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
A. E. Seker, B. Zafer, I. Gonzalez-Martino, M. Yucetepe
Summary: This study investigates the impact of front and aft wall modifications on the sound pressure level response of the M219 cavity at transonic speed. The results show that modifications to the aft wall are more effective in reducing noise than modifications to the front wall. Mixed configurations of the most effective wall modifications further reduce the frequency and amplitude of pressure oscillations.
Article
Engineering, Chemical
Nima Fallah Jouybari, T. Staffan Lundstroem
Summary: Large eddy simulations were conducted in a channel partially filled with spherical particles to investigate the effect of turbulence mixing and channeling effect on passive scalar transport from the channel wall. It was found that the distance between particles, particle diameter, and gap thickness play important roles in influencing passive scalar transport. The channeling effect was identified as the most significant parameter affecting the scalar transport rate in the study.
Article
Mechanics
Sergio Pirozzoli
Summary: In this study, direct numerical simulations (DNS) of the Navier-Stokes equations were used to investigate the statistics of passive scalars in turbulent flow within a smooth straight pipe. The results showed that the organization of passive scalars was similar to the axial velocity field at moderate Prandtl numbers, but impaired at low and high Prandtl numbers. The mean scalar profiles exhibited logarithmic overlap layers and universal parabolic distributions in the core part of the flow at particular Prandtl numbers. Accurate predictive formulas for the mean scalar profiles were derived using the nearly universal eddy diffusivity.
JOURNAL OF FLUID MECHANICS
(2023)
Article
Thermodynamics
Asghar Noormohammadi, Bing-Chen Wang
Summary: The turbulent dispersion of passive concentration from a vertical line source in fully-developed channel flow is studied using direct numerical simulation (DNS). Statistical moments of velocity and concentration fields, PDFs of concentration fluctuations, and energetic eddy wavelengths are analyzed to understand turbulent transport processes. Plume development involves turbulent convective and diffusive stages, with meandering ratio being small near the ground and within the turbulent diffusive stage. PDFs of concentration fluctuations are sensitive to both wall-normal and downstream distances from the source.
INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER
(2021)
Article
Engineering, Aerospace
Parshwanath S. Doshi, Datta V. Gaitonde, Emma D. Gist, Mark N. Glauser
Summary: This study develops a passive control strategy to alleviate the instability effects of supersonic multistream engines. By adjusting the splitter plate trailing-edge and interfering with the internal forcing mechanism, the study successfully reduces the tonal content and increases the streamwise vorticity introduced by the control.
Article
Physics, Multidisciplinary
P. Morel, Shaokang Xu, O. D. Gurcan
Summary: The study of two-dimensional passive scalar turbulence using a k-space diffusion model based on a third order differential approximation provides general expressions for local nonlinear interactions in Fourier space. The steady state solutions recover Kraichnan-Kolmogorov phenomenology and various passive scalar spectra. Numerical solutions confirm the analytical results for energy and passive scalar injections and dissipations over a wide range of scales.
JOURNAL OF PHYSICS A-MATHEMATICAL AND THEORETICAL
(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
Engineering, Mechanical
Pankaj Kumar Raushan, Santosh Kumar Singh, Koustuv Debnath
Summary: This investigation presents an estimate of deviation from isotropic turbulence in grid-generated turbulence influenced by the bottom boundary. It analyzes the turbulence triangle, Eigen values, and invariant functions in near and far field regions with different solidity ratios, and examines the third-order moments of velocity fluctuations and the ratio of momentum flux to turbulent kinetic energy in the frequency domain. The study also reveals the anisotropy of Reynolds stress, showing a closed looping trend in the near field region and an open looping trend in the far-field region of the grid. Additionally, probability distribution functions are used to describe the physical behavior of velocity time-series of random fluctuating components in the stream-wise directions.
PROCEEDINGS OF THE INSTITUTION OF MECHANICAL ENGINEERS PART C-JOURNAL OF MECHANICAL ENGINEERING SCIENCE
(2021)
Article
Engineering, Marine
Pankaj Kumar Raushan, Santosh Kumar Singh, Koustuv Debnath
Summary: This study provides turbulence characteristics of oscillating flow through passive grid under rigid boundary influence through experimental approach. It analyses turbulent length scales, local Reynolds numbers, and randomness degree in the oscillating flow environment. The study also examines deviation from isotropic turbulence and presents turbulence triangle, Eigen values, and invariant functions for three oscillating flow cases downstream of the grid.
