Three-Dimensional Nonlinear Modeling of MHD Instabilities for Low-q Plasma on J-TEXT

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.

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The impact of three dimensional MHD instabilities on the generation of warm dense matter using a MA-class linear transformer driver

High Energy Density Physics ◽

10.1016/j.hedp.2017.07.001 ◽

2017 ◽

Vol 24 ◽

pp. 50-55 ◽

Cited By ~ 2

Author(s):

P.-A. Gourdain ◽

C.E. Seyler

Keyword(s):

Three Dimensional ◽

Dense Matter ◽

Warm Dense Matter ◽

Mhd Instabilities ◽

Linear Transformer Driver ◽

The Impact

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The Development of a Split-tail Heliosphere and the Role of Non-ideal Processes: A Comparison of the BU and Moscow Models

The Astrophysical Journal ◽

10.3847/1538-4357/ac2fa6 ◽

2021 ◽

Vol 923 (2) ◽

pp. 179

Author(s):

M. Kornbleuth ◽

M. Opher ◽

I. Baliukin ◽

M. Gkioulidou ◽

J. D. Richardson ◽

...

Keyword(s):

Magnetic Field ◽

Solar Magnetic Field ◽

Three Dimensional ◽

Magnetic Field Effects ◽

The North ◽

Mhd Instabilities ◽

North And South ◽

Numerical Treatments ◽

Numerical Approaches

Abstract Global models of the heliosphere are critical tools used in the interpretation of heliospheric observations. There are several three-dimensional magnetohydrodynamic (MHD) heliospheric models that rely on different strategies and assumptions. Until now only one paper has compared global heliosphere models, but without magnetic field effects. We compare the results of two different MHD models, the BU and Moscow models. Both models use identical boundary conditions to compare how different numerical approaches and physical assumptions contribute to the heliospheric solution. Based on the different numerical treatments of discontinuities, the BU model allows for the presence of magnetic reconnection, while the Moscow model does not. Both models predict collimation of the solar outflow in the heliosheath by the solar magnetic field and produce a split tail where the solar magnetic field confines the charged solar particles into distinct north and south columns that become lobes. In the BU model, the interstellar medium (ISM) flows between the two lobes at large distances due to MHD instabilities and reconnection. Reconnection in the BU model at the port flank affects the draping of the interstellar magnetic field in the immediate vicinity of the heliopause. Different draping in the models cause different ISM pressures, yielding different heliosheath thicknesses and boundary locations, with the largest effects at high latitudes. The BU model heliosheath is 15% thinner and the heliopause is 7% more inwards at the north pole relative to the Moscow model. These differences in the two plasma solutions may manifest themselves in energetic neutral atom measurements of the heliosphere.

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A complete direct approach to nonlinear modeling of dielectric elastomer plates

Acta Mechanica ◽

10.1007/s00707-019-02529-1 ◽

2019 ◽

Vol 230 (11) ◽

pp. 3923-3943 ◽

Cited By ~ 2

Author(s):

Elisabeth Hansy-Staudigl ◽

Michael Krommer ◽

Alexander Humer

Keyword(s):

Free Energy ◽

Nonlinear Modeling ◽

Three Dimensional ◽

Direct Approach ◽

Thin Plates ◽

Elastic Behavior ◽

Dielectric Elastomers ◽

Novel Approach ◽

Dimensional Finite Element ◽

Three Dimensional Finite Element

Abstract In this paper, we present a complete direct approach to nonlinear modeling of thin plates, which are made of incompressible dielectric elastomers. In particular, the dielectric elastomers are assumed to exhibit a neo-Hookean elastic behavior, and the effect of electrostatic forces is incorporated by the purely electrical contribution to the augmented Helmholtz free energy. Our approach does not involve any extraction-type procedure from the three-dimensional energy to derive the plate augmented free energy, but directly postulates the form of this energy for the structural plate problem treated in this paper. Results computed within the framework of this novel approach are compared to results available in the literature as well as to our own three-dimensional finite element solutions. A very good agreement is found.

