Multi-physics Capabilities Research Articles

WITHDRAWN: Design of partial discharge measurement model for internal cavities in high voltage power cables

The phenomenon of partial discharge (PD) in power cables can result in insulation degradation and eventual failure if left undetected and unaddressed. As a result, the measurement of PD is key to evaluating the performance of insulation diagnostics in the power cables. This paper presents a PD measurement model for internal cavities in XLPE insulating material for medium voltage power cables. The proposed PD measurement model is designed using the COMSOL Multiphysics software as a finite element analysis (FEA) tool added to MATLAB environment, specifically tailored for power cables. The proposed PD measurement model uses the multiphysics capabilities of COMSOL to simulate the electrical discharges behavior within power cables. The model considers factors such as cable geometry, material properties, cavity size, applied voltage and numerical conditions to accurately capture the PD characteristics. Distributions of both electric potential and electric field were studied before and after occurrence of PD across the internal cavity. According to the results, it has been noticed that the discharge magnitude mainly depends on the cavity diameter; as increasing cavity diameter leads to increasing the magnitude of the measured PD. Moreover, the leakage current magnitude is recorded during the PD event period. The proposed model also enables the evaluation of different cable designs, insulation materials, and operating conditions to optimize cable performance and mitigate PD risks.

Application of Modelica/TRANSFORM to system modeling of the molten salt reactor experiment

The molten salt reactor (MSR), being a liquid-fueled reactor, exhibits a strong coupling between neutronics and thermal hydraulics originating from the simultaneous utilization of the fuel as the coolant. Analysis of the dynamic behavior of MSRs thus necessitates the use of coupled multiphysics tools. This work leverages the multiphysics capabilities of the Modelica-based, open-source component library Transient Simulation Framework of Reconfigurable Modules (TRANSFORM) and demonstrates its ability to simulate the behavior of an MSR with the focus on modeling the Molten Salt Reactor Experiment (MSRE). The model employs 1D thermal-hydraulic components with a coarse radial and axial discretization of the active core region approximating the design of the MSRE. The power generation within each node is determined by neutron point kinetics which are modified to account for the effects of fuel circulation. Using the developed model, neutronic and thermal-hydraulic behavior under steady-state conditions is characterized and compared to experimental data and alternative computational codes. Some discrepancies are found but most of them are explained by the modeling choices and uncertainties in input data. Performance of the model under transient conditions is then investigated by simulating experiments conducted on the MSRE; the results are again benchmarked against reference data. Overall, good agreement is attained.

A perspective on large-scale simulation as an enabler for novel biorobotics applications.

Our understanding of the complex mechanisms that power biological intelligence has been greatly enhanced through the explosive growth of large-scale neuroscience and robotics simulation tools that are used by the research community to perform previously infeasible experiments, such as the simulation of the neocortex's circuitry. Nevertheless, simulation falls far from being directly applicable to biorobots due to the large discrepancy between the simulated and the real world. A possible solution for this problem is the further enhancement of existing simulation tools for robotics, AI and neuroscience with multi-physics capabilities. Previously infeasible or difficult to simulate scenarios, such as robots swimming on the water surface, interacting with soft materials, walking on granular materials etc., would be rendered possible within a multi-physics simulation environment designed for robotics. In combination with multi-physics simulation, large-scale simulation tools that integrate multiple simulation modules in a closed-loop manner help address fundamental questions around the organization of neural circuits and the interplay between the brain, body and environment. We analyze existing designs for large-scale simulation running on cloud and HPC infrastructure as well as their shortcomings. Based on this analysis we propose a next-gen modular architecture design based on multi-physics engines, that we believe would greatly benefit biorobotics and AI.

ALEGRA: Finite element modeling for shock hydrodynamics and multiphysics

ALEGRA is a multiphysics finite-element shock hydrodynamics code, under development at Sandia National Laboratories since 1990. Fully coupled multiphysics capabilities include transient magnetics, magnetohydrodynamics, electromechanics, and radiation transport. ALEGRA is used to study hypervelocity impact, pulsed power devices, and radiation effects. The breadth of physics represented in ALEGRA is outlined here, along with simulated results for a selected hypervelocity impact experiment.

