3D Code Research Articles

Theoretical studies of equilibrium beta limit in LHD plasmas

This study deals with the equilibrium beta limit for high-beta plasmas of the Large Helical Device using a 3D equilibrium calculation code, HINT, which is an initial value solver based on the relaxation method without an assumption of nested flux surfaces. For the finite beta equilibrium, due to the nonlinear 3D equilibrium response, the flux surface breaking begins, and the magnetic field line becomes stochastic in the peripheral region. However, although the magnetic axis shifts until the conventional theoretical beta limit, the separatrix limiting the equilibrium does not appear in the plasma core. For the high beta equilibrium, breaking of the force balance begins in the strongly stochastized region. To keep the force balance in that region, the pressure gradient decreases and the fixed profile is relaxed. As a result, the volume averaged beta, which is equivalent to the plasma stored energy, saturates, although the peak beta increases. The beta value, where the force balance begins breaking in the inside of the stochastic region, is proposed as a new index of the equilibrium beta limit for the typical heliotron-type stellarator. According to this new index of the equilibrium beta limit, the achieved beta value in the experiment of the Large Helical Device is still lower than the equilibrium beta limit. This suggests that if the heating power can be increased, the achieved beta value may still increase.

Two-dimensional study of charring ablative materials using finite volume method

Numerical simulation of charring ablative materials using finite volume (F.V) method is presented in this paper and a new modeling approach for pyrolysis gas mass flux production for multi-dimensional analyses is proposed. Pyrolysis gas mass flux produced in carbon-phenolic ablation process is solved by a user defined transport equation. User defined functions (UDFs) are developed in FLUENT 6.3 to consider the equilibrium surface thermochemistry (EST) model of carbon ablation in air including the diffusion and sublimation. Source terms of energy and pyrolysis gas equations, temperature-dependent boundary conditions, material properties variations and wall recession are all implemented in these UDFs. Also, Spring-based smoothing method is utilized as the grid motion technique. Furthermore, one-dimensional (1D) thermal response of the stagnation point is investigated using a finite difference (F.D) FORTRAN code. To ensure the accuracy of the proposed multi-dimensional modeling, a comparison is made between the published data and the computational results achieved by 2D F.V method at the stagnation point and the 1D F.D outcome. It is found that the predictions for the centerline temperature rise in the 2D analysis is generally higher than those of the 1D code. Also, the maximum ablation mass flux and the maximum recession are smaller compared to 1D predictions. This approach provides an in-depth study of a charring material under heat loads in situations where the classical 1D approach fails, e.g. anisotropic materials, sharp geometries and insulator-backup material interface.

Evaluation Performance of Two-Dimensional Multi-Diagonal Code Using Polarization and Wavelength of OCDMA System

In this paper, a new encoder/decoder technique has employed two orthogonal polarization states (vertical and horizontal) of a two-dimensional optical code, which combined polarization and wavelength scheme (p/w). This technique employed in order to increase the number of users in the FTTH network. In addition, Optical Fiber Systems (OFS) and Free Space Optics (FSO) scenarios were utilized with different Spectral Amplitude Coding Optical Code Division Multiple Access (SAC-OCDMA) codes. The FTTH network based on incoherent SAC-OCDMA is tested by using the One and Two Dimensional Multi-Diagonal (1D-MD, 2D-MD) codes and 1D and 2D Zero Cross Correlation (ZCC) codes. The results show that the number of the total supported homes for the 2D codes is doubled as a comparison with 1D codes. As well as, the simulation results show the performance of MD code is better presented than ZCC in both OFS and FSO scenarios

SlicerArduino: A Bridge between Medical Imaging Platform and Microcontroller.

Interaction between medical image platform and external environment is a desirable feature in several clinical, research, and educational scenarios. In this work, the integration between 3D Slicer package and Arduino board is introduced, enabling a simple and useful communication between the two software/hardware platforms. The open source extension, programmed in Python language, manages the connection process and offers a communication layer accessible from any point of the medical image suite infrastructure. Deep integration with 3D Slicer code environment is provided and a basic input–output mechanism accessible via GUI is also made available. To test the proposed extension, two exemplary use cases were implemented: (1) INPUT data to 3D Slicer, to navigate on basis of data detected by a distance sensor connected to the board, and (2) OUTPUT data from 3D Slicer, to control a servomotor on the basis of data computed through image process procedures. Both goals were achieved and quasi-real-time control was obtained without any lag or freeze, thus boosting the integration between 3D Slicer and Arduino. This integration can be easily obtained through the execution of few lines of Python code. In conclusion, SlicerArduino proved to be suitable for fast prototyping, basic input–output interaction, and educational purposes. The extension is not intended for mission-critical clinical tasks.