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Accurate simulation of draped fabric sheets with nonlinear modeling

Textile Research Journal ◽

10.1177/00405175211039573 ◽

2021 ◽

pp. 004051752110395

Author(s):

Yin Chen ◽

Q Jane Wang ◽

Mengqi Zhang

Keyword(s):

Simulation Model ◽

Nonlinear Modeling ◽

Three Dimensional ◽

Numerical Approach ◽

Polyester Fabric ◽

Shape Reconstruction ◽

Reconstruction Method ◽

Waist Size ◽

Drape Simulation ◽

Dimensional Shape

This paper reports a numerical approach, based on a nonlinear particle spring model and a collision detection procedure, to simulate the shape of a draped cloth, or a flexible sheet, together with a simple but precise three-dimensional shape reconstruction method for real fabric applications. The latter is utilized to verify the accuracy of the proposed drape simulation model. The drapes of four types of fabric on a cylinder are simulated, and the results are compared with the reconstructed shapes of the same cloths; the results show an excellent agreement. The simulation model is further used to calculate the shapes of skirts of different materials and sizes, and the effects of fabric parameters, length, and waist size are numerically investigated. The results reveal that under the same conditions, the behaviors of different materials are affected by their properties in terms of stiffness coefficients of the springs. The silk skirt looks soft and fluttering; the outer contour curve of the skirt simulated for the polyester fabric appears relatively smoother, but the shape of the cotton skirt seems to be stiffer. The skirt made of fabric of 10% cotton and 90% polyester combines the characteristics of the polyester and cotton fabric.

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A SIMPLE GEOMETRICAL STRUCTURE UNDERLYING SPEECH SIGNALS OF THE JAPANESE VOWEL /a/

International Journal of Bifurcation and Chaos ◽

10.1142/s0218127496001892 ◽

1996 ◽

Vol 06 (01) ◽

pp. 149-160 ◽

Cited By ~ 21

Author(s):

ISAO TOKUDA ◽

RYUJI TOKUNAGA ◽

KAZUYUKI AIHARA

Keyword(s):

Cross Sections ◽

Initial Conditions ◽

Nonlinear Modeling ◽

Three Dimensional ◽

Principal Component ◽

Coordinate Space ◽

Speech Signals ◽

Vowel Sound ◽

Modeling Analysis ◽

Sensitive Dependence

We provide several pieces of evidence for possible chaotic dynamics in the irregular behavior of normal speech signals of the Japanese vowel /a/. First, principal component analysis demonstrates that a simple geometric structure underlying the complex speech signal is well reconstructed in a three-dimensional delay-coordinate space. Observations of the reconstructed speech trajectory at multiple cross sections also display speech dynamics with stretching, folding and compressing. Second, Lyapunov spectrum analysis indicates sensitive dependence on initial conditions with a positive Lyapunov exponent for the speech signals of several different speakers. Third, nonlinear modeling analysis with an artificial neural network shows that the nonlinear dynamics of the vowel sound is well reproduced by a deterministic dynamical model.

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Nonlinear Modeling of the Dynamical Behavior of the Three-Dimensional Elastic Beam

IFAC Proceedings Volumes ◽

10.3182/20120215-3-at-3016.00036 ◽

2012 ◽

Vol 45 (2) ◽

pp. 205-209

Author(s):

Khanh Quang Luu ◽

Dirk Söffker

Keyword(s):

Nonlinear Modeling ◽

Dynamical Behavior ◽

Three Dimensional ◽

Elastic Beam

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Nonlinear Modeling of 3D Open-Cell Foams

10.1115/imece1999-0519 ◽

1999 ◽

Author(s):

Yu Wang ◽

Alberto M. Cuitiño

Keyword(s):

