Article
Mechanics
A. Gorbunova, G. Balarac, L. Canet, G. Eyink, V. Rossetto
Summary: The study uses direct numerical simulations to test recent theoretical predictions in a three-dimensional incompressible fluid. Results show agreement with predictions from the Functional Renormalization Group (FRG) and can be explained as a consequence of sweeping. Additionally, there is a crossover in the two-point spatiotemporal correlations of the velocity modulus from Gaussian to exponential decay.
Article
Environmental Sciences
Berengere S. Dejeans, Julia C. Mullarney, Iain T. MacDonald
Summary: The study examines velocity and turbulence patterns in a sediment-laden river, revealing deficiencies in model performance in simulating turbulent kinetic energy dissipation rates, particularly around river bends. Results indicate that turbulence distributions show larger variations vertically than longitudinally, with the river's bathymetry and geometry playing a key role in controlling turbulence structure.
WATER RESOURCES RESEARCH
(2022)
Article
Physics, Multidisciplinary
A. A. Abrashkin
Summary: An analytical description of unsteady edge waves over a uniform slope is proposed, assuming that the waves are excited by time-harmonic external pressure with inhomogeneous spatial distribution. The problem is considered in Lagrangian variables and an exact solution of the hydrodynamic equations is obtained, generalizing the stationary Gerstner-Constantin solution. The proposed model describes the dynamics of coastal splashes of arbitrary initial shape and has the ability to describe waves both propagating and standing in the longshore direction.
JOURNAL OF PHYSICS A-MATHEMATICAL AND THEORETICAL
(2022)
Article
Mechanics
Zeeshan Saeed, Elizabeth Weidner, Blair A. Johnson, Tracy L. Mandel
Summary: Through theoretical analysis, it is demonstrated how buoyancy shapes flow behavior by enhancing mean shear and increasing the conversion of mean kinetic energy into turbulent kinetic energy. This study also highlights the primary role of buoyancy in strengthening the eddy vorticity in plumes through enhancing mean flow and mean shear.
Article
Multidisciplinary Sciences
Juan Ignacio Polanco, Nicolas P. Muller, Giorgio Krstulovic
Summary: The understanding of turbulent flows presents a challenge in physics, with recent research showing a connection between velocity circulation statistics in quantum and classical turbulence.
NATURE COMMUNICATIONS
(2021)
Article
Mechanics
Zhiwen Cui, Lihao Zhao
Summary: Finite-time Lyapunov exponents (FTLEs) and Lyapunov vectors (LVs) are powerful tools for analyzing Lagrangian coherent structures (LCSs) in fluid flows. A new method is proposed in this study to compute FTLEs and LVs by calculating eigenvectors and eigenvalues of the left Cauchy-Green tensor, avoiding the singularity problem in matrices. In 2D cases, LCSs appear as filaments induced by vortices, while in 3D cases, LCSs are sheet-like structures among the vortices.
Article
Environmental Sciences
Konstantin Korotenko, Alexander Osadchiev, Vasiliy Melnikov
Summary: This study investigates the generation and evolution of the Northeast Caucasian Current (NCC) in the Black Sea and its impact on river plumes. The findings reveal the significant role of topographically generated cyclonic eddies in self-cleansing and cross-shelf transport of riverine matter.
Letter
Physics, Multidisciplinary
V. N. Grebenev, M. Waclawczyk, M. Oberlack
Summary: The comment by Frewer and Khujadze is rejected due to fundamental mathematical errors, as Grebenev et al discussed the conformal invariance of zero-vorticity characteristics in the 2D vorticity equation. Frewer and Khujadze attempted to show inconsistency with the normalization constraint by replacing the infinitesimals derived by others. In reality, the invariance of this constraint follows straightforwardly in the transformations derived in the paper.
JOURNAL OF PHYSICS A-MATHEMATICAL AND THEORETICAL
(2021)
Article
Meteorology & Atmospheric Sciences
Jens Soeder, Christoph Zuelicke, Michael Gerding, Franz-Josef Luebken
Summary: The study showed a correlation between turbulence strength and the depth of tropopause folds, and the asymmetric vertical distribution of turbulence may be related to the tropopause fold life cycle.
JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES
(2021)
Article
Mechanics
Xingyu Ma, Xuan Gong, Nan Jiang
Summary: We experimentally investigate the pulsating circular jet flow at moderate Reynolds numbers using time-resolved particle image velocimetry. The study shows that the pulsation effect modulates the entire potential core and the axisymmetric shear layer, forming larger-scale vortices with phase correlation. The pulsation increases turbulent mixing and extends fluid entrainment in the radial direction. Analysis of the dynamic modes reveals inhibition of low-frequency off-the-axis helical structures and strengthening of the axisymmetric jet column mode. Vortex formation mainly occurs during the deceleration phase, while a shock-like wave front is formed during acceleration.
