Article
Mechanics
Naveen Rohilla, Partha S. Goswami
Summary: This article explores the variation of local isotropy of fluid fluctuations and the decrease of the Kolmogorov constant in particle-laden turbulent channel flows. The author also adopts a new modeling technique using large-eddy simulation (LES) to predict fluid phase statistics without solving simultaneous particle phase equations. This study provides insights into the phenomena of drastic collapse in turbulence intensity.
JOURNAL OF FLUID MECHANICS
(2023)
Article
Mechanics
Yan Xia, Zhaosheng Yu, Zhaowu Lin, Yu Guo
Summary: This study establishes correlations between the interfacial terms and the fluid dissipation rate equation and Reynolds stress equations in particle-laden flows, providing an accurate mathematical model and method for simulating particle-induced turbulence.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Mechanics
Amelie Ferran, Nathanael Machicoane, Alberto Aliseda, Martin Obligado
Summary: We conducted an experimental study on the gravitational settling velocity of dense, sub-Kolmogorov inertial particles in different turbulent flow conditions. Using a phase Doppler particle analyzer, we measured the settling velocity of micrometer-sized water droplets in a low-speed wind tunnel. We explored a wide range of turbulence parameters, including Reynolds numbers, Rouse numbers, and volume fractions, to analyze the effects on particle settling velocity.
JOURNAL OF FLUID MECHANICS
(2023)
Article
Mechanics
Holger Grosshans, Claus Bissinger, Mathieu Calero, Miltiadis Papalexandris
Summary: Through direct numerical simulations, we found that under certain density ratios and Coulombic-to-gravitational force ratios, electrostatic forces play a dominant role in the vortical motion of particles, affecting their distribution within the duct.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Mathematics, Applied
Qiming Zhu, Minjiang Zhu, Jinhui Yan
Summary: This paper extends the application of isogeometric analysis (IGA) to particle-laden flows based on Eulerian-Eulerian description. By using non-uniform rational B-spline (NURBS) functions and a residual-based variational multiscale (VMS) formulation, the coupled systems of equations are solved, enabling accurate prediction of flow/particle statistics with a relatively lower mesh resolution.
MATHEMATICAL MODELS & METHODS IN APPLIED SCIENCES
(2022)
Article
Thermodynamics
Yang Liu, Jiatong Liu, Shu Li, Guohui Li, Lixing Zhou
Summary: A new particle subgrid scale model is proposed to consider the effect of gas flow on particle motions. A second-order moment two-phase turbulence model is used to model multiphase gas-particle turbulent flow, with a four-way coupling strategy to describe the interactions among gas-particle, particle-gas, and particle-particle collisions. Results show that predictions are well agreed with experimental data, and there are significant differences in vortex structures and distributions between gas and particle flow in swirling and non-swirling conditions.
Article
Engineering, Multidisciplinary
Kerlyns Martinez Rodriguez, Mireille Bossy, Radu Maftei, Seyedafshin Shekarforush, Christophe Henry
Summary: This article presents a new data-driven spatial decomposition algorithm that allows for the splitting of a domain containing point particles into elementary cells with spatially-uniform distributions of particles. By using statistical information, the algorithm extracts an optimal spatial decomposition, providing more accurate and mesh-independent predictions for studying particle agglomeration.
APPLIED MATHEMATICAL MODELLING
(2021)
Article
Mechanics
Sourabh Apte, Thibault Oujia, Keigo Matsuda, Benjamin Kadoch, Xiaoliang He, Kai Schneider
Summary: Direct numerical simulation is used to investigate the effects of turbulent flow on the transport, clustering, and deposition of fine particles in a face-centred cubic porous unit cell. The results show that particle clustering occurs at large volumes and is enhanced with increasing Stokes number.
JOURNAL OF FLUID MECHANICS
(2022)
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
Mechanics
S. Beetham, R. O. Fox, J. Capecelatro
Summary: In this study, model closures for multiphase Reynolds-averaged Navier-Stokes (RANS) equations are developed using sparse regression and Eulerian-Lagrangian simulations to ensure accuracy and robustness of the models across different flow conditions. The focus is on capturing the dynamics of gas-particle flows, particularly the generation of particle clusters and interphase momentum exchange, in a compact and algebraic manner.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Mechanics
Sofia Angriman, Amelie Ferran, Florencia Zapata, Pablo J. Cobelli, Martin Obligado, Pablo D. Mininni
Summary: This study investigates the three-dimensional clustering of velocity stagnation points, vorticity nulls, and inertial particles in turbulent flows with different large-scale flow geometries by combining direct numerical simulations and particle tracking velocimetry. The results show that although the flows have different topologies in terms of null clustering, the behavior of particles is similar in all cases, indicating the clustering of Taylor-scale neutrally buoyant particles as inertial particles.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Mechanics
Kyle Pietrzyk, Jeremy A. K. Horwitz, Fady M. Najjar, Roger W. Minich
Summary: This study analyzes particle-laden, isotropic turbulence in three dimensions to understand the dynamics of inertial particles from a kinetic energy perspective. By identifying data trends, it is found that particles tend to accumulate in regions of low flow kinetic energy over time, as they lose kinetic energy and slow down in such regions. A particle kinetic energy equation is derived and hypotheses regarding the temporal change of particle kinetic energy and particle behavior are evaluated using simulation data. The steady-state probability density function of particle kinetic energy is derived using a Fokker-Planck equation. The model fits the simulation data well and provides a tool for investigating preferential concentration and predicting particle kinetic energy in turbulent flows.
