Field Computation Research Articles

Alya toward exascale: algorithmic scalability using PSCToolkit

In this paper, we describe an upgrade of the Alya code with up-to-date parallel linear solvers capable of achieving reliability, efficiency and scalability in the computation of the pressure field at each time step of the numerical procedure for solving a Large Eddy Simulation formulation of the incompressible Navier–Stokes equations. We developed a software module in the Alya’s kernel to interface the libraries included in the current version of PSCToolkit, a framework for the iterative solution of sparse linear systems, on parallel distributed-memory computers, by Krylov methods coupled to Algebraic MultiGrid preconditioners. The Toolkit has undergone various extensions within the EoCoE-II project with the primary goal of facing the exascale challenge. Results on a realistic benchmark for airflow simulations in wind farm applications show that the PSCToolkit solvers significantly outperform the original versions of the Conjugate Gradient method available in the Alya’s kernel in terms of scalability and parallel efficiency and represent a very promising software layer to move the Alya code toward exascale.

Rapid computation of steady state acoustic fields in heterogeneous and nonlinear media using the Acoustic Field Propagator

The Acoustic Field Propagator is a method for rapidly computing steady state complex acoustic fields in homogeneous media from spatially arbitrary single frequency sources. Here, an extension of the Acoustic Field Propagator to the computation of steady state fields in arbitrary heterogeneous, absorbing and nonlinear media, using nested iterations of the Convergent Born Series and a multi-frequency Helmholtz equation expansion, will be described.

Dynamics of settling disks in a cross-flow

Physical properties of rocks depend strongly on its grain packing which is determined by the natural process involving fluid-structure interaction during deposition. Here, we address the dynamics of settling solids with different sizes in a cross-flow numerically. This is an important aspect in rock formation process. Computational fluid-structure interaction usually involves the use of body-conformed grid. For the case of solid moving in a viscous fluid, the body-conformed grid has to be reconstructed in every time iteration which can be time consuming. The so-called Immersed Boundary method can be used to eliminate this grid reconstruction process. In this study, we use the couple of Immersed Boundary and Lattice Boltzmann Method (usually termed as IBLBM). In lattice Boltzmann, one does not require solving Poisson equation for pressure and a computation of intermediate field as in the usual fractional step procedure since velocity and pressure field can be obtained from the locally solved distribution function. These advantages make IBLBM can be easily employed. In this study, we perform simulations on the dynamics of a cluster of disks with two different values of diameter in a cross-flow. We compute the velocity distribution of the disks to study the sedimentation dynamics and we compare the results with a sedimentation process in a quiescent fluid. For the solid-fluid density ratio of 5 and incoming flow Reynolds number of 12, the velocity distribution is close to the normal distribution as also observed in the case of sedimentation in quiescent fluid.

Enabling support for Octave within the FOCUS software package

FOCUS, the “Fast Object-Oriented C+ + Simulator” (https://www.egr.msu.edu/∼fultras-web/), is a free software package that enables rapid calculations of continuous-wave and transient pressure fields generated by single transducers and phased arrays. FOCUS achieves small errors in relatively short computation times through linear memory-efficient calculations with the fast nearfield method. This capability extends to quick and accurate biomedical imaging simulations within FOCUS. Moreover, FOCUS supports some nonlinear pressure calculations, such as the continuous-wave and transient Khokhlov-Zabolotskaya-Kuznetsov (KZK) equations for circular and spherical transducers. Additionally, the Angular Spectrum Approach (ASA), a frequency-domain solution to linear computational methods, ideal for large volumetric field computations, is also included within the FOCUS package. Initial success with MATLAB motivates the creation of an Octave version that replicates the core functionalities of the original FOCUS package. GNU Octave is similar to MATLAB, but unlike MATLAB, Octave is a free software. Building and compiling FOCUS in Octave required a few minor alterations due to discrepancies in syntax and function calls. The use of Octave-compiled MEX files simplified the conversion process while introducing addition memory overhead compared to rewriting C+ + code for Oct-file structuring. The performance and capabilities of FOCUS in Octave are demonstrated and discussed.

Numerical computation of magnetic field with melting heat and homogeneous-heterogeneous chemical reaction effects on oblique stagnation flow of variable viscosity micropolar Fe3O4 nanofluids

The complex micro-structural characteristics of electro-conductive sol gel materials require simultaneous consideration of magneto-hydrodynamics, micro-rheology and also physico-chemical phenomena. In this editorial, a mathematical model is therefore developed to simulate the steady-state, oblique (non-orthogonal) stagnation flow of electro-conductive micropolar magneto-nano-liquid flow impacting on an extending horizontal plane under the impact of transverse magnetic field. To capture the sophisticated physico-chemistry, the simultaneous presence of homogeneous and heterogeneous chemical reactions is considered. Viscosity depending upon temperature is taken into consideration with Reynolds’ exponential model. Tiwari-Das and Maxwell-Garnett nano-liquid models are deployed which modifies density, thermal conductivity and electrical conductivity with volume fraction of nano-sized particles.

