Numerical study of coorbital thermal torques on cold or hot satellites

ABSTRACT We evaluate the thermal torques exerted on low-mass planets embedded in gaseous protoplanetary discs with thermal diffusion, by means of high-resolution three-dimensional hydrodynamics simulations. We confirm that thermal torques essentially depend on the offset between the planet and its corotation, and find a good agreement with analytic estimates when this offset is small compared to the size of the thermal disturbance. For larger offsets that may be attained in discs with a large pressure gradient or a small thermal diffusivity, thermal torques tend towards an asymptotic value broadly compatible with results from a dynamical friction calculation in an unsheared medium. We perform a convergence study and find that the thermal disturbance must be resolved over typically 10 zones for a decent agreement with analytic predictions. We find that the luminosity at which the net thermal torque changes sign matches that predicted by linear theory within a few percents. Our study confirms that thermal torques usually supersede Lindblad and corotation torques by almost an order of magnitude for low-mass planets. As we increase the planetary mass, we find that the ratio of thermal torques to Lindblad and corotation torques is progressively reduced, and that the thermal disturbance is increasingly distorted by the horseshoe flow. Overall, we find that thermal torques are dominant for masses up to an order of magnitude larger than implemented in recent models of planetary population synthesis. We finally briefly discuss the case of stellar or intermediate-mass objects embedded in discs around active galactic nuclei.

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A Numerical Study on the Large Compressive Deformations of Closed-Celled Rubber Foams

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.444-445.23 ◽

2013 ◽

Vol 444-445 ◽

pp. 23-26

Author(s):

Zhi Geng Fan

Keyword(s):

Strain Energy ◽

Potential Model ◽

Numerical Study ◽

Three Dimensional ◽

Face Centered Cubic ◽

Energy Potential ◽

Compressive Stresses ◽

Order Of Magnitude ◽

Face Centered ◽

In Cells

Three dimensional (3D) cubic models with spherical pores ranged as Face-Centered Cubic (FCC) lattices are constructed to simulate the microstructures of rubber foams with various relative densities. The Mooney-Rivlin strain energy potential model is adopted to characterize the hyperelasticity of the constituent solid from which the foams are made. Large compressive deformations of closed-celled rubber foams are calculated by the iterative algorithm. Numerical results show that with the decreasing of foam relative densities, the effects of air pressures in cells on foam compressive stresses increase. When the ratio of initial Yangs modulus of cell material to the initial air pressure in cells reaches 2 order of magnitude, the influence of air pressures in cells can neglect.

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Three-dimensional boundary-layer equations in regions with large pressure gradient

Fluid Dynamics ◽

10.1007/bf01013858 ◽

1974 ◽

Vol 6 (5) ◽

pp. 762-768

Author(s):

G. M. Bam-Zelikovich

Keyword(s):

Boundary Layer ◽

Pressure Gradient ◽

Three Dimensional ◽

Boundary Layer Equations ◽

Large Pressure ◽

Large Pressure Gradient ◽

Dimensional Boundary

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Stellar populations and ionised gas in central spheroidal galaxies

Proceedings of the International Astronomical Union ◽

10.1017/s1743921320002410 ◽

2020 ◽

Vol 15 (S359) ◽

pp. 469-472

Author(s):

Vanessa Lorenzoni ◽

Sandro B. Rembold

Keyword(s):

Stellar Population ◽

Synthesis Method ◽

Galactic Nuclei ◽

Stellar Populations ◽

High Mass ◽

Population Synthesis ◽

The Galaxy ◽

History Of ◽

Low Mass ◽

Spheroidal Galaxies

We investigate the stellar populations and ionised gas properties of a sample of central spheroidal galaxies in order to better constrain their history of star formation and gas excitation mechanism. We select galaxies from Spheroids Panchromatic Investigation in Different Environmental Regions (SPIDER) catalogue and separate these galaxies in different regimes of halo and galaxy mass. To characterise the stellar population properties of these galaxies we use the stellar population synthesis method with the Starlight code, and the presence of ionised gas is identified by measurements of the Hα equivalent width. We analyse how these properties behave as a function of the galaxy stellar mass and the parent halo mass. A trend is observed in the sense of increased ionised gas emission for low-mass centrals in high-mass halos. We interpret this trend in a scenario of intracluster medium (ICM) cooling versus active galactic nuclei (AGN) feedback in a Bondi accretion context.

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Numerical Study of a Gravitating System of Colliding Particles; Formation and Dynamics of Discs

Symposium - International Astronomical Union ◽

10.1017/s0074180900015618 ◽

1975 ◽

Vol 69 ◽

pp. 287-295

Author(s):

A. Brahic

Keyword(s):

Numerical Study ◽

Finite Thickness ◽

Three Dimensional ◽

Galactic Nuclei ◽

Inelastic Collisions ◽

Dimensional System ◽

Central Mass ◽

System Of Particles ◽

Gravitating Systems ◽

Three Dimensional System

The study of gravitating systems of colliding particles has many potential astrophysical applications, for instance the dynamics of Saturn's ring, the formation of the solar system, the flattening of protogalaxies and the evolution of galactic nuclei. We consider numerically a three-dimensional system of particles moving in the gravitational field of a central mass point and interacting through inelastic collisions. After a very fast flattening, the system forms a disc of finite thickness: this disc spreads slowly, and collisions still occur. A central condensation is formed and there is an outward flux of angular momentum. The energy which is continually lost in the inelastic collisions is obtained at the expense of the bodies which fall inwards.