Article
Meteorology & Atmospheric Sciences
Andreas Doernbrack, Peter Bechtold, Ulrich Schumann
Summary: High-resolution flight data obtained from HALO aircraft during SOUTHTRAC are used to determine eddy dissipation rates and their correlation with ambient airflow and internal gravity waves. Turbulence events are strongly correlated with elevated shear values, while overturning gravity waves do not play a role.
JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES
(2022)
Article
Mathematics, Applied
Feng Liu, Hantao Liu, Hongkai Zhao, Pengfei Lyu
Summary: The inverse energy cascade in homogeneous isotropic turbulence is described using an eigenvalue method, quantitatively capturing the backward energy transfer process and applicable to both isotropic turbulence and resolved velocity fields. This method, based on the product of eigenvalues of the rate-of-strain tensor, is easier to obtain compared to traditional velocity derivative skewness S-k, and has potential for extension to anisotropic turbulence. The presented description aims to inspire future research on modeling the backward energy transfer process and improve the accurate prediction of complex flows.
APPLIED MATHEMATICS AND MECHANICS-ENGLISH EDITION
(2021)
Article
Environmental Sciences
Enrico Ferrero, Stefano Alessandrini, Scott Meech, Christopher Rozoff, Dietmar Oettl
Summary: In this study, two different parameterisations for wind velocity-component standard deviations are compared. The results of model simulations using these parameterisations are compared in terms of mean concentration and concentration standard deviation, using statistical indexes and scatter- and qq-plots.
AIR QUALITY ATMOSPHERE AND HEALTH
(2023)
Article
Mechanics
Bo Liu, Zhen-Hua Wan, Xi-Yun Lu, Luo-Qin Liu
Summary: The present study combines the functional modeling strategy with the classic structural modeling strategy to model the pressure Hessian tensor using deep neural networks. The model accurately predicts the flow topology, especially in the strain-production-dominant regions. The accuracy of the model is validated through both a priori and a posteriori tests.
Article
Thermodynamics
Damiano Auliano, Manuel Auliano, Erling Naess
Summary: In this study, numerical simulations and experimental data are used to investigate heat transfer in water flow in a uniformly heated asymmetric channel. The simulations predict the experimental data within a reasonable margin, with larger deviations at higher Reynolds numbers. A recirculation phenomenon is observed in the upper part of the channel, which plays an important role in enhancing heat transfer. The thickness of the thermal boundary layer and the conductive sublayer is determined experimentally and numerically, with the latter thinning due to the recirculation region.
INTERNATIONAL JOURNAL OF THERMAL SCIENCES
(2023)
Article
Mechanics
Majid Bastankhah, Carl R. Shapiro, Sina Shamsoddin, Dennice F. Gayme, Charles Meneveau
Summary: Motivated by the need to mitigate power reduction and unsteady loading of downstream turbines, this study develops an analytical model to predict the shape of curled wakes. By estimating the vorticity distribution at the wake edge and considering the wake as a vortex sheet, the model describes the time evolution of the wake shape. The model is validated against simulations and experiments, and shows a universal solution for curled wakes with suitable dimensionless variables.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Mechanics
Mitchell Fowler, Tamer A. Zaki, Charles Meneveau
Summary: A large eddy simulation wall model is developed based on a formal interpretation of quasi-equilibrium that governs momentum balance. The model includes a relaxation time scale that ensures self-consistency with assumed quasi-equilibrium conditions. The new approach allows for formally distinguishing between quasi-equilibrium and additional, non-equilibrium contributions to wall stress.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Mechanics
Kristofer M. Womack, Ralph J. Volino, Charles Meneveau, Michael P. Schultz
Summary: This study conducted experiments on flows with regular and random roughness elements and found that there were minor differences in flow statistics between the regular and random arrangements at the same density. The observed differences in surface flow parameters were mainly due to the presence of secondary flows. Contrary to expectations, these secondary flows were present over the random surfaces and not discernible over the regular surfaces. Additionally, the local turbulent boundary layer profiles did not scale with local wall shear stress but appeared to scale with local turbulent shear stress above the roughness canopy.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Mechanics
A. K. Aiyer, C. Meneveau
Summary: In this study, the dispersion characteristics of slightly buoyant droplets in a turbulent jet were investigated using large eddy simulations (LES). The model accurately captured the differential, size-based dispersion characteristics of the droplets with finer grid resolutions. Moreover, similarity solution and subgrid-scale models were used to predict the concentration profiles and turbulent concentration flux of the droplets, and the results showed good agreement with experimental data and high-resolution LES simulations.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Physics, Fluids & Plasmas
Yuan Luo, Yipeng Shi, Charles Meneveau
Summary: The study demonstrates that equivalent predictions can be obtained by recursively modulating model terms at a single level instead of integrating the stochastic model at multiple levels and scales. The statistical properties of the model compare well with direct numerical simulation and experimental data.