Strain Energy ◽

Nonlinear Modeling ◽

Three Dimensional ◽

Strain Energy Function ◽

Nonlinear Material ◽

Open Cell ◽

Wide Range ◽

Open Cell Foams ◽

Explicit Correlation ◽

Strain Energy Functions

Abstract In this article, we present a hyperelastic model for light and compliant open cell foams with an explicit correlation between microstructure and macroscopic behavior. The model describes a large number of three dimensional structures with regular and irregular cells. The theory is based on the formulation of strain-energy function accounting for stretching which is the main deformation mechanism in this type of materials. Within the same framework, however, bending, shear and twisting energies can also be incorporated. The formulation incorporates nonlinear kinematics which traces the evolution of the structure during loading process and its effects on the constitutive behavior, including the cases where configurational transformations are present leading to non-convex strain-energy functions. Also nonlinear material effects at local or beam level are introduced to accommodate a wide range of different material behaviors. Since the micromechanical formulation presented here has explicit correlation with the foam structure, it preserves in the constitutive relation the symmetries or directional properties of the corresponding structures, including the cases of re-entrant foams which exhibit negative Poisson’s ratio effects. The model captures the central features exhibit by these materials. Predictions of the model for macroscopic uniaxial strain are presented in this article.

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Three-dimensional distortions of the tokamak plasma boundary: boundary displacements in the presence of saturated MHD instabilities

Nuclear Fusion ◽

10.1088/0029-5515/54/8/083007 ◽

2014 ◽

Vol 54 (8) ◽

pp. 083007 ◽

Cited By ~ 4

Author(s):

I.T. Chapman ◽

D. Brunetti ◽

P. Buratti ◽

W.A. Cooper ◽

J.P. Graves ◽

...

Keyword(s):

Three Dimensional ◽

Plasma Boundary ◽

Tokamak Plasma ◽

Mhd Instabilities

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Dynamics and Control of the Bucket-Wheel Excavator: Part I — Dynamic Modeling of Bucket-Wheel Boom

Volume 6: 10th International Conference on Multibody Systems, Nonlinear Dynamics, and Control ◽

10.1115/detc2014-35224 ◽

2014 ◽

Cited By ~ 1

Author(s):

Quang Khanh Luu ◽

Dirk Söffker

Keyword(s):

Working Conditions ◽

Nonlinear Modeling ◽

Dynamical Behavior ◽

Three Dimensional ◽

Beam Theory ◽

Higher Order ◽

Operating Conditions ◽

Flexible Beam ◽

Dynamics And Control ◽

External Forces

Bucket-Wheel excavators (BWE) represent a specific type of complex machine system used in mining technology. During operation, the system is exposed to a number of external forces and disturbances like digging resistances on the Bucket-Wheel that cause transverse, longitudinal, and torsional vibrations. All vibrations will affect to normal working conditions, operational effectiveness, and may under specific conditions also effect the stability of the BWE. To increase working conditions advanced control systems can be applied controlling the dynamics, especially induced structural vibrations. In order to analyze and synthesize a controller for the above mentioned system, adequate modeling to describe the dynamical behavior of the system under real operating conditions is necessary. In a previous investigation, it was assumed that the Bucket-Wheel boom can be modeled as a flexible beam using the Euler-Bernoulli beam theory. Additionally it is assumed that the boom is attached to the excavator turning platform. The nonlinear modeling of the three-dimensional elastic boom considering the elasticity of suspending cables and also couplings resulting from geometrical nonlinear deformations is presented. Here the known modeling approach of higher order is used and extended to model the Bucket-Wheel boom of a Bucket-Wheel-Excavator including guided rotating motion in combination with digging resistance forces. The dynamic phenomena resulting from the higher-order modeling including higher-order geometrical couplings as well as the external excitations on the dynamic behavior of the Bucket-Wheel boom are analyzed in detail. Intensive simulation studies are realized demonstrating the effect of higher-order couplings as well as resulting destabilizing effects from the modeling.

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