A Design and Optimization Methodology for Liquid Metal Fast Reactors

A liquid metal fast reactor (LMFR) design and optimization methodology (DOM) has been developed. The methodology effectively explores a search space by initially sampling the search space, excluding invalid design samples prior to performing expensive multiphysics analysis, and then performing local searches of the design space. The design samples are evaluated using the multiphysics capabilities of the LUPINE LMFR simulation suite. Two studies have been performed to demonstrate DOM. First, the Westinghouse long-life core lead fast reactor (WLFR) is optimized. This reactor is 950 MW th and fueled with uranium nitride (UN) fuel which has a natural nitrogen isotopic abundance. The objective of the optimization is the reduction of the levelized fuel cycle cost (LFCC) while complying with the design constraints. Considering the challenges associated with using natural nitrogen in nitride fuel, a second study was performed to design a competitive 15N-enriched UN-fueled long-life core LFR. Based on this design, the cost of the 15N enrichment process necessary to achieve a competitive LFCC was calculated.

Toward a Fully Integrated Multiphysics Simulation Framework for Fusion Blanket Design

Fusion is an attractive clean-energy solution, thanks to its various advantages, such as reduced radioactivity, little high-level nuclear waste, ample fuel supplies, and increased safety. However, the harsh operating environment introduced by a complex fusion plasma system makes design and integration of fusion blankets incredibly challenging and time-consuming. This work focuses on developing a fully integrated multiphysics simulation framework based on an advanced open-source platform—the Multiphysics Object-Oriented Simulation Environment (MOOSE)—to alleviate the difficulties in fusion blanket design and integration. MOOSE is a massively parallel finite element/volume multiphysics simulation platform that has been widely adopted within the nuclear fission community. Even though fission and fusion are fundamentally different, they involve similar multiphysics phenomena. A fully integrated open-source multiphysics simulation framework tailored for the fusion blanket design will be implemented by leveraging the well-established multiphysics capabilities in MOOSE. Once successfully developed, this fully integrated framework will rapidly evaluate a blanket design concept and offer insights for subsequent iterations. As the first step, we will mainly aim to integrate neutronics analysis, system thermal hydraulics simulation, and full 3-D heat transfer calculations. The efficacy of the integrated framework will be verified using an innovative solid ceramic blanket design. While the project’s final goal is to enable a fully integrated multiphysics simulation platform for various fusion blanket concepts, this work, as a preliminary step, will mainly focus on a solid ceramic breeder helium-cooled blanket.

Demonstration of a coupled computational fluid dynamics approach for modelling non-water cooled small modular reactors

This paper provides an overview of the capabilities of a new toolset that is being developed at Canadian Nuclear Laboratories for modelling advanced non-water cooled small modular reactor concepts. Throughout the study, a technology agnostic approach was adopted. The integrated toolset includes computational fluid dynamics, neutronics and system thermalhydraulics codes to handle a range of multi-physics capabilities. The toolset has been applied to two different non-water cooled SMR concepts: molten salt and prismatic gas-cooled reactors. A step-wise approach was used in which the models were first tested using standalone codes, followed by execution of coupled-code simulations. This paper demonstrates the application of the toolset to gas-cooled and molten-salt reactor concepts, including transient simulations using the CFD code STAR-CCM+ coupled with the Monte Carlo neutronics code Serpent 2 and with the system thermalhydraulics code RELAP5-3D. The scenarios considered include a step reactivity insertion and a pump trip for the molten salt reactors. Overall, the results obtained so far demonstrates the potential of the developed methodology at CNL in simulating the non-water cooled concepts.

Rattlesnake: A MOOSE-Based Multiphysics Multischeme Radiation Transport Application

Advanced reactor concepts span the spectrum from heat pipe–cooled microreactors, through thermal and fast molten-salt reactors, to gas- and salt-cooled pebble bed reactors. The modeling and simulation of each of these reactor types comes with their own geometrical complexities and multiphysics challenges. However, the common theme for all nuclear reactors is the necessity to be able to accurately predict neutron distribution in the presence of multiphysics feedback. We argue that the current standards of modeling and simulation, which couple single-physics, single-reactor-focused codes via ad hoc methods, are not sufficiently flexible to address the challenges of modeling and simulation for advanced reactors. In this work, we present the Multiphysics Object Oriented Simulation Environment (MOOSE)–based radiation transport application Rattlesnake. The use of Rattlesnake for the modeling and simulation of nuclear reactors represents a paradigm shift away from makeshift data exchange methods, as it is developed based on the MOOSE platform with its very natural form of shared data distribution. Rattlesnake is well equipped for addressing the geometric and multiphysics challenges of advanced reactor concepts because it is a flexible finite element tool that leverages the multiphysics capabilities inherent in MOOSE. This paper focuses on the concept and design of Rattlesnake. We also demonstrate the capabilities and performance of Rattlesnake with a set of problems including a microreactor, a molten-salt reactor, a pebble bed reactor, the Advanced Test Reactor at the Idaho National Laboratory, and two benchmarks: a multiphysics version of the C5G7 benchmark and the LRA benchmark.