PHYSICAL REVIEW FLUIDS
(2022)
Article
Physics, Fluids & Plasmas
Wen Wu, Charles Meneveau, Rajat Mittal, Alberto Padovan, Clarence W. Rowley, Louis Cattafesta
Summary: The response of a turbulent separation bubble to zero-net-mass-flux actuation is investigated via direct numerical simulations. The results demonstrate that the length of the separation bubble can be reduced by forming vortex pairs at the appropriate excitation frequencies. In addition, the time-averaged structures exhibit a high sensitivity to the actuation.
PHYSICAL REVIEW FLUIDS
(2022)
Article
Physics, Fluids & Plasmas
Mostafa Aghaei-Jouybari, Jung -Hee Seo, Junlin Yuan, Rajat Mittal, Charles Meneveau
Summary: The force partitioning method is used to analyze the pressure-induced drag for turbulent flow over rough walls. The study quantifies the contributions of rotation-dominated vortical regions and strain-dominated regions to the pressure drag, and investigates the effects of surface geometry on drag. The results suggest that the phi field, which encodes surface geometry, can be used to parametrize the surface drag.
PHYSICAL REVIEW FLUIDS
(2022)
Article
Physics, Fluids & Plasmas
Samvit Kumar, Charles Meneveau, Gregory Eyink
Summary: A model for the structure function tensor was proposed, incorporating the effect of anisotropy as a linear perturbation to the standard isotropic form. The analysis extends the spectral approach proposed by Ishihara et al., and valid in the inertial range of turbulence. Observations were made regarding the countergradient correlation between Fourier modes of wall-normal and streamwise velocity components near the Kolmogorov scale.
PHYSICAL REVIEW FLUIDS
(2022)
Editorial Material
Mechanics
Charles Meneveau, Colm-Cille P. Caulfield
JOURNAL OF FLUID MECHANICS
(2022)
Article
Physics, Fluids & Plasmas
Ghanesh Narasimhan, Dennice F. Gayme, Charles Meneveau
Summary: Large eddy simulations are used to study the effects of veer on wind turbine wakes in the atmospheric boundary layer. The study finds that veer causes sideways wake deformation, but this can be predicted using a simple correction.
PHYSICAL REVIEW FLUIDS
(2022)
Article
Physics, Multidisciplinary
Yinghe Qi, Charles Meneveau, Greg A. Voth, Rui Ni
Summary: Fluid elements in turbulence deform through stretching and folding. The dynamics of folding are depicted by projecting the material deformation tensor onto the largest stretching direction and tracking the evolution of material curvature. Direct numerical simulations reveal that curvature growth exhibits two stages: a linear stage dominated by folding of fluid elements through persistent velocity Hessian, followed by an exponential-growth stage driven by stretching of already strongly bent fluid elements. This transition leads to strong curvature intermittency, which can be explained by a proposed curvature-evolution model. The link between velocity Hessian and folding provides a new understanding of the energy cascade and mixing in turbulence beyond the traditional linear stretching dynamics.
PHYSICAL REVIEW LETTERS
(2023)
Article
Physics, Fluids & Plasmas
Ruifeng Hu, Perry L. Johnson, Charles Meneveau
Summary: This paper introduces a generalized dynamic resuspension model for particles rolling on a surface with fractal-like multiscale roughness elements, called the multiscale asperity model (MSAM). Non-Gaussian stochastic models are compared with a Gaussian stochastic model for the flow velocity seen by a particle. The results show that the non-Gaussian stochastic flow models improve the prediction of the fraction of particles remaining on the wall after a given exposure time to turbulent flow.
PHYSICAL REVIEW FLUIDS
(2023)
Article
Mechanics
Hanxun Yao, Tamer A. Zaki, Charles Meneveau
Summary: Based on the generalized local Kolmogorov-Hill equation, this study examines the definition of entropy and entropy generation for turbulence. The results from direct numerical simulations confirm the validity of the fluctuation relation in non-equilibrium thermodynamics for turbulent flows in the inertial range.
JOURNAL OF FLUID MECHANICS
(2023)
Article
Environmental Sciences
James C. McWilliams, Charles Meneveau, Edward G. Patton, Peter P. Sullivan
Summary: Recent high-resolution large-eddy simulations of a stable atmospheric boundary layer are analyzed and compared with observations. The simulations are judged to be converged based on the collapse of vertical profiles of winds, temperature, and turbulence moments. The subfilter-scale motions extracted from the simulations are in good agreement with observations. The data from the simulations will be made available to the research community.
Article
Mechanics
Mitchell Fowler, Tamer A. Zaki, Charles Meneveau
Summary: The recent LaRTE approach is a wall model for large-eddy simulations (LES) that separates equilibrium and non-equilibrium wall-stress dynamics. The model shows good agreement with various non-equilibrium channel flows and provides insights into wall-stress physics.
JOURNAL OF FLUID MECHANICS
(2023)