SOL-KiT—Fully implicit code for kinetic simulation of parallel electron transport in the tokamak Scrape-Off Layer

Here we present a new code for modelling electron kinetics in the tokamak Scrape-Off Layer (SOL). SOL-KiT (Scrape-Off Layer Kinetic Transport) is a fully implicit 1D code with kinetic (or fluid) electrons, fluid (or stationary) ions, and diffusive neutrals. The code is designed for fundamental exploration of non-local physics in the SOL and utilizes an arbitrary degree Legendre polynomial decomposition of the electron distribution function, treating both electron–ion and electron–atom collisions. We present a novel method for ensuring particle and energy conservation in inelastic and superelastic collisions, as well as the first full treatment of the logical boundary condition in the Legendre polynomial formalism. To our knowledge, SOL-KiT is the first fully implicit arbitrary degree harmonic kinetic code, offering a conservative and self-consistent approach to fluid–kinetic comparison with its integrated fluid electron mode. In this paper we give the model equations and their discretizations, as well as showing the results of a number of verification/benchmarking simulations. Program summaryProgram Title: SOL-KiTCPC Library link to program files:http://dx.doi.org/10.17632/7p44sdfnnp.1Licencing provisions: GNU GPLv3Programming language: Fortran 90Nature of problem:Fluid models of parallel transport in the Scrape-Off Layer (SOL) fail to account for the fact that the electron distribution function is often far from a Maxwellian, and kinetic effects have been linked to discrepancies between experiment and fluid modelling[1]. A kinetic treatment of electrons in the SOL requires detailed accounting of collisional processes, especially those with neutral particles, as well as a proper implementation of the logical boundary condition at the material surface[2]. Furthermore, the ability to identify differences between fluid and kinetic modelling using self-consistent comparison is desirable.Solution method: Electrons are modelled either as a fluid, or kinetically, maintaining self-consistency between models. All equations are solved using finite difference and the implicit Euler method, with fixed-point iteration. The kinetic approach is based on solving the Vlasov–Fokker–Planck–Boltzmann equation, decomposed in Legendre polynomials. Equations for the harmonics (or electron fluid equations) are solved alongside fluid equations for the ions, Ampère–Maxwell’s law for the electric field, as well as a diffusive–reactive Collisional-Radiative model for the evolution of hydrogenic atomic states. Each individual operator is built into a matrix, combined with all other operators, and the matrix equation arising from the Euler method is solved using the PETSc library, with MPI parallelization.Additional comments:This article presents the physical and numerical outline of the code, and is accompanied by html documentation, a small test suite based on benchmarking runs presented below, as well as instructions and means for compiling and executing SOL-KiT. Special focus in the article is given to the novel numerical and model aspects in the greater context of the developed software.

Detecting Topological Order at Finite Temperature Using Entanglement Negativity.

We propose a diagnostic for finite temperature topological order using "topological entanglement negativity," the long-range component of a mixed-state entanglement measure. As a demonstration, we study the toric code model in d spatial dimensions for d=2,3,4, and find that when topological order survives thermal fluctuations, it possesses a nonzero topological entanglement negativity, whose value is equal to the topological entanglement entropy at zero temperature. Furthermore, we show that the Gibbs state of 2D and 3D toric code at any nonzero temperature, and that of 4D toric code above a certain critical temperature, can be expressed as a convex combination of short-range entangled pure states, consistent with the absence of topological order.