Article
Mechanics
Stefano Olivieri, Ianto Cannon, Marco E. Rosti
Summary: This study investigates the modulation of turbulence caused by the presence of finite-size dispersed particles. Bluff (isotropic) spheres and slender (anisotropic) fibres are compared to understand how the shape of the objects influences the carrier flow. While both objects, at a fixed mass fraction but different Stokes number, lead to similar bulk effects characterized by large-scale energy depletion, a scale-by-scale analysis reveals intrinsic differences in the alteration of the whole spectrum. For bluff objects, the classical energy cascade shrinks in its extension but retains its energy content and typical features, while for slender objects, an alternative energy flux mediated by fluid-solid coupling is found.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Engineering, Electrical & Electronic
Jinzhui Li, Jun Yao, Yanlin Zhao, Chi-Hwa Wang
Summary: The study investigated the electrostatic effect on particle transport in particle-laden turbulent pipe flows at Re-b = 44000 by coupling LES with Lagrange particle tracking technology. Three particle St numbers were considered to compare the electrostatic effect on particle behavior, showing that electrostatics destroyed particle aggregation and caused particle-ejection delay and particle-sweep premature effects.
JOURNAL OF ELECTROSTATICS
(2021)
Article
Mechanics
Marco Crialesi-Esposito, Marco Edoardo Rosti, Sergio Chibbaro, Luca Brandt
Summary: A numerical study was conducted on emulsions in homogeneous and isotropic turbulence at Re-lambda = 137, revealing the energy transport behavior and factors influencing it. The analysis showed that energy is consistently transported from large to small scales by the interface, with droplet size distributions following specific scaling laws.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Mechanics
Josin Tom, Maurizio Carbone, Andrew D. Bragg
Summary: Expressing the evolution equations for the filtered velocity gradient tensor in the strain-rate eigenframe allows for a better understanding of processes such as strain self-amplification and vortex stretching. Statistical analysis of the eigenframe equations across scales shows non-Gaussian fluctuations in the rotation rate and highly nonlinear behavior in the anisotropic pressure Hessian. Sub-grid stress correlations and the role of the sub-grid term in regularizing the system are also highlighted, providing insights for improving Lagrangian models of the FVGT.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Mechanics
X. Q. He, A. D. Bragg, Y. L. Xiong, P. Fischer
Summary: This study used direct numerical simulations to investigate the behavior of a rotating two-dimensional flow that is heated at its equator, where buoyancy and Coriolis forces lead to rich flow behavior. The research found a non-monotonic dependence of flow properties on the Rossby number for a given Rayleigh number, and large-scale mean circulations strongly influenced by rotation.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Mechanics
Tian Ma, Hendrik Hessenkemper, Dirk Lucas, Andrew D. Bragg
Summary: This study experimentally investigates the properties of bubble-laden turbulent flows at different scales, with a focus on flow kinetic energy, energy transfer, and extreme events. The results show that the flow exhibits anisotropy and the degree of anisotropy increases with the order of the structure functions. The energy transfer associated with the horizontal velocity component is downscaled, while the energy transfer associated with the vertical component is upscaled. The probability density functions of velocity increments indicate that extreme values become more likely with decreasing Reynolds number, contrary to single-phase turbulence. Visualization of extreme events reveals intense small-scale velocity increments near the turbulent/non-turbulent interface at the boundary of the bubble wake.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Mechanics
Andrew D. Bragg, Adam L. Hammond, Rohit Dhariwal, Hui Meng
Summary: Expanding on recent observations, this study provides detailed experimental data on the radial distribution function (rdf) of inertial particles in isotropic turbulence for different Stokes numbers (St). The results indicate explosive growth of rdf with decreasing separation, showing a r(-6) scaling near the collision radius regardless of St or particle radius. By correcting errors in previous theories and comparing with experiments, this study reveals significant underestimation of rdf by previous theory and explores alternative mechanisms that fail to explain the discrepancy. This suggests the presence of new, unidentified physical mechanisms that require further investigation and new theories.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Mechanics
Mohammadreza Momenifar, Enmao Diao, Vahid Tarokh, Andrew D. Bragg
Summary: This study applies a physics-informed deep learning technique based on vector quantisation to compress three-dimensional turbulent flow simulations, generating a discrete low-dimensional representation. The accuracy of the model is validated using statistical, comparison-based similarity, and physics-based metrics. Compared to a conventional autoencoder, this model demonstrates significant improvements in compression ratio and mean square error. This compression model is an attractive solution for situations requiring fast, high-quality, and low-overhead encoding and decoding of large data.
