Solver Code Research Articles

Numerical simulation of RHIC polarized proton run 17 spin flipper experiments

RHIC nine-magnet spin flipper has been operated successfully during RHIC polarized proton Run 17, with 97% spin flip efficiency achieved. The results show the importance of mirror resonance removal, small spin tune spread, and proper spin flipper driving tune sweep speed. Detailed spin tracking simulations, based on a Lorentz force and Thomas-BMT differential equation numerical solver code for accuracy, have been carried out to understand the experimental results. Agreement within measurement accuracy is obtained at injection energy, 23.8 GeV. It is not as tight at 255 GeV, reasons for that are exposed. These measurements and numerical studies allow to determine the sensitivity of spin-flip efficiency to the dispersion slopes at the two Siberian snakes and to the ac dipole frequency sweep speed. They also provide guidance for future developments at BNL’s electron-ion collider. Published by the American Physical Society 2024

A GPU based accelerated solver for simulation of heat transfer during metal casting process

The metal casting process, which is one of the key drivers of the manufacturing industry, involves several physical phenomena occurring simultaneously like fluid flow, phase change, and heat transfer which affect the casting yield and quality. Casting process modeling involves numerical modeling of these phenomena on a computer. In recent decades, this has become an inevitable tool for foundry engineers to make defect-free castings. To expedite computational time graphics processing units (GPUs) are being increasingly used in the numerical modeling of heat transfer and fluid flow. Initially, in this work a CPU based implicit solver code is developed for solving the 3D unsteady energy equation including phase change numerically using finite volume method which predicts the thermal profile during solidification in the metal casting process in a completely filled mold. To address the computational bottleneck, which is identified as the linear algebraic solver based on the bi-conjugate gradient stabilized method, a GPU-based code is developed using Compute Unified Device Architecture toolkit and was implemented on the GPU. The CPU and GPU based codes are then validated against a commercial casting simulation code FLOW-3D CAST® for a simple casting part and against in-house experimental results for gravity die casting of a simple geometry. Parallel performance is analyzed for grid sizes ranging from 10 × 10 × 10 to 210 × 210 × 210 and for three time-step sizes. The performance of the GPU code based on occupancy and throughput is also investigated. The GPU code exhibits a maximum speedup of 308× compared to the CPU code for a grid size of 210 × 210 × 210 and a time-step size of 2 s.

Modeling of Condensations in Coronal Loops Produced by Impulsive Heating with Variable Frequencies and Locations

We present the results of models of impulsively heated coronal loops using the 1D hydrodynamic Adaptively Refined Godunov Solver code. The impulsive heating events (which we refer to as nanoflares) are modeled by discrete pulses of energy along the loop. We explore the occurrence of cold condensations due to the effective equivalent of thermal nonequilibrium in loops with steady heating, and examine its dependence on nanoflare timing and intensity and also nanoflare location along the loop, including randomized distributions of nanoflares. We find that randomizing the distribution of nanoflares, both in time/intensity and location, diminishes the likelihood of condensation occurring as compared to distributions with regularly occurring nanoflares with the same average properties. The usual criteria that condensation is favored for heating near loop footpoints and with high cadences are more strict for randomized (as opposed to regular) nanoflare distributions, and for randomized distributions the condensations stay in the loop for a shorter amount of time. That said, condensation can sometimes occur in cases where the average values of parameters (frequency or location) are beyond the critical limits above which condensation does not occur for corresponding steady, non-randomized values of those parameters. These properties of condensation occurring due to randomized heating can be used in the future to investigate the diagnostics of coronal heating mechanisms.

