Article
Mechanics
Someshwar Sanjay Ade, Lakshmana Dora Chandrala, Kirti Chandra Sahu
Summary: The size distribution of child droplets resulting from dual-bag fragmentation of a water drop is studied using shadowgraphy and digital in-line holography techniques. The fragmentation of the parent drop contributes to small droplet atomization, while core drop disintegration leads to larger fragments. The dual-bag fragmentation exhibits a bi-modal size distribution, while the single-bag breakup shows a tri-modal size distribution. An analytical model developed by Jackiw & Ashgriz accurately predicts the experimentally observed droplet volume probability density for dual-bag fragmentation.
JOURNAL OF FLUID MECHANICS
(2023)
Article
Thermodynamics
Arun Ravi Varma, Umair Ahmed, Markus Klein, Nilanjan Chakraborty
Summary: The relationship between turbulent burning velocity, bending effect, and flame surface area is discussed, along with the effects of tangential strain rate, normal strain rate, displacement speed, and curvature.
COMBUSTION AND FLAME
(2021)
Article
Engineering, Chemical
Zongyao Wei, Yifei Wang, Ziwei Wu, Xin Peng, Guangsuo Yu, Fuchen Wang
Summary: The experimental study focused on the flow characteristics of turbulent falling film along a vertical Perspex plate, utilizing ultrasonic Doppler velocimetry. Results indicated that increasing Reynolds number led to a shorter development region and accelerated the film into a steady flow state, with velocity gradient changes influenced by interfacial wave amplitudes and liquid collision with different velocity directions.
INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH
(2021)
Article
Thermodynamics
J. M. Avellaneda, F. Bataille, A. Toutant, G. Flamant
Summary: Direct Numerical Simulations are used to analyze the influence of key boundary conditions and flow characteristics on entropy generation rate statistics in a highly anisothermal forced convective turbulent channel flow. The study shows the significant influence of the thermal boundary condition type on the fluctuations of the entropy generation rate.
INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER
(2021)
Article
Energy & Fuels
HsuChew Lee, Abouelmagd Abdelsamie, Peng Dai, Minping Wan, Andrei N. Lipatnikov
Summary: This article uses numerical simulations to study the characteristics of seven highly turbulent lean hydrogen-air flames. The results show that using the mixture-averaged model significantly increases the turbulent burning velocity, especially in lean flames. The turbulence length scale also affects the burning velocity, and the fuel consumption rate exhibits universality in different cases.
Article
Thermodynamics
Haochen Liu, Zifei Yin, Jialing Le, Hong Liu
Summary: A new subgrid turbulent combustion model for LES is proposed, based on the eddy dissipation concept (EDC) and subgrid dissipation concept (SDC). The model allows for direct computation of fine structure quantities by establishing the relationship between subgrid quantities and fine structure ones. The SDC model shows satisfactory predictions and improvement compared to the standard EDC model in the tested premixed and non-premixed flame cases, while being relatively insensitive to grid resolution.
COMBUSTION AND FLAME
(2023)
Article
Green & Sustainable Science & Technology
Ayesha Sohail, Maryam Noor, R. Ellahi, Sadiq M. Sait
Summary: In the development of solar energy heating systems in the oil and petroleum industries, a detailed understanding of turbulent flow regimes through computational analysis is deemed necessary and challenging. The standard kappa - epsilon turbulence model is commonly used in diesel combustion applications. Accurate analysis of turbulent mixing for controlled combustion requires computational analysis of dynamical and kinematic properties. This study focuses on total flux analysis for solar energy systems in the oil industry through artificial intelligence optimization and graphical analysis of viscous fluids.
SUSTAINABLE ENERGY TECHNOLOGIES AND ASSESSMENTS
(2021)
Article
Thermodynamics
Muyang Wang, Takuya Yurikusa, Yasuhiko Sakai, Koji Iwano, Yasumasa Ito, Yi Zhou, Yuji Hattori
Summary: Direct numerical simulations were conducted to study the interscale transfer of turbulent energy in grid-generated turbulence with low Reynolds numbers. The results showed that the turbulent dissipation constant varied for different Reynolds numbers. Scale-by-scale analysis indicated a balance between the nonlinear transfer term and the dissipation term, while the contribution of the advection term varied in the downstream region. Further analysis of one-point statistics revealed a decrease in coherence among the advection term, dissipation term, and diffusion term at small scales in certain conditions.