MULTI-PHYSICS TRANSIENT SIMULATIONS WITH TRIPOLI-4®

In this work, we present the first dynamic calculations performed with the Monte Carlo neutron transport code TRIPOLI-4R with thermal-hydraulics feedback. For this purpose, the Monte Carlo code was extended for multi-physics capabilities and coupled to the thermal-hydraulics subchannel code SUBCHANFLOW. As a test case for the verification of transient simulation capabilities, a 3x3-assembly mini-core benchmark based on the TMI-1 reactor is considered with a pin-by-pin description. Two reactivity excursion scenarios initiated by control-rod movement are simulated starting from a critical state and compared to analogous simulations performed using the Serpent 2 Monte-Carlo code. The time evolution of the neutron power, fuel temperature, coolant temperature and coolant density are analysed to assess the multi-physics capabilities of TRIPOLI-4. The stabilizing e_ects of thermal-hydraulics on the neutron power appear to be well taken into account. The computational requirements for massively parallel calculations are also discussed.

A Collision-based Domain Decomposition scheme for large-scale depletion with the Serpent 2 Monte Carlo code

In the framework of the EU Horizon 2020 McSAFE project, high-fidelity multiphysics capabilities are being developed to carry out large-scale burnup calculations for Light Water Reactors. As part of this effort, the Serpent 2 Monte Carlo code has been coupled to thermalhydraulics and fuel-performance codes, with the final objective of performing fully coupled full-core pin-by-pin simulations. To enable memory scalability, needed for these massive problems, a Collision-based Domain Decomposition (CDD) scheme has been implemented in Serpent 2. The methodology is based on data decomposition for burnable materials and a domain decomposition particle-tracking algorithm, and is shown here to provide the required memory scalability and computational performance, with up to 50% speedup efficiency at 5,120 cores. The application of the CDD feature is demonstrated in a pin-by-pin depletion calculation for a Pre-Konvoi PWR reactor.

Are you using the right tools in computational electromagnetics?

Have you ever wondered why we use certain computational electromagnetics methods and how we decide on the choice of tools for modeling problems in electromagnetics? Though true for any field, particularly in electrodynamics, there is a gap between current practitioners' knowledge and knowhow about different tools and the state‐of‐the‐art developments. Rapid advancements made in material science and (nano)‐fabrication techniques are demanding new tools with multiscale and multiphysics capabilities. In this article, we cover the recent developments and highlight capabilities and limitations of different electromagnetic modeling tools. One has to answer a series of questions about modeling constraints and objectives before picking the appropriate tool. We aim to clarify some of the misconceptions, discuss limits and capabilities of some of the popular electromagnetic modeling tools, and provide a few practical tips, so that applied physicists and engineers can make informed decisions while choosing appropriate tools for their applications.

Advances in Multiphysics Modeling for Parallel Finite-Element Code Suite ACE3P

Developed by SLAC, the advanced computational electromagnetics three-dimensional parallel (ACE3P) code suite is a comprehensive set of parallel finite-element codes for multiphysics modeling of particle accelerators. Running on massively parallel computer platforms for high fidelity and high accuracy simulation, ACE3P enables rapid virtual prototyping of accelerator and radio frequency (RF) component design, optimization, and analysis. Recent advances of ACE3P have been focused on the implementation of advanced numerical algorithms, enhancement of multiphysics capabilities, and integration of ACE3P with other particle beams and plasmas codes toward end-to-end simulations in accelerators, and improvement of code performance on the state-of-the-art high-performance computing (HPC) platforms for large-scale RF modeling in accelerator applications and beyond. In this article, we will present a nonlinear electromagnetic (EM) eigensolver for damping calculation of resonant modes for cavities coupled with waveguides, the thermal solver for accurate evaluation of heat loads in superconducting RF (SRF) cavity power coupler, the elastic solver for investigation of SRF cavity cryomodule (CM) bowing due to thermal effect, the frequency-domain mechanical solver for studying SRF cavity mechanical oscillation modes, the particle tracking code for dark current simulation in SRF CM using a hybrid MPI+OpenMP parallel programming model, and the time-domain solver for high-fidelity modeling of EM wave propagation for powering midfield medical devices in human body. All the simulations have been performed on the computing resources at the National Energy Research Scientific Computing Center, and the impact of HPC on multiphysics modeling will be discussed.

