Article
Physics, Fluids & Plasmas
K. Tanaka, K. Nagaoka, K. Ida, H. Yamada, T. Kobayashi, S. Satake, M. Nakata, T. Kinoshita, Y. Ohtani, T. Tokuzawa, H. Takahashi, F. Warmer, K. Mukai, S. Murakami, R. Sakamoto, H. Nakano, M. Osakabe, T. Morisaki, M. Nunami, T. Tala, T. Tsujimura, Y. Takemura, M. Yokoyama, R. Seki, H. Igami, Y. Yoshimura, S. Kubo, T. Shimozuma, T. Akiyama, I Yamada, R. Yasuhara, H. Funaba, M. Yoshinuma, M. Goto, T. Oishi, S. Morita, G. Motojima, M. Shoji, S. Masuzaki, C. A. Michael, L. N. Vacheslavov
Summary: Isotope effects play a significant role in predicting future reactor operations, and extensive studies have been conducted on isotope effects in transport in the Large Helical Device (LHD). Results show that Deuterium plasma in LHD offers better accessibility to internal transport barriers, with reduced ion heat flux due to anti-gyro-Bohm scaling. Different turbulence structures were found in the mixing and non-mixing states of Deuterium and Hydrogen particle transports.
PLASMA PHYSICS AND CONTROLLED FUSION
(2021)
Article
Mechanics
Umesh Unnikrishnan, Hongfa Huo, Xingjian Wang, Vigor Yang
Summary: This paper presents a systematic investigation of large eddy simulation (LES) and subgrid scale (SGS) modeling with application to transcritical and supercritical turbulent mixing and combustion. It highlights the uncertainty in extending LES formalism to high-pressure real-fluid flows and reexamines the theoretical framework and assumptions in the context of real-fluid mixing and combustion.
Article
Astronomy & Astrophysics
Roland Grappin, Andrea Verdini, W-C Mueller
Summary: This study assesses two different approaches to understanding the turbulent cascade in the solar wind, including wind expansion. The results show that in the expanding case, the relative cross helicity decreases and the spectral index converges to an asymptotic value, while in the homogeneous simulations, the relative cross helicity increases and pinning occurs.
ASTROPHYSICAL JOURNAL
(2022)
Article
Mechanics
Xin-Lei Zhang, Ming-Ming Ge, Guang-Jian Zhang, Olivier Coutier-Delgosha
Summary: The RANS method coupling with cavitation model is a practical tool for predicting cavitating flows, but traditional RANS methods do not consider the compressibility effects induced by cavitation, requiring critical modeling of compressibility effects for predicting unsteady cavitating flows.
Article
Mechanics
Nilanjan Chakraborty, Umair Ahmed, Markus Klein, Hong G. Im
Summary: This study analyzed the relative alignment of pressure Hessian eigenvectors with reactive scalar gradient and strain rate eigenvectors in turbulent premixed flames. The results show that the reactive scalar gradient tends to align with the most extensive strain rate eigendirection or the most compressive strain rate eigendirection depending on the parameters. The eigenvectors of pressure Hessian do not perfectly align with the reactive scalar gradient and mainly act to reduce the scalar gradient in the zone of high dilatation rate.
Article
Construction & Building Technology
Akula Venkatram, Jeffrey Weil
Summary: This paper examines the applicability of the eddy diffusivity/gradient model for modeling dispersion of pollutants in confined spaces, and validates its effectiveness through re-analysis of data. The study found that the gradient transport model provides adequate descriptions of concentration measurements and allows for a detailed examination of the relationship between ventilation rate and material dose associated with aerosol releases. It also concludes with implications on mitigating exposure to aerosols such as airborne virus or bacteria.
Article
Computer Science, Interdisciplinary Applications
D. Dupuy, N. Odier, C. Lapeyre
Summary: This paper examines a data-driven approach for modeling the wall shear stress in large-eddy simulation of high Reynolds number wall-bounded turbulent flows. The model is a multilayer perceptron based on flow information near the wall, and it is able to extrapolate to unseen flow conditions. The model is verified using filtered numerical data and implemented in wall-modeled large-eddy simulations, showing its ability to discriminate developed wall turbulence and separated regions.
JOURNAL OF COMPUTATIONAL PHYSICS
(2023)
Article
Mechanics
M. Taha, S. Zhao, A. Lamorlette, J. L. Consalvi, P. Boivin
Summary: The pressure-based hybrid lattice-Boltzmann method proposed by Farag et al. was evaluated for simulating buoyancy driven flows. Validation studies on different cases and comparison with experimental results showed good overall agreement in terms of mean and fluctuation quantities, as well as global entrainment.