Beyond [formula omitted]CDM with [formula omitted]CDM: Criticalities and solutions of Padé Cosmography

Recently, cosmography emerged as a valuable tool to effectively describe the vast amount of astrophysical observations without relying on a specific cosmological model. Its model-independent nature ensures a faithful representation of data, free from theoretical biases. Indeed, the commonly assumed fiducial model, the ΛCDM, shows some shortcomings and tensions between data at late and early times that need to be further investigated. In this paper, we explore an extension of the standard cosmological model by adopting the f(z)CDM approach, where f(z) represents the cosmographic series characterizing the evolution of recent universe driven by dark energy. To construct f(z), we take into account the Padé series, since this rational polynomial approximation offers a better convergence at high redshifts than the standard Taylor series expansion. Several orders of such an approximant have been proposed in previous works, here we want to answer the questions: What is the impact of the cosmographic series choice on the parameter constraints? Which series is the best for the analysis? So, we analyze the most promising ones by identifying which order is preferred in terms of stability and goodness of fit. Theoretical predictions of the f(z)CDM model are obtained by the Boltzmann solver code and the posterior distributions of the cosmological and cosmographic parameters are constrained by a Monte Carlo Markov Chains analysis. We consider a joint data set of cosmic microwave background temperature measurements from the Planck collaboration, type Ia supernovae data from the latest Pantheon+ sample, baryonic acoustic oscillations and cosmic chronometers data. In conclusions, we state which series can be used when only late time data are used, while which orders has to be considered in order to achieve the necessary stability when large redshifts are considered.

Thermodynamic and environmental performance of a Kalina-based multigeneration cycle with biomass ancillary firing for power, water and hydrogen production

The performance of a Kalina-based multigeneration cycle for power, water, and hydrogen production is investigated from thermo-environmental, sustainability, and thermo-economic perspectives. The plant comprises a gas turbine (GT), Kalina cycle (KC), and vapor absorption system (VAS) as the bottoming cycle and an integrated domestic water heater and proton-electron membrane (PEM) electrolyzer for hydrogen production. The system's models were simulated with Engineering Equation Solver (EES) codes. The results indicate a net energy efficiency of 53.48% and exergy efficiencies of 50.05 %, with an additional 30,178 kW of products from the bottoming cycles. The GT contributed approximately 85.81 % of the overall exergy destruction. The system's exergo-thermal index (ETI) stood at 1.713, with the GT only having an ETI of 2.106. Similarly, the exergetic sustainability index (ESI) of the multigeneration plant was not greater than 2.04. The exergoeconomic analysis shows a low average energy cost from the GT, estimated at 0.836 $/GJ, compared to the Kalina subsystem, which stood at 6.53 $/GJ. The thermodynamic and cost evaluation of the system demonstrates substantial benefits from the plant, which kept the hydrogen production rate at 0.1524 kg/hr.

Active generation and control of radial electric field by local neutral beamlets injection in tokamaks

The radial electric field plays an important role in plasma confinement in tokamaks and can be generated through neutral beam injection. In this study, we propose a model for calculating the radial electric field resulting from tangential local neutral beamlet injection, aiming to externally control and improve plasma confinement. The Neutral beamlet ion and Energetic particles Orbit mover and Electric field solver code has been developed to analyze this issue, and its simulation results have been validated against results from other codes as well as measurements from correlation reflectometers. The charge separation is primarily caused by the redistribution and loss of beam ions due to magnetic gradient and curvature drift as well as collision effects, and it is maintained through continuous beamlet injection. The electric field is calculated using Poisson’s equation, taking into account both classical and neoclassical polarization effects. The results demonstrate that despite the high losses and low heating efficiency associated with localized beamlets, they are capable of generating a significant radial electric field characterized by a steep gradient. This presents opportunities for external control of the electric field, potentially enhancing plasma confinement.

Influence of Design Parameters on Mechanical Behavior of Multi-Bolt, Countersunk C/SiC Composite Joint Structure.

Aerospace vehicle connection constructions are in urgent need of joint structures with excellent aerodynamic profiles and environmental adaptability. To address issues such as poor aerodynamic profile, material thermal expansion coefficient mismatch, and limited joint structure evaluation indexes, a multi-bolt, countersunk C/SiC composite joint structure is presented in this study. The development of a 3D Hashin progressive damage model and its dedicated solver code is presented. The validity of the model is confirmed by comparing simulation results with experimental data. Three evaluation indexes are proposed, peak load, weight increment efficiency, and bolt load distribution, to thoroughly evaluate the mechanical performance of multi-bolt, countersunk C/SiC composite joint structures. Using the proposed model and evaluation indices, we evaluate sixteen different designs of multi-bolt, countersunk C/SiC composite joint structures and analyze how design parameters affect their mechanical properties and damage patterns. The results show that the best mechanical properties of the joint structure are achieved when the ratio of bolt pitch to through hole diameter is 3, the ratio of bolt spacing between columns to through hole diameter is 4, the ratio of the distance between the free edge of the substrate to through hole diameter is 1.5, the ratio of through hole diameter to specimen thickness is 1.7, and the ratio of the distance between the edge of the substrate to through hole diameter is 1.5.

