Article
Computer Science, Interdisciplinary Applications
Hao-Ran Liu, Chong Shen Ng, Kai Leong Chong, Detlef Lohse, Roberto Verzicco
Summary: The study introduces a new discretization scheme for the biharmonic term of the Cahn-Hilliard equation, which significantly reduces computational costs while maintaining accuracy. Through large-scale computations, the method demonstrates excellent performance in terms of efficiency and accuracy.
JOURNAL OF COMPUTATIONAL PHYSICS
(2021)
Article
Engineering, Aerospace
Anirban Garai, Scott M. Murman
Summary: Traditional adjoint variables in turbulent chaotic flows exhibit exponential growth, but most proposed methods are computationally prohibitive for practical problems. This paper evaluates a cost-effective stabilization approach for adjoints of turbulent flows inspired by studying the adjoint-energy budget. The resulting adjoint and parameter sensitivity from this approach are compared with the shadow adjoint approach for the minimal flow unit.
Article
Mechanics
Chi-An Yeh, Muralikrishnan Gopalakrishnan Meena, Kunihiko Taira
Summary: This study introduces a network-based modal analysis technique utilizing Katz centrality to identify key dynamical paths for amplifying perturbations on time-varying base flows, with broadcast modes revealing sensitive regions in the fluid-flow network. The application to two-dimensional decaying isotropic turbulence highlights the importance of vortex dipoles in perturbation spreading, demonstrating the effectiveness of modifying turbulent evolution through flow perturbation. This network-inspired approach presents a novel use of network analysis for guiding flow control efforts, particularly for time-varying base flows.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Engineering, Civil
G. Duan, T. Takemi
Summary: This study examines gustiness for wind speed, fluctuations, turbulence intensities, and fluxes in real urban topography. Results show a strong linear scaling of gustiness with the plan-area index in neutral, stable, and unstable stratification flows. Building-height variability and effective frontal-area index are argued to be more appropriate scaling parameters for gustiness.
JOURNAL OF WIND ENGINEERING AND INDUSTRIAL AERODYNAMICS
(2021)
Article
Computer Science, Interdisciplinary Applications
Xin-Lei Zhang, Heng Xiao, Guo-Wei He, Shi-Zhao Wang
Summary: This study investigates how to enhance the reconstruction of turbulent mean flows by simultaneously incorporating velocity observations and different sources of wall quantities using ensemble Kalman methods. The results demonstrate that incorporating various disparate data sources can improve the accuracy of flow-field estimation.
COMPUTERS & FLUIDS
(2021)
Article
Engineering, Aerospace
Jiachen Lu, Jinping Li, Ziming Song, Wei Zhang, Chao Yan
Summary: This study quantifies the uncertainties in heat transfer and pressure and identifies their main contributors. The results show that the uncertainty in heat transfer is higher than that in pressure, and freestream velocity, freestream static pressure, and fin angles are the key parameters influencing heat transfer.
AEROSPACE SCIENCE AND TECHNOLOGY
(2022)
Article
Computer Science, Interdisciplinary Applications
Guiyu Cao, Liang Pan, Kun Xu
Summary: The study investigates the performance of high-order gas-kinetic scheme (HGKS) for the direct numerical simulation (DNS) of compressible turbulence up to the supersonic regime. A parallel HGKS code is developed for large-scale computation using domain decomposition and message passing interface (MPI). The tests verify the scalability, efficiency, accuracy, and robustness of the parallel implementation under various flow conditions, showing comparable performance with high-order finite difference schemes for nearly incompressible turbulence and advantages for supersonic turbulent flow simulation based on the kinetic formulation.