Interfacial mixing in high-energy-density matter with a multiphysics kinetic model.

We have extended a recently developed multispecies, multitemperature Bhatnagar-Gross-Krook model [Haack et al., J. Stat. Phys. 168, 822 (2017)JSTPBS0022-471510.1007/s10955-017-1824-9], to include multiphysics capabilities that enable modeling of a wider range of physical conditions. In terms of geometry, we have extended from the spatially homogeneous setting to one spatial dimension. In terms of the physics, we have included an atomic ionization model, accurate collision physics across coupling regimes, self-consistent electric fields, and degeneracy in the electronic screening. We apply the model to a warm dense matter scenario in which the ablator-fuel interface of an inertial confinement fusion target is heated, but for larger length and time scales and for much higher temperatures than can be simulated using molecular dynamics. Relative to molecular dynamics, the kinetic model greatly extends the temperature regime and the spatiotemporal scales over which we are able to model. In our numerical results we observe hydrogen from the ablator material jetting into the fuel during the early stages of the implosion and compare the relative size of various diffusion components (Fickean diffusion, electrodiffusion, and barodiffusion) that drive this process. We also examine kinetic effects, such as anisotropic distributions and velocity separation, in order to determine when this problem can be described with a hydrodynamic model.

Estimating the effects of homogenized fuel temperature in group constant generation using Serpent 2

We extend the multi-physics capabilities of the Serpent 2 Monte Carlo code to coupled burnup calculations by implementing the Stochastic Implicit Euler depletion scheme with thermal feedback. We use these new multi-physics capabilities for the verification of the traditional way of generating group constants using an effective flat fuel temperature profile during the burnup calculation. We investigate the effects of this approximation on the generated nuclide compositions, group constants as well as the results on the simulation of the initial cycle of the EPR reactor using the ARES core simulator.The main findings state that while the use of an effective temperature model leads to significant differences in the radial nuclide distributions, the assembly wide homogenized group constants are reproduced fairly well and the effects on the simulation of the EPR initial cycle are modest, although interesting axial and radial power redistribution can be observed due to the slower speed of gadolinium burnout when effective fuel temperatures were used. The results indicate that better results for the full core calculations could be obtained by using a separate effective temperature for the burnable absorber rods in the burnup calculation and by considering the fuel temperature history effect in the group constant parametrization.

Numerical Analysis on the Effect of Boom Sprayer Collecting Plate Angle to the Distribution of Granular Fertilizers

Optimization of boom sprayer collecting plate angle is a tedious procedure if it is done fully experimental. This paper demonstrates that the optimization process is more practical by simulation analysis validate through logical reflection of particles. This study is carrying out through simulating the distribution parts of the boom sprayer by using the commercial software, ANSYS. The multiphysics capabilities of ANSYS enable ANSYS to carrying out this simulation. The simulation is carrying out by manipulating the angle of the collecting plate, 32o, 60o,90o and 120o of the boom sprayer to find the optimum range of angle that will produce a good distribution for different sizes of the granular fertilizers and air velocity of the blower. The constant variables in this simulation are the atmospheric pressure of 1 atm and the particles size of Potassium K is 1mm. There are 60 per cent of the images produce by ANSYS, through observing the number of stream lines and the angle of distribution show that the optimum angle is between 32o to 60o. For further study, in order to increase the accuracy, the simulation is further validate through experiment. It is preferred to carry up the experiment through scaled down model without causing any changes to the current design and in order to be carrying out in the lab.

Coupled neutronics–fuel behavior calculations in steady state using the Serpent 2 Monte Carlo code

This paper describes the recent developments in the multi-physics capabilities of the Serpent Monte Carlo code concerning coupled multi-physics calculations with fuel behavior feedback. We cover the structure and operation of the fuel behavior interface in Serpent 2 as well as the coupled calculation routines implemented for steady state multi-physics calculations with any internally or externally coupled solver. The intended solution flow and code-to-code communication in internally and externally coupled multi-physics simulations is described alongside with the stochastic approximation based solution relaxation methods implemented in Serpent.The two-level multi-physics coupling scheme in Serpent 2 is demonstrated by obtaining a coupled solution for the neutronics–fuel behavior problem using first the internally coupled FINIX fuel behavior module and then the externally coupled ENIGMA fuel performance code in a 3D assembly geometry. Parameters such as maximum pellet centerline temperatures can be evaluated from the coupled solution. The temperature fields obtained from the coupled solution are also used to estimate the effect of the detailed radial representation of the fuel temperature distribution compared to various radially averaged effective fuel temperature representations. The convergence of the coupled solution is investigated alongside the possibility to speed up the convergence by using the Uniform Fission Sites method.