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Assessment of Methods for Calculating LNG Pump Tower Loads

Journal of Offshore Mechanics and Arctic Engineering ◽

10.1115/1.4050964 ◽

2021 ◽

pp. 1-41

Author(s):

Michael Thome ◽

Jens Neugebauer ◽

Ould el Moctar ◽

Thomas E. Schellin

Keyword(s):

Structural Design ◽

Numerical Study ◽

Three Dimensional ◽

Navier Stokes ◽

Detached Eddy Simulation ◽

Field Methods ◽

Statistical Measures ◽

Delayed Detached Eddy Simulation ◽

Tower Structure ◽

Order Of Magnitude

Abstract This paper presents a comparative numerical study on LNG (Liquefied Natural Gas) pump tower loads, while focusing on two aspects. First, are impact loads relevant for the structural design of LNG pump towers and, second, in which way does fluid-structure interaction influence these loads? Numerical simulations of the multiphase problem were conducted using viscous field methods. First, Unsteady Reynolds-Averaged Navier-Stokes (URANS) equations, extended by the Volume of Fluid (VoF) approach, were used to simulate, at model scale, the flow inside a three-dimensional LNG tank without the tower structure. Then, these results were used to validate the numerical method against model test measurements. Afterwards, motion periods and amplitudes were systematically varied in the flow simulations. Flow velocities and accelerations along the positions of the main structural members of the pump tower were extracted and used as input data for load approximations based on the Morison equation. Finally, these load approximations were compared to loads determined from solving the Delayed Detached Eddy Simulation (DDES). Time histories as well as statistical measures of global loads acting on the entire and the simplified tower structure were of the same order of magnitude. However, their time evolution differed, especially at their peaks, and this was considered significant for structural design.

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Detection, Averaging, and 3D Reconstruction of Biological Specimens on Hypercubes (Transputer-based) Computers

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100181026 ◽

1990 ◽

Vol 48 (1) ◽

pp. 454-455

Author(s):

Jose-Maria Carazo ◽

I. Benavides ◽

S. Marco ◽

J.L. Carrascosa ◽

E.L. Zapata

Keyword(s):

3D Reconstruction ◽

3D Structure ◽

Three Dimensional ◽

Software Tools ◽

Mapping Method ◽

Computer Architectures ◽

Parallel Computer ◽

Reconstruction Process ◽

Computing Power ◽

Order Of Magnitude

Obtaining the three-dimensional (3D) structure of negatively stained biological specimens at a resolution of, typically, 2 - 4 nm is becoming a relatively common practice in an increasing number of laboratories. A combination of new conceptual approaches, new software tools, and faster computers have made this situation possible. However, all these 3D reconstruction processes are quite computer intensive, and the middle term future is full of suggestions entailing an even greater need of computing power. Up to now all published 3D reconstructions in this field have been performed on conventional (sequential) computers, but it is a fact that new parallel computer architectures represent the potential of order-of-magnitude increases in computing power and should, therefore, be considered for their possible application in the most computing intensive tasks.We have studied both shared-memory-based computer architectures, like the BBN Butterfly, and local-memory-based architectures, mainly hypercubes implemented on transputers, where we have used the algorithmic mapping method proposed by Zapata el at. In this work we have developed the basic software tools needed to obtain a 3D reconstruction from non-crystalline specimens (“single particles”) using the so-called Random Conical Tilt Series Method. We start from a pair of images presenting the same field, first tilted (by ≃55°) and then untilted. It is then assumed that we can supply the system with the image of the particle we are looking for (ideally, a 2D average from a previous study) and with a matrix describing the geometrical relationships between the tilted and untilted fields (this step is now accomplished by interactively marking a few pairs of corresponding features in the two fields). From here on the 3D reconstruction process may be run automatically.

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Scanning-tunneling spectroscopy on conjugated polymer films

MRS Proceedings ◽

10.1557/proc-771-l4.3 ◽

2003 ◽

Vol 771 ◽

Author(s):

M. Kemerink ◽

S.F. Alvarado ◽

P.M. Koenraad ◽

R.A.J. Janssen ◽

H.W.M. Salemink ◽

...

Keyword(s):

Polymer Films ◽

Conjugated Polymer ◽

Three Dimensional ◽

Field Enhancement ◽

Direct Consequence ◽

Scanning Tunneling Spectroscopy ◽

Tunneling Spectroscopy ◽

Band Alignment ◽

Scanning Tunneling ◽

Order Of Magnitude

AbstractScanning-tunneling spectroscopy experiments have been performed on conjugated polymer films and have been compared to a three-dimensional numerical model for charge injection and transport. It is found that field enhancement near the tip apex leads to significant changes in the injected current, which can amount to more than an order of magnitude, and can even change the polarity of the dominant charge carrier. As a direct consequence, the single-particle band gap and band alignment of the organic material can be directly obtained from tip height-voltage (z-V) curves, provided that the tip has a sufficiently sharp apex.

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