Article
Mechanics
K. Osawa, Y. Minamoto, M. Shimura, M. Tanahashi
Summary: A new technique based on the Voronoi diagram is used to quantify the clustering of fine-scale dissipative vortices. It is found that velocity gradient events are more intense and intermittent with a higher number density of fine-scale vortices. Fine-scale vortex clusters accumulate among stronger vortices rather than accumulating all vortices in the flow.
Article
Mechanics
John B. Bell, Andrew Nonaka, Alejandro L. Garcia, Gregory Eyink
Summary: The study investigates the effect of thermal fluctuations in the dissipation range of homogeneous isotropic turbulence using fluctuating hydrodynamics. It confirms theoretical predictions regarding the dominance of these fluctuations in the energy spectrum at length scales comparable to the Kolmogorov length and the presence of Gaussian thermal equipartition in the far-dissipation range.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Mechanics
L. Djenidi, R. A. Antonia
Summary: The study shows that there are differences in the solutions of the Karman-Howarth equation between forced turbulence and decaying turbulence, mainly due to the generation of large-scale motions in forced turbulence. As the Reynolds number increases, the impact of forcing on small scales decreases, allowing the KHEq solutions to agree well with spectrally based solutions at scales unaffected by forcing.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Mechanics
Qinmin Zheng, Jianchun Wang, Md Mahbub Alam, Bernd R. Noack, Hui Li, Shiyi Chen
Summary: In this study, the transfer of internal energy fluctuation in stationary compressible isotropic turbulence was numerically investigated, where the spectra of velocity, pressure, density, and temperature exhibited scaling laws in the inertial range. The dominance of the solenoidal component over the dilatational component, and the roles of thermal conduction and vibrational relaxation in the dissipation of energy fluctuations were highlighted.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Mechanics
Jin-Han Xie, Shi-Di Huang
Summary: Through simulations of an idealized isotropic convection system, we provide evidence for the existence of Bolgiano-Obukhov (BO) scaling in Rayleigh-Benard convection (RBC) and establish its association with the inverse kinetic energy cascade. We also observe strong intermittent effects in the buoyancy field, but not in the velocity.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Mechanics
Maurizio Carbone, Michael Wilczek
Summary: Statistically homogeneous flows follow exact kinematic relations, with the Betchov homogeneity constraints being one of the most well-known and extensively used homogeneity relations. These relations have significant implications for the dynamics of fluids and turbulent energy cascade.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Mechanics
Miguel P. Encinar, Javier Jimenez
Summary: The algorithm introduced by Jimenez (J. Fluid Mech., vol. 854, 2018, R1) is used to identify the flow patterns of causal significance in three-dimensional isotropic turbulence. The study finds that the dimensions of the perturbations introduced in the flow are controlled by the kinetic energy content and the enstrophy and dissipation, and affect their significance in the flow. Strain is found to be more efficient than vorticity in propagating the perturbation contents to other regions of the flow. The findings suggest that manipulating strain-dominated vortex clusters is more effective in controlling turbulent flows.
JOURNAL OF FLUID MECHANICS
(2023)
Article
Mechanics
Alberto Vela-Martin
Summary: The study reveals that intense vorticity synchronizes to large-scale dynamics in two independent turbulent flows, despite the presence of chaos. This synchronization is mainly influenced by the stretching of vorticity vector by large-scale rate-of-strain tensor, supporting vortex stretching as a fundamental inter-scale mechanism in turbulence.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Mechanics
Kazuhiro Inagaki
Summary: This study investigates the impact of helicity on scale-similar structures of turbulence, revealing that the energy cascade process in the scale-similar range is completely independent of helicity. Additionally, it is found that the helicity cascade is slightly non-local in scales compared to the energy cascade.
JOURNAL OF FLUID MECHANICS
(2021)
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
Mechanics
Farid Aligolzadeh, Markus Holzner, James R. Dawson
Summary: The interaction between small-scale vortical structures and the surrounding fluid is investigated using experimental and numerical data. The flow across the boundary of vortex structures is examined, and a non-Gaussian distribution of entrainment velocity is observed. The enstrophy transport equation is analyzed to quantify the inviscid and viscous components of the entrainment/detrainment process. The study also compares the findings with the Burgers vortex model.
JOURNAL OF FLUID MECHANICS
(2023)
Article
Mechanics
Miguel P. Encinar
Summary: Three-dimensional turbulent flows enhance velocity gradients through strong nonlinear interactions. The 'Betchov' relations define a length scale, and it is found that isotropic cascade models need not distinguish between vortex stretching and strain self-amplification.
JOURNAL OF FLUID MECHANICS
(2023)
Article
Mechanics
Karim Shariff, Gerrit E. Elsinga
Summary: In this study, viscous vortex layers subjected to a more general uniform strain are considered, including discussion of different stable solutions. It is shown that vorticity inherently decays over time when a<1, unless boundary conditions maintain a supply of vorticity, and that for a>1, steady states have a sheath of opposite sign vorticity.
Article
Mechanics
A. Ababaei, B. Rosa, J. Pozorski, L. -P. Wang
Summary: This study investigates the dynamics of inertial particles in turbulence and found that considering lubrication forces and gravity can affect the relative velocities and distribution functions of particles in the near-contact region. However, the effect is minimal away from contact regions, and mass loading significantly impacts collision statistics.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Engineering, Mechanical
Joo Young Bang, Nimish Pujara
Summary: We investigated random-jet-stirred homogeneous turbulence generated in a vertical octagonal prism-shaped tank with jet arrays on four of the eight vertical faces. We found that the turbulence is homogeneous at all scales in the central region of the tank, spanning multiple integral scales in all directions. Using four jet arrays allows for higher turbulence intensity and Reynolds number compared to previous facilities. By varying the array-to-array distance and algorithm parameters, we were able to control the turbulence scales and Reynolds number.
EXPERIMENTS IN FLUIDS
(2023)