The deal.II library, Version 9.2

Arndt, Daniel; Bangerth, Wolfgang; Blais, Bruno; Clevenger, Thomas C.; Fehling, Marc; Grayver, Alexander; Heister, Timo; Heltai, Luca; Kronbichler, Martin; Maier, Matthias; Münch, Peter; Pelteret, Jean-Paul; Rastak, Reza; Tomaš, Ignacio; Turcksin, Bruno; Wang, Zhuoran; Wells, David

doi:10.1515/jnma-2020-0043

Cited by 158 publications

(134 citation statements)

References 31 publications

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“…B m n,r is radial magnetic field which is (numerically) computed for a given Earth conductivity model driven by a unit amplitude ( ε = 1) SH source, and is the corresponding external part of the radial magnetic field. B m n,r has in this study been numerically computed using a finite element code (Arndt et al 2020;Grayver and Kolev 2015;Grayver et al 2019). Formulae for the (5) unit amplitude SH source can be found, for example, in Guzavina et al (2018).…”

Section: Treatment Of Induced Fieldsmentioning

confidence: 99%

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The CHAOS-7 geomagnetic field model and observed changes in the South Atlantic Anomaly

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Kloss

Olsen

et al. 2020

Earth Planets Space

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206

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We present the CHAOS-7 model of the time-dependent near-Earth geomagnetic field between 1999 and 2020 based on magnetic field observations collected by the low-Earth orbit satellites Swarm, CryoSat-2, CHAMP, SAC-C and Ørsted, and on annual differences of monthly means of ground observatory measurements. The CHAOS-7 model consists of a time-dependent internal field up to spherical harmonic degree 20, a static internal field which merges to the LCS-1 lithospheric field model above degree 25, a model of the magnetospheric field and its induced counterpart, estimates of Euler angles describing the alignment of satellite vector magnetometers, and magnetometer calibration parameters for CryoSat-2. Only data from dark regions satisfying strict geomagnetic quiet-time criteria (including conditions on IMF $$B_z$$ B z and $$B_y$$ B y at all latitudes) were used in the field estimation. Model parameters were estimated using an iteratively reweighted regularized least-squares procedure; regularization of the time-dependent internal field was relaxed at high spherical harmonic degree compared with previous versions of the CHAOS model. We use CHAOS-7 to investigate recent changes in the geomagnetic field, studying the evolution of the South Atlantic weak field anomaly and rapid field changes in the Pacific region since 2014. At Earth’s surface a secondary minimum of the South Atlantic Anomaly is now evident to the south west of Africa. Green’s functions relating the core–mantle boundary radial field to the surface intensity show this feature is connected with the movement and evolution of a reversed flux feature under South Africa. The continuing growth in size and weakening of the main anomaly is linked to the westward motion and gathering of reversed flux under South America. In the Pacific region at Earth’s surface between 2015 and 2018 a sign change has occurred in the second time derivative (acceleration) of the radial component of the field. This acceleration change took the form of a localized, east–west oriented, dipole. It was clearly recorded on ground, for example at the magnetic observatory at Honolulu, and was seen in Swarm observations over an extended region in the central and western Pacific. Downward continuing to the core–mantle boundary, we find this event originated in field acceleration changes at low latitudes beneath the central and western Pacific in 2017.

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Section: Treatment Of Induced Fieldsmentioning

confidence: 99%

“… has in this study been numerically computed using a finite element code (Arndt et al. 2020 ; Grayver and Kolev 2015 ; Grayver et al. 2019 ).…”

Section: Field Modellingmentioning

confidence: 99%

The CHAOS-7 geomagnetic field model and observed changes in the South Atlantic Anomaly

Finlay

Kloss

Olsen

et al. 2020

Earth Planets Space

192

206

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“…For the results referred to as "three-dimensional", a laterally heterogeneous conductivity shell of 1/4° resolution was used to account for the variations in the ocean bathymetry and thickness of sediments. For the one-dimensional case, transfer function were calculated analytically, whereas three-dimensional transfer functions were calculated numerically by solving Maxwell's equations in a spherical shell with a Finite Element code GoFEM (Arndt et al, 2020;Grayver et al, 2019;Grayver & Kolev, 2015). Figure 2 shows one-dimensional transfer functions and corresponding discrete impulse responses.…”

Section: Transfer Functions and Impulse Responsesmentioning

confidence: 99%

Time‐Domain Modeling of Three‐Dimensional Earth's and Planetary Electromagnetic Induction Effect in Ground and Satellite Observations

2021

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In practice, the complication behind modeling EM induction in geomagnetic observations is twofold. First, one needs to assume a subsurface conductivity model. A number of regional and global conductivity models exist. This study will not focus on how these models are constructed and whether they represent the subsurface accurately, even though inaccurate conductivity models may bias results. It is expected that our knowledge about the electrical structure of the subsurface will continuously improve, allowing for the construction of more accurate models at different scales (Kelbert, 2020). Second, even if a distribution of

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“…The material parameters are given in Table 2. The model was implemented in the finite element library Deal.ii [37].…”

Section: Operating Phase: Effect Of Forming-induced Residual Stressmentioning

confidence: 99%

Towards an holistic account on residual stresses in full-forward extruded rods

et al. 2021

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An holistic view is attempted towards prediction of the effect of residual stresses induced by full-forward extrusion on fatigue life of workpieces during operation. To study the effect of constitutive model on the accuracy of forming simulations, a combined nonlinear isotropic/kinematic hardening model as well as the isotropic hardening part of the same model are calibrated based on five compression-tension-compression uniaxial stress experiments. A full-forward extrusion finite element model is developed adapting both the aforementioned hardening plasticity models and the predicted residual stress states at the surface of the workpiece are compared against that of a corresponding forming experiment. Results show residual stress predictions of remarkable accuracy by the FE-models with the isotropic hardening model. The effect of residual stresses on fatigue life of the workpiece is qualitatively studied by uncoupled multiscale simulations featuring gradient crystal plasticity at the microscale. While the effective (homogenized) macroscale response indicates elastic response during a macroscopically cyclic loading, plasticity accompanying reduction of residual stresses is still present at the microscale within, e.g. grain boundaries.

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The deal.II library, Version 9.2

Abstract: This paper provides an overview of the new features of the finite element library deal.II, version 9.2.

Cited by 158 publications

References 31 publications

The CHAOS-7 geomagnetic field model and observed changes in the South Atlantic Anomaly

The CHAOS-7 geomagnetic field model and observed changes in the South Atlantic Anomaly

Time‐Domain Modeling of Three‐Dimensional Earth's and Planetary Electromagnetic Induction Effect in Ground and Satellite Observations

Towards an holistic account on residual stresses in full-forward extruded rods

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