Article
Mechanics
Lei Shi, Yefang Wang
Summary: This study investigates the transitional flows around forward and reversed hydrofoils at different incidences using the SST gamma-(Re) over tilde (theta t) transition model, with a focus on the dynamics of the transition process. The results show that the reverse dynamic vortex near the flow separation point plays a key role in the transition process.
EUROPEAN JOURNAL OF MECHANICS B-FLUIDS
(2021)
Article
Physics, Fluids & Plasmas
J. Q. Xu, X. D. Peng, G. Z. Hao, W. Chen, J. Q. Li, H. P. Qu, J. C. Li, G. Z. Ren, X. X. He, Y. G. Li
Summary: The characteristics of zonal flows (ZFs) in ion temperature gradient (ITG) turbulence during the formation of internal transport barrier (ITB) have been investigated by nonlinear gyrokinetic simulations. The study reveals that the entropy generated by ion heat flux is significantly decreased while the zonal flow amplitude is enhanced and ion heat transport is reduced when ITB is fully developed. This suggests that long and medium radial scale turbulences are strongly suppressed by the zonal flow shear, and the zonal flow gains more energy from background turbulence when ITB is triggered.
PHYSICS OF PLASMAS
(2022)
Article
Astronomy & Astrophysics
Yan Yang, Moritz Linkmann, Luca Biferale, Minping Wan
Summary: In this study, numerical simulations were used to investigate the response of magnetohydrodynamics (MHD) to large-scale stochastic forcing mechanisms. The results show that injecting magnetic field has a significant impact on the total flux of kinetic energy transfer. Additionally, it was found that there are different energy transfer directions in heterochiral and homochiral components of the flux in different channels.
ASTROPHYSICAL JOURNAL
(2021)
Article
Physics, Fluids & Plasmas
G. Lo-Cascio, E. Gravier, T. Reveille, M. Lesur, Y. Sarazin, X. Garbet, L. Verner, K. Lim, A. Guillevic, V Grandgirard
Summary: Two methods for producing transport barriers through strong shear of the E x B poloidal flow were investigated using GYSELA gyrokinetic simulations. The results show that when a certain threshold of shear rate and linear growth rate is reached, there is an increase in pressure and a decrease in turbulent heat diffusivity coefficient, indicating the formation of a transport barrier. This behavior is a result of reduced turbulence intensity, which is strongly correlated with the shearing of turbulent structures.
Article
Physics, Multidisciplinary
Aristeides D. Papadopoulos, Johan Anderson, Eun-jin Kim, Michail Mavridis, Heinz Isliker
Summary: A geometrical method for assessing stochastic processes in plasma turbulence is investigated, using a Riemannian metric on the phase space to compute distances between thermodynamic states. This method provides a geometric approach to understand stochastic processes, such as order-disorder transitions. The study focuses on gyrokinetic simulations of ion-temperature-gradient (ITG)-mode-driven turbulence in the W7-X stellarator.
Article
Mechanics
In Mei Sou, Yun-Ta Wu, Philip L. -F. Liu
Summary: Six consecutive solitary waves were generated to study the flow structures during the uprush-downwash interactions in the swash zone. The cross-shore velocity fields were captured using particle image velocimetry. Two different wave conditions with different wave-height-to-water-depth ratios were examined. The study found that the uprush-downwash interaction reaches quasi-steady state from the third solitary wave, and the flow structures differ between the two wave conditions.
JOURNAL OF FLUID MECHANICS
(2023)
Article
Mechanics
J. R. C. King, S. J. Lind, B. D. Rogers, P. K. Stansby, R. Vacondio
Summary: For turbulent bubbly flows, the cost of multi-phase simulations that resolve both the liquid and bubbles is high. A more cost-effective alternative is to resolve large scales and model small-scale bubbles using sub-resolution closures. This study introduces a large eddy simulation smoothed particle hydrodynamics (SPH) scheme for simulations of bubbly flows, coupling a discrete bubble model with the SPH framework for the continuous liquid phase.
