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
Mechanics
Sicheng Li, Yanguang Long, Jinjun Wang
Summary: This study investigates the geometrical and dynamic properties of the turbulent/non-turbulent interface in separation and reattachment flow. The interface properties vary consistently with the vortex structure and are strongly influenced by the shear motion of the fluid and the shedding vortex. This study provides new insights into turbulent diffusion and the effects of separated flow and shedding vortices on the interface properties.
Article
Mechanics
L. G. Sarasua, D. Freire, C. Cabeza, A. C. Marti
Summary: The study focuses on the rise and fall of axisymmetric fountains in stratified environments, determining critical collapse conditions and expressing spreading height as a function of multiple parameters. Numerical simulations were performed to validate the quantitative agreement between the generalized model and experimental measurements.
Article
Physics, Fluids & Plasmas
Hongping Wang, Zixuan Yang, Ting Wu, Shizhao Wang
Summary: The study analyzed the energy spectra, production spectra, and interscale energy transfer spectra for turbulent channel flows at two Reynolds numbers. It found that large-scale and small-scale flow fields exhibit different flow structures, and the large scales may have a self-sustaining mechanism similar to that of the near-wall region.
PHYSICAL REVIEW FLUIDS
(2021)
Article
Mechanics
M. Gauding, M. Bode, Y. Brahami, E. Varea, L. Danaila
Summary: The study investigates the combined effect of internal and external intermittency on the statistical properties of temporally evolving planar turbulent jet flows at different Reynolds numbers. The analysis shows that structure functions exhibit self-preservation in both the core and shear layer of the jet, regardless of the normalization scales used. The impact of external intermittency on small-scale turbulence is demonstrated by a growing departure from self-similarity towards the flow edge.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Mathematics, Applied
Aleksandar Badza, Trent W. Mattner, Sanjeeva Balasuriya
Summary: Lagrangian coherent structures (LCSs) are time-varying entities that capture the most influential transport features of a flow. This article systematically investigates whether LCS methods are self-consistent in their conclusions under the uncertainty of realistic Eulerian velocity data. The methods detecting full-dimensional coherent flow regions are found to be significantly more robust than those detecting lower-dimensional flow barriers.
PHYSICA D-NONLINEAR PHENOMENA
(2023)
Article
Mechanics
Tie Wei, Daniel Livescu
Summary: This study investigates proper scaling in turbulent planar plumes using a scaling patch approach, determining appropriate scales for mean velocity, temperature, Reynolds shear stress, and turbulent heat flux. It highlights the critical role of mean transverse flow in the scaling of turbulent planar plumes.
Article
Mechanics
D. Freire Caporale, N. Barrere, Arturo C. Marti, C. Cabeza, L. G. Sarasua
Summary: In this study, we analyze the flow organization of turbulent fountains in stratified media under different conditions using three-dimensional finite-time Lyapunov exponents. The dominant Lagrangian coherent structures responsible for the transport barriers exhibit a similar shape in the different configurations studied. We propose a criterion for delimiting the boundary surface of the uprising fountain and quantify the entrainment and re-entrainment rates under fully developed flow conditions. Finally, we apply our analysis to the selective inverted sink and identify turbulence as the primary mechanism favoring the device's efficiency.
Article
Mechanics
Ethan Pickering, Georgios Rigas, Oliver T. Schmidt, Denis Sipp, Tim Colonius
Summary: Linear resolvent analysis of turbulent mean-flow fields can qualitatively capture characteristics of coherent structures in turbulent flows. By using a data-driven approach to optimize the eddy viscosity, the agreement between resolvent and SPOD modes can be substantially improved, reaching over 90% agreement at certain frequencies. A fixed model for eddy viscosity with a single constant can also provide substantial agreement between different modes in turbulent jets.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Physics, Fluids & Plasmas
Marco Boetti, Maarten van Reeuwijk, Alexander Liberzon
Summary: This study uses DNS to investigate the properties of the turbulent/nonturbulent interface (TNTI) between two layers of stratified fluids, focusing on the role of potential enstrophy Pi(2) as a marker and introducing an alternative length scale eta(Pi) based on potential enstrophy. It shows the self-similarity of small scale statistics of the TNTI in different turbulence forcing cases, as well as the similarity between the two different turbulent flows in the proximity of TNTI.