Article
Automation & Control Systems
Xiaobo Zhang, Zhanxue Wang, Li Zhou
Summary: The present study aims to address the issue of accuracy degradation in the traditional zero-dimensional variable cycle engine (VCE) model due to the multi-angle characteristics in the core-driven fan stage (CDFS). A two-dimensional model was established using the streamline curvature method, and a multi-level VCE model was developed to integrate the CDFS characteristics. The simulation results show that the proposed multi-level modeling approach is time-efficient and significantly improves optimal thrust and specific fuel consumption compared to the traditional zero-dimensional VCE model.
JOURNAL OF THE FRANKLIN INSTITUTE-ENGINEERING AND APPLIED MATHEMATICS
(2023)
Article
Physics, Fluids & Plasmas
X. -T. Yan, Y. -W. Sun, L. Li, Y. -Q. Liu, N. -N. Bao, A. Loarte, S. Pinches, B. -N. Wan
Summary: This study investigates Neoclassical toroidal viscosity (NTV) torque and induced toroidal momentum transport caused by resonant magnetic perturbation (RMP) for International Thermonuclear Experimental Reactor (ITER) scenarios through numerical modeling. The NTV torque is calculated using the NTVTOK code with the bounce-drift resonant effect, and the toroidal rotation evolution is modeled by solving a toroidal momentum transport equation. The results show that the variation of RMP coil phasing leads to different types of plasma response and different features of NTV torque and toroidal momentum transport. The bounce-drift resonant effect enhances NTV torque and induces more significant toroidal rotation variation compared to simulations with the bounce-averaged NTV model. With the initial rotation of the ITER design, plasma rotation is braked by NTV torque but may be sustained at a moderate amplitude due to electron contributions to NTV torque. Moreover, initially static or slowly rotating plasma can be accelerated by NTV torque towards either co-I-p or counter-I-p direction, suggesting that NTV torque can serve as a momentum source for plasma with low torque injection, such as radio-frequency heated plasma.
Article
Agricultural Engineering
Jeremy Z. Yan, Prashant Kumar, Wolfgang Rauch
Summary: This study investigates the impact of turbulent diffusion on mixing of biochemical reaction models and develops a new codebase called CHAD to incorporate and validate turbulent diffusion. The findings show that the implemented models accurately capture turbulent diffusion and reveal that thermal turbulent diffusion significantly influences mixing.
BIORESOURCE TECHNOLOGY
(2024)
Article
Mechanics
Subhojit Kadia, Nils Ruether, Ismail Albayrak, Elena Pummer
Summary: This study used OpenFOAM(R) to simulate turbulence-driven secondary currents in supercritical narrow channel flows. The results showed small deviations between the numerical and experimental results for longitudinal velocity, but differences were observed for secondary currents, vertical turbulence intensity, and Reynolds shear stress, especially for cases with higher flow nonuniformity. The aspect ratio (channel width to flow depth) played an important role in the formation and impact of secondary currents.
Article
Thermodynamics
Zhenyuan Tang, Bo Shi, Xueying Li, Jing Ren
Summary: This study investigates the influence of micro-ribs on turbulent momentum and heat transport in micro-ribbed channel flow by Large Eddy Simulation. The results show that micro-ribs enhance heat transport and weaken momentum transport.
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
Anuj Kumar, Martin Rieth, Opeoluwa Owoyele, Jacqueline H. Chen, Tarek Echekki
Summary: In this study, principal component (PC) transport is used to accelerate the direct numerical simulation (DNS) of turbulent combustion flows by implementing machine learning techniques. DNS based on the transport of thermochemical scalars is carried out to validate the approach, and the results show that surrogate PC DNS is able to reproduce both instantaneous profiles and statistics associated with turbulence and flame properties. Furthermore, parametric simulations with surrogate PC DNS are found to be much more cost-effective than full 3D DNS with species and energy transport.
COMBUSTION AND FLAME
(2023)
Article
Physics, Fluids & Plasmas
Masaki Osakabe, Hiromi Takahashi, Hiroshi Yamada, Kenji Tanaka, Tatsuya Kobayashi, Katsumi Ida, Satoshi Ohdachi, Jacobo Varela, Kunihiro Ogawa, Masahiro Kobayashi, Katsuyoshi Tsumori, Katsunori Ikeda, Suguru Masuzaki, Masahiro Tanaka, Motoki Nakata, Sadayoshi Murakami, Shigeru Inagaki, Kiyofumi Mukai, Mizuki Sakamoto, Kazunobu Nagasaki, Yasuhiro Suzuki, Mitsutaka Isobe, Tomohiro Morisaki, The Lhd Experiment Group
Summary: In recent deuterium experiments on the large helical device (LHD), we have explored techniques to increase the electron and ion temperatures in plasmas. We observed important phenomena such as the isotope effect in the formation of internal transport barrier and the simultaneous formation of edge transport barrier and divertor detachment. Additionally, the contributions of negative-ion based neutral beam injector research and tritium mass balance study to fusion reactor development are discussed.