JOURNAL OF FLUID MECHANICS
(2023)
Article
Mechanics
A. Chauhan, S. Gupta, C. Sasmal
Summary: This study presents a numerical investigation of viscoelastic fluid flows in porous media. It is found that geometric disorder increases chaotic fluctuations in the flow, which is attributed to the formation of preferential paths and highly curved streamlines. The chaotic flow behavior is strongly influenced by the competition between strain-hardening and shear-thinning behaviors of the viscoelastic fluid.
Article
Physics, Fluids & Plasmas
J. Citrin, S. Maeyama, C. Angioni, N. Bonanomi, C. Bourdelle, F. J. Casson, E. Fable, T. Goerler, P. Mantica, A. Mariani, M. Sertoli, G. Staebler, T. Watanabe
Summary: Previous studies suggested that ETG turbulence could lead to an anti-gyroBohm isotope scaling in JET high-performance hybrid H-mode scenarios. However, a comparison study with higher-fidelity turbulence modeling invalidates this claim and shows that ion-scale turbulence with magnetic field perturbations can match the power balance fluxes within temperature gradient error margins. Multiscale gyrokinetic simulations from two distinct codes also demonstrate the absence of significant ETG heat flux, indicating that simple rules-of-thumb are insufficient criteria for its onset.
Article
Mechanics
Teng Xiao, Bin Xie, Xi Deng, Yanping Du
Summary: In this work, high-fidelity numerical solvers for turbulent cavitation flows were developed and used to simulate cavitation and supercavitation. The proposed solver utilizes the VOF function, interface capture method, and mass transfer models to accurately resolve cavitation bubble structures. The simulations show better agreement with experimental data and theoretical solutions compared to previous works, validating the high-fidelity predictions of the proposed solver for turbulent cavitation simulations.
Article
Physics, Fluids & Plasmas
Marie-Luise Maier, Ravi A. Patel, Nikolaos Prasianakis, Sergey Churakov, Hermann Nirschl, Mathias J. Krause
Summary: Reactive particulate systems play a crucial role in process engineering applications, and modeling can be a powerful tool for optimizing process conditions. The study introduces a new generic modeling framework using a combination of lattice Boltzmann method and discrete-element method to capture relevant aspects of reactive particle fluid flows.
Article
Engineering, Chemical
Jun-Sen Li, Li-Tao Zhu, Wei-Cheng Yan, Taha Abbas Bin Rashid, Qun-Jie Xu, Zheng-Hong Luo
Summary: The study found that the impact of different turbulence models on predictions of fluidization processes in the mesoscale gas-solid flow system varies. By utilizing a hybrid model and different turbulence closure models in a circulating fluidized bed CFB, more accurate predictions of flow characteristics can be achieved.
Article
Physics, Multidisciplinary
Jonathan Skipp, Sergey Nazarenko
Summary: In this study, we investigate the thermodynamic equilibrium spectra of the Charney-Hasegawa-Mima (CHM) equation under its weakly nonlinear limit. By exploring the influence of the third invariant, we find that the variety of equilibrium spectra in the CHM system is significantly enriched. We also characterize the singular limits of these spectra, where condensates occur, and show that they are associated with characteristic structures observed in CHM systems of finite size.
JOURNAL OF PHYSICS A-MATHEMATICAL AND THEORETICAL
(2022)
Review
Energy & Fuels
Simone Ferrari, Riccardo Rossi, Annalisa Di Bernardino
Summary: This review provides an overview of laboratory and numerical techniques for investigating turbulent flows, highlighting their advantages, disadvantages, main fields of application, and trends. A bibliometric analysis reveals a projected dominant trend of numerical simulations over laboratory experiments in the field of turbulence. However, both experimental and numerical techniques have their own strengths and weaknesses and are indispensable in turbulent flow research.
