Article
Thermodynamics
Anuj Kumar, Ketan Yogi, S. V. Prabhu
Summary: The study focuses on the heat transfer characteristics of a single-phase liquid jet impingement on a flat surface subjected to heat flux. The effects of nozzle diameter, nozzle to plate spacing, and Reynolds number on the local Nusselt number distribution are investigated. The study proposes semi-empirical correlations for predicting the local Nusselt number distribution within a maximum deviation of 20%. Comparison between free surface and submerged jet shows higher local Nusselt number for the submerged jet.
INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER
(2023)
Article
Thermodynamics
Mehdi Rahimi Takami, Davood Domiri Ganji, Mojtaba Aghajani Delavar, Shahriar Bozorgmehri
Summary: This study utilized the lattice Boltzmann method to investigate diffusion phenomena in SOFC, focusing on estimating diffusion coefficients through dimensionless numbers and exploring the impacts of inlet velocity, steam-to-carbon ratio, current density, and porosity on diffusion processes. Additionally, the study revealed the significant effects of molar ratio variations in hydrogen and water, as well as the importance of changes in operating parameters on the Prandtl number.
JOURNAL OF THERMAL ANALYSIS AND CALORIMETRY
(2021)
Article
Thermodynamics
Xiaoxue Huang, Shuisheng He
Summary: This study investigates the low Prandtl number convection of an axisymmetric turbulent lead-bismuth eutectic (LBE) jet discharged into a heated confined geometry using large eddy simulation. The results demonstrate differences between liquid metal and ordinary fluids, suggesting that standard turbulence models may not be suitable for modeling such flows. The study also compares the behavior of LBE jet with a high-pressure water jet and observes self-preserving characteristics of temperature distribution.
INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER
(2022)
Article
Mechanics
Alexander Bukva, Kevin Zhang, Nicholas Christopher, Jean-Pierre Hickey
Summary: The study evaluated Reynolds-averaged Navier-Stokes (RANS) turbulent closures for predicting turbulent boundary layers with transpiration cooling through comparison with a high-fidelity direct numerical simulation database. The RANS models performed well in qualitatively estimating velocity and thermal boundary layer evolution at low blowing ratios, but significant differences were observed at higher blowing ratios.
Article
Thermodynamics
Xiaoxue Huang, Shuisheng He
Summary: This study investigates the negatively buoyant jet of liquid metal at a low Prandtl number using large eddy simulation, showing that standard turbulence models are not suitable for this flow. Comparisons with different Prandtl number conditions are made to study fluid similarity.
INTERNATIONAL COMMUNICATIONS IN HEAT AND MASS TRANSFER
(2022)
Article
Mechanics
Feng Liu, Cun-liang Liu, Lin Ye, Li-quan Wang, Fan Zhang, Bing-ran Li
Summary: The k-epsilon and SST models have limited accuracy in calculating film cooling effectiveness, so this study proposes a modified k-omega model that improves the mixing effect in the mixing zone of the two fluids by correcting the flow field with the mass species conservation equation.
Article
Mechanics
Amrapalli Garanaik, Subhas Karan Venayagamoorthy
Summary: A new insight into inferring diapycnal diffusivity in stably stratified turbulent flows is obtained based on physical scaling arguments and high-resolution direct numerical simulation data. The study shows that the diapycnal diffusivity can be decomposed into a diapycnal length scale and a diapycnal velocity scale, which can be related to the measurable Ellison length scale and vertical turbulent velocity scale through a turbulent Froude number scaling analysis.
Article
Thermodynamics
Guoqiang Wu, Sheng Chen
Summary: This paper investigates the collision between a moving droplet and a moving particle with heat transfer using the lattice Boltzmann method and a modified immersed boundary method. The influence of Prandtl number (0.1 <= Pr <= 10) and Grashof number (-100 <= Gr <= 100) is considered. The results indicate that the vertical velocity of the particle (Uz) increases with the increment of Pr and Gr. Uz is divided into three stages based on Pr and Gr >= 0, and four stages for Gr = -100. Particularly, in the last stage (when the droplet separates from the particle), Uz only varies slightly.
INTERNATIONAL COMMUNICATIONS IN HEAT AND MASS TRANSFER
(2023)
Article
Nuclear Science & Technology
Yiqi Yu, Emily Shemon, Elia Merzari
Summary: The Westinghouse Electric Company is developing a high-capacity nuclear power plant using lead-cooled fast reactor technology. The low Prandtl number of lead compared to water affects the thermal boundary layer and requires a different turbulent Prandtl number for accurate simulation. The study uses Large Eddy Simulation to investigate the flow and heat transfer in a rod bundle with liquid metal flows, finding that a higher Prandtl number can significantly reduce the predicted Nusselt number.
