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
Mechanics
Mateus C. Guimaraes, Fernando T. Pinho, Carlos B. da Silva
Summary: A new theory is proposed to describe the conformation state of polymer chains in free turbulent shear flows of viscoelastic fluids. The theory shows the existence of minimum and maximum solvent dissipation reduction asymptotes and four different polymer deformation regimes, based on self-similarity arguments and new scaling relations for the turbulent flux of conformation tensor. In addition, analytical solutions for the self-similar transverse profiles of the conformation tensor components are obtained. The theory is validated through excellent agreement with direct numerical simulations employing the FENE-P rheological model.
JOURNAL OF NON-NEWTONIAN FLUID MECHANICS
(2024)
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
Mechanics
Andrea Andreolli, Maurizio Quadrio, Davide Gatti
Summary: The turbulent plane Poiseuille and Couette flows have the same geometry but are driven by pressure gradient and shear, respectively. A new concept of flow efficiency and effectiveness is introduced to compare different flows, showing that Couette flows are less efficient but more effective due to their more effective laminar component. They dissipate a smaller percentage of total power via turbulent dissipation, attributed to stronger large-scale structures contributing less significantly to dissipation.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Mechanics
S. L. Tang, R. A. Antonia, L. Djenidi
Summary: In this study, we analyze the approach towards local isotropy in statistically stationary turbulent shear flows using the transport equations for the fourth-order moments of the velocity derivative. It is found that, as the Taylor microscale Reynolds number increases, the large-scale contribution gradually decreases and the small-scale motion becomes more locally isotropic. The rate at which local isotropy is approached depends on the weakening of the large-scale forcing, which is controlled by the magnitude of the non-dimensional velocity shear parameter.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Mechanics
H. Sadeghi, M. Oberlack, M. Gauding
Summary: This study derives new scaling laws for passive scalar statistical quantities in temporally and spatially evolving plane turbulent jet flows using Lie symmetry analysis, filling the gaps in classical self-similarity analysis. The newly derived scaling laws exhibit self-similarity up to the third moments, in contrast to classical laws which primarily show self-similarity for the first moments.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Mechanics
S. Arun, A. Sameen, Balaji Srinivasan, Sharath S. Girimaji
Summary: This study examines the definition and transport equation of the scale-space energy density function for compressible flows. It first defines the energy density function and then analyzes data from mixing layers to study the scale-space behavior at different Mach numbers. The research shows that production is influenced by long-distance interactions, whereas pressure dilatation effects are more localized.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Mechanics
Patricio Clark Di Leoni, Tamer A. Zaki, George Karniadakis, Charles Meneveau
Summary: By analyzing the Karman-Howarth equation for filtered-velocity fields in turbulent flows, it is shown that the two-point correlation between the filtered strain-rate and subfilter stress tensors is central in the evolution of filtered-velocity correlation functions. Statistical a priori tests based on two-point correlations enable rigorous and physically meaningful studies of turbulence models. It is found that using fractional gradient orders rather than classical gradients in eddy-viscosity models can lead to stronger non-local correlations.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Mechanics
Sean Symon, Simon J. Illingworth, Ivan Marusic
Summary: The study analyzes the energy transfer between scales in two types of plane Poiseuille flow, with streamwise-constant streaks identified as the dominant energy-producing modes. Eddy viscosity is found to be an effective model for the nonlinear terms in the resolvent analysis. However, it fails to respect the conservative nature of the nonlinear energy transfer, leading to less effective modeling for scales that receive energy from the nonlinear terms.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Mechanics
Matthew A. Subrahmanyam, Brian J. Cantwell, Juan J. Alonso
Summary: This paper introduces a mixing length model for turbulent shear stress in pipe flow and provides a universal velocity profile. The velocity profile accurately approximates both experimental and simulated data in various flow conditions, making it significant for studying the statistical properties of flow.
