scholarly journals The benchmark halo giant HD 122563: CNO abundances revisited with three-dimensional hydrodynamic model stellar atmospheres

2018 ◽  
Vol 475 (3) ◽  
pp. 3369-3392 ◽  
Author(s):  
R Collet ◽  
Å Nordlund ◽  
M Asplund ◽  
W Hayek ◽  
R Trampedach
Keyword(s):  
Hydrodynamic Model ◽  
Three Dimensional ◽  
Stellar Atmospheres ◽  
Cno Abundances

scholarly journals The relationship between photometric and spectroscopic oscillation amplitudes from 3D stellar atmosphere simulations

2021 ◽  
Author(s):  
Yixiao Zhou ◽  
Thomas Nordlander ◽  
Luca Casagrande ◽  
Meridith Joyce ◽  
Yaguang Li ◽  
...  
Keyword(s):  
Radial Velocity ◽  
Three Dimensional ◽  
Quantitative Relationship ◽  
Stellar Atmospheres ◽  
Spectral Lines ◽  
Wavelength Shift ◽  
The Sun ◽  
Theoretical Derivation ◽  
Velocity Amplitude ◽  
Good Agreement

Abstract We establish a quantitative relationship between photometric and spectroscopic detections of solar-like oscillations using ab initio, three-dimensional (3D), hydrodynamical numerical simulations of stellar atmospheres. We present a theoretical derivation as proof of concept for our method. We perform realistic spectral line formation calculations to quantify the ratio between luminosity and radial velocity amplitude for two case studies: the Sun and the red giant ε Tau. Luminosity amplitudes are computed based on the bolometric flux predicted by 3D simulations with granulation background modelled the same way as asteroseismic observations. Radial velocity amplitudes are determined from the wavelength shift of synthesized spectral lines with methods closely resembling those used in BiSON and SONG observations. Consequently, the theoretical luminosity to radial velocity amplitude ratios are directly comparable with corresponding observations. For the Sun, we predict theoretical ratios of 21.0 and 23.7 ppm/[m s−1] from BiSON and SONG respectively, in good agreement with observations 19.1 and 21.6 ppm/[m s−1]. For ε Tau, we predict K2 and SONG ratios of 48.4 ppm/[m s−1], again in good agreement with observations 42.2 ppm/[m s−1], and much improved over the result from conventional empirical scaling relations which gives 23.2 ppm/[m s−1]. This study thus opens the path towards a quantitative understanding of solar-like oscillations, via detailed modelling of 3D stellar atmospheres.

Modeling residence time with a three-dimensional hydrodynamic model: Linkage with chlorophyll a in a subtropical estuary

2013 ◽  
Vol 268 ◽  
pp. 93-102 ◽  
Author(s):  
Yongshan Wan ◽  
Chelsea Qiu ◽  
Peter Doering ◽  
Mayra Ashton ◽  
Detong Sun ◽  
...  
Keyword(s):  
Chlorophyll A ◽  
Residence Time ◽  
Hydrodynamic Model ◽  
Three Dimensional ◽  
Subtropical Estuary

Three-dimensional hydrodynamic model of concrete tetrahedral frame revetments

2009 ◽  
Vol 8 (4) ◽  
pp. 338-342 ◽  
Author(s):  
Zhu Gao ◽  
Xing Li ◽  
Hong-wu Tang ◽  
Zheng-hua Gu
Keyword(s):  
Hydrodynamic Model ◽  
Three Dimensional

Three-Dimensional Thermo-Hydrodynamic Model

2014 ◽  
pp. 19-72
Author(s):  
Dominique Bonneau ◽  
Aurelian Fatu ◽  
Dominique Souchet
Keyword(s):  
Hydrodynamic Model ◽  
Three Dimensional

scholarly journals Effects of morphology in controlling propagation of density currents in a reservoir using uncalibrated three-dimensional hydrodynamic modeling

2020 ◽  
Author(s):  
Behnam Zamani ◽  
Manfred Koch ◽  
Ben R. Hodges
Keyword(s):  
Hydrodynamic Model ◽  
Large Scale ◽  
Three Dimensional ◽  
Density Current ◽  
Density Currents ◽  
Large Reservoir ◽  
Bottom Water Temperature ◽  
The Difference ◽  
Basin Morphology ◽  
Southwest Iran

In this study, effects of basin morphology are shown to affect density current hydrodynamics of a large reservoir using a three-dimensional (3D) hydrodynamic model that is validated (but not calibrated) with in situ observational data. The AEM3D hydrodynamic model was applied for 5-month simulations during winter and spring flooding for the Maroon reservoir in southwest Iran, where available observations indicated that large-scale density currents had previously occurred. The model results were validated with near-bottom water temperature measurements that were previously collected at five locations in the reservoir. The Maroon reservoir consists of upper and lower basins that are connected by a deep and narrow canyon. Analyses of simulations show that the canyon strongly affects density current propagation and the resulting differing limnological characteristics of the two basins. The evolution of the Wedderburn Number, Lake Number, and Schmidt stability number are shown to be different in the two basins, and the difference is attributable to the morphological separation by the canyon. Investigation of the background potential energy (BPE) changes along the length of the canyon indicated that a density front passes through the upper section of the canyon but is smoothed into simple filling of the lower basin. The separable dynamics of the basins has implications for the complexity of models needed for representing both water quality and sedimentation.

scholarly journals 3D non-LTE line formation of neutral carbon in the Sun

2019 ◽  
Vol 624 ◽  
pp. A111 ◽  
Author(s):  
A. M. Amarsi ◽  
P. S. Barklem ◽  
R. Collet ◽  
N. Grevesse ◽  
M. Asplund
Keyword(s):  
Three Dimensional ◽  
Solar Spectrum ◽  
Neutral Hydrogen ◽  
Stellar Atmospheres ◽  
Impact Excitation ◽  
Solar Photosphere ◽  
Late Type ◽  
Current Standard ◽  
Standard Value ◽  
Good Agreement

Carbon abundances in late-type stars are important in a variety of astrophysical contexts. However C I lines, one of the main abundance diagnostics, are sensitive to departures from local thermodynamic equilibrium (LTE). We present a model atom for non-LTE analyses of C I lines, that uses a new, physically-motivated recipe for the rates of neutral hydrogen impact excitation. We analyse C I lines in the solar spectrum, employing a three-dimensional (3D) hydrodynamic model solar atmosphere and 3D non-LTE radiative transfer. We find negative non-LTE abundance corrections for C I lines in the solar photosphere, in accordance with previous studies, reaching up to around 0.1 dex in the disk-integrated flux. We also present the first fully consistent 3D non-LTE solar carbon abundance determination: we infer log ɛC = 8.44 ± 0.02, in good agreement with the current standard value. Our models reproduce the observed solar centre-to-limb variations of various C I lines, without any adjustments to the rates of neutral hydrogen impact excitation, suggesting that the proposed recipe may be a solution to the long-standing problem of how to reliably model inelastic collisions with neutral hydrogen in late-type stellar atmospheres.

scholarly journals Assessing vertical diffusion in a stratified lake using a three‐dimensional hydrodynamic model

2019 ◽  
Vol 34 (5) ◽  
pp. 1131-1143 ◽  
Author(s):  
Fei Dong ◽  
Chenxi Mi ◽  
Michael Hupfer ◽  
Karl‐Erich Lindenschmidt ◽  
Wenqi Peng ◽  
...  
Keyword(s):  
Hydrodynamic Model ◽  
Three Dimensional ◽  
Vertical Diffusion ◽  
Stratified Lake
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