Adiabatic switching in time-dependent Fourier grid Hamiltonian method: some test cases

1996 ◽  
Vol 206 (3) ◽  
pp. 315-324 ◽  
Author(s):  
S. Adhikari ◽  
P. Dutta ◽  
S.P. Bhattacharyya
Keyword(s):  
Time Dependent ◽  
Test Cases ◽  
Hamiltonian Method ◽  
Adiabatic Switching

scholarly journals Inclusion of a time-dependent, non-local convection theory in a stellar evolution code

2006 ◽  
Vol 2 (S239) ◽  
pp. 314-316 ◽  
Author(s):  
Achim Weiss ◽  
Martin Flaskamp
Keyword(s):  
Velocity Field ◽  
Local Time ◽  
Stellar Evolution ◽  
Time Dependent ◽  
Test Cases ◽  
The Sun ◽  
Specific Test ◽  
Non Local ◽  
Convective Boundaries

AbstractThe non-local, time-dependent convection theory of Kuhfuß (1986) in both its one- and three-equation form has been implemented in the Garching stellar evolution code. We present details of the implementation and the difficulties encountered. Specific test cases have been calculated, among them a 5 M⊙ star and the Sun. These cases point out deficits of the theory. In particular, the assumption of an isotropic velocity field leads to too extensive overshooting and has to be modified at convective boundaries. Some encouraging aspects are indicated as well.

scholarly journals Time-dependent radiation hydrodynamics on a moving mesh

2020 ◽  
Vol 493 (4) ◽  
pp. 5397-5407 ◽  
Author(s):  
Philip Chang ◽  
Shane W Davis ◽  
Yan-Fei Jiang(姜燕飞)
Keyword(s):  
Large Scale ◽  
Momentum Conservation ◽  
Conservation Equation ◽  
Time Dependent ◽  
Moving Mesh ◽  
Test Cases ◽  
Multiple Sources ◽  
Linear Waves ◽  
Implicit Solver ◽  
Coupling Time

ABSTRACT We describe the structure and implementation of a radiation hydrodynamic solver for manga, the moving-mesh hydrodynamics module of the large-scale parallel code, Charm N-body GrAvity solver (changa). We solve the equations of time-dependent radiative transfer (RT) using a reduced speed of light approximation following the algorithm of Jiang et al. By writing the RT equations as a generalized conservation equation, we solve the transport part of these equations on an unstructured Voronoi mesh. We then solve the source part of the RT equations following Jiang et al. using an implicit solver, and couple this to the hydrodynamic equations. The use of an implicit solver ensures reliable convergence and preserves the conservation properties of these equations even in situations where the source terms are stiff due to the small coupling time-scales between radiation and matter. We present the results of a limited number of test cases (energy conservation, momentum conservation, dynamic diffusion, linear waves, crossing beams, and multiple shadows) to show convergence with analytic results and numerical stability. We also show that it produces qualitatively the correct results in the presence of multiple sources in the optically thin case.

An Improved Bounded Gradient Maximization Method for Interface-Capturing VOF Simulations

2009 ◽  
Author(s):  
Brandon Witbeck ◽  
D. Keith Walters
Keyword(s):  
High Resolution ◽  
Phase Interface ◽  
Time Dependent ◽  
Test Cases ◽  
Discretization Scheme ◽  
Spatial Discretization ◽  
Two Phase ◽  
Initial Development ◽  
Interface Capturing ◽  
The Stability

A new high-resolution spatial discretization scheme is presented for the volume-of-fluid (VOF) method. This scheme is an adaptation of the previously published bounded gradient maximization (BGM) scheme [1]. This scheme resolves the phase interface without any explicit geometrical reconstruction of the interface. A net upwind bias in each cell ensures the stability of the scheme, and face limiting satisfies the boundedness criteria at the cell faces to prevent variable overshoot. In contrast to most existing methods, no method using “switching” between upwind-biased and downwind-biased discretization is employed to gain method stability. This paper presents the initial development and implementation of a time-dependent version of the method. Test cases are performed for a number of 2-D and 3-D two-phase flows on both structured and unstructured meshes. Results indicate that the method performs well in maintaining the resolution of the phase interface.

Adiabatic switching for time‐dependent electric fields

1988 ◽  
Vol 29 (12) ◽  
pp. 2604-2610 ◽  
Author(s):  
Márcia A. G. Scialom ◽  
Rafael J. Iório
Keyword(s):  
Electric Fields ◽  
Time Dependent ◽  
Adiabatic Switching

Linear Visco-Resistive Computations of Magnetohydrodynamic Waves: I. The Code and Test Cases

1994 ◽  
Vol 144 ◽  
pp. 503-505
Author(s):  
R. Erdélyi ◽  
M. Goossens ◽  
S. Poedts
Keyword(s):  
Resonant Absorption ◽  
Numerical Code ◽  
Mhd Waves ◽  
Test Cases ◽  
Numerical Accuracy ◽  
Element Discretization ◽  
Flux Tubes ◽  
Magnetohydrodynamic Waves ◽  
Viscosity Coefficients ◽  
Magnetic Flux Tubes

AbstractThe stationary state of resonant absorption of linear, MHD waves in cylindrical magnetic flux tubes is studied in viscous, compressible MHD with a numerical code using finite element discretization. The full viscosity tensor with the five viscosity coefficients as given by Braginskii is included in the analysis. Our computations reproduce the absorption rates obtained by Lou in scalar viscous MHD and Goossens and Poedts in resistive MHD, which guarantee the numerical accuracy of the tensorial viscous MHD code.

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