015 ◽  
Author(s):  
Darioush G. Barhaghi ◽  
Daniel Lörstad
Keyword(s):  
Gas Turbine ◽  
Turbulence Models ◽  
Velocity Fields ◽  
Heat Losses ◽  
Gas Turbine Combustor ◽  
Finite Rate ◽  
Dump Combustor ◽  
Turbulent Models ◽  
Physical Phenomena ◽  
Temperature And Velocity Fields

Modelling combustion in gas turbine combustors remains to be a challenge since several different physical phenomena interact in the process. One of the most important aspects of the combustion in a gas turbine combustor is the chemistry-turbulence interaction. In order to study the effect of the combustion and turbulence models, a dump combustor geometry is selected. Two combustion models namely, finite rate chemistry and flamelet based models, together with different turbulent models including LES 1eq k-model, RANS k-epsilon and k-omega models are implemented using both CFX and OpenFoam codes. The predicted temperature and velocity fields are compared to the existing experimental results. It is shown that different turbulence models behave very differently and there are large discrepancies between the experimental and predicted results. Some part of the discrepancies may be due to unknown heat losses through the combustor wall in the experiment.

Extended FK domain migration ? An efficient variable velocity algorithm

1989 ◽  
Vol 20 (2) ◽  
pp. 281 ◽  
Author(s):  
P. Whiting
Keyword(s):  
Constant Velocity ◽  
Velocity Fields ◽  
Variable Velocity ◽  
Data Set ◽  
Significant Performance ◽  
Original Time ◽  
The Cost ◽  
Arbitrary Velocity ◽  
Special Case ◽  
Time Stretching

Constant velocity FK domain migration, as developed by Stolt in 1978, has significant performance advantages over all other commercially available migration algorithms.However, even with Stolt's pre-migration time stretching (or psuedo-depth conversion), this algorithm suffers serious accuracy problems in the presence of any significant velocity variations. This paper develops a method of extending the accuracy of FK domain migration to steep dips in arbitrary velocity fields. The basis of the new method is the partitioning of the unmigrated data set into dip ranges and computing unique time stretching factors for each. Stolt's original time stretching is shown to be the zero-dip special case of this more general algorithm. Following the separate migration of the partitions, the data is merged to form a correctly migrated data set. As few as four partitions is shown to produce very significant improvements. Even though Extended FK Domain Migration is a few times slower than conventional FK domain migration, it can still produce accuracy comparable to phase shift migration at a fraction of the cost.

C. The Continuous Spectrum of Pulsating Variable Stars

1967 ◽  
Vol 28 ◽  
pp. 177-206
Author(s):  
J. B. Oke ◽  
C. A. Whitney
Keyword(s):  
Continuous Spectrum ◽  
Variable Stars ◽  
Velocity Fields ◽  
The Other ◽  
Line Spectrum ◽  
Direct Information ◽  
Thermodynamic Structure ◽  
Diagnostic Interpretation ◽  
Pulsating Variable Stars ◽  
The Continuum

Pecker:The topic to be considered today is the continuous spectrum of certain stars, whose variability we attribute to a pulsation of some part of their structure. Obviously, this continuous spectrum provides a test of the pulsation theory to the extent that the continuum is completely and accurately observed and that we can analyse it to infer the structure of the star producing it. The continuum is one of the two possible spectral observations; the other is the line spectrum. It is obvious that from studies of the continuum alone, we obtain no direct information on the velocity fields in the star. We obtain information only on the thermodynamic structure of the photospheric layers of these stars–the photospheric layers being defined as those from which the observed continuum directly arises. So the problems arising in a study of the continuum are of two general kinds: completeness of observation, and adequacy of diagnostic interpretation. I will make a few comments on these, then turn the meeting over to Oke and Whitney.

TEM visualization of surface replicated acid and base catalyzed sol-gel glasses

1986 ◽  
Vol 44 ◽  
pp. 448-449
Author(s):  
George C. Ruben ◽  
Merrill W. Shafer
Keyword(s):  
Elevated Temperatures ◽  
Sol Gel ◽  
Basic Medium ◽  
Glass Transition Point ◽  
Structural Space ◽  
Acid And Base ◽  
Organometallic Precursors ◽  
New Processing ◽  
Gel Glasses ◽  
Physical Phenomena

Traditionally ceramics have been shaped from powders and densified at temperatures close to their liquid point. New processing methods using various types of sols, gels, and organometallic precursors at low temperature which enable densificatlon at elevated temperatures well below their liquidus, hold the promise of producing ceramics and glasses of controlled and reproducible properties that are highly reliable for electronic, structural, space or medical applications. Ultrastructure processing of silicon alkoxides in acid medium and mixtures of Ludox HS-40 (120Å spheres from DuPont) and Kasil (38% K2O &62% SiO2) in basic medium have been aimed at producing materials with a range of well defined pore sizes (∼20-400Å) to study physical phenomena and materials behavior in well characterized confined geometries. We have studied Pt/C surface replicas of some of these porous sol-gels prepared at temperatures below their glass transition point.

Central kiloparsec of NGC 1326 observed with SINFONI

2020 ◽  
Vol 638 ◽  
pp. A53
Author(s):  
Nastaran Fazeli ◽  
Gerold Busch ◽  
Andreas Eckart ◽  
Françoise Combes ◽  
Persis Misquitta ◽  
...  
Keyword(s):  
Black Hole ◽  
Galaxy Evolution ◽  
Near Infrared ◽  
Velocity Fields ◽  
Molecular Gas ◽  
Nearby Galaxy ◽  
Stellar Content ◽  
Stellar Rotation ◽  
Supermassive Black Hole ◽  
Integral Field Spectrograph

Gas inflow processes in the vicinity of galactic nuclei play a crucial role in galaxy evolution and supermassive black hole growth. Exploring the central kiloparsec of galaxies is essential to shed more light on this subject. We present near-infrared H- and K-band results of the nuclear region of the nearby galaxy NGC 1326, observed with the integral-field spectrograph SINFONI mounted on the Very Large Telescope. The field of view covers 9″ × 9″ (650 × 650 pc2). Our work is concentrated on excitation conditions, morphology, and stellar content. The nucleus of NGC 1326 was classified as a LINER, however in our data we observed an absence of ionised gas emission in the central r ∼ 3″. We studied the morphology by analysing the distribution of ionised and molecular gas, and thereby detected an elliptically shaped, circum-nuclear star-forming ring at a mean radius of 300 pc. We estimate the starburst regions in the ring to be young with dominating ages of < 10 Myr. The molecular gas distribution also reveals an elongated east to west central structure about 3″ in radius, where gas is excited by slow or mild shock mechanisms. We calculate the ionised gas mass of 8 × 105 M⊙ completely concentrated in the nuclear ring and the warm molecular gas mass of 187 M⊙, from which half is concentrated in the ring and the other half in the elongated central structure. The stellar velocity fields show pure rotation in the plane of the galaxy. The gas velocity fields show similar rotation in the ring, but in the central elongated H2 structure they show much higher amplitudes and indications of further deviation from the stellar rotation in the central 1″ aperture. We suggest that the central 6″ elongated H2 structure might be a fast-rotating central disc. The CO(3–2) emission observations with the Atacama Large Millimeter/submillimeter Array reveal a central 1″ torus. In the central 1″ of the H2 velocity field and residual maps, we find indications for a further decoupled structure closer to a nuclear disc, which could be identified with the torus surrounding the supermassive black hole.

Sign in / Sign up

Export Citation Format

Share Document