DIC to evaluate a model composite system cracking due to CTE mismatch

Coefficient of thermal expansion (CTE) mismatch in composites under temperature variation can lead to the system cracking. In this study, Digital Image Correlation (DIC) was used to investigate this phenomenon in a model composite system (MCS) composed of a single cylindrical inclusion into a ceramic mortar matrix. Temperature variation experiments assisted by DIC were conducted to evaluate the CTE mismatch of the MCS and to observe its cracking. An analytical model was used to fit the experimental radial displacement field of the MCS, which allowed the computation of the inelastic maximum principal strain field, highlighting the radial crack pattern. The crack initiation and propagation were evaluated via damaged elements in the interface region and the computation of the average Mean Crack Opening Displacement and Surface Crack Density for crack regions. This methodology is appliable for a single inclusion MCS, with improvement perspectives for application in multiple inclusions MCS.

Efficient method for modeling large-scale arrays of optical nanoresonators based on the coupling theory of quasinormal mode.

We propose an efficient method for calculating the electromagnetic field of a large-scale array of optical nanoresonators based on the coupling theory of quasinormal mode (QNM). In this method, two approaches of the scattered-field reconstruction and stationary-phase-principle calculated plane-wave expansion are developed to obtain the regularized QNM (RQNM) in different regions. This accurate and efficient calculation of RQNM resolves the far-field divergence issue of QNMs in the QNM-coupling theory, thus enabling a rapid computation of the electromagnetic field of a large-scale array of optical nanoresonators, which is a challenging task for full-wave numerical methods. Using this method, we consider the numerical example of the radiation problem of a single point source in a large-scale periodic array of optical nanoantennas. In comparison to full-wave numerical methods, this method significantly reduces the computation time by 1∼2 orders of magnitude while maintaining accuracy. The high computational efficiency and physical intuitiveness of the method enables to clarify the impact of array size (exceeding 50 × 50 wavelengths), period and field-coupling range (far beyond the tight-binding approximation) on the optical response. The proposed method and results can provide an efficient tool and guidance for the design of large-scale arrays of optical nanoresonators.

Validating a UK Geomagnetically Induced Current Model Using Differential Magnetometer Measurements

AbstractExtreme space weather can damage ground‐based infrastructure such as power lines, railways and gas pipelines through geomagnetically induced currents (GICs). Modeling GICs requires knowledge about the source magnetic field and the electrical conductivity structure of the Earth to calculate ground electric fields during enhanced geomagnetic activity. The electric field, in combination with detailed information about the power grid topology, enable the modeling of GICs in high‐voltage (HV) power lines. Directly monitoring GICs in substations is possible with a Hall probe, but scarcely realized in the UK. Therefore we deployed the differential magnetometer method (DMM) to measure GICs at 12 sites in the UK power grid. The DMM includes the installation of two fluxgate magnetometers, one directly under a power line affected by GICs, and one as a remote site. The difference in recordings of the magnetic field at each instrument yields an estimate of the GICs in the respective power line segment via the Biot‐Savart law. We collected data across the UK in 2018–2022, monitoring HV line segments where previous research indicated high GIC risk. We recorded magnetometer data during several smaller storms that allow detailed analysis of our GIC model. For the ground electric field computations we used recent magnetotelluric (MT) measurements recorded close to the DMM sites. Our results show that there is strong agreement in both amplitude and signal shape between measured and modeled line and substation GICs when using our HV model and the realistic electric field estimates derived from MT data.

Optimal Control for a Superconducting Hybrid MagLev Transport System with Multirate Multisensors in a Smart Factory.

Recently, magnetic levitation systems have been applied and studied in various industrial fields. In particular, in-tracktype magnetic levitation conveyor systems are actively studied since they can effectively minimize electromagnetic effects in processes that require a highly clean environment. In this type of system, diverse and multiple sensors are structurally required so that the control performance of an integrated system is primarily governed by the slowest measuring sensor. This paper proposes a multisensor fusion compensator to integrate the outputs obtained from various sensors into one output with the single fastest time rate. Since the state of the system is estimated at a fast time rate, the optimal controller also guarantees fast performance and stability. The computation of electromagnetic fields and the control performance of the considered superconducting hybrid system were analyzed using a computer simulation based on finite element methods.

Nanoscale Topography of Anodic TiO2 Nanostructures Is Crucial for Cell-Surface Interactions.