Article
Physics, Fluids & Plasmas
M. Kobayashi, R. Seki, Y. Hayashi, T. Oishi, K. Tanaka, Y. Takemura, K. Ida, T. Kinoshita, K. Mukai, S. Morita, S. Masuzaki
Summary: This study examines the compatibility between good core plasma performance and divertor heat load mitigation by analyzing the interaction between cold edge plasma and core plasma transport, specifically the edge transport barrier (ETB), in LHD. It is found that the application of resonant magnetic perturbation (RMP) widens the edge stochastic layer and enhances impurity radiation, leading to stable detachment operation. However, as the detachment deepens, the resistive pressure gradient-driven MHD mode is excited, which degrades the ETB. Despite this, the core transport decreases to maintain the global plasma stored energy. Furthermore, a comparison between deuterium and hydrogen plasmas shows that deuterium plasmas exhibit better global confinement.
Article
Physics, Fluids & Plasmas
K. Ida, R. M. McDermott, C. Holland, M. J. Choi, L. M. Yu, T. Kobayashi, J. M. Kwon, Y. Kosuga
Summary: This conference report summarizes the contributions and discussions at the joint meeting of the 9th Asia Pacific-Transport Working Group (APTWG) & EU-US Transport Task Force (TTF) workshop. The meeting focused on various aspects of transport and physics, including the isotope effect, turbulence spreading and coupling, interplay between magnetohydrodynamic topology/instability and turbulent transport, interaction between energetic particle driven instability and transport, and model reduction and experiments for validation.
Article
Physics, Multidisciplinary
G. Motojima, S. Masuzaki, T. Morisaki, K. Y. Watanabe, M. Kobayashi, K. Ida, R. Sakamoto, M. Yoshinuma, R. Seki, H. Nuga, T. Tsujimura, C. Suzuki, M. Emoto, Y. Tsuchibushi, T. Murase, Y. Takeiri
Summary: The study shows that divertor pumping can effectively control stable plasma density and electron temperature by changing the magnetic axis position, especially in high plasma electron density and inner magnetic axis configuration.
Article
Computer Science, Interdisciplinary Applications
Y. Morishita, S. Murakami, M. Yokoyama, G. Ueno
Summary: This article introduces a data assimilation system, ASTI, for integrated transport simulation of fusion plasma. By assimilating the measured temperature and density data, ASTI is able to predict and control the behavior of fusion plasma.
COMPUTER PHYSICS COMMUNICATIONS
(2022)
Article
Physics, Fluids & Plasmas
Y. Yamamoto, S. Murakami, C. C. Chang, S. T. A. Kumar, J. N. Talmadge, K. M. Likin, D. T. Anderson
Summary: This study observes the spontaneous plasma flows in electron cyclotron heating plasmas and evaluates the parallel flow driven by ECH force. The obtained results show reasonable agreement with experiments, indicating that the radial electron current generated by ECH could drive the parallel flow.
Article
Physics, Fluids & Plasmas
R. Lunsford, S. Masuzaki, F. Nespoli, N. Ashikawa, E. P. Gilson, D. A. Gates, K. Ida, G. Kawamura, T. Morisaki, A. Nagy, T. Oishi, M. Shoji, C. Suzuki, M. Yoshinuma
Summary: Controlled particulate injections have shown positive effects on plasma wall conditions, with experiments demonstrating improvement across a range of parameters. Successful injections are confirmed by both spectroscopic measurements and real-time camera signals, paving the way for further development of real-time boronization techniques.
Article
Physics, Multidisciplinary
M. Kobayashi, K. Tanaka, K. Ida, Y. Hayashi, Y. Takemura, T. Kinoshita
Summary: Turbulence spreading induced by magnetic fluctuation is observed at the boundary region of the large helical device. Density fluctuation excited at the sharp boundary cannot propagate into the boundary due to the blocking effect of pressure gradient. However, when magnetic fluctuation appears at the boundary, density fluctuation starts to penetrate the edge layer and the pressure gradient decreases. This increase in density fluctuation leads to the reduction of divertor heat load.
