scholarly journals Numerical Simulations of Nano-Scale Magnetization Dynamics

10.5772/23745 ◽  
2011 ◽  
Author(s):  
Paul Horley ◽  
Vitor Vieira ◽  
Jesus Gonzalez-Hernandez ◽  
Vitalii Dugaev ◽  
Jozef Barnas
Keyword(s):  
Numerical Simulations ◽  
Magnetization Dynamics ◽  
Nano Scale

THERMAL RELAXATION IN MAGNETIC MATERIALS: A SURVEY

SPIN ◽  
2013 ◽  
Vol 03 (02) ◽  
pp. 1330005 ◽  
Author(s):  
IVO KLIK ◽  
CHING-RAY CHANG
Keyword(s):  
Numerical Simulations ◽  
Magnetic Materials ◽  
Curie Point ◽  
Statistical Physics ◽  
Stochastic Dynamics ◽  
Thermal Relaxation ◽  
Bloch Equation ◽  
Numerical Calculations ◽  
Magnetization Dynamics ◽  
Thermal Agitation

This paper presents a survey of the methods of statistical physics which are applied to the problem of thermal agitation in magnetic materials. The main focus of the work is the stochastic dynamics described by the Landau-Lifshitz-Gilbert equation for which most analytic results are known, and which has been most commonly used in numerical simulations. We also present the much more recent Landau–Lifshitz–Bloch equation and the numerical calculations describing magnetization dynamics close to the Curie point. The paper is concluded by a description of the newly introduced jump-noise and of the Barkhausen jumps.

Saturation mechanism and generated viscosity in gravito-turbulent accretion disks

2020 ◽  
Vol 640 ◽  
pp. A53
Author(s):  
L. Löhnert ◽  
S. Krätschmer ◽  
A. G. Peeters
Keyword(s):  
Growth Rate ◽  
Numerical Simulations ◽  
Accretion Disks ◽  
Gravitational Instability ◽  
Turbulent Viscosity ◽  
Radial Distance ◽  
Maximum Growth ◽  
Wave Number ◽  
Radiative Cooling ◽  
Mixing Length

Here, we address the turbulent dynamics of the gravitational instability in accretion disks, retaining both radiative cooling and irradiation. Due to radiative cooling, the disk is unstable for all values of the Toomre parameter, and an accurate estimate of the maximum growth rate is derived analytically. A detailed study of the turbulent spectra shows a rapid decay with an azimuthal wave number stronger than ky−3, whereas the spectrum is more broad in the radial direction and shows a scaling in the range kx−3 to kx−2. The radial component of the radial velocity profile consists of a superposition of shocks of different heights, and is similar to that found in Burgers’ turbulence. Assuming saturation occurs through nonlinear wave steepening leading to shock formation, we developed a mixing-length model in which the typical length scale is related to the average radial distance between shocks. Furthermore, since the numerical simulations show that linear drive is necessary in order to sustain turbulence, we used the growth rate of the most unstable mode to estimate the typical timescale. The mixing-length model that was obtained agrees well with numerical simulations. The model gives an analytic expression for the turbulent viscosity as a function of the Toomre parameter and cooling time. It predicts that relevant values of α = 10−3 can be obtained in disks that have a Toomre parameter as high as Q ≈ 10.

CHARACTERIZATION OF SPLASH-PLATE ATOMIZERS USING NUMERICAL SIMULATIONS

2007 ◽  
Vol 17 (4) ◽  
pp. 347-380 ◽  
Author(s):  
Mohammad P. Fard ◽  
Denise Levesque ◽  
Stuart Morrison ◽  
Nasser Ashgriz ◽  
J. Mostaghimi
Keyword(s):  
Numerical Simulations
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