Article
Astronomy & Astrophysics
Krzysztof Stasiewicz, Bengt Eliasson
Summary: We demonstrate that quasi-adiabatic electron heating in quasi-perpendicular shocks is supported by measurements obtained from NASA's MMS mission, with the temperature Tｅ perpendicular to proportional to B1 + α, where B is the magnetic field strength and α represents departure from adiabaticity. Our findings show that most situations exhibit negative α, resulting in a redistribution of perpendicular energy gain from adiabatic heating to the parallel direction, leading to a lower isotropic temperature increase. However, positive α is observed in cases where the stochastic heating of electrons is activated by the E x B wave acceleration mechanism, resulting in a higher temperature increase.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Physics, Fluids & Plasmas
V. V. Bulanin, E. Z. Gusakov, V. K. Gusev, G. Zadvitskiy, C. Lechte, S. Heuraux, V. B. Minaev, A. V. Petrov, Yu. V. Petrov, N. V. Sakharov, N. Teplova, A. Yu. Yashin
PLASMA PHYSICS REPORTS
(2020)
Article
Physics, Fluids & Plasmas
E. Z. Gusakov, A. Yu Popov
PLASMA PHYSICS AND CONTROLLED FUSION
(2020)
Article
Physics, Multidisciplinary
A. A. Belokurov, G. Abdullina, L. G. Askinazi, V. V. Bulanin, L. Chone, A. D. Gurchenko, E. Z. Gusakov, T. P. Kiviniemi, V. A. Kornev, S. Krikunov, D. Kouprienko, S. Lashkul, S. Lebedev, S. Leerink, P. Niskala, A. Petrov, D. Razumenko, A. S. Tukachinsky, A. Yu Yashin, N. A. Zhubr
Article
Physics, Fluids & Plasmas
K. A. Razumova, V. F. Andreev, L. G. Eliseev, M. Y. Kantor, N. Kasyanova, S. E. Lysenko, A. Melnikov
Summary: The article describes processes linked to energy confinement in tokamak plasmas from the perspective of self-organization, extending the analysis to regimes with barriers and magnetic islands. It discusses the structure of the radial heat flux that carries energy from the plasma while maintaining a close pressure profile to the experimentally observed self-consistent profile.
PLASMA PHYSICS AND CONTROLLED FUSION
(2021)
Article
Physics, Fluids & Plasmas
Timo P. Kiviniemi, Eero Hirvijoki, Antti J. Virtanen
Summary: In this study, the impact of the size of collision cells on the accuracy of binary-collision algorithms is numerically investigated, particularly in the context of full-f fusion plasma simulations. The implications of fluctuating magnetic and electric fields on the conserved quantities in drift-kinetic formulations are discussed, along with potential ways to improve the accuracy of the algorithms with minor modifications.
JOURNAL OF PLASMA PHYSICS
(2021)
Article
Instruments & Instrumentation
V. V. Bulanin, A. Y. Yashin, A. V. Petrov, V. K. Gusev, V. B. Minaev, M. I. Patrov, Y. V. Petrov, D. V. Prisiazhniuk, V. I. Varfolomeev
Summary: This article discusses the use of a four-frequency microwave Doppler backscattering system in the compact spherical tokamak Globus-M, with hardware adequate for studying the peripheral plasma. The multichannel DBS system is based on duplicating a dual homodyne detection circuit for four incident Ka-band frequencies, with specific requirements for antenna tilt adjustments. Experimental results using DBS diagnostics on the Globus-M tokamak are presented to demonstrate its efficiency.
REVIEW OF SCIENTIFIC INSTRUMENTS
(2021)
Article
Physics, Fluids & Plasmas
C. J. Ham, A. Bokshi, D. Brunetti, G. Bustos Ramirez, B. Chapman, J. W. Connor, D. Dickinson, A. R. Field, L. Frassinetti, A. Gillgren, J. P. Graves, T. P. Kiviniemi, S. Leerink, B. McMillan, S. Newton, S. Pamela, C. M. Roach, S. Saarelma, J. Simpson, S. F. Smith, E. R. Solano, P. Strand, A. J. Virtanen
Summary: The study focuses on the physics of the tokamak pedestal and its significance in determining fusion power for potential power plants. The research attempts to improve understanding of reactor-relevant pedestals, but faces challenges in predictive modeling due to uncertainties in density and temperature profiles. Additionally, it highlights the detrimental effects of type I ELMs on plasma facing components in reactor-relevant regimes, and explores alternative methods to avoid these large ELMs.