Numerical simulation of chemically reacting Darcy-Forchheimer flow of Buongiorno Maxwell fluid with Arrhenius energy in the appearance of nanoparticles

This investigation is designated for studying the inspiration of Darcy-Forchheimer flow of Maxwell nano fluid with nonlinear marvels of thermal radiation and bio convection of motile germs due to porous stretched sheet. Arrhenius energy, thermophoresis and convective Nield boundary conditions are novel aspects of this research. The exploration of heat and mass transfer in electrical conducting Maxwell fluid in the manifestation of nanoparticles is scrutinized. The misappropriate similarity functions are used to convert the couple of governing PDEs in to nonlinear set of ODEs. The resulting fasten of ODEs are numerically solved by applying the appropriate numerical tool shooting procedure with MATLAB solver code bvp4c. The encouragement of renowned parameters including Peclet number, Prandtl number, Bioconvective Lewis number, Rayleigh number, thermophoresis, Lewis number, Brownian motion and Hartmann number on momentum, energy, concentration and germ density profile has been deliberated in form of graphs and tables. We declared that the velocity curve declined for the developing value of inertia coefficient K1, magnetic number M and Deborah number Γ. The improvement in the values of the activation energy E growth in the temperature distribution.

Computation of Inviscid Flow Past SARAS Aircraft with Sideslip Using A Multi-block Grid

The computation of the flow past an aircraft configuration is a fairly difficult task due to the complexity of the geometry. A powerful multi-block grid generation tool and a robust, well-validated flow solver code are required to compute such a complex flow. A large number of blocks are needed to discretize the flow field and hence considerable time and effort is required to generate a suitable computational grid. If the flow is symmetric, without any sideslip, it is only necessary to solve the flow past half of the aircraft, but for flow with side slip it becomes essential to solve the flow past the complete aircraft, which introduces additional difficulties. This paper describes the computation of inviscid flow past the SARAS aircraft, with sideslip, using a multi-block grid containing sixty-six blocks. An improved blocking strategy is used to keep the number of blocks to a minimum. A detailed analysis of the computed flows, along with a comparison of the aerodynamic coefficients with available experimental results, is presented here. The code has been validated by showing that a symmetric solution is obtained for a symmetric flow condition and the correct anti-symmetry is achieved for flows with opposite sideslip. The computed results show a good agreement with the experimental data.

A Nonintrusive POD-PCE Scheme for Uncertainty Quantification of Stochastic EM Problems

The quantification of parameter uncertainty is of particular interest to the computational electromagnetic (EM) community resulting in fast and efficient intrusive and nonintrusive stochastic numerical algorithms. Among these, the nonintrusive-based stochastic algorithms are the preferred choice due to their flexibility in combining with the deterministic EM solver, unlike intrusive, requiring in-house EM solver code. This letter proposes a nonintrusive method to quantify the uncertainty that can be used along with the commercial EM solvers. The proposed method utilizes the proper orthogonal decomposition (POD) method to generate the low-dimensional basis of the original problem. The unknown stochastic electric field is obtained as a linear combination of this low-dimensional basis. The unknown coefficients are computed by interpolating over the initial stochastic response using polynomial chaos expansion (PCE). This method requires only <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1\%$</tex-math> </inline-formula> of the total computation time taken by the Monte Carlo (MC) method, and the results are shown to be accurate.