NUCLEAR ENGINEERING AND DESIGN
(2023)
Article
Mechanics
Romain Alis, Sebastien Tanguy, Kalyani Kentheswaran, Olivier Rouzaud, Jean-Luc Estivalezes
Summary: In this paper, Direct Numerical Simulations are used to investigate the interaction between a vaporising spherical droplet and a high-temperature vapour flow. The simulations show quantitative agreement with previous correlations on the Nusselt number, but new trends are obtained by varying the Prandtl number. The analysis of the total force acting on the droplet reveals the importance of the component related to phase change, and a simple semi-empirical model is proposed to describe this force. Additionally, a new dimensionless number based on the ratio between the Spalding and Prandlt numbers is highlighted to describe the flow around the droplet.
INTERNATIONAL JOURNAL OF MULTIPHASE FLOW
(2023)
Article
Physics, Particles & Fields
Naima Ziani, Kamel Khelifa-Kerfa, Yazid Delenda
Summary: In this study, we address the issues of clustering and nonglobal logarithms for jet shapes in the process of Higgs/vector boson production with a single hard jet at hadron colliders. We performed both analytical fixed-order calculations and all-orders estimations for the specific invariant mass distribution of the highest-p(t) jet, using various jet algorithms. Our results, derived in the eikonal (soft) limit, show good agreement with next-to-leading order results and experimental data from the CMS collaboration after accounting for non-perturbative effects.
EUROPEAN PHYSICAL JOURNAL C
(2021)
Article
Mechanics
Megumi Akashi, Takatoshi Yanagisawa, Ataru Sakuraba, Felix Schindler, Susanne Horn, Tobias Vogt, Sven Eckert
Summary: The study examines the topology and temporal dynamics of turbulent Rayleigh-Benard convection in a liquid metal with a low Prandtl number inside a box with specific dimensions. Results show similarities to the jump rope vortex structure discovered in a different configuration, with the coexistence of multiple recirculating swirls. This complex flow behavior leads to variations in velocity and Nusselt number oscillations.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Thermodynamics
Gaurav Shukla, Nitin Dutt Chaturvedi
Summary: Hydrogen management in an uncertain environment is important and a novel framework and analysis for minimizing compression work in hydrogen allocation network is proposed. Stochastic and robust optimization approaches are used to convert uncertainty into deterministic equivalents and find the most appropriate solutions.
Article
Thermodynamics
Imran Mokashi, Asif Afzal, Sher Afghan Khan, Nur Azam Abdullah, Muhammad Hanafi Bin Azami, R. D. Jilte, Olusegun David Samuel
Summary: This article analyzes the heat transfer situation in a battery pack cooled by flowing fluid using artificial neural network models. It is found that conductivity ratio and heat generation term do not improve the average Nusselt number (Nu(avg), while Prandtl number and Reynolds number vary it significantly in each step. Additionally, Nu(avg) is found to continuously increase with increasing Re, but for oils, an increase in Pr and Re results in a significant decrease in Nu(avg).
INTERNATIONAL JOURNAL OF THERMAL SCIENCES
(2021)
Article
Thermodynamics
Geert Brethouwer
Summary: Rotation has a significant impact on flows and transport processes in engineering applications, but its effects are not fully understood. In this study, numerical simulations are used to investigate the influence of rotation on heat and momentum transfer in Couette and Taylor-Couette flows. It is found that anti-cyclonic rotation initially increases the Nusselt numbers for momentum and heat transfer, but they decrease and approach unity at high rotation rates. The Reynolds analogy factor also increases with rotation, indicating that the heat transfer can become faster than momentum transfer.
INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER
(2023)
Article
Physics, Fluids & Plasmas
V. K. Zotta, L. Garzotti, F. J. Casson, D. Frigione, F. Kochl, E. Lerche, P. Lomas, F. Rimini, M. Sertoli, D. Van Eester, R. Gatto, C. Mazzotta, G. Pucella
Summary: The fusion performance of ELMy H-mode 50-50 DT plasmas was predicted using the JINTRAC suite of codes and the QuaLiKiZ transport model. The simulations analyzed the sensitivity of the predictions to plasma parameters and auxiliary heating power, showing that a fusion power of 10 MW should be achievable under a wide range of assumptions, while higher fusion power approaching 15 MW could be achieved with particularly pure plasmas and additional heating power of 40 MW.
Article
Physics, Fluids & Plasmas
A. R. Field, F. J. Casson, D. Fajardo, C. Angioni, C. D. Challis, J. Hobirk, A. Kappatou, Hyun-Tae Kim, E. Lerche, A. Loarte, J. Mailloux
Summary: Screening of high-Z (W) impurities from the plasma periphery by temperature gradient has been demonstrated in the JET-ILW tokamak. Careful optimization of the hybrid scenario allows for the expulsion of W impurities from the confined plasma, resulting in sustained high performance. Measurements show a net efflux of impurities between edge-localised modes (ELMs), with some W re-entering during ELMs.
