Article
Physics, Multidisciplinary
Tianyi Li, Lian Shen
Summary: This study combines theoretical and computational methods to investigate the initial impact of turbulent wind on a calm water surface and analyzes the process of wind-wave generation based on Phillips theory. The study reveals that the wave energy grows following a quartic law during the early stages of wave generation and provides numerical evidence of the resonance mechanism, which plays a crucial role in the heterogeneous distribution of wave energy in the spectral space.
COMMUNICATIONS PHYSICS
(2023)
Article
Mechanics
Gen Wu, Le Fang, Jin Zhang
Summary: This paper introduces a new synthetic turbulence method called AEM and applies it to generate inlet conditions in the open-source software code_saturne. By comparing with direct numerical simulation and synthetic eddy method, the ability of AEM to accurately predict turbulent kinetic energy profiles is validated. Parametric analysis is also conducted to discuss the specific effect of each factor.
Article
Mechanics
A. Rouhi, M. K. Fu, D. Chandran, A. Zampiron, A. J. Smits, I. Marusic
Summary: Turbulent drag reduction through streamwise travelling waves is investigated over a wide range of Reynolds numbers. Wall-resolved large-eddy simulations are conducted to examine how the frequency and wavenumber of the travelling wave influence the drag reduction. The study finds that the level of turbulence attenuation, and hence drag reduction, changes with the near-wall Stokes layer protrusion height. A range of frequencies is identified where the Stokes layer attenuates turbulence and increases the drag reduction, while outside this range, the strong Stokes shear strain leads to a drop in drag reduction.
JOURNAL OF FLUID MECHANICS
(2023)
Article
Mechanics
Jiaxing Song, Fenghui Lin, Nansheng Liu, Xi-Yun Lu, Bamin Khomami
Summary: The flow physics of inertio-elastic turbulent Taylor-Couette flow with a radius ratio of 0.5 in the Reynolds number range of 500 to 8000 was investigated through direct numerical simulation. The study revealed two distinct regimes of turbulence dynamics as Reynolds number increases, with either nonlinear elastic forces or inertial forces dominating the flow physics in the low and high Reynolds number regimes, impacting the flow structures in the bulk and near-wall regions differently. Examination of the flow-microstructure coupling analysis showed the triggering of elastic Gortler instability in the near-wall region, leading to the formation of small-scale elastic vortical structures known as elastic Gortler vortices with longer average life span compared to their Newtonian counterparts.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Engineering, Environmental
Qi Chang, Shengbin Di, Ji Xu, Wei Ge
Summary: Particle-resolved direct numerical simulation was conducted on a 4-baffled cylindrical stirred tank with a 6-pitched blade turbine-downflow (PBTD) impeller for the first time. The study revealed the significant impact of particle inertia and turbulence intensity on the system operation.
CHEMICAL ENGINEERING JOURNAL
(2021)
Article
Mechanics
Wei Gao, Ravi Samtaney, David H. Richter
Summary: In this study, two-way coupled direct numerical simulation is performed to investigate the particle-laden flow in an open channel at a friction Reynolds number of 5186. The turbulent modification by particles is examined through comparison of statistical quantities. It is found that particles weaken the large-scale and very-large-scale motions in the inner and outer layers, and also alter the spatial structures of coherent structures.
JOURNAL OF FLUID MECHANICS
(2023)
Article
Mechanics
Lingxin Zhang, Kai Peng, Xueming Shao, Jian Deng
Summary: This study numerically investigates the dynamics of gas bubbles rising freely under buoyancy at low Reynolds numbers, focusing on clustering morphology and velocity fluctuations' probability density functions. The research reveals that the probability density functions for bubble velocity fluctuations exhibit distinct behavior at high gas fractions compared to high Reynolds number experiments, indicating that strong bubble-bubble interactions trigger turbulent flow efficiently.