A trium test on beyond ΛCDM triggering parameters

We performed a Bayesian study on three beyond ΛCDM phenomenological triggering parameters, the growth index γ, the dark energy equation of state parameter ω and the lensing deviation from the GR prediction parameter Σ, using the latest cosmological geometric, growth and lensing probes, all in a consistent implementation within the modified gravity cosmological solver code MGCLASS. We find, when we combined all our probes, i.e. the cosmic microwave background (CMB), the baryonic acoustic oscilation (BAO), the growth measurements fσ 8 and the 3×2pt joint analysis of weak lensing and galaxy clustering in photometric redshift surveys, assuming flat space, constraints compatible with general relativity and ΛCDM with ω = -1.025 ± 0.045, and Σ = 0.992 ± 0.022 at the 68% level, while γ = 0.633±0.044 is still within ∼ 2σ from the ΛCDM value of γ ∼ 0.55, and that when Σ is considered as constant; while γℓ = -0.025 ±0.045 when the lensing parameter is parameterised as function of a lensing index, introduced for the first time in this work, as Σ(z) = Ωm(z)γℓ .

How to Plot Heatlines?

Abstract In non-isothermal flows, heatlines are used to depict the energy flow from hot surface to cold surface and help in visualizing the strength of the convective heat transfer as compared to the conductive heat transfer. Traditionally, researchers have plotted heatlines by solving heat-function equation in their solvers during the runtime. However, this requires access to the solver code and is time-consuming to implement. Further, the literature available so far only concerns simple geometric shapes. This work aims to document out-of-the-box methods for the visualization of heatlines which can be done as a post-processing exercise. A comparison of streamlines and heatlines, is at first presented to enhance the understanding of the application of heatlines in heat transfer problems and use the same technique in post-processing computer programs for visualizing heatlines. The procedures to plot heatlines using commercial (tecplot and cfd-post) and open-source (paraview) tools are presented. Illustrative examples of different computational geometries from past literature are validated to establish the efficacy of the method. Further, the method can be also applied to plot heatlines for complex geometries which is not feasible with the traditional approaches.

Electron-scale current sheets and energy dissipation in 3D kinetic-scale plasma turbulence with low electron beta

Abstract 3D kinetic-scale turbulence is studied numerically in the regime where electrons are strongly magnetized (the ratio of plasma species pressure to magnetic pressure is βe = 0.1 for electrons and βi = 1 for ions). Such a regime is relevant in the vicinity of the solar corona, the Earth’s magnetosheath, and other astrophysical systems. The simulations, performed using the fluid-kinetic spectral plasma solver (SPS) code, demonstrate that the turbulent cascade in such regimes can reach scales smaller than the electron inertial scale, and results in the formation of electron-scale current sheets (ESCS). Statistical analysis of the geometrical properties of the detected ESCS is performed using an algorithm based on the medial axis transform. A typical half-thickness of the current sheets is found to be on the order of electron inertial length or below, while their half-length falls between the electron and ion inertial length. The pressure-strain interaction, used as a measure of energy dissipation, exhibits high intermittency, with the majority of the total energy exchange occurring in current structures occupying approximately 20% of the total volume. Some of the current sheets corresponding to the largest pressure-strain interaction are found to be associated with Alfvénic electron jets and magnetic configurations typical of reconnection. These reconnection candidates represent about 1% of all the current sheets identified.

Strong shock solutions in symmetric wedge flows: Unphysical or unstable?

This paper investigates the strong shock solutions in a supersonic wedge experimentally, analytically, and numerically. Experiments and computations are conducted on scaled-down models for the two types of shock reflection to be possible. The time-resolved schlieren observation of the flow evolution revealed that the shock formation is a highly dynamic transition of the starting shock from a strong Mach reflection (MR) to a weak regular reflection (RR) via a strong RR reflection over a constant shock wave angle for a wedge angle less than the detachment criterion angle for the shock transition. However, when the wedge angle is greater than the detachment criterion angle, the shock moves over the wedge with the MR structures of diminishing Mach stem height at a constant incident shock wave angle. These intermediate shock reflections are found to be unstable and oscillate at high amplitude and low frequencies to upstream pressure fluctuations. The nature of the intermediate shock reflection during the shock transition over the wedge has also been studied using an unsteady second-order two-dimensional compressible Navier–Stokes solver code with shear stress transport k-ω turbulence modeling. The computed flow parameters around the intermediate shock reflections confirmed that these are indeed strong shock reflections believed to be unphysical in steady wedge flows.