Article
Mathematics, Applied
Cagil Kirezci, Alexei T. Skvortsov, Daniel Sgarioto, Alexander V. Babanin
Summary: We investigated the dispersion of tracer particles through numerical simulations of ensemble nonlinear gravity waves on a fluid surface. By using the concepts of passive Lagrangian markers and insights from weak wave turbulence theory, we validated fundamental predictions for particle kinematics associated with scaling laws and probability density functions. These results improve our understanding of wave-driven transport phenomena and the development of high-fidelity models for transport processes in geophysical systems.
PHYSICA D-NONLINEAR PHENOMENA
(2023)
Article
Thermodynamics
Girish Kini, Srinivas Garimella
Summary: Surfactants can enhance heat and mass transfer in ammonia-water absorption by reducing surface tension, with 500 PPM of 1-octanol or 2-ethyl-1-hexanol recommended for significant improvement. Addition of surfactants improves absorber conductance by approximately 30% in a heat pump system, guiding intensification of various heat and mass transfer processes.
INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER
(2021)
Article
Nanoscience & Nanotechnology
Di Qi, Eric Vanden-Eijnden
Summary: A computational strategy based on large deviation theory is used to study the anomalous statistical features of turbulent surface waves propagating past an abrupt depth change. The strategy accurately captures the non-Gaussian features of the wave height distributions, particularly their asymmetric tails and high skewness. This approach shows potential for a general class of nonlinear Hamiltonian systems with highly non-Gaussian statistics.
Review
Mathematics, Applied
M. S. Jolly, D. Wirosoetisno
Summary: In this paper, we investigate the evolution of a passive tracer theta governed by a velocity field u(x, t). Based on the work of Batchelor et al. in 1959, we probabilistically prove that the tracer spectrum follows a power law scaling with large wavenumbers and for small enough random synthetic three-dimensional incompressible velocity fields. We also relax some assumptions on the velocity and tracer source.
PHYSICA D-NONLINEAR PHENOMENA
(2023)
Article
Multidisciplinary Sciences
Yun Mao, Yiwu Zhu, Yijun Wang, Ying Guo
Summary: In this paper, we propose a passive CVQKD system based on an atmospheric turbulence channel model. The system utilizes spectrum resources in the terahertz band and improves performance through the use of an adaptive optics unit. The results confirm the utility of high-rate and long-distance CVQKD in practical implementations.
Article
Mechanics
L. Biferale, K. Gustavsson, R. Scatamacchia
JOURNAL OF FLUID MECHANICS
(2019)
Article
Mathematics, Applied
L. Biferale, F. Bonaccorso, M. Buzzicotti, P. Clark Di Leoni, K. Gustavsson
Article
Mechanics
Muhammad Zubair Sheikh, Kristian Gustavsson, Diego Lopez, Emmanuel Leveque, Bernhard Mehlig, Alain Pumir, Aurore Naso
JOURNAL OF FLUID MECHANICS
(2020)
Article
Physics, Multidisciplinary
J. Meibohm, K. Gustavsson, J. Bec, B. Mehlig
NEW JOURNAL OF PHYSICS
(2020)
Article
Mechanics
Z. Cui, A. Dubey, L. Zhao, B. Mehlig
JOURNAL OF FLUID MECHANICS
(2020)
Article
Multidisciplinary Sciences
Martin Mojica-Benavides, David D. van Niekerk, Mite Mijalkov, Jacky L. Snoep, Bernhard Mehlig, Giovanni Volpe, Mattias Goksor, Caroline B. Adiels
Summary: This study utilized a diffusion-limited microfluidic system to mimic the structure of a multicellular organ, demonstrating that a group of oscillating yeast cells can form subpopulations of spatially differentiated and temporally synchronized cells under certain conditions. The intricate interplay of intracellular biochemical reaction networks and intercellular communication, along with the fluid dynamics of the reaction chamber, plays a critical role in generating the synchronized cell populations. The results of the study, which were experimentally tested and reproducible, suggest that the observed spontaneous community development resembles zoned cell differentiation in multicellular organs.