Article
Mechanics
J. Jablonska, M. Kozubkova, M. Mahdal, P. Marcalik, J. Tuma, M. Bojko, L. Hruzik
Summary: Mathematical modeling is applied to predict cavitation in hydraulic components and systems. A new method based on a multiphase turbulent mathematical model is proposed to solve the dynamics of cavitation by adding air into the mixture. The study shows that the influence of air is significant in the multiphase model.
Article
Mechanics
Suming Wang, Wenhua Zhang, Xinyi Wang, Xiaobin Li, Hongna Zhang, Fengchen Li
Summary: This paper conducts direct numerical simulations of viscoelastic drag-reducing turbulence (DRT) to investigate the essence of its maximum drag reduction (MDR) state. The results show that the MDR state can be both inertial turbulence (IT) and elasto-inertial turbulence (EIT), with the dominant dynamics shifting from IT-related to EIT-related dynamics as the maximum extension length (L) of polymers increases. These findings provide insights for breaking through the MDR limit. Rating: 8/10.
JOURNAL OF FLUID MECHANICS
(2023)
Article
Mechanics
Jiaxing Song, Nansheng Liu, Xi-Yun Lu, Bamin Khomami
Summary: Three-dimensional elastic turbulence in Taylor-Couette flows of dilute polymer solutions has been achieved and studied through direct numerical simulations. A novel flow transition pathway from elastically dominated turbulence to solitary vortex pairs and eventually to purely elastic turbulence is observed by decreasing fluid inertia. The dominant flow features in the elastic turbulence regime are large-scale unsteady vortex pairs and small-scale traveling waves. Furthermore, the study concludes that the production of turbulent kinetic energy in purely elastic turbulence is solely due to the stochastic nature of polymer stretch/relaxation.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Mechanics
Hua Zhou, Evatt R. Hawkes, Timothy C. W. Lau, Rey Chin, Graham J. Nathan, Haiou Wang
Summary: Point-particle direct numerical simulations were used to quantify the turbulence modulation and particle responses in a turbulent particle-laden jet in the two-way coupled regime. The results showed that the presence of particles both reduced and increased the gas-phase turbulent kinetic energy in different regions. The particle response to the gas-phase flow was found to be stronger in the axial velocity component.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Mechanics
Jie Yao, Saleh Rezaeiravesh, Philipp Schlatter, Fazle Hussain
Summary: This study conducted direct numerical simulations of flow in a smooth circular pipe and obtained various turbulence statistics. A comparison with other simulations and experiments revealed small but noticeable differences. The friction factor deviated from the Prandtl friction law at low and high Reynolds numbers. The wall shear stress fluctuations and axial turbulence intensity in the pipe were lower than in the channel, but the difference decreased with increasing Reynolds number.
JOURNAL OF FLUID MECHANICS
(2023)
Article
Mechanics
W. Cheng, D. I. Pullin, R. Samtaney, X. Luo
Summary: This study presents numerical simulation and mean-flow modelling of statistically stationary plane Couette-Poiseuille flow in a parameter space (Re, theta). The results show the transition from Couette-type to Poiseuille-type flow, and the agreement between simulations and models suggests that the mean skin-friction Reynolds number on the bottom wall changes sign at a critical value of theta(c)(Re).
JOURNAL OF FLUID MECHANICS
(2023)
Article
Chemistry, Physical
Mohammad Abo Jabal, Ekhlas Homede, Anna Zigelman, Ofer Manor
Summary: The experiment found that the Marangoni vortices, temperature variations, and wetting dynamics in sessile drops all vary concurrently in time and with the initial composition. In particular, maximum intensity levels of these phenomena were observed when the initial toluene proportion in the drops was 60%.
JOURNAL OF COLLOID AND INTERFACE SCIENCE
(2021)
Article
Mechanics
Yangwei Liu, Weibo Zhong, Yumeng Tang
Summary: The paper establishes theoretical relationships between Q series vortex criteria, eigenvalue-based vortex criteria, and the Rortex method based on LT criterion, and visually analyzes their physical meanings and interrelations on the LT-plane. The LTcri-based method effectively reflects local swirling patterns, provides new interpretations of vortex criteria, and shows potential in analyzing vortex dynamics and distinguishing swirling patterns of complex vortices.
