3,083 research outputs found
Simulation of high temperature superconductors and experimental validation
In this work, we present a parallel, fully-distributed finite element numerical framework to simulate the low-frequency electromagnetic behaviour of superconducting devices, which efficiently exploits high performance computing platforms. We select the so-called H-formulation, which uses the magnetic field as a state variable. Nédélec elements (of arbitrary order) are required for an accurate approximation of the H-formulation for modelling electromagnetic fields along interfaces between regions with high contrast medium properties. An h-adaptive mesh refinement technique customized for Nédélec elements leads to a structured fine mesh in areas of interest whereas a smart coarsening is obtained in other regions. The composition of a tailored, robust, parallel nonlinear solver completes the exposition of the developed tools to tackle the problem. First, a comparison against experimental data is performed to show the availability of the finite element approximation to model the physical phenomena. Then, a selected state-of-the-art 3D benchmark is reproduced, focusing on the parallel performance of the algorithms.Peer ReviewedPostprint (author's final draft
Optimization of the Superconducting Linear Magnetic Bearing of a Maglev Vehicle
Considering the need for cost/performance prediction and optimization of
superconducting maglev vehicles, we develop and validate here a 3D finite
element model to simulate superconducting linear magnetic bearings. Then we
reduce the 3D model to a 2D model in order to decrease the computing time. This
allows us to perform in a reasonable time a stochastic optimization considering
the superconductor properties and the vehicle operation. We look for the
permanent magnet guideway geometry that minimizes the cost and maximizes the
lateral force during a displacement sequence, with a constraint on the minimum
levitation force. The displacement sequence reproduces a regular maglev vehicle
operation with both vertical and lateral movements. For the sake of comparison,
our reference is the SupraTrans prototype bearing. The results of the
optimization suggest that the bearing cost could be substantially reduced,
while keeping the same performances as the initial design. Alternatively, the
performances could be significantly improved for the same original cost
Bernoulli Potential, Hall Constant and Cooper Pairs Effective Masses in Disordered BCS Superconductors
It is analyzed what fundamental new information for the properties of the
superconductors can be obtained by systematic investigation of the Bernoulli
effect. It is shown that it is a tool to determine the effective mass of Cooper
pairs, the volume density of charge carriers, the temperature dependence of the
penetration depth and condensation energy. The theoretical results for
disordered and anisotropic gap superconductors are systematized for this aim.
For clean-anisotropic-gap superconductors is presented a simple derivation for
the temperature dependence of the penetration depthComment: 13 pages, 3 figures, LaTeX 2e, New figure and reference
Self-assembled nanorods in YBCO matrix : a computational study of their effects on critical current anisotropy
In order to understand how the doping with self-assembled nanorods of different sizes and concentrations as well as applied magnetic fields affect the critical current anisotropy in YBa2Cu3O7-x (YBCO) thin films close to YBCO c-axis, we present an extensive and systematic computational study done by molecular dynamics simulation. The simulations are also used to understand experimentally measured J(c)(theta) curves for BaHfO3, BaZrO3 and BaSnO3 doped YBCO thin films with the help of nanorod parameters obtained from transmission electron microscopy measurements. Our simulations reveal that the relation between applied and matching field plays a crucial role in the formation of J(c)(theta)-peak around YBCO c-axis (c-peak) due to vortex-vortex interactions. We also find how different concentrations of different size nanorods effect the shape of the c-peak and explain how different features, such as double c-peak structures, arise. In addition to this, we have quantitatively explained that, even in an ideal superconductor, the overdoping of nanorods results in decrease of the critical current. Our results can be widely used to understand and predict the critical current anisotropy of YBCO thin films to improve and develop new pinscapes for various transport applications
3D Modeling of the Magnetization of Superconducting Rectangular-Based Bulks and Tape Stacks
In recent years, numerical models have become popular and powerful tools to
investigate the electromagnetic behavior of superconductors. One domain where
this advances are most necessary is the 3D modeling of the electromagnetic
behavior of superconductors. For this purpose, a benchmark problem consisting
of superconducting cube subjected to an AC magnetic field perpendicular to one
of its faces has been recently defined and successfully solved. In this work, a
situation more relevant for applications is investigated: a superconducting
parallelepiped bulk with the magnetic field parallel to two of its faces and
making an angle with the other one without and with a further constraint on the
possible directions of the current. The latter constraint can be used to model
the magnetization of a stack of high-temperature superconductor tapes, which
are electrically insulated in one direction. For the present study three
different numerical approaches are used: the Minimum Electro-Magnetic Entropy
Production (MEMEP) method, the -formulation of Maxwell's equations and the
Volume Integral Method (VIM) for 3D eddy currents computation. The results in
terms of current density profiles and energy dissipation are compared, and the
differences in the two situations of unconstrained and constrained current flow
are pointed out. In addition, various technical issues related to the 3D
modeling of superconductors are discussed and information about the
computational effort required by each model is provided. This works constitutes
a concrete result of the collaborative effort taking place within the HTS
numerical modeling community and will hopefully serve as a stepping stone for
future joint investigations
Proposal of a novel design for linear superconducting motor using 2G tape stacks
This paper presents a new design for a su-
perconducting linear motor (SLM). This SLM uses stacks
of second-generation (2G) superconducting tapes, which
are responsible for replacing yttrium barium copper oxide
bulks. The proposed SLM may operate as a synchronous
motor or as a hysteresis motor, depending on the load
force magnitude. A small-scale linear machine prototype
with 2G stacks was constructed and tested to investigate
the proposed SLM topology. The stator traveling magnetic
field wave was represented by several Nd-Fe-B permanent
magnets. A relative movement was produced between the
stator and the stack, and the force was measured along the
displacement. This system was also simulated by the finite
element method, in order to calculate the induced currents
in the stack and determine the electromagnetic force. The
H-formulation was used to solve the problem, and a power
law relation was applied to take into account the intrin-
sically nonlinearity of the superconductor. The simulated
and measured results were in accordance. Simulated re-
sults were extrapolated, proving to be an interesting tool to
scale up the motor in future projects. The proposed motor
presented an estimated force density of almost 500 N/kg,
which is much higher than any linear motor.This work was supported in part by the following agencies: CNPq/CAPES/INERGE, CNPq—Ci ˆ encias sem Fronteiras, FAPERJ, Catalan Government 2014- SGR-753, CONSOLIDER Excellence Network MAT2014-56063-C2-1-R and MAT2015-68994-REDC, Eurofusion EU COST ACTIONS MP1201/ MP1014/PPPT-WPMAG 2014, EUROTAPES FP7-NMP-Large-2011- 280432, FORTISSIMO FP7-2013-ICT-609029, and Spanish Govern- ment Agencies—Severo Ochoa Programme Centres of Excellence in R&D. (Corresponding author: Guilherme G. Sotelo.
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