JOURNAL OF TURBULENCE
(2022)
Article
Environmental Sciences
Shuolin Li, Andrew D. Bragg, Gabriel Katul
Summary: The article discusses the vertical distribution of suspended sediment concentration and derives the turbulent flux of sediments using a co-spectral budget model, which can be used in suspended sediment and other fine particle transport models.
WATER RESOURCES RESEARCH
(2022)
Article
Meteorology & Atmospheric Sciences
T. Waterman, A. D. Bragg, G. Katul, N. Chaney
Summary: Earth system models and mesoscale models have been using increasingly complex parameterization schemes for the atmospheric boundary layer. This study evaluates existing parameterizations for the surface boundary conditions of potential temperature variance (PTV) and finds that the existing schemes are acceptable over a variety of surface conditions. However, they perform poorly over heterogeneous surfaces and rough landscapes. Attempts to improve the results using canopy structure and surface roughness characteristics did not significantly enhance the predictive power of the models. There is no strong evidence indicating that large scale circulations cause substantial deviations from textbook models.
JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES
(2022)
Article
Mechanics
Josin Tom, Maurizio Carbone, Andrew D. Bragg
Summary: This study investigates the settling mechanism of particles in two-way coupled flows using direct numerical simulations, and reveals the contribution of eddies of different scales to particle settling. In contrast to previous studies, the preferential sweeping mechanism still plays an important role in two-way coupled flows.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Mechanics
Xiaolong Zhang, Rohit Dhariwal, Gavin Portwood, Stephen M. de Bruyn Kops, Andrew D. Bragg
Summary: In this study, budgets of turbulent kinetic energy (TKE) and turbulent potential energy (TPE) at different scales in sheared, stably stratified turbulence are analyzed using a filtering approach. The results show that buoyancy always converts TKE to TPE at larger scales, and the probability of locally convecting regions increases as scale decreases. Additionally, contributions from sub-grid fields are significant in governing the fluxes between scales.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Mechanics
Xiao-Qiu He, Yong-Liang Xiong, Andrew D. Bragg, Patrick Fischer, Hamid Kellay
Summary: This study investigates the effect of tilt on two-dimensional turbulent thermal convection using direct numerical simulation. The results show that the tilt angle and Rayleigh number have significant effects on the flow patterns and characteristics.
Article
Physics, Fluids & Plasmas
Y. Zhang, A. D. Bragg, G. Wang
Summary: Transport equations for heavy inertial particles in turbulent boundary layers can be derived from a PDF equation. The traditional closure approach using a quasinormal approximation (QNA) leads to large quantitative errors. This study proposes a closure approximation based on an asymptotic solution, which is consistent with known asymptotic predictions and performs better than the QNA approach when the viscous Stokes number is large.
PHYSICAL REVIEW FLUIDS
(2023)
Article
Mechanics
Xiaolong Zhang, Maurizio Carbone, Andrew D. Bragg
Summary: The recent model effectively handles the unclosed terms in the equation for fluid velocity gradient and shows good agreement with DNS data. However, it generates large fluctuations and substantial errors in predicting passive scalar gradients. By incorporating information on scalar gradient production along the particle's trajectory history, the modified model improves predictions and aligns well with DNS data. Nevertheless, the model breaks down beyond Re-lambda approximately 500.
JOURNAL OF FLUID MECHANICS
(2023)
Article
Physics, Fluids & Plasmas
Colin J. Denzel, Andrew D. Bragg, David H. Richter
Summary: This paper develops a simple stochastic model based on direct numerical simulation to accurately describe the residence times of particles in a particle-laden turbulent flow. The model takes into account the competition between gravity settling and particle-turbulence interaction. Despite its simplicity, the model provides quantitatively accurate predictions of the distribution of particle residence times in the flow. The independent roles of gravity and inertia in governing these residence times are also investigated by varying the Stokes numbers and settling velocities.
PHYSICAL REVIEW FLUIDS
(2023)
Article
Geosciences, Multidisciplinary
Shuolin Li, Andrew D. Bragg, Gabriel Katul
Summary: This study investigates the behavior of suspended particles in turbulent flows and discusses the difference in particle settling velocity in turbulence and still water. By incorporating virtual mass and Basset history forces, the inconsistencies between conventional models and laboratory experiments are resolved. This research is significant for modeling particle settling in turbulence.
GEOPHYSICAL RESEARCH LETTERS
(2023)
Proceedings Paper
Computer Science, Software Engineering
Mohammadreza Momenifar, Enmao Diao, Vahid Tarokh, Andrew D. Bragg
Summary: In this study, a physics-informed Deep Learning technique based on vector quantization is applied to compress large-scale data from simulations of turbulent flows. The model achieves high compression ratios and low mean square errors while preserving the statistical characteristics of the flow.
DCC 2022: 2022 DATA COMPRESSION CONFERENCE (DCC)
(2022)