Article
Multidisciplinary Sciences
Luuk J. Blaauw, Detlef Lohse, Sander G. Huisman
Summary: Using the Taylor-Couette geometry, we studied the impact of salt on drag reduction caused by bubbles in the flow. The drag reduction was found to decrease as the salt concentration increased, from 40% in fresh water to 15% in sea water. The presence of salts inhibited coalescence events, resulting in smaller bubbles and decreased drag reduction.
PHILOSOPHICAL TRANSACTIONS OF THE ROYAL SOCIETY A-MATHEMATICAL PHYSICAL AND ENGINEERING SCIENCES
(2023)
Article
Physics, Fluids & Plasmas
Christopher J. Howland, Roberto Verzicco, Detlef Lohse
Summary: Motivated by ice ablation in salt water, this study investigates the heat and salt fluxes in two-scalar vertical convection using three-dimensional direct numerical simulations. The salinity field drives the convection while heat is transported as passive scalar. The diffusivity ratio of heat and salt affects the scalar fluxes, with heat transport determined by a turbulent Prandtl number of Prt approximate to 1 and double-diffusive effects being negligible.
PHYSICAL REVIEW FLUIDS
(2023)
Article
Computer Science, Interdisciplinary Applications
Youssef Saade, Detlef Lohse, Daniel Fuster
Summary: We extend the all-Mach solver proposed by Fuster and Popinet (2018) [1] to account for heat diffusion between two compressible phases. By solving a coupled system of equations for pressure and temperature, our code improves the robustness and accuracy of the solver compared to classical explicit discretization schemes. Several test cases are used to validate the implementation, including comparisons with spectral methods and analytical solutions. The code is also applied to the study of sonoluminescent bubbles, Rayleigh collapse, and bubble collapse near a rigid boundary, demonstrating the importance of thermal effects in these phenomena.
JOURNAL OF COMPUTATIONAL PHYSICS
(2023)
Article
Mechanics
Pierre Chantelot, Detlef Lohse
Summary: Gas film and nonlinear advection are two physical mechanisms affecting the rebounding of impacting drops. We reveal the dominance of the nonlinear advection regime through impacts on superheated surfaces. By measuring the gas film thickness under impacting drops, we provide evidence for the transition from the surface tension to the nonlinear inertia dominated regime.
JOURNAL OF FLUID MECHANICS
(2023)
Article
Mechanics
Vatsal Sanjay, Pierre Chantelot, Detlef Lohse
Summary: Using numerical simulations, we investigate how viscous stresses and gravity inhibit drop rebound by opposing capillarity. We find that the initial spreading stage can be decoupled from the later retraction and take-off, and propose a criterion for the transition from bouncing to non-bouncing regime. The criterion is in excellent agreement with the numerical results. We also elucidate the mechanisms of bouncing inhibition in the heavy and viscous drop limiting regimes.
JOURNAL OF FLUID MECHANICS
(2023)
Article
Mechanics
On-Yu Dung, Pim Waasdorp, Chao Sun, Detlef Lohse, Sander G. Huisman
Summary: We investigate how the injection of large bubbles modifies the spectrum of a passive scalar in a turbulent flow. We find that the spectral scaling behavior of a turbulent multiphase thermal mixing layer is triggered to exhibit a -3 scaling when large bubbles with gas volume fractions up to 5% are injected. At low gas volume fractions, a -5/3 scaling is observed at intermediate frequencies, but as the gas volume fraction increases, this scaling becomes less pronounced and is replaced by a steeper -3 slope at larger frequencies. We also identify the frequency scale of the transition from the -5/3 scaling to the -3 scaling and show its dependence on the gas volume fraction.