Predictive simulations for plasma scenarios in the SMART tokamak

The SMall Aspect Ratio Tokamak (SMART) is a new spherical machine that is currently being constructed at the University of Seville (Mancini et al., 2021; Agredano-Torres et al., 2021). The operation of SMART will cover three different phases reaching an inductive plasma current (IP) of more than 500 kA, a toroidal magnetic field (BT) of 1 T and a pulse length of 500 ms (Mancini et al., 2021; Agredano-Torres et al., 2021). The main goal of the SMART tokamak is to study high plasma confinement regimes in a broad triangularity range (-0.5≤δ≤0.5) (Doyle et al., 2021; Doyle et al., 2021). While in phase 1 the ohmic heating alone is expected to provide enough power to access the H-mode, in phase 2 and phase 3 the access to the H-mode will be ensured by applying Neutral Beam Injection (NBI) as external heating system. The NBI will consist of one injector at 25 keV and 1 MW of power. The overall design of the NBI, including injection geometry, energy and power have been optimized using the ASCOT5 code (Hirvijoki et al., 2021). The SMART scenarios have been developed with the help of the free boundary equilibrium solver code FIESTA (Cunningham, 2013) coupled to the linear time independent, rigid plasma model RZIP (Lazarus et al., 1990) to calculate the target equilibria for all the different operational phases. To assess the feasibility of those scenarios, predictive modelling needs to be included to evaluate properly the evolution of the temperatures, density profiles for both electrons and ions. To this extent, the 1.5D transport code ASTRA (Pereverzev and Yushmanov, 2002) has been used including models for the ohmic current, bootstrap current and current driven by NBI. This contribution discusses the electron and ion density and temperature profiles obtained for various scenarios for phase 1 and 2 and presents the design study of the NBI.

ICRF heating schemes for the HL-2M tokamak

The HL-2M tokamak is a new medium-sized tokamak at SouthWestern Institute of Physics. Two of its key missions are to achieve 10 keV ion temperature and investigate the behavior of energetic particles relevant to burning plasmas. A 6 MW ion cyclotron range of frequencies (ICRF) heating power is embedded in the next upgrade program of HL-2M. In order to facilitate the engineering design of the ICRF system, this paper analyses the main ICRF heating schemes for HL-2M, in terms of ion heating and energetic ion generation in particular. D(H) minority heating and the 2nd harmonic D will act as the main ion heating schemes, for which the optimal RF frequency range 27–33 MHz, antenna parallel wavenumber k // ∼ 8 m−1 are proposed and strong single pass absorption is expected under typical HL-2M plasma parameters. Full wave simulations carried out via TORIC/steady-state Fokker–Planck quasilinear solver and TRANSP codes suggest that by adopting three ion scheme or synergetic heating on neutral beam injection D ions by the 2nd harmonic D, energetic ions with energy at MeV level can be produced. This study shows that ICRF heating could play significant roles in ion heating, energetic ion generation in HL-2M.

Efficiency Enhancement of a Dual-Band Magnetically Insulated Line Oscillator Using a Modulation Cavity

In this article, performance enhancement of a dual-band magnetically insulated line oscillator (DBMILO) using a modulation cavity has been presented. In the proposed design, a modulation cavity has been introduced in between the slow wave structure (SWS) of the output end, which lessens the energy spread of the modulated beam electrons. The impact of the modulation cavity on the transmission characteristics and the operating frequency of the modified DBMILO are investigated through electromagnetic (EM) simulation. The dimensions of the modulation cavity are optimized to ensure approximately the same operating frequency in the modified design. The RF behavior of the proposed and conventional design is examined through the particle-in-cell (PIC) solver code. For the input dc voltage and current of 500 kV and 56 kA, respectively, the output power of the conventional DBMILO provides ~3.6 GW with 12.8% efficiency, whereas the proposed DBMILO with modulation cavity generates ~4.8 GW with 17.1% efficiency. The microwave frequency in both cases is 3.4 and 10.1 GHz. Compared to the conventional DBMILO, the power efficiency of DBMILO with modulation cavity enhances by 33%.