PHYSICAL REVIEW LETTERS
(2022)
Article
Physics, Fluids & Plasmas
T. I. Tsujimura, T. Kobayashi, K. Tanaka, K. Ida, K. Nagaoka, M. Yoshinuma, I. Yamada, H. Funaba, R. Seki, S. Satake, T. Kinoshita, T. Tokuzawa, N. Kenmochi, H. Igami, K. Mukai, M. Goto, Y. Kawamoto
Summary: A plasma with a quasi-steady-state hollow electron-temperature profile can be generated using off-axis electron cyclotron heating. The formation of this profile can be explained by adding the outward heat convection term to the diffusion term in the energy conservation equation. The non-locality of the non-diffusive contribution in electron thermal transport was directly observed.
PHYSICS OF PLASMAS
(2022)
Article
Instruments & Instrumentation
F. J. Arellano, M. Yoshinuma, K. Ida
Summary: This study explored the use of a spatial heterodyne spectrometer to measure the toroidal flow velocity and ion temperature of C6+ impurity ion. The measurements obtained with the instrument were found to be consistent with those obtained using a conventional dispersive spectrometer.
REVIEW OF SCIENTIFIC INSTRUMENTS
(2022)
Article
Biochemistry & Molecular Biology
Shunzaburo Ono, Masaaki Komatsu, Akira Sakai, Hideki Arima, Mie Ochida, Rina Aoyama, Suguru Yasutomi, Ken Asada, Syuzo Kaneko, Tetsuo Sasano, Ryuji Hamamoto
Summary: In this study, a deep learning-based method for automated endocardial border detection and left ventricular functional assessment in two-dimensional echocardiographic videos was developed. The method showed high accuracy in segmenting the left ventricular cavity and estimating echocardiographic indexes. Among the four segmentation methods tested, UNet++ performed the best. This method has the potential to support examiners and improve workflow in echocardiography.
Article
Biochemistry & Molecular Biology
Akira Sakai, Masaaki Komatsu, Reina Komatsu, Ryu Matsuoka, Suguru Yasutomi, Ai Dozen, Kanto Shozu, Tatsuya Arakaki, Hidenori Machino, Ken Asada, Syuzo Kaneko, Akihiko Sekizawa, Ryuji Hamamoto
Summary: Diagnostic support tools based on AI have shown high performance in medical fields, but lack of explanatory power in AI decisions makes it challenging to establish trust with medical professionals. Visualizing the internal representation of deep neural networks can enhance explanation and boost confidence in AI decisions. Using deep learning-based explainable representation improves the performance of fetal cardiac ultrasound screening, providing evidence of the potential of explainable AI to augment examiner capabilities.
Article
Physics, Fluids & Plasmas
F. Nespoli, K. Tanaka, S. Masuzaki, N. Ashikawa, M. Shoji, E. P. Gilson, R. Lunsford, T. Oishi, K. Ida, M. Yoshinuma, Y. Takemura, T. Kinoshita, G. Motojima, M. Osakabe, N. Kenmochi, G. Kawamura, C. Suzuki, A. Nagy, A. Bortolon, N. A. Pablant, A. Mollen, N. Tamura, D. A. Gates, T. Morisaki
Summary: An improvement in the confinement regime of the Large Helical Device has been observed, characterized by reduced turbulent fluctuations, upon the injection of boron powder into the plasma. This article presents the experimental observations of increased plasma temperature and decreased turbulent fluctuations across the plasma cross section, using a larger database. Powder penetration modeling and analysis of neoclassical electric field and fluxes support the interpretation of the experimental results. The article also reports evidence of the temperature improvement depending on powder injection rates, density, and heating power, while the plasma turbulence response varies depending on the initial conditions.
Article
Physics, Fluids & Plasmas
T. Kobayashi, M. Yoshinuma, W. Hu, K. Ida
Summary: This paper proposes a tomography approach to reconstruct a phase-space structure. It is challenging to obtain a sufficiently high signal intensity in a single detector bin for the phase-space resolved diagnostic system that requires signal decomposition in real-space, velocity-space, and time. To overcome this difficulty, three different sets of data with different integration directions are used simultaneously to attempt a reconstruction of the original structure in the phase-space by tomography. The proposed method is demonstrated using a synthetic dataset in a real diagnostic setup and shown to successfully reconstruct the time evolution of a phase-space perturbation induced by Landau damping.
PHYSICS OF PLASMAS
(2023)
Article
Computer Science, Information Systems
Akira Sakai, Masafumi Yagi, Suguru Yasutomi, Kazuki Mizuno, Kanata Suzuki, Keiichi Goto
Summary: This study develops an inspection method for high-attenuation frozen materials using machine learning and applies it to assess the freshness of frozen tuna. The experiments show that all machine learning algorithms can classify the freshness of frozen tuna with statistical significance. Furthermore, an improvement in classification performance is observed by increasing the number of signals used.