Obtaining the Similarity Value of Human Body Motions Through Their Sub Motions

This article proposes a method of measuring human body motions by using the similarity measure through a 3D chain code. The method of deriving pauses in human body motions and splitting a motion into sub motions by pauses are also introduced. The requirements of sub motions to represent the similar parts between two motions are clearly explained. The pause waveform of basic human body motions is obtained and is used to split motions into sub motions. Two options of the proposed method are evaluated by experiments. The tests for statistical significance are used in evaluating the effectiveness of the method. The result shows that the first option of the method is effective in enhancing the performing time. It is shown that the proposed method is effective in measuring the similarity of human body motions.

Multi-View Polarimetric Scattering Cloud Tomography and Retrieval of Droplet Size

Tomography aims to recover a three-dimensional (3D) density map of a medium or an object. In medical imaging, it is extensively used for diagnostics via X-ray computed tomography (CT). We define and derive a tomography of cloud droplet distributions via passive remote sensing. We use multi-view polarimetric images to fit a 3D polarized radiative transfer (RT) forward model. Our motivation is 3D volumetric probing of vertically-developed convectively-driven clouds that are ill-served by current methods in operational passive remote sensing. Current techniques are based on strictly 1D RT modeling and applied to a single cloudy pixel, where cloud geometry defaults to that of a plane-parallel slab. Incident unpolarized sunlight, once scattered by cloud-droplets, changes its polarization state according to droplet size. Therefore, polarimetric measurements in the rainbow and glory angular regions can be used to infer the droplet size distribution. This work defines and derives a framework for a full 3D tomography of cloud droplets for both their mass concentration in space and their distribution across a range of sizes. This 3D retrieval of key microphysical properties is made tractable by our novel approach that involves a restructuring and differentiation of an open-source polarized 3D RT code to accommodate a special two-step optimization technique. Physically-realistic synthetic clouds are used to demonstrate the methodology with rigorous uncertainty quantification.

On the Velocity Drift between Ions in the Solar Atmosphere

Abstract The solar atmosphere is composed of many species, which are populated at different ionization and excitation levels. The upper chromosphere, transition region, and corona are nearly collisionless. Consequently, slippage between, for instance, ions and neutral particles, or interactions between separate species, may play important roles. We have developed a 3D MFMS numerical code (Ebysus) to investigate such effects. Ebysus is capable of treating species (e.g., hydrogen, helium, etc.) and fluids (neutrals, excited and ionized elements) separately, including nonequilibrium ionization, momentum exchange, radiation, thermal conduction, and other complex processes in the solar atmosphere. Treating different species as different fluids leads to drifts between different ions and an electric field that couples these motions. The coupling for two ionized fluids can lead to an anti-phase rotational motion between them. Different ionized species and momentum exchange can dissipate this velocity drift, i.e., convert wave kinetic energy into thermal energy. High-frequency Alfvén waves driven by, e.g., reconnection thought to occur in the solar atmosphere, can drive such multi-ion velocity drifts.

AstroSeis: A 3D Boundary Element Modeling Code for Seismic Wavefields in Irregular Asteroids and Bodies

Abstract We developed a 3D elastic boundary element method computer code, called AstroSeis, to model seismic wavefields in a body with an arbitrary shape, such as an asteroid. Besides the AstroSeis can handle arbitrary surface topography, it can deal with a liquid core in an asteroid model. Both the solid and liquid domains are homogenous in our current code. For seismic sources, we can use single forces or moment tensors. The AstroSeis is implemented in the frequency domain, and the frequency-dependent Q can be readily incorporated. The code is in MATLAB (see Data and Resources), and it is straightforward to set up the model to run the code. The frequency-domain calculation is advantageous to study the long-term elastic response of a celestial body due to a cyclic force, such as the tidal force, with no numerical dispersion issue suffered by many other methods requiring volume meshing. Our AstroSeis has been benchmarked with other methods such as normal-mode summation and the direct solution method. This open-source AstroSeis will be a useful tool to study the interior and surface processes of asteroids.