Article
Physics, Fluids & Plasmas
D. Fajardo, C. Angioni, F. J. Casson, A. R. Field, P. Maget, P. Manas
Summary: The impact of rotation, collisionality, and trapped particle fraction on neoclassical impurity transport in tokamaks is studied. The study reveals that at high Mach number and low collisionality, a window of operation opens where the impurity temperature screening effect increases with rotation. However, with increasing collisionality, this effect diminishes and the temperature gradient drives an inward impurity flux in the presence of rotation. The boundaries between these regimes are calculated and plasma parameters achieved in recent experiments are found to access the beneficial regime.
PLASMA PHYSICS AND CONTROLLED FUSION
(2023)
Article
Physics, Fluids & Plasmas
A. Ho, J. Citrin, C. D. Challis, C. Bourdelle, F. J. Casson, J. Garcia, J. Hobirk, A. Kappatou, D. L. Keeling, D. B. King, F. Koechl, E. Lerche, C. F. Maggi, J. Mailloux
Summary: This study applies the coupled JINTRAC and QuaLiKiz-neural-network (QLKNN) model to investigate the ohmic current ramp-up phase of a JET D discharge. It reveals the role of transport on the Te hollowing, which is caused by the isotope effect on the electron-ion energy exchange. The study demonstrates the potential of neural network surrogates for fast routine analysis and discharge design, but discrepancies between QuaLiKiz and QLKNN impurity transport behavior were found, suggesting further investigation into the turbulent component of heavy impurity transport.
Article
Physics, Fluids & Plasmas
Paulo Rodrigues, Duarte Borba, Francesca Cella, Rui Coelho, Jorge Ferreira, Antonio Figueiredo, Mervi Mantsinen, Fernando Nabais, Sergei Sharapov, Paula Siren
Summary: A recent model is used to explain the properties of Alfvenic activity observed on JET plasmas below the frequency of toroidicity-induced Alfven eigenmodes (TAEs). The frequency gaps predicted by the model result from high-order harmonics of the geodesic field-line curvature caused by plasma shaping and give rise to high-order geodesic acoustic eigenmodes (HOGAEs), their frequency value being close to one-half of the TAEs one. The theoretical predictions of HOGAE frequency and radial location are in fair agreement with measurements in JET experiments.
Article
Physics, Fluids & Plasmas
M. F. F. Nave, E. Delabie, J. Ferreira, J. Garcia, D. King, M. Lennholm, B. Lomanowski, F. Parra, P. R. Fernandez, J. Bernardo, M. Baruzzo, M. Barnes, F. Casson, J. C. Hillesheim, A. Hubber, E. Joffrin, A. Kappatou, C. F. Maggi, A. Mauriya, L. Meneses, M. Romanelli, F. Salzedas
Summary: The isotope effect on intrinsic rotation was investigated at JET tokamak, comparing experiments in hydrogen, deuterium and tritium. Two rotation reversals per isotope type were observed in plasma density scans, with a clear dependence on isotope mass at higher densities. The core rotation magnitude was found to vary with isotope mass, showing stronger co-current rotation in hydrogen, and intrinsic rotation characteristics changed along with stronger thermal energy confinement in tritium.
Article
Physics, Fluids & Plasmas
A. Mishchenko, A. Biancalani, M. Borchardt, A. Bottino, S. Briguglio, R. Dumont, J. Ferreira, J. P. Graves, T. Hayward-Schneider, R. Kleiber, A. Koenies, E. Lanti, Ph Lauber, H. Leyh, Z. X. Lu, H. Lutjens, B. McMillan, M. Campos Pinto, E. Poli, B. Rettino, B. Rofman, J. N. Sama, C. Slaby, F. Vannini, L. Villard, G. Vlad, X. Wang, F. Widmer, F. Zonca
Summary: This article introduces a software stack being developed as part of a European coordinated effort on tools for burning plasma modelling. The project is organized under the E-TASC initiative and is supported by the Advanced Computing Hubs. It aims to develop codes and release the software stack to the EUROfusion community.
PLASMA PHYSICS AND CONTROLLED FUSION
(2023)
Review
Chemistry, Analytical
Bruno Goncalves, Paulo Varela, Antonio Silva, Filipe Silva, Jorge Santos, Emanuel Ricardo, Alberto Vale, Raul Luis, Yohanes Nietiadi, Artur Malaquias, Jorge Belo, Jose Dias, Jorge Ferreira, Thomas Franke, Wolfgang Biel, Stephane Heuraux, Tiago Ribeiro, Gianluca De Masi, Onofrio Tudisco, Roberto Cavazzana, Giuseppe Marchiori, Ocleto D'Arcangelo
Summary: Providing energy from fusion and scaling up the process efficiently and economically is a major challenge in engineering. Plasma Position Reflectometry (PPR) plays an important role in future fusion machines by monitoring plasma position and shape. It uses radar methods in microwave and millimetre wave frequency ranges to measure density profile for plasma control.