PHYSICAL REVIEW FLUIDS
(2021)
Article
Mechanics
Akhil Nekkanti, Oliver T. Schmidt
Summary: This study demonstrates four applications of spectral proper orthogonal decomposition (SPOD) on turbulent jet data: low-rank reconstruction, denoising, frequency-time analysis, and prewhitening. Results show that SPOD can effectively reconstruct flow fields, remove noise, and analyze the time-frequency characteristics. Additionally, SPOD-based frequency-time analysis reveals the direct association between the occurrence of large-scale flow structures and high-energy events.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Mechanics
Ming Yu, Dong Sun, QingQing Zhou, PengXin Liu, XianXu Yuan
Summary: In this study, we used direct numerical simulation databases to investigate the evolution of turbulent statistics and coherent structures in hypersonic turbulent boundary layers subjected to oblique shock waves. We found that large-scale structures are amplified within the interaction zone and gradually decay downstream, leading to discrepancies between the predictions of Reynolds-Averaged Navier-Stokes simulations and the actual flow behavior. To address this issue, we proposed refining the model parameters as functions of wall pressure and other flow quantities, leading to improved accuracy in predicting various flow properties downstream of the interaction zone.
Article
Mechanics
Milad Samie, Vlad Aparece-Scutariu, Philippe Lavoie, Dong-hyuk Shin, Andrew Pollard
Summary: This study uses direct numerical simulation to investigate three-dimensional vortical and very-large-scale coherent structures in a turbulent round jet at a Reynolds number of 7300. The results show the importance of horseshoe vortices in the jet and the existence of symmetric and asymmetric horseshoe vortices that affect the high and low momentum regions in the flow.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Mechanics
L. Weber, S. Gabriel, A. G. Class
Summary: The extraction of statistical information is crucial for numerical studies of bubbly flow. This study demonstrates the application and benefits of combining Voronoi diagrams with a constrained K-Means clustering algorithm for analyzing bubbly flows, and shows good agreement with empirical values from the literature. It concludes that this method provides good estimates of spatial distributions and can derive local histograms more consistently.
Article
Mechanics
Mohammad Javad Sayyari, Jinyul Hwang, Kyung Chun Kim
Summary: This study examines the capability of an unsupervised deep learning network to capture large-scale structures in a fully developed turbulent channel flow. The results demonstrate that the generative adversarial network accurately presents statistical data and successfully predicts structural characteristics hidden in the training dataset. Additionally, the study finds that larger-scale structures exhibit more aggressive waviness behavior, leading to an increase in the number of vortical structures surrounding low-momentum structures.
Article
Mechanics
G. E. Elsinga, C. B. da Silva
JOURNAL OF FLUID MECHANICS
(2019)
Article
Mechanics
Tomoaki Watanabe, Carlos B. da Silva, Koji Nagata
JOURNAL OF FLUID MECHANICS
(2019)
Article
Computer Science, Interdisciplinary Applications
Ryosuke Nagata, Tomoaki Watanabe, Koji Nagata, Carlos B. da Silva
COMPUTERS & FLUIDS
(2020)
Article
Mechanics
S. Parvar, C. B. da Silva, F. T. Pinho
JOURNAL OF NON-NEWTONIAN FLUID MECHANICS
(2020)
Article
Mechanics
Mateus C. Guimaraes, Nuno Pimentel, Fernando T. Pinho, Carlos B. da Silva
JOURNAL OF FLUID MECHANICS
(2020)
Article
Physics, Fluids & Plasmas
T. Watanabe, C. B. da Silva, K. Nagata
PHYSICAL REVIEW FLUIDS
(2020)
Article
Mechanics
S. Parvar, C. B. da Silva, F. T. Pinho
Summary: In this study, the laminar flat plate boundary-layer flow solution for a finitely extensible nonlinear elastic model with Peterlin's closure fluids is revisited by relaxing assumptions related to the conformation tensor. An approximate similarity solution is obtained through order of magnitude analysis and the use of similarity-like variables. The proposed solution is more accurate than the original solution and provides insights into the behavior of the system under low elasticity conditions.