RF plasma simulations using the TOMATOR 1D code: a case study for TCV helium ECRH plasmas

The 1-dimensional reaction-diffusion-convection code TOMATOR-1D describes plasma production by RF waves inside a tokamak using the Braginskii continuity and heat balance equations. The model simulates self-consistent radial density and temperature profiles for magnetised plasma mixtures of hydrogen and helium. The model reproduces the density profiles of X2 electron cyclotron resonance heating (ECRH) plasmas on TCV and proposes a Bohm-like poloidal magnetic field dependent scaling for anomalous diffusion and a convection scaling that results from drifts in the toroidal magnetic field configuration. A relation is proposed between the anomalous diffusion and the outward convection in toroidal plasmas. It is found that the EC absorption efficiency decreases at higher power, which is understood from the acceleration of electrons beyond the optimal energy for the electron impact ionisation of helium. A dramatic increase of the absorption efficiency is seen at intermediate vertical magnetic field values of which results in the highest density plasmas. Losses along the field lines in the vertical direction become dominant at higher fields which effectively reduces the plasma density in these discharges. To arrive at predictive capabilities towards ECRH plasmas on JT-60SA and ITER, the proposed scalings, subsuming dependencies on the torus major radius and the toroidal field strength, need to be validated in a multi-machine study.

Geometry definition and performance assessment of Tesla turbines for ORC

The Tesla turbine - also known as friction, viscous or bladeless turbine - is a peculiar expander, which generates power through viscous entrainment. In the last years, it has gained a renewed appeal due to the rising of distributed power generation applications. Indeed, this expander is not suitable to large size power generation, but it could become a breakthrough technology in the low power ranges, due to its characteristics of low cost and reliability. The current study presents a design approach to the Tesla turbine, applied to organic working fluids (R1233zd(E), R245fa, R1234yf, n-Hexane). Three fundamental geometric parameters are identified (rotor channel width/inlet diameter ratio, rotor outlet/inlet diameter ratio, throat width ratio) and their effects on the performance are analysed. The geometry of the turbine has been defined and the assessment of the performance potential is run, applying a 2D code for the viscous flow solution, considering real compressible fluid properties. For all the investigated working fluids, an efficiency higher than 60% has been achieved, with the defined geometry, under suitable thermo fluid-dynamic conditions.

Simulation and process optimization for laser marking of submillimetre rasterizing 2D code on stainless steel

The simulation and process optimization for laser marking of submillimetre rasterizing 2D code on stainless steel are investigated. For 50CrVA stainless steel, the temperature field of material during laser marking is obtained by numerical modeling. The results show that temperature change in the depth direction and oxidation degree of laser radiation region are the fundamental reasons for the contrast of 2D code, but the temperature change occurs in the radius direction for the print growth. The threshold of laser average power and [Formula: see text] frequency for an identifiable submillimetre 2D code are, respectively, 3.0 W and 100 KHz, which matches the simulation well within normal operating conditions. It is also found that an increase of the pulses number effectively improves the contrast and the appearance consistency of modules in DM code. Besides, corrosion tests show that the corrosion resistance of submillimetre 2D code is greatly improved by covering a layer of transparent polyurethane coating. Finally, a sample of submillimetre 2D code marked on cylindrical tool with diameter of 1 mm is obtained. In conclusion, the method could obtain submillimetre code with high reading quality and corrosion resistance by minimizing the characteristic edge over-burn effects, which provides theoretical basis and experimental method for identification of small parts.

Multi-component optimization of a vertical inline pump based on multi-objective pso and artificial neural network

The vertical inline pump is a single-stage single-suction centrifugal pump with a curved inlet pipe before the impeller, which is widely used in where the constraint is installation space. In this paper, with the objective functions of efficiencies at 0.5Qd, 1.0Qd, and 1.5Qd, a multi-objective optimization on inlet pipe and impeller was proposed to broaden the efficient operating period of a vertical inline pump. Two 5th order Bezier curves were adopted to fit the shape of the mid curve of the inlet pipe and the trend of the blade angle of the impeller. Fourteen design variables were selected after the data-mining process. 300 sample cases were generated using Latin hypercube sampling (LHS), and they were solved by 3D RANS code to obtain the objective functions. The feed-forward artificial neural network with a hidden layer and an output layer was adopted to fit the two objective functions and the 14 design variables. The Pareto frontiers were generated for the three objectives using multi-objective particle swarm optimization (MOPSO), and three different configurations on the Pareto front are selected for detailed study by computational fluid dynamics (CFD). The results showed that the profile of the inlet pipe and the blade have a dramatic impact on the performance of the vertical inline pump. The Pareto frontiers reported that the performance under the overload condition usually keeps stable when the nominal efficiency is lower than 82 %, or the part-load efficiency is lower than 62 %, and it will decrease rapidly after that. After optimization, the improvement of efficiencies at the part-load condition and nominal condition of the picked case were 9.65 % and 7.95 %, respectively.