Article
Physics, Fluids & Plasmas
T. P. Kiviniemi, A. J. Virtanen, H. Systa, L. Chone, S. Leerink, E. Hirvijoki
Summary: The study found a clear effect of poloidally localized atom source on the bootstrap current in the tokamak pedestal, especially for thermal particles. However, this effect largely disappears for cold particles.
PLASMA PHYSICS AND CONTROLLED FUSION
(2021)
Article
Physics, Multidisciplinary
E. Z. Gusakov, A. Yu. Popov
Summary: This study predicts the trapping of a lower hybrid wave in the tokamak edge transport barrier, which can significantly reduce the excitation threshold for the absolute parametric decay instability in electron cyclotron resonance heating experiments. This process is similar to stimulated Raman scattering instability in laser physics and can cause anomalous scattering of the pump wave.
PHYSICAL REVIEW LETTERS
(2022)
Article
Physics, Fluids & Plasmas
E. Z. Gusakov, A. Yu Popov
Summary: The study predicts the trapping of high harmonic ion Bernstein waves in a magnetic island with a plasma density maximum, leading to a decrease in the primary instability saturation level and substantial suppression of anomalous absorption of the pump wave.
PLASMA PHYSICS AND CONTROLLED FUSION
(2021)
Article
Physics, Fluids & Plasmas
Salomon Janhunen, Gabriele Merlo, Alexey Gurchenko, Evgeniy Gusakov, Frank Jenko, Timo Kiviniemi
Summary: This study observed electron density fluctuations at the electron Larmor radius scales using the enhanced scattering diagnostic on the FT-2 tokamak. Gyrokinetic GENE simulations were used to investigate the presence of turbulence from the electron temperature gradient driven instability. The results showed that ion-scale turbulence is responsible for most of the transport via trapped electron modes and impurities merge the spectrum of ion and electron scale instabilities into a continuum.
PLASMA PHYSICS AND CONTROLLED FUSION
(2022)
Article
Physics, Fluids & Plasmas
E. Z. Gusakov, A. Y. Popov
Summary: This study investigates the induced scattering parametric decay instability of ordinary microwaves, leading to the excitation of lower hybrid or electron plasma waves within a tokamak edge transport barrier. Numerical estimates of the instability threshold and growth rate for this scenario are provided for O1-mode ECRH at ITER and O2-mode ECRH and CTS experiments at ASDEX Upgrade, indicating the possibility of investigating these phenomena.
Article
Physics, Fluids & Plasmas
A. Y. Popov, A. A. Nagovitsin, E. Z. Gusakov
Summary: The dispersion equation for metastable states in a finite tower of eigenmodes of trapped upper hybrid waves with a non-monotonic density profile is derived and solved analytically and numerically. The influence of UH eigenmode damping due to radiation losses on the saturation level of the two-UH-plasmon low-threshold parametric decay instability is analyzed. Transitions from the odd-step number secondary decay saturation cascade to the even one and vice versa, caused by radiation loss variation, are investigated and shown to result in a substantial change of the anomalous absorption.
PLASMA PHYSICS AND CONTROLLED FUSION
(2022)
Article
Physics, Fluids & Plasmas
P. Tretinnikov, E. Gusakov, S. Heuraux
Summary: This paper provides an analytical description of the collective Thomson scattering (CTS) experiment, specifically focusing on the distortion of probing microwave beams due to plasma edge turbulence. The effect of turbulence on the registered frequency spectrum distortion is evaluated for plasma parameters similar to those expected in ITER.
PHYSICS OF PLASMAS
(2023)
Article
Physics, Fluids & Plasmas
P. V. Tretinnikov, A. Yu. Popov, E. Z. Gusakov, S. Heuraux
Summary: The saturation level of the Upper-Hybrid-plasmon low-threshold parametric decay instability (PDI) depends on the beam width of the pump wave. Edge plasma turbulence can cause significant distortion of the pump beam, resulting in changes to the PDI characteristics. Numerical evaluations show that moderate turbulence has minimal effect on PDI characteristics, but high turbulence levels lead to increased threshold and reduced growth rate. It is noteworthy that anomalous absorption remains slightly reduced regardless of the edge turbulence regimes.
PHYSICS OF PLASMAS
(2023)
