Finite Volume Central Schemes for Three-Dimensional Ideal MHD

2008 ◽  
pp. 323-330
Author(s):  
P. Arminjon ◽  
R. Touma
Keyword(s):  
Finite Volume ◽  
Three Dimensional ◽  
Central Schemes ◽  
Ideal Mhd

scholarly journals Can Multi-threaded Flux Tubes in Coronal Arcades Support a Magnetohydrodynamic Avalanche?

Solar Physics ◽  
2021 ◽  
Vol 296 (8) ◽  
Author(s):  
J. Threlfall ◽  
J. Reid ◽  
A. W. Hood
Keyword(s):  
Magnetic Fields ◽  
Three Dimensional ◽  
Coronal Loops ◽  
Flux Tubes ◽  
Single Thread ◽  
Mhd Instabilities ◽  
Mhd Instability ◽  
Mhd Simulations ◽  
Ideal Mhd ◽  
Model Geometry

AbstractMagnetohydrodynamic (MHD) instabilities allow energy to be released from stressed magnetic fields, commonly modelled in cylindrical flux tubes linking parallel planes, but, more recently, also in curved arcades containing flux tubes with both footpoints in the same photospheric plane. Uncurved cylindrical flux tubes containing multiple individual threads have been shown to be capable of sustaining an MHD avalanche, whereby a single unstable thread can destabilise many. We examine the properties of multi-threaded coronal loops, wherein each thread is created by photospheric driving in a realistic, curved coronal arcade structure (with both footpoints of each thread in the same plane). We use three-dimensional MHD simulations to study the evolution of single- and multi-threaded coronal loops, which become unstable and reconnect, while varying the driving velocity of individual threads. Experiments containing a single thread destabilise in a manner indicative of an ideal MHD instability and consistent with previous examples in the literature. The introduction of additional threads modifies this picture, with aspects of the model geometry and relative driving speeds of individual threads affecting the ability of any thread to destabilise others. In both single- and multi-threaded cases, continuous driving of the remnants of disrupted threads produces secondary, aperiodic bursts of energetic release.

Combined Microstructure and Heat Transfer Modeling of Carbon Nanotube Thermal Interface Materials1

2016 ◽  
Vol 138 (4) ◽  
Author(s):  
Sridhar Sadasivam ◽  
Stephen L. Hodson ◽  
Matthew R. Maschmann ◽  
Timothy S. Fisher
Keyword(s):  
Heat Transfer ◽  
Thermal Resistance ◽  
Finite Volume ◽  
Pressure Dependence ◽  
Matrix Material ◽  
Three Dimensional ◽  
Coarse Grain ◽  
Total Thermal Resistance ◽  
Thermal Interface ◽  
Cnt Arrays

A microstructure-sensitive thermomechanical simulation framework is developed to predict the mechanical and heat transfer properties of vertically aligned CNT (VACNT) arrays used as thermal interface materials (TIMs). The model addresses the gap between atomistic thermal transport simulations of individual CNTs (carbon nanotubes) and experimental measurements of thermal resistance of CNT arrays at mesoscopic length scales. Energy minimization is performed using a bead–spring coarse-grain model to obtain the microstructure of the CNT array as a function of the applied load. The microstructures obtained from the coarse-grain simulations are used as inputs to a finite volume solver that solves one-dimensional and three-dimensional Fourier heat conduction in the CNTs and filler matrix, respectively. Predictions from the finite volume solver are fitted to experimental data on the total thermal resistance of CNT arrays to obtain an individual CNT thermal conductivity of 12 W m−1 K−1 and CNT–substrate contact conductance of 7 × 107 W m−2 K−1. The results also indicate that the thermal resistance of the CNT array shows a weak dependence on the CNT–CNT contact resistance. Embedding the CNT array in wax is found to reduce the total thermal resistance of the array by almost 50%, and the pressure dependence of thermal resistance nearly vanishes when a matrix material is introduced. Detailed microstructural information such as the topology of CNT–substrate contacts and the pressure dependence of CNT–opposing substrate contact area are also reported.

Three-Dimensional Parametric Finite-Volume Homogenization of Periodic Materials with Multi-Scale Structural Applications

2018 ◽  
Vol 10 (04) ◽  
pp. 1850045 ◽  
Author(s):  
Qiang Chen ◽  
Guannan Wang ◽  
Xuefeng Chen
Keyword(s):  
Finite Volume ◽  
Three Dimensional ◽  
Functionally Graded ◽  
Attractive Alternative ◽  
Matrix Assembly ◽  
Functionally Graded Composite ◽  
Multi Scale ◽  
Hexahedral Elements ◽  
Stiffness Matrices ◽  
Structural Applications

In order to satisfy the increasing computational demands of micromechanics, the Finite-Volume Direct Averaging Micromechanics (FVDAM) theory is developed in three-dimensional (3D) domain to simulate the multiphase heterogeneous materials whose microstructures are distributed periodically in the space. Parametric mapping, which endorses arbitrarily shaped and oriented hexahedral elements in the microstructure discretization, is employed in the unit cell solution. Unlike the finite-element (FE) technique, the expressions for local stiffness matrices are derived explicitly, enabling efficient global stiffness matrix assembly using an easily implementable algorithm. To demonstrate the accuracy and efficiency of the proposed theory, the homogenized moduli and localized stress distributions produced by the FE analyses are given for comparisons, where excellent agreement is always obtained for the 3D microstructures with different geometrical and material properties. Finally, a multi-scale stress analysis of functionally graded composite cylinders is conducted. This extension further increases the FVDAM’s range of applicability and opens new opportunities for pursuing other areas, providing an attractive alternative to the FE-based approaches that may be compared.

A Quasi-three-dimensional Finite-volume Shallow Water Model for Green Water on Deck

2013 ◽  
Vol 57 (03) ◽  
pp. 125-140
Author(s):  
Daniel A. Liut ◽  
Kenneth M. Weems ◽  
Tin-Guen Yen
Keyword(s):  
Shallow Water ◽  
Finite Volume ◽  
Time Domain ◽  
Degrees Of Freedom ◽  
Initial Conditions ◽  
Three Dimensional ◽  
Green Water ◽  
Water Model ◽  
Ship Motions ◽  
Shallow Water Model

A quasi-three-dimensional hydrodynamic model is presented to simulate shallow water phenomena. The method is based on a finite-volume approach designed to solve shallow water equations in the time domain. The nonlinearities of the governing equations are considered. The methodology can be used to compute green water effects on a variety of platforms with six-degrees-of-freedom motions. Different boundary and initial conditions can be applied for multiple types of moving platforms, like a ship's deck, tanks, etc. Comparisons with experimental data are discussed. The shallow water model has been integrated with the Large Amplitude Motions Program to compute the effects of green water flow over decks within a time-domain simulation of ship motions in waves. Results associated to this implementation are presented.

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