Article
Physics, Fluids & Plasmas
D. Kennedy, M. Giacomin, F. J. Casson, D. Dickinson, W. A. Hornsby, B. S. Patel, C. M. Roach
Summary: In this study, a linear gyrokinetic analysis is conducted to investigate the electromagnetic microinstabilities in a high-beta, reactor-scale, tight-aspect-ratio tokamak called Spherical Tokamak for Energy Production. The results reveal that the dominant instabilities at ion binormal scales are a hybrid version of the kinetic ballooning mode (KBM) instability, with contributions from the ion temperature gradient and trapped electrons, while collisional microtearing modes (MTMs) are sub-dominantly unstable at similar scales. The different radial scales of the hybrid-KBM and MTM are also observed. The study examines the sensitivity of these instabilities to physics parameters and discusses potential mitigation mechanisms. Benchmarking and testing with multiple gyrokinetic codes provide confidence in the accuracy of the results, setting the stage for further nonlinear studies in future research.
Article
Physics, Fluids & Plasmas
S. Gabriellini, L. Garzotti, V. K. Zotta, C. Bourdelle, F. J. Casson, J. Citrin, D. Frigione, R. Gatto, C. Giroud, F. Koechl, P. Lomas, M. Marin, S. Menmuir, G. Pucella, F. Rimini, D. van Eester, JET Contributors
Summary: We present a fully predictive modelling of two JET-ILW high-performance baseline plasmas, comparing a Ne seeded shot and an equivalent unseeded one. The results suggest that the improved performance of the Ne seeded shot is due to a combination of turbulence stabilization and improved pedestal parameters.
Article
Physics, Fluids & Plasmas
J. Garcia, F. J. Casson, L. Frassinetti, D. Gallart, L. Garzotti, H. -t. Kim, M. Nocente, S. Saarelma, F. Auriemma, J. Ferreira, S. Gabriellini, A. Ho, P. Huynh, K. K. Kirov, E. Lerche, M. J. Mantsinen, V. K. Zotta, Z. Stancar, D. M. A. Taylor, D. Van Eester, C. D. Challis, JET Contributors
Summary: For more than a decade, an unprecedented predict-first activity has been carried out to predict fusion power and provide guidance to the DTE2 campaign. It is shown that detailed physics-based predictions are necessary and a combination of different modeling complexities and an extended interplay between modeling and experiment are essential for reliable predictions of D-T plasmas.
Article
Physics, Fluids & Plasmas
H. J. C. Oliver, S. E. Sharapov, Z. Stancar, M. Fitzgerald, E. Tholerus, B. N. Breizman, M. Dreval, J. Ferreira, A. Figueiredo, J. Garcia, N. Hawkes, D. L. Keeling, P. G. Puglia, P. Rodrigues, R. A. Tinguely
Summary: The Joint European Torus conducted an experimental campaign using a mixture of deuterium (D) and tritium (T) plasma and observed a high-frequency mode known as the toroidal Alfven eigenmode (TAE). Through simulations and calculations, it was found that the TAE can be driven by beam ions with high toroidal mode numbers, while alpha particles contribute less to the driving force. Radiative damping was identified as the dominant damping mechanism. The observed TAE matched the calculated results.
Article
Physics, Fluids & Plasmas
Hyun-Tae Kim, Fulvio Auriemma, Jorge Ferreira, Stefano Gabriellini, Aaron Ho, Philippe Huynh, Krassimir Kirov, Rita Lorenzini, Michele Marin, Michal Poradzinski, Nan Shi, Gary Staebler, Ziga Stancar, Gediminas Stankunas, Vito Konrad Zotta, Emily Belli, Francis J. Casson, Clive Challis, Jonathan Citrin, Dirk van Eester, Emil Fransson, Daniel Gallart, Jeronimo Garcia, Luca Garzotti, Renato Gatto, Joerg Hobirk, Athina Kappatou, Ernesto Lerche, Andrei Ludvig-Osipov, Costanza Maggi, Mikhail Maslov, Massimo Nocente, Ridhima Sharma, Alessandro Di Siena, Par Strand, Emmi Tholerus, Dimitriy Yadykin
Summary: The JET experiments provide an opportunity to validate D-T fusion power predictions and support future device design and operation preparation. The core integrated modelling with TRANSP, JINTRAC, and ETS coupled with a quasilinear turbulent transport model was validated against the measured data in 2021 JET D-T discharges. The good statistical agreement confirms the accuracy of D-T fusion power calculations, and similarities were found between the predictive modelling of D-T and counterpart D discharges.