Hydrodynamic performance analysis of a new hybrid wave energy converter system using OpenFOAM

In this research study, a newly proposed hybrid device of Wave Energy Converters (WEC) is investigated by considering computational fluid dynamic (CFD)-based numerical wave tanks (NWTs). The open-source CFD code solver, OpenFOAM (Open Field Operation and Manipulation) is implemented, which is numerically solved the Reynolds-averaged Navier–Stokes (RANS) equations to simulate the two-phase flow. The hybrid system consists of an Oscillating Water Column (OWC) and a point absorber (Wavestar) device installed in a shared platform. The main goal is to recognize how wave diffractions caused by the adjacent floating body could affect the rate of power absorption by the Fixed-OWC. This aim is followed by a 2D numerical analysis of three different installation configurations, variable intervals between the Wavestars' buoy and the Fixed-OWCs' front wall, in four different wavelengths with and without Power Take-Off (PTO). Finally, the efficiency characteristics of the integrated system such as free surface velocity and air pressure within the chamber, besides floating body motions are investigated and compared for the hybrid system. Although the overall assessment for 28 different case studies reveals an efficiency reduction in some cases, the superiority of this hybrid plan is recording several incremental efficiency rates.

Mathematical simulation and optimization of a waste energy recovery for an internal combustion engine integrated with ScCO2 cycle and modified Kalina cycle

In the current research, thermodynamic simulation of a waste heat recovery system (WHRS) for an internal combustion engine (ICE) employing a ScCO2 cycle, an ORC, and a modified Kalina cycle integrated with a thermoelectric generator is developed. The energy, exergy, and exergo-economic are applied to evaluate the suggested system. An engineering equation solver (EES) code combined with Matlab software is developed to conduct a thermodynamic simulation and multi-objective optimization of the waste heat recovery plant. The results represent in the suggested system the energy efficiency, exergy efficiency, and net output power are 26.33 %, 51.69 %, and 2657 kW, respectively. About 70.5 % of the overall exergy destruction of the proposed system belongs to the heat exchanger 1, generator, thermoelectric 1, and compressor. The economic analysis results show that the thermoelectric 1, ORC turbine, compressor and Kalina turbine have the highest purchase equipment cost in the designed system. Calculations show that the thermoelectric 1, and Kalina turbine have the highest potential for optimization and minimizing their value of relative cost difference. In the parametric analysis, four variables were investigated, which is a base for multi-objective optimization in three schemes. The introduced multi-objective scenarios provide appropriate data for a designer to propose the new waste heat recovery plants.

Verification and validation of the Alternative Nonlinear Two-phase Subchannel (ANTS) code

The Alternative Nonlinear Two-phase Subchannel solver (ANTS) code was written to provide a fast-running, steady-state, pin-resolved modeling and simulation tool for analysis of common boiling water reactor (BWR) geometry and common operating conditions. ANTS has been integrated into the Virtual Environment for Reactor Application (VERA) core simulator software, where it can be used to provide a thermal/hydraulic (T/H) subchannel solution that is then used to provide neutronic feedback as well as perform the fuel depletion and temperature solution. This paper presents the rigorous analysis performed on the ANTS code, which includes both code and solution verification testing, benchmarking with the existing two-phase subchannel capability in VERA, CTF, and validation testing using popular two-phase experiments such as PWR Sub-channel and Bundle Tests (PSBT), BWR Full-size Fine-mesh Bundle Tests (BFBT), Risø, and FRIGG. This assessment was used to qualify ANTS for its intended applications before its use for core-scale, multiphysics BWR simulations. In general, it was found that agreement with experimental data was good; errors were within the range of experimental data uncertainty. Furthermore, code and solution verification confirmed that the governing equations and the most important closure terms were correctly implemented and behaving as expected.