INTERNATIONAL JOURNAL OF HEAT AND FLUID FLOW
(2022)
Article
Environmental Sciences
N. B. Lakshmi, Vijayakumar S. Nair, S. Suresh Babu
Summary: This study estimated the shortwave radiative effects of absorbing aerosols over the Indian landmass using a combination of spaceborne and ground-based observations, finding that pre-monsoon aerosol loading is mainly influenced by mineral dust and high aerosol warming within the planetary boundary layer is mainly caused by carbonaceous aerosols.
REMOTE SENSING OF ENVIRONMENT
(2021)
Article
Engineering, Aerospace
Sivaramakrishnan Malathi Ananth, Aditya Vaid, Nagabhushana Rao Vadlamani, Massimiliano Nardini, Melissa Kozul, Richard D. Sandberg
Summary: Several high-resolution scale-resolving simulations are conducted to investigate the influence of riblets on the mean and turbulent statistics of a zero-pressure-gradient boundary layer. It is found that riblets can effectively reduce the viscous drag in the turbulent regime, and V-shaped riblets with sharp tips have slightly better performance than curved riblets. In the transitional flow regime, the coherent structures over riblets are predominantly spanwise oriented, and a leading-edge ramp is shown to minimize the additional spurt in the turbulent kinetic energy caused by the abrupt surface change.
Article
Engineering, Chemical
Le Zhao, Dadong Liu, Jichao Lin, Liguo Chen, Songying Chen, Guichao Wang
Summary: This paper investigates the effects of spatial resolution on the estimated turbulent dissipation rate and its impact on particle-bubble interactions. Using direct numerical simulation of a homogeneous isotropic turbulence, the true values of turbulent dissipation rate are obtained and compared with estimated values at different spatial resolutions. The underestimation of turbulent dissipation rate is found to correlate with the spatial resolution relative to the Kolmogorov length scales, highlighting the importance of understanding turbulence effects on particle-bubble interactions.
MINERALS ENGINEERING
(2023)
Article
Geosciences, Multidisciplinary
Yi Wang, Yumei He, Juan Li
Summary: This study investigates the water content gradient in the mantle transition zone through the analysis of X phase reflections. The results show that in the southern and southwestern regions of China, the P wave velocity gradient is low, indicating a uniform water content. In contrast, in the northeastern region of Asia, the P wave velocity gradient is high, suggesting a decreasing water content from the 410-km depth. This provides seismic evidence for water infiltrating into the mantle transition zone from a hydrous layer above the 410 and diffusing widely after long-term subduction.
GEOPHYSICAL RESEARCH LETTERS
(2022)
Article
Energy & Fuels
Vishnu Mohan, Marco Herbert, Markus Klein, Nilanjan Chakraborty
Summary: The influence of flame brush area on the turbulent burning velocity parameterizations for non-unity Lewis number flames has been evaluated. It was found that the choice of projected flame brush area strongly affects the definition of the turbulent burning velocity. Models for turbulent burning velocity provide reasonably accurate predictions for the unity Lewis number case but underpredict values for Lewis numbers smaller than unity. Scaling relations have been used to extend these parameterizations for non-unity Lewis numbers and these revised expressions show improved accuracy.
Article
Engineering, Multidisciplinary
Siva P. R. Muppala
Summary: In this study, an algebraic premixed turbulent model is validated for molecular transport effects in hydrogen-blended fuel. Three variants of the model are presented, incorporating the influence of turbulent flame speed and Lewis number on flame diffusion. Experimental data is compared with theoretical predictions, confirming the accuracy of the model.
ALEXANDRIA ENGINEERING JOURNAL
(2022)
Article
Physics, Multidisciplinary
Q. H. Liu
Summary: This article introduces the finite difference method for discrete functions and the formalism of discrete calculus of variations to determine the true solution of the function. By comparing second-order variations, the exact distributions of Boltzmann, Bose, and Fermi systems can be obtained without requiring an infinitely large number of particles.
Article
Physics, Multidisciplinary
K. Gustaysson, M. Z. Sheikh, D. Lopez, A. Naso, A. Pumir, B. Mehlig
NEW JOURNAL OF PHYSICS
(2019)
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)
Article
Physics, Fluids & Plasmas
J. Meibohm, B. Mehlig