JOURNAL OF COMPUTATIONAL PHYSICS
(2022)
Article
Mechanics
Dario Vincenzi, Takeshi Watanabe, Samriddhi Sankar Ray, Jason R. Picardo
Summary: This paper investigates polymer scission in turbulent flows through stochastic modeling and direct numerical simulations, studying the characteristics of both passive and active polymers. The results show that the reduction of kinetic energy dissipation is maximized by an intermediate polymer relaxation time, where polymers stretch significantly but do not break too quickly.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Physics, Multidisciplinary
M. Davoodianidalik, H. Punzmann, H. Kellay, H. Xia, M. Shats, N. Francois
Summary: This study provides experimental evidence for the existence of fluctuation-induced forces mediated by turbulent fluctuations in confined turbulence. The strength of this long-range interaction is dependent on the wall separation and energy injection rate in the turbulent flow. The mechanism of force generation is rooted in the nontrivial fluid-wall coupling, where coherent flow structures are guided by the cavity walls.
PHYSICAL REVIEW LETTERS
(2022)
Article
Mathematics, Interdisciplinary Applications
Tommaso Alberti, Francois Daviaud, Reik V. Donner, Berengere Dubrulle, Davide Faranda, Valerio Lucarini
Summary: Turbulent flows exhibit complex dynamics characterized by non-hyperbolic chaos, randomness, state-dependent persistence, and unpredictability. The concept of universality of turbulent attractors is shown to be invalid as their properties depend on the scale of observation. These changing attractors, which we term chameleon attractors, highlight the dynamic nature of turbulence.
CHAOS SOLITONS & FRACTALS
(2023)
Article
Physics, Multidisciplinary
G. Prabhudesai, S. Perrard, F. Petrelis, S. Fauve
Summary: This study investigates the spatiotemporal coherence of turbulent velocity fluctuations and demonstrates that it decays exponentially with distance, depending on the flow properties. The observed law appears to be a generic property of turbulent flows, as it is consistent in two different flows.
PHYSICAL REVIEW LETTERS
(2022)
Article
Mechanics
Jun Ho Lee, Hyunseok Kim, Jubeom Lee, Hyungmin Park
Summary: In this study, upward turbulent bubbly pipe flow was investigated to understand the bubble-induced turbulence modulation of the liquid-phase flow. Using two-phase particle image velocimetry, bubbly flow fields in a vertical pipe were obtained for different Reynolds numbers, revealing that bubbles energize flow structures at different length scales, enhancing turbulence across the entire pipe. Moreover, the highest void fraction observed led to local turbulence suppression near the pipe wall due to milder liquid velocity gradients.
Article
Multidisciplinary Sciences
Alexandre Vilquin, Julie Jagielka, Simeon Djambov, Hugo Herouard, Patrick Fisher, Charles-Henri Bruneau, Pinaki Chakraborty, Gustavo Gioia, Hamid Kenai
Summary: The study experimentally shows the relationship between frictional force and roughness in soap film flows, revealing differences in the proportionality of the frictional force to roughness in 2D and 3D flows. This finding is consistent with a competing theory linking frictional force to the turbulent spectrum via spectral exponents in different dimensions.
Article
Mechanics
Mathieu Calero, Holger Grosshans, Miltiadis V. Papalexandris
Summary: In this study, direct numerical simulations (DNS) are conducted to investigate the electrification phenomenon in turbulent channel flow of liquid dielectrics. The results demonstrate that turbulence significantly enhances the transport of electric charge in the bulk of the flow, and the electrification rate increases with the turbulence intensity. Furthermore, the budget analysis of the charge-density variance reveals a balance between molecular transport and turbulent transport. Finally, a closed-form expression for the mean charge-density profile is proposed based on the gradient assumption, which agrees well with the DNS results.
Article
Mechanics
S. F. Lewin, C. P. Caulfield
Summary: Motivated by the variation of local shear produced by internal waves in the ocean, this study investigates the effect of a time-dependent shear forcing on the evolution and mixing of turbulence produced by Kelvin-Helmholtz instability (KHI) through direct numerical simulations. The results demonstrate that turbulence produced by KHI with a decelerating shear mixes in a distinctly different way from the flow with constant background shear, with characteristics more in common with convectively driven flows.
JOURNAL OF FLUID MECHANICS
(2022)
