Article
Engineering, Aerospace
Kalyani Bhide, Shaaban Abdallah
Summary: This study characterizes the turbulence in rectangular supersonic jets by directly evaluating various mechanisms in the turbulent kinetic energy (TKE) budget equation. The results show that TKE production is the major source term, while the pressure-dilatation term acts as a sink throughout the development of the jet. The diffusion term has the highest contribution from triple-velocity correlations, followed by pressure diffusion and molecular diffusion.
Article
Engineering, Aerospace
Huiying Zhang, Xiaohua Wu
Summary: Velocity gradient tensor invariants are used for extracting flow physics near the turbulent and nonturbulent interfaces (TNTIs) of cylinder and airfoil wakes with vortex shedding. Conditional sampling on fuzzy-cluster-method-resolved TNTIs is performed using a novel subzone approach. The results suggest that properties of wake TNTIs depend more on the degree of vortex shedding and less on the degree of wake symmetry. Random relative orientation between the vorticity vector and the TNTI normal is observed in the trough subzone of wake TNTIs.
Article
Mechanics
Megan K. Richards, Oluwaseun E. Coker, Jose Florido, Rhiannon A. M. Nicholls, Andrew N. Ross, Gabriel G. Rooney
Summary: This study investigates the flow in and around two vertically and horizontally offset plumes. An analytical potential flow model is developed using the Milne-Thomson circle theorem to represent the flow due to adjacent circular and point sources. The predictions of this model are compared against Reynolds-averaged Navier-Stokes simulations and show good agreement, including the location of the stagnation point between the two plumes.
JOURNAL OF FLUID MECHANICS
(2023)
Article
Mechanics
Kannan Sundaravadivelu, Rafik Absi
Summary: This study presents an improved method for solving the turbulent kinetic energy equation in the near wall region of turbulent flows, with comparisons showing good agreement with experimental data. Results also indicate that beyond a certain Re-tau value, turbulent kinetic energy profiles collapse, remaining independent of the Reynolds number.
Article
Mechanics
Kianoosh Yousefi, Fabrice Veron, Marc P. Buckley
Summary: By analyzing high-resolution laboratory measurements of airflow velocity above wind-generated surface waves, it was found that turbulent kinetic energy (TKE) and wave kinetic energy (WKE) production differ at different heights, indicating energy transfer between different components. Additionally, interactions between turbulence and wave perturbations show distinct energy transfer patterns.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Thermodynamics
Aritra Roy Choudhury, Kameswararao Anupindi
Summary: In this study, a planar turbulent offset wall-jet with heat transfer is numerically investigated using large-eddy simulation (LES). The flow characteristics, thermal characteristics, and turbulent kinetic energy of the jet are analyzed. The evolution of Nusselt number on the wall exhibits three distinct peaks correlated with the change-of-sign of the wall skin-friction coefficient. The flow domain can be categorized into recirculation, impingement, and wall-jet regions, and distinct flow and thermal characteristics are observed in different regions.
INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER
(2022)
Article
Mechanics
Khashayar F. Kohan, Susan J. Gaskin
Summary: This study investigates the effect of a zero-mean-flow turbulent ambient on the geometry of the turbulent/turbulent interface (TTI) of an axisymmetric jet and compares it with the traditional turbulent/non-turbulent interface (TNTI). The results show that the ambient turbulence enhances radial transport of concentration and scalar fluctuations within the jet, resulting in steeper mean and root-mean-square scalar conditional jumps across the TTI layer compared with those of the TNTI. The presence of ambient turbulence also stretches and corrugates the interface surface area.
JOURNAL OF FLUID MECHANICS
(2022)
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
Engineering, Aerospace
Huiying Zhang, David E. Rival, Xiaohua Wu
Summary: This study investigated turbulent and nonturbulent interfaces (TNTIs) in aerodynamic flows past a NACA-0012 airfoil, using direct numerical simulation and methods such as the threshold-free fuzzy cluster method and joint probability density function-based method for TNTI identification. The curvature of TNTIs was found to be influenced by the transitional state of the flow.
Article
Meteorology & Atmospheric Sciences
Bicheng Chen, Marcelo Chamecki
Summary: Large-eddy simulations were conducted to investigate the effects of gentle topography on the turbulent kinetic energy (TKE) budget within a uniform model forest. Results show that the effects of topography are primarily located in the upper canopy and above, mainly due to mean advection of TKE. The horizontally averaged TKE budget for both idealized and real gentle topographies is almost similar to that for flat terrain, with the mean vertical advection of TKE being as important as horizontal advection at topography crests.
JOURNAL OF THE ATMOSPHERIC SCIENCES
(2023)
Article
Meteorology & Atmospheric Sciences
Bing Tong, Jianping Guo, Yinjun Wang, Jian Li, Yuxing Yun, Raman Solanki, Ning Hu, Honglong Yang, Huirong Li, Jianghua Su, Qianshan He, Yue Zhou, Kui Zhang, Yong Zhang
Summary: Turbulence kinetic energy (TKE) varies with different convection regimes and shows different trends under different atmospheric stability conditions. The correlation between TKE and related variables is influenced by the convective regime, but the correlation trends between TKE and specific variables (BP and SP) are similar across the four tower sites. This study highlights the importance of considering different convection regimes when investigating TKE characteristics.
ATMOSPHERIC RESEARCH
(2022)
Article
Oceanography
P. Tedesco, J. Gula, P. Penven, C. Menesguen
Summary: Western boundary currents, such as the Agulhas Current, are characterized by strong mesoscale variability and interactions between eddies and topography. In this study, a regional numerical simulation was used to assess the main energy sinks of mesoscale eddies in the Agulhas Current region. The results showed that eddy-topography interactions play a major role in energy dissipation, with transfers occurring towards bottom-intensified time-mean currents, generation of higher baroclinic modes, and bottom friction. The local generation of mesoscale eddies was found to dominate the net energy budget, contrary to the common belief that mesoscale eddies decay along western boundaries.
JOURNAL OF PHYSICAL OCEANOGRAPHY
(2022)
Article
Geosciences, Multidisciplinary
C. M. Liu, J. B. Cao, T. Y. Wang, X. N. Xing
Summary: We report intense energy transfer observed within a plasma jet in the Earth's midtail, with strong electromagnetic turbulences and intermittent sub-ion-scale structures generating intense fluctuating electric fields and currents. The anisotropic turbulence is carried by kinetic Alfvenic waves, causing electron heating and acceleration. These findings highlight the crucial role of turbulent flux pileup regions in energy transfer in the magnetosphere.
GEOPHYSICAL RESEARCH LETTERS
(2022)
Article
Mechanics
Alais Hewes, Laurent Mydlarski
Summary: In this study, a novel three-wire thermal-anemometry-based probe is used to investigate the evolution of multiple scalars and velocity in turbulent coaxial jets. The results show that increasing momentum flux ratios lead to complex effects, including the decrease in size of the potential core and the increase in scalar fluctuations. However, the evolution of statistics describing the velocity field is slower. Additionally, the mixing near the beginning of the fully merged region is less effective at higher momentum flux ratios. The study suggests that the mixing process in coaxial jets can be controlled by considering the differences between M<1 and M>1 scenarios.
JOURNAL OF FLUID MECHANICS
(2023)
Article
Mechanics
Milad Samie, Philippe Lavoie, Andrew Pollard
Summary: Through experiments and numerical simulation, coherent structures in turbulent round jets are found to consist of hierarchical eddy structures and very-large-scale motions, with the latter being dominated by helical structures.
JOURNAL OF FLUID MECHANICS
(2021)
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)