JOURNAL OF FLUID MECHANICS
(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
Mechanics
Taye Melaku Taddesse, Joseph Mathew
Summary: This study investigates the velocity field characteristics of stationary, turbulent twin round jets. Large-eddy simulations were conducted to obtain the flow fields, revealing that the two jets develop independently and merge into a single jet with an elliptic cross-section downstream. The merged jet becomes circular after a certain distance. The fluctuation levels of the merged jet scale with the local maximum mean velocity, and the mean streamwise velocity reaches a peak at a certain distance from the inflow plane. The velocity and length scales of the merged jet are connected to the input parameters through simple relations, and the far field development can be scaled using intrinsic scales.
JOURNAL OF FLUID MECHANICS
(2022)
Review
Mechanics
Michael D. Graham, Daniel Floryan
Summary: Wall-bounded turbulence exhibits persistent patterns called coherent structures, which are important for transport processes. Recent research has focused on exact coherent states (ECS) in wall-bounded parallel flows, which are non-turbulent, nonlinear solutions resembling coherent structures in turbulence.
ANNUAL REVIEW OF FLUID MECHANICS, VOL 53
(2021)
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
Mechanics
Cheng Cheng, Wei Shyy, Lin Fu
Summary: A new methodology was developed to assess the distribution of wall-attached eddies, revealing that the SIAs depend on the Reynolds number at low and medium Reynolds numbers, saturating at 45 degrees as the Reynolds number increases. The average SIA reported in previous experimental studies was shown to be the result of the additive effect of multi-scale attached eddies.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Engineering, Mechanical
Maxime Coulaud, Jean Lemay, Claire Deschenes
JOURNAL OF FLUIDS ENGINEERING-TRANSACTIONS OF THE ASME
(2019)
Article
Engineering, Mechanical
L. Djenidi, Md. Kamruzzaman, L. Dostal
EXPERIMENTS IN FLUIDS
(2019)
Article
Mechanics
L. Djenidi, R. A. Antonia, S. L. Tang
JOURNAL OF FLUID MECHANICS
(2019)
Article
Mechanics
J. Lemay, L. Djenidi, R. A. Antonia, A. Benaissa
JOURNAL OF FLUID MECHANICS
(2019)
Article
Engineering, Environmental
Patrice Roberge, Jean Lemay, Jean Ruel, Andre Begin-Drolet
COLD REGIONS SCIENCE AND TECHNOLOGY
(2019)
Article
Engineering, Mechanical
Abhishek Mishra, Harekrishna Yadav, Lyazid Djenidi, Amit Agrawal
EXPERIMENTS IN FLUIDS
(2020)
Article
Mechanics
N. N. Anika, L. Djenidi, S. Tardu
JOURNAL OF FLUID MECHANICS
(2020)
Article
Mechanics
S. L. Tang, R. A. Antonia, L. Djenidi, Y. Zhou
JOURNAL OF FLUID MECHANICS
(2020)
Article
Engineering, Mechanical
Maxime Coulaud, Jean Lemay, Claire Deschenes
JOURNAL OF FLUIDS ENGINEERING-TRANSACTIONS OF THE ASME
(2020)
Article
Mechanics
L. Djenidi, R. A. Antonia
Article
Mechanics
Jean Lemay, Lyazid Djenidi, Robert Antonia
Article
Engineering, Environmental
Patrice Roberge, Jean Lemay, Jean Ruel, Andre Begin-Drolet
Summary: This study proposes a method for estimating the effective LWC in wind farms using a thermal-based ice sensor, which was calibrated with data from 8 icing events and showed better sensitivity and accuracy.
COLD REGIONS SCIENCE AND TECHNOLOGY
(2021)
Article
Engineering, Environmental
Patrice Roberge, Jean Lemay, Jean Ruel, Andre Begin-Drolet
Summary: Analyzing the performance of wind turbines in cold climate conditions is complex. Building robust power curve models and ice detection thresholds are crucial for comparing turbine performance. This paper presents a method for constructing a simple power curve model and proposes effective ice detection thresholds and performance evaluation tools.
COLD REGIONS SCIENCE AND TECHNOLOGY
(2022)