Scattering of ion cyclotron range of frequency waves by filaments and ELMs

The scattering of ion cyclotron range of frequency (ICRF) waves by filaments and ELMs has been comprehensively studied via modeling. The influence of filaments on the propagation of ICRF waves is studied by building a 2D COMSOL model which solves the wave equation. It is benchmarked against the Mie scattering theoretical model. Cases either with perfect matching layer boundary condition or with poloidal periodic boundary condition are considered. Parameter scans, including the filament density, the filament radius, the number of filaments as well as the distance between filaments, are performed. Then, the influence of ELMs on the propagation of ICRF waves in realistic geometry is studied by importing density distributions calculated by 3D non-linear MHD code JOREK into the 3D antenna code RAPLICASOL. The evolution of density and wave fields during an ELM is analyzed for cases with a low and high scrape-off layer density, respectively. Both the COMSOL simulation and the realistic simulation with JOREK and RAPLICASOL show that the wave fields and Poynting flux can be significantly and globally modified by the ELM filaments. Due to the mutual influence of many density filaments, radially elongated and poloidally distributed stripe structures of the wave fields develop, leading to poloidally inhomogeneous wave fields. Furthermore, the influence of ELMs on the antenna power and antenna coupling resistance is investigated with experimental results in ASDEX Upgrade.

Tridimensional Long-Term Finite Element Analysis of Reinforced Concrete Structures with Rate-Type Creep Approach

This paper presents a general procedure for a rate-type creep analysis (based on the use of the continuous retardation spectrum) which avoids the need of recalculating the Kelvin chain stiffness elements at each time step. In this procedure are incorporated three different creep constitutive relations, two recommended by national codes such as the ACI (North-American) and EC2 (European) building codes and one by the RILEM research association. The approximate expressions of the different creep functions with the corresponding Dirichlet series are generated using the continuous retardation spectrum approach based on the Post–Widder formula. The proposed rate-type formulation is implemented into a 3D finite element code and applied to study the long-term deflections of a prestressed concrete bridge built in Romania, which crosses a wide artificial channel that connects the Danube river to the port of Constanta in the Black Sea.

Projected global stability of high beta MAST-U spherical tokamak plasmas

Assessment of the limits of stability of tokamak plasmas is key to operation in high fusion performance ranges without disruption of the plasma current. Projected equilibria have been generated for the MAST-U spherical tokamak experiment, an upgrade of the previous MAST device, in order to prepare for operation. These equilibria are scanned in pressure and current profiles, and assessed with the DCON and MARS-F stability codes to find the so-called ‘no-wall’ beta limit, above which resistive wall mode instabilities can be expected in the absence of other stabilising effects. The no-wall limit was generally found to increase as plasma internal inductance increased. The equilibria are also assessed for the ‘with-wall’ limit, theoretically the highest achievable performance point, again with the DCON and MARS-F codes, including different approximate axisymmetric walls, and with the VALEN code which includes a 3D model of the surrounding conducting structure. Similar limits were found, despite the difference between the 2D and 3D codes in the treatment of the wall. Conducting passive stabilisation plates, which were newly installed in MAST-U, are in a region of significant mode perturbation when the plasma βN is sufficiently high and eddy currents are driven in these structures. Due to the increased stabilising effect of the wall in MAST-U vs. MAST, a significant gap exists between the approximate no-wall limits of βN/li = 6.71 and 7.13, found from DCON and MARS-F respectively, and the with-wall limits of βN/li = 8.23 and 8.53 for the equilibrium profiles analysed in this study. This opens a region of high beta operating space in MAST-U for potentially stable operation if non-ideal effects or active control can stabilise the resistive wall mode.

