scholarly journals 6.5. Hydrodynamical simulations as probes for the structure of the galactic center

1998 ◽  
Vol 184 ◽  
pp. 271-272
Author(s):  
K. Wada ◽  
T. Minezaki ◽  
K. Sakamoto ◽  
H. Fukuda
Keyword(s):  
Numerical Modeling ◽  
Numerical Simulations ◽  
Mass Distribution ◽  
Galactic Center ◽  
Dynamical Behavior ◽  
Interstellar Gas ◽  
Interstellar Gas In Galaxies ◽  
Dynamical Parameters ◽  
Pattern Speed ◽  
Hydrodynamical Simulations

Numerical modeling of the interstellar gas in galaxies is an effective approach to infer galactic gravitational structure. This is because the dynamical behavior of gas is very sensitive to the background gravitational potential. Since the dynamical resonances depend closely on the mass distribution and the pattern speed of the non-axisymmetric component, it is possible to determine these dynamical parameters by comparison of numerical simulations and gas observations.

scholarly journals Hydrodynamical Simulations of the Barred Spiral Galaxy NGC 1365

1996 ◽  
Vol 157 ◽  
pp. 413-415
Author(s):  
P. A. B. Lindblad ◽  
P. O. Lindblad ◽  
E. Athanassoula
Keyword(s):  
Gravitational Field ◽  
Gas Dynamics ◽  
Rotation Curve ◽  
Barred Galaxies ◽  
Mosaic Image ◽  
Dynamical Parameters ◽  
Pattern Speed ◽  
Barred Spiral Galaxy ◽  
Hydrodynamical Simulations ◽  
Ngc 1365

Several authors have explored the field of gas dynamics in barred systems. One of the aims of these investigations was to compare the model gaseous response, due to some assumed underlying stellar gravitational field, with observed gas density distribution and kinematics of barred galaxies. The gas is known to respond in a highly non-linear way, and therefore should give clues to dynamical parameters like the mass distribution, positions and existence of principal resonances and thereby the pattern speed.High resolution HI data now exist for NGC 1365 (Jörsäter & van Moorsel 1995), and the kinematical HI data have been combined with optical long slit measurements to obtain the velocity field (Lindblad et al. 1995) used for extracting the rotation curve, representing the axisymmetric forces in NGC 1365, and for comparisons with models. A mosaic image of NGC 1365 in the J-band was used to compute the perturbing potential used in the models.

scholarly journals Magnetic Fields in the Disk-Halo Interface

1991 ◽  
Vol 144 ◽  
pp. 169-174
Author(s):  
Yoshiaki Sofue
Keyword(s):  
Magnetic Fields ◽  
Large Scale ◽  
Spiral Galaxies ◽  
Galactic Center ◽  
Interstellar Gas ◽  
Outer Disk ◽  
Vertical Field ◽  
Interstellar Gas In Galaxies ◽  
Halo Gas

A review is given of large-scale magnetic fields in disks and halos of spiral galaxies. A particular attention is given to vertical field structures, and we discuss their origin and implication on their interaction with halo gas. We point out that the disk-halo magnetic interface plays an important role in circulation of interstellar gas in galaxies, in particular a large-scale circulartion from the galactic center to outer disk regions.

scholarly journals A Review of Numerical Simulations of Secondary Flows in River Bends

Water ◽  
2021 ◽  
Vol 13 (7) ◽  
pp. 884
Author(s):  
Rawaa Shaheed ◽  
Abdolmajid Mohammadian ◽  
Xiaohui Yan
Keyword(s):  
Numerical Modeling ◽  
Numerical Simulations ◽  
Secondary Flow ◽  
Cross Section ◽  
Turbulence Models ◽  
Main Flow ◽  
Secondary Flows ◽  
River Bends ◽  
River Cross Section ◽  
River Bend

River bends are one of the common elements in most natural rivers, and secondary flow is one of the most important flow features in the bends. The secondary flow is perpendicular to the main flow and has a helical path moving towards the outer bank at the upper part of the river cross-section, and towards the inner bank at the lower part of the river cross-section. The secondary flow causes a redistribution in the main flow. Accordingly, this redistribution and sediment transport by the secondary flow may lead to the formation of a typical pattern of river bend profile. It is important to study and understand the flow pattern in order to predict the profile and the position of the bend in the river. However, there are a lack of comprehensive reviews on the advances in numerical modeling of bend secondary flow in the literature. Therefore, this study comprehensively reviews the fundamentals of secondary flow, the governing equations and boundary conditions for numerical simulations, and previous numerical studies on river bend flows. Most importantly, it reviews various numerical simulation strategies and performance of various turbulence models in simulating the flow in river bends and concludes that the main problem is finding the appropriate model for each case of turbulent flow. The present review summarizes the recent advances in numerical modeling of secondary flow and points out the key challenges, which can provide useful information for future studies.