Anodic titanium dioxide (TiO2) nanostructures, i.e., obtained by electrochemical anodization, have excellent control over the nanoscale morphology and have been extensively investigated in biomedical applications owing to their sub-100 nm nanoscale topography range and beneficial effects on biocompatibility and cell interactions. Herein, we obtain TiO2 nanopores (NPs) and nanotubes (NTs) with similar morphologies, namely, 15 nm diameter and 500 nm length, and investigate their characteristics and impact on stem cell adhesion. We show that the transition of TiO2 NPs to NTs occurs via a pore/wall splitting mechanism and the removal of the fluoride-rich layer. Furthermore, in contrast to the case of NPs, we observe increased cell adhesion and proliferation on nanotubes. The enhanced mesenchymal stem cell adhesion/proliferation seems to be related to a 3-fold increase in activated integrin clustering, as confirmed by immunogold labeling with β1 integrin antibody on the nanostructured layers. Moreover, computations of the electric field and surface charge density show increased values at the inner and outer sharp edges of the top surfaces of the NTs, which in turn can influence cell adhesion by increasing the bridging interactions mediated by proteins and molecules in the environment. Collectively, our results indicate that the nanoscale surface architecture of the lateral spacing topography can greatly influence stem cell adhesion on substrates for biomedical applications.

Macroparticle Collisionality in PIC solver

This paper presents a new numerical technique for the calculation of the Coulomb interaction between nearby charged particles. The efficiency of this method is demonstrated by distributing charged particles in a three dimensional sphere for an amount of particles, Npar , ranging from 1 × 105 to 1.6 × 106. Using the presented method, the computation of the mean field and Coulomb near field interaction can be performed separately.

A Modified Fixed-Point Iteration Algorithm for Magnetic Field Computation With Hysteresis Models

A Modified Fixed-Point Iteration Algorithm for Magnetic Field Computation With Hysteresis Models

A world without bees: new insights from Australia for managing sustainability in a changing climate

Insect pollination is essential for many flowering plants that underpin agriculture and food production, as well as the ecological management of terrestrial environments. Several studies report that insect pollination is responsible for over 33% of food production, worth more than 200 billion US$/year to the international economy. Traditionally, honeybees (<i>Apis mellifera</i>) and bumblebees ( Bombus terrestris</i>) are used as managed species for agricultural crop pollination. These insects are also an important model species for improving scientific understanding of bee sensory processing. With increased awareness of the value of pollination in a changing world, it is important to better understand alternative pollinators, especially how different species tolerate changing environmental conditions. This review encapsulates a decade of comparative research that was principally conducted in Australia, a uniquely placed island continent that facilitates insights into complex processes operating over evolutionary time. Using a combination of field biology, imaging and computer modelling, it has been possible to establish that changes in pollinators result in significant changes in flower colour signaling independent of plant phylogeny. This work proves that pollinator distributions act as a selective factor on the success of plants. We highlight the limitations of current knowledge about the distributions of pollinators caused by data collection constraints. We then present tangible solutions for how technological applications such as mining of information from social network sites, and the use of imaging data combined with artificial intelligence can enhance our understanding of pollinator networks to help manage sustainable food production in a changing world.

Multi-Physics Field Computation for Microwave Heating of Multi-Mobile Components Based on Transformation Optics and Implicit Function

This paper proposed a method based on transformation optics, implicit function, and level set methods to solve the challenge of multi-physics simulation of a microwave heating cavity with two different motion modes. A 3D computation model with a rotating turntable, a lifting support rod, and a sample is proposed as a detailed demonstration. Based on the theory of transformation optics, the rotating turntable is surrounded by two circles with a time-varying, inhomogeneous and anisotropy medium, and the electric field in the moving region is rotated by controlling the two mediums. The implicit function and level set methods compute the lifting motion by setting the properties of the lifting region as a function of space and time. The correctness of the proposed method is verified by comparing the proposed method’s results with the discrete position’s results, and then its accuracy is further verified by experiment. Subsequently, compared with the implicit function and level set methods only, the proposed method is more accurate. Finally, the effects of lifting motion, rotating motion and lifting motion (i.e., spiral motion) on microwave heating uniformity and heating efficiency were analyzed, respectively.

Analytical Model of 3-D Helical Solenoids for Efficient Computation of Dynamic EM Fields, Complex Inductance, and Radiation Resistance

Analytical Model of 3-D Helical Solenoids for Efficient Computation of Dynamic EM Fields, Complex Inductance, and Radiation Resistance

Indoor soundscape design of autonomous vehicles that comprehensively applies acoustic characteristics of architectural space type

According to the paradigm shift in the indoor space design of future autonomous vehicles, the indoor space of the vehicle was classified according to the purpose of use and the optimal soundscape design for each type was proposed. The vehicle selected for the measurement can be the basic type of future autonomous vehicles, a relatively wide van suitable for building space investigation, and the space target was selected as spaces for listening to music, working (meeting), and resting. Accordingly, for the soundscape design, an audible sound source was produced and used for evaluation by conducting a sound field survey and computer simulation inside the vehicle. The indoor soundscape of the vehicle was evaluated by providing binaural sound source in the auditory test environment. The evaluation indicators were selected based on the indoor soundscape parameters in the architectural spaces such as concert halls and office buildings.