The GAPS programme at TNG

Context. Exoplanets orbiting very close to their parent star are strongly irradiated. This can lead the upper atmospheric layers to expand and evaporate into space. The metastable helium (He I) triplet at 1083.3 nm has recently been shown to be a powerful diagnostic to probe extended and escaping exoplanetary atmospheres. Aims. We perform high-resolution transmission spectroscopy of the transiting hot Jupiter HD 189733 b with the GIARPS (GIANO-B + HARPS-N) observing mode of the Telescopio Nazionale Galileo, taking advantage of the simultaneous optical+near infrared spectral coverage to detect He I in the planet’s extended atmosphere and to gauge the impact of stellar magnetic activity on the planetary absorption signal. Methods. Observations were performed during five transit events of HD 189733 b. By comparison of the in-transit and out-of-transit GIANO-B observations, we computed high-resolution transmission spectra. We then used them to perform equivalent width measurements and carry out light-curves analyses in order to consistently gauge the excess in-transit absorption in correspondence with the He I triplet. Results. We spectrally resolve the He I triplet and detect an absorption signal during all five transits. The mean in-transit absorption depth amounts to 0.75 ± 0.03% (25σ) in the core of the strongest helium triplet component. We detect night-to-night variations in the He I absorption signal likely due to the transit events occurring in the presence of stellar surface inhomogeneities. We evaluate the impact of stellar-activity pseudo-signals on the true planetary absorption using a comparative analysis of the He I 1083.3 nm (in the near-infrared) and the Hα (in the visible) lines. Using a 3D atmospheric code, we interpret the time series of the He I absorption lines in the three nights not affected by stellar contamination, which exhibit a mean in-transit absorption depth of 0.77 ± 0.04% (19σ) in full agreement with the one derived from the full dataset. In agreement with previous results, our simulations suggest that the helium layers only fill part of the Roche lobe. Observations can be explained with a thermosphere heated to ~12 000 K, expanding up to ~1.2 planetary radii, and losing ~1 g s−1 of metastable helium. Conclusions. Our results reinforce the importance of simultaneous optical plus near infrared monitoring when performing high-resolution transmission spectroscopy of the extended and escaping atmospheres of hot planets in the presence of stellar activity.

Effects of the Circuit Arrangement on the Thermal Performance of Double U-Tube Ground Heat Exchangers

Given that the issue of variations in geometrical parameters of the borehole heat exchanger (BHE) revolves around the phenomenon of thermal resistance, a thorough understanding of these parameters is beneficial in enhancing thermal performance of BHEs. The present study seeks to identify relative changes in the thermal performance of double U-tube BHEs triggered by alterations in circuit arrangements, as well as the shank spacing and the borehole length. The thermal performance of double U-tube BHEs with different configurations is comprehensively analyzed through a 3D transient numerical code developed by means of the finite element method. The sensitivity of each circuit configuration in terms of the thermal performance to variations of the borehole length and shank spacing is investigated. The impact of the thermal interference between flowing legs, namely thermal short-circuiting, on parameters affecting the borehole thermal resistance is addressed. Furthermore, the energy exchange characteristics for different circuit configurations are quantified by introducing the thermal effectiveness coefficient. The results indicate that the borehole length is more influential than shank spacing in increasing the discrepancy between thermal performances of different circuit configurations. It is shown that deviation of the averaged-over-the-depth mean fluid temperature from the arithmetic mean of the inlet and outlet temperatures is more critical for lower shank spacings and higher borehole lengths.

Dynamical ℓ -boson stars: Generic stability and evidence for nonspherical solutions

$\ell$-boson stars are static, spherical, multi-field self-gravitating solitons. They are asymptotically flat, finite energy solutions of Einstein's gravity minimally coupled to an odd number of massive, complex scalar fields. A previous study assessed the stability of $\ell$-boson stars under spherical perturbations, finding that there are both stable and unstable branches of solutions, as for single-field boson stars ($\ell=0$). In this work we probe the stability of $\ell$-boson stars against non-spherical perturbations by performing numerical evolutions of the Einstein-Klein-Gordon system, with a 3D code. For the timescales explored, the $\ell$-boson stars belonging to the spherical stable branch do not exhibit measurable growing modes. We find, however, evidence of zero modes; that is, non-spherical perturbations that neither grow nor decay. This suggests the branching off towards a larger family of equilibrium solutions: we conjecture that $\ell$-boson stars are the enhanced isometry point of a larger family of static (and possibly stationary), non-spherical multi-field self-gravitating solitons.