Dynamics of a Supported Cylinder in Axial Flow

2011 ◽  
Vol 99-100 ◽  
pp. 1059-1062
Author(s):  
Ji Duo Jin ◽  
Ning Li ◽  
Zhao Hong Qin
Keyword(s):  
Nonlinear Dynamics ◽  
Numerical Analysis ◽  
Numerical Simulations ◽  
Nonlinear Model ◽  
Dynamical Behavior ◽  
Axial Flow ◽  
Viscous Force ◽  
Friction Drag ◽  
Flutter Instability ◽  
Nonlinear Force

The nonlinear dynamics are studied for a supported cylinder subjected to axial flow. A nonlinear model is presented for dynamics of the cylinder supported at both ends. The nonlinear terms considered here are the quadratic viscous force and the structural nonlinear force induced by the lateral motions of the cylinder. Using two-mode discretized equation, numerical simulations are carried out for the dynamical behavior of the cylinder to explain the flutter instability found in the experiment. The results of numerical analysis show that at certain value of flow velocity the system loses stability by divergence, and the new equilibrium (the buckled configuration) becomes unstable at higher flow leading to post-divergence flutter. The effect of the friction drag coefficients on the behavior of the system is investigated.

Optimal Synchronization of a Memristive Chaotic Circuit

2016 ◽  
Vol 26 (06) ◽  
pp. 1650093 ◽  
Author(s):  
Michaux Kountchou ◽  
Patrick Louodop ◽  
Samuel Bowong ◽  
Hilaire Fotsin ◽  
Jurgen Kurths
Keyword(s):  
Numerical Simulations ◽  
Chaos Synchronization ◽  
Chaotic Systems ◽  
Analog Circuit ◽  
Electronic Circuit ◽  
Dynamical Behavior ◽  
Circuit Implementation ◽  
Chaotic Circuit ◽  
Dynamical Properties ◽  
Analog Circuit Implementation

This paper deals with the problem of optimal synchronization of two identical memristive chaotic systems. We first study some basic dynamical properties and behaviors of a memristor oscillator with a simple topology. An electronic circuit (analog simulator) is proposed to investigate the dynamical behavior of the system. An optimal synchronization strategy based on the controllability functions method with a mixed cost functional is investigated. A finite horizon is explicitly computed such that the chaos synchronization is achieved at an established time. Numerical simulations are presented to verify the effectiveness of the proposed synchronization strategy. Pspice analog circuit implementation of the complete master-slave-controller systems is also presented to show the feasibility of the proposed scheme.

Dynamical imprint of interstellar gas on persistence of spiral structure in galaxies

2017 ◽  
Vol 13 (S334) ◽  
pp. 296-297
Author(s):  
Soumavo Ghosh ◽  
Chanda J. Jog
Keyword(s):  
Time Scale ◽  
Spiral Structure ◽  
Density Wave ◽  
Disk Galaxies ◽  
Interstellar Gas ◽  
Spiral Arms ◽  
Pattern Speed

AbstractThe persistence of the spiral structure in disk galaxies has long been debated. In this work, we investigate the dynamical influence of interstellar gas on the persistence of the spiral arms in disk galaxies. We show that the gas helps the spiral arms to survive for longer time-scale (~ a few Gyr). Also, we show that the addition of gas in calculation is necessary for getting a stable density wave corresponding to the observed pattern speed of the spiral arms.

scholarly journals Numerical simulations of the dynamical behavior of the SK model

1998 ◽  
Vol 2 (4) ◽  
pp. 495-500 ◽  
Author(s):  
E. Marinari ◽  
G. Parisi ◽  
D. Rossetti
Keyword(s):  
Numerical Simulations ◽  
Dynamical Behavior

DYNAMICS OF A PREY-DEPENDENT DIGESTIVE MODEL WITH STATE-DEPENDENT IMPULSIVE CONTROL

2012 ◽  
Vol 22 (04) ◽  
pp. 1250092 ◽  
Author(s):  
LINNING QIAN ◽  
QISHAO LU ◽  
JIARU BAI ◽  
ZHAOSHENG FENG
Keyword(s):  
Numerical Simulations ◽  
Analytical Method ◽  
Impulsive Control ◽  
Dynamical Behavior ◽  
Sufficient Conditions ◽  
Period Doubling ◽  
Lambert W Function ◽  
Impulsive Effect ◽  
State Dependent ◽  
Theoretical Results

In this paper, we study the dynamical behavior of a prey-dependent digestive model with a state-dependent impulsive effect. Using the Poincaré map and the Lambert W-function, we find the analytical expression of discrete mapping. Sufficient conditions are established for transcritical bifurcation and period-doubling bifurcation through an analytical method. Exact locations of these bifurcations are explored. Numerical simulations of an example are illustrated which agree well with our theoretical results.

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