Multiphysics implementation of advanced soil mechanics models

Using multiphysics computer codes has become a useful tool to solve systems of partial differential equations. However, these codes do not always allow for the free introduction of implicitly defined state functions when automatic differentiation is used to compute the iteration matrix. This makes it considerably more difficult to solve geomechanical problems using non-linear constitutive models. This paper proposes a method for overcoming this difficulty based on multiphysics capabilities. The implementation of the well-known Barcelona basic model is described to illustrate the application of the method. For this purpose, without including formulation details addressed by other authors, the fundamentals of its implementation in a finite element code are described. Examples that demonstrate the scope of the proposed methodology are also presented.

Process modeling of cavity molded composite flex beams

Continuous fiber reinforced composite materials are extensively being used in helicopter dynamic structures. Preimpregnated fibers or prepregs are used to produce high quality composite rotor yokes/flex beams. One process in particular known as cavity molding, is frequently used to process high quality thick composite details with exceptionally precise dimensions by using a platen press to apply heat and pressure to rigid tooling and thereby entice the prepreg within to cure into the shape of the confines of an internal cavity. The objective of the research described here is to develop a mathematical model for glass/epoxy prepreg which simulates the resin flow, heat transfer, consolidation and curing of cavity-molded flex beams which varies significantly with location. An enhanced understanding of the mechanisms involved will help significantly improve the cost-effectivity of molding process development. The current work is focused on process modeling of composite flex beams which are manufactured by cavity molding. The cure kinetics of such parts is particularly difficult to model because tool/part geometries are complex. The combined effects of heat transferred by the tool and heat spontaneously generated by the reacting thermoset during cure results in significant gradients of resin advancement throughout the part. The temperature spikes that result from internally-generated exothermic heat cannot be quickly dissipated because of the low thermal conductivity of composite. Various governing equations are presented here that describe the resin cure kinetics, thermal energy balance and flow during the process. A general-purpose, finite-element package with multiphysics capabilities is used for simulating the non-isothermal prepreg-press process, the degrees of cure and temperature field distribution at different cross-sections.

SPIS Multitimescale and Multiphysics Capabilities: Development and Application to GEO Charging and Flashover Modeling

While it demonstrated its capability to simulate many common situations, Spacecraft Plasma Interaction Software (SPIS) open source code lacked the possibility to model more challenging situations. The major cases of interest were identified as related to either multitimescale or multiphysical situations. Two major improvements were brought to SPIS code to answer these needs. The first one was an implicit circuit solver with an automatic determination of time steps. The implemented Newton-type algorithm makes use of a predictor for the plasma current variations when surface potentials change. The second major development was a multiphysical model for electrons. The approach consisted in using equilibrium or dynamical electron models in two different zones and connecting these zones at their boundary through a Child-Langmuir (CL)-type condition. Fulfilling this condition dynamically determines the location of the boundary and the electron current to be injected from the dense thermal zone to the space-charge zone. These new features were then used to simulate validation and application cases. The first one consisted in modeling a charging situation in GEO, which had been modeled with NASA charging analyzer (NASCAP) codes and published. Concerning the multiphysical model of electrons, the loop controlling the CL condition was first tested on elementary cases, exhibiting a good qualitative and quantitative behavior. It was then applied to the modeling of a ground experiment performed in JONAS plasma tank at the Office National d'Etudes et Recherches Aerospatiales, i.e., the expansion of the flashover generated by an electrostatic discharge over a precharged solar array coupon, leading to its neutralization.

OOFEM — an Object-oriented Simulation Tool for Advanced Modeling of Materials and Structures

The aim of this paper is to describe the object-oriented design of the finite element based simulation code. The overall, object-oriented structure is described, and the role of the fundamental classes is discussed. The paper discusses the advanced parallel, adaptive, and multiphysics capabilities of the OOFEM code, and illustrates them on the basis of selected examples.