Frequency Effect on Electromagnetic States Emitted from High Voltage Overhead Power Lines and Busbar Substation

Electrical power systems represent an immense source of electromagnetic radiation spanning a wide frequency range, encompassing low-frequency, transient states, and high-frequency emissions. The radiation poses a significant self-pollution challenge for electric and electronic devices situated in close proximity to these systems. The present article aims to address this research, and provides a comprehensive review of the electromagnetic effects and pollution at differences frequency’s ranges encompassing power systems network. In the context of the low-frequency range, the computation of electric and magnetic fields is conducted using quasi-static principles. To validate the behavior at high frequencies due to power line currents, Schelkunoff’s approach is employed. Additionally, transient electromagnetic fields are analyzed using an exact analytical method. The results of computer simulations are compared with previously published and measured data for low-frequency regime and transient overvoltage conditions, verifying their consistency. Additionally, high-frequency results are presented and corroborated through the utilization of a numerical electromagnetic code (NEC-4). These analyses underscore the valuable role of computer-based calculations in examining the electromagnetic environment of power system networks.

Dynamical correlations in simple disorder and complex disorder liquids

Liquids in equilibrium exhibit two types of disorder, simple and complex. Typical simple disorder liquid is liquid nitrogen, or weakly polar liquids. Complex liquids concern those who can form long lived local assemblies, and cover a large range from water to some soft matter and biological liquids. The existence of such structures leaves characteric features upon the atom-atom correlation functions, concerning both atoms which directly participate to these structures and those who do not. The question we ask here is: do these features have also characteristic dynamical aspects, which could be tracked through dynamical correlation functions? Herein, we compare the van Hove function, intermediate scattering function and the dynamical structure factor, for both types of liquids, using force field models and computer simulations. The calculations reveal the paradoxical fact that neighbouring atom correlations for simple disorder liquids relax slower than that for complex disorder liquids, while prepeak features typical of complex disorder liquids relax even slower. This is an indication of the existence of fast kinetic self-assembly processes in complex disorder liquids, while the lifetime of such assemblies itself is quite slow. This is further confirmed by the existence of a very low-k dynamical pre-peak uncovered in the case of water and ethanol.

A fast natural convection algorithm based on dividing fluid development stages

We develop a numerical method for fast computation of natural convection, which proposes a new dimensionless number (Fs) to characterize the degree of influence of convection on the temperature field in the flow field and determines the moment of pause for the updating of the flow field by designing judgmental conditions to delineate the stage of development of the flow field, where the loosely coupled computation is turned on to improve the efficiency of the transient temperature field computation. The accuracy of the algorithm is verified using an experimental case of a standard model of natural convection, and the robustness of the algorithm is verified by specifying different monitoring boundaries and setting different numbers of monitoring steps, and the algorithm is applied to a model of natural convection in the equipment in the cabin of the vehicle. The results show that the computational speed is increased by 8.8, 6.4, and 3.5 times after turning on the loosely coupled computation in the first, second, and third development phases, respectively, and the average errors of the monitored point temperatures are 0.7%, 0.1%, and 0.028%, respectively. By monitoring the change in Fs during the loosely coupled computation, the error of the first development stage under the variable boundary is reduced by 95.1%, and the computation speed is 2.2 times faster than that of the second development stage.

An Isogeometric Over-Deterministic Method (IG-ODM) to Determine Elastic Stress Intensity Factor (SIF) and T-Stress

In order to examine the significance of Stress Intensity Factor and T-stress (K-T parameters) in modeling pressure-cracked structures, we propose a novel method known as the Isogeometric Over-Deterministic Method IG-ODM. IG-ODM utilizes the computation of stress and displacement fields through Extended Isogeometric Analysis to improve the geometry and enhance the crack. Subsequently, these results are incorporated into the Williams expression, resulting in a set of deterministic equations that can be solved using a common solving method; this particular combination has never been attempted before. IG-ODM enables the computation of stress intensity factor SIF, T-stress, and higher-order parameters in the Williams expansion. To validate the effectiveness of this method, we conducted tests on a single-edge uniaxial-stress-cracked plate and a central uniaxial-stress-cracked plate. The results showed an error ranging from 0.06% to 2%. The obtained results demonstrate accuracy and satisfaction when compared to existing findings.