Article
Mechanics
Ricardo P. Xavier, Miguel A. C. Teixeira, Carlos B. da Silva
Summary: This study investigates the characteristics of velocity fluctuations in turbulent flows using theoretical analysis and numerical simulations, revealing the asymptotic laws for variance of velocity fluctuations, Taylor micro-scale, and viscous dissipation rate at different distances from turbulent/non-turbulent interface. The results are confirmed to be independent of Reynolds number and applicable to other flow configurations with appropriate kinetic energy spectra.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Mechanics
Marco Zecchetto, Carlos B. da Silva
Summary: The study reveals that the statistics of small-scale motions within the turbulent/non-turbulent interface layer are universal, with minor deviations near the outer surface of the layer. The proposed normalization method allows for a clearer identification of the viscous superlayer and the turbulent sublayer within the TNTI layer.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Mechanics
S. Parvar, C. B. da Silva, F. T. Pinho
Summary: Direct numerical simulations and large-eddy simulations are used to evaluate the DSIM model for turbulent viscoelastic planar jets. The model shows good performance in inhomogeneous turbulent flows and is able to accurately reproduce flow structures and statistics. The DSIM model is also applicable to other free shear flows of viscoelastic fluids.
Article
Engineering, Multidisciplinary
S. Parvar, C. B. da Silva, F. T. Pinho
Summary: An approximate self-similar solution is proposed for the steady laminar mixing layer flow of viscoelastic fluids, and the effects of Weissenberg number, maximum polymer extensibility, and viscosity ratio are investigated. The solution exhibits self-similar behavior at low elasticity levels but deviates and becomes local with increasing levels of elasticity.
JOURNAL OF ENGINEERING MATHEMATICS
(2022)
Article
Mechanics
Hugo Abreu, Fernando T. Pinho, Carlos B. da Silva
Summary: In this study, direct numerical simulations were used to analyze the turbulent entrainment mechanism for viscoelastic fluids. The results showed that the interaction between the vorticity field and the polymer stresses in the turbulent/non-turbulent interface layer caused a new mechanism called viscoelastic production. This mechanism had an impact on the enstrophy dynamics, and at high Weissenberg numbers, the enstrophy tended to be concentrated into thin vortex sheets. Furthermore, it was found that the reduction in entrainment rates observed in turbulent flows of viscoelastic fluids, compared with Newtonian fluids, was due to a decrease in the surface area and fractal dimension of the irrotational boundary.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Thermodynamics
Saeed Parvar, Carlos B. da Silva, Fernando Pinho
Summary: This paper proposes an approximate self-similar solution for the thermal boundary layer flow, and investigates the effects of viscoelasticity and viscous dissipation on the boundary layer characteristics. At low elasticity levels, the solution exhibits global self-similar behavior, but as the flow elasticity increases, the self-similarity is lost and elasticity-dependent results show local variations.
INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER
(2022)
Article
Mechanics
Mateus C. Guimaraes, Fernando T. Pinho, Carlos B. da Silva
Summary: This study employs the FENE-P model to conduct direct numerical simulations and investigate the far-field region of turbulent wakes of viscoelastic fluids. The results show new scaling laws for various parameters and are well supported by the numerical simulations. When the Weissenberg and Deborah numbers are sufficiently large, turbulent viscoelastic wakes exhibit distinctive behavior compared to Newtonian wakes.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Physics, Fluids & Plasmas
A. A. Ghira, G. E. Elsinga, C. B. da Silva
Summary: This study investigates the characteristics of intense vorticity structures (IVS) or worms in high Reynolds number isotropic turbulence using direct numerical simulations. The results confirm most of the previously observed IVS characteristics, but reveal differences in the scaling of the mean length of the IVS at higher Reynolds numbers.
PHYSICAL REVIEW FLUIDS
(2022)