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
(2021)
Article
Physics, Fluids & Plasmas
F. Jiang, L. Zhao, H. Andersson, K. Gustavsson, A. Pumir, B. Mehlig
Summary: The study investigates the torque acting on particles in a uniform flow by numerically solving the Navier-Stokes equations. It shows that the angular dependence of the torque remains qualitatively correct for low Reynolds numbers, but systematic deviations from theoretical predictions occur as Reynolds numbers increase. The numerical results provide justification for recent theories on the orientation statistics of ice crystals in turbulent flow.
PHYSICAL REVIEW FLUIDS
(2021)
Article
Physics, Fluids & Plasmas
Darci Collins, Rami J. Hamati, Fabien Candelier, Kristian Gustavsson, Bernhard Mehlig, Greg A. Voth
Summary: The isotropic helicoid proposed by Lord Kelvin nearly 150 years ago has been experimentally confirmed to exist, with its chiral coupling attributed to hydrodynamic interactions between the nonchiral vanes. This coupling effect is small due to the nature of the interactions.
PHYSICAL REVIEW FLUIDS
(2021)
Article
Physics, Fluids & Plasmas
Jan Meibohm, Vikash Pandey, Akshay Bhatnagar, Kristian Gustavsson, Dhrubaditya Mitra, Prasad Perlekar, Bernhard Mehlig
Summary: In the dynamics of small, heavy identical particles in turbulence, the formation of singularities known as caustics leads to significant fluctuations in spatial particle-number density and collision velocities. While caustic formation for particles with large inertia is akin to Kramers escape, for particles with small inertia, caustics tend to form near trajectories with specific histories of fluid-velocity gradients characterized by low vorticity and violent strain surpassing a certain threshold. A theory is developed to explain these findings in terms of an optimal path to caustic formation in the small inertia limit.
PHYSICAL REVIEW FLUIDS
(2021)
Article
Mechanics
Jingran Qiu, Navid Mousavi, Kristian Gustavsson, Chunxiao Xu, Bernhard Mehlig, Lihao Zhao
Summary: Marine micro-organisms face challenges in navigation and survival in complex flow patterns, with studies using reinforcement learning to determine optimal strategies. Interestingly, motile micro-organisms primarily rely on local cues for survival decisions rather than accessing global information.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Physics, Fluids & Plasmas
Jingran Qiu, Navid Mousavi, Lihao Zhao, Kristian Gustavsson
Summary: Many plankton species migrate vertically in the ocean using a gyrotactic mechanism. This study proposes an active mechanism for gyrotactic stability that allows alignment with, or against, gravity. The mechanism is minimally affected by turbulence and is more effective than passive mechanisms.
PHYSICAL REVIEW FLUIDS
(2022)
Article
Physics, Fluids & Plasmas
A. Dubey, K. Gustavsson, G. P. Bewley, B. Mehlig
Summary: This article reveals the complex dependency in droplet collision dynamics through bifurcation analysis, and predicts the strong spatial clustering near certain saddle points.
PHYSICAL REVIEW FLUIDS
(2022)
Proceedings Paper
Computer Science, Artificial Intelligence
Michele Buzzicotti, Luca Biferale, Fabio Bonaccorso, Patricio Clark Di Leoni, Kristian Gustavsson
Summary: The theoretical and numerical results discussed finding the path that minimizes navigation time in a complex fluid under realistic constraints. The study contrasts Optimal Navigation control with Reinforcement Learning algorithms and shows that RL algorithms can find quasi-optimal solutions even in chaotically evolving flow configurations. The approach can be applied to various setups, including navigation under imperfect environmental forecast or with different models for moving vessels.
AIXIA 2020 - ADVANCES IN ARTIFICIAL INTELLIGENCE
(2021)
Review
Computer Science, Artificial Intelligence
Frank Cichos, Kristian Gustavsson, Bernhard Mehlig, Giovanni Volpe
NATURE MACHINE INTELLIGENCE
(2020)