JOURNAL OF FLUID MECHANICS
(2023)
Article
Mechanics
Vatsal Sanjay, Srinath Lakshman, Pierre Chantelot, Jacco H. H. Snoeijer, Detlef Lohse
Summary: When a liquid drop falls on a solid substrate, the air film between them delays the contact. For impacts on smooth substrates, the air film can prevent wetting and cause bouncing. This paper investigates bouncing phenomena on viscous liquid films that mimic atomically smooth substrates and explores their repellency. The study reveals the mechanisms associated with the bouncing and non-bouncing transition and predicts the characteristics of drop impact using experiments, simulations, and a minimal model.
JOURNAL OF FLUID MECHANICS
(2023)
Article
Physics, Applied
Maaike Rump, Uddalok Sen, Roger Jeurissen, Hans Reinten, Michel Versluis, Detlef Lohse, Christian Diddens, Tim Segers
Summary: In practical applications of inkjet printing, the intermittent idle periods of printhead nozzles lead to evaporation of ink from the nozzle exit. This evaporation results in concentration gradients within the multicomponent inks, which can directly and indirectly affect the jetting process, reproducibility, and print quality. This study investigates selective evaporation of water-glycerol mixtures from an inkjet nozzle through experiments, analytical modeling, and numerical simulations. The research sheds light on the complex physiochemical hydrodynamics associated with ink drying at printhead nozzles and contributes to the stability and reproducibility of inkjet printing.
PHYSICAL REVIEW APPLIED
(2023)
Article
Physics, Fluids & Plasmas
Yuki Wakata, Ning Zhu, Xiaoliang Chen, Sijia Lyu, Detlef Lohse, Xing Chao, Chao Sun
Summary: In this study, we investigate the Leidenfrost temperature for hot solid substrates with different thermal diffusivities and surface roughnesses. A phenomenological model is developed based on experimental data, which considers the thermal diffusivity of the solid substrate and establishes the relationship between surface roughness and vapor film thickness. The generality of this model is supported by experimental data for various liquids and solid substrates, providing a theoretical prediction of the Leidenfrost temperature and a comprehensive understanding of the Leidenfrost effect.
PHYSICAL REVIEW FLUIDS
(2023)
Article
Mechanics
You-An Lee, Detlef Lohse, Sander G. Huisman
Summary: We experimentally investigate the early-stage scalar mixing and transport with solvent exchange in a quasi-2D jet. Different modes of fluid supply, continuous injection and finite volume injection, are studied to analyze the starting jet and puff behaviors. The results show that the lack of continuous fluid supply in the puff leads to different characteristics in transport, entrainment, mixing, and nucleation.
INTERNATIONAL JOURNAL OF MULTIPHASE FLOW
(2023)
Article
Mechanics
Nikolas O. Aksamit, Robert Hartmann, Detlef Lohse, George Haller
Summary: Mathematical developments in the theory of objective coherent structures have improved our understanding of the material organization of complex fluid flows. However, there is limited investigation into these objectively defined transport barriers in 3-D unsteady flows with complicated spatiotemporal dynamics. Our study utilizes simulations to uncover the interplay between different types of barriers in turbulent rotating Rayleigh-Bénard convection.
JOURNAL OF FLUID MECHANICS
(2023)
Article
Mechanics
Jochem G. Meijer, Yanshen Li, Christian Diddens, Detlef Lohse
Summary: When an immiscible oil drop is immersed in a stably stratified ethanol-water mixture, it undergoes a transition from levitating to bouncing due to the oscillatory instability of the Marangoni flow on the drop's surface. The bouncing characteristics of the drop, such as jumping height and rising and sinking time, are studied in relation to the control parameters of drop radius, stratification strength, and drop viscosity. Experimental observations are backed by a simplified dynamical analysis and numerical simulations to verify the drag coefficients.
JOURNAL OF FLUID MECHANICS
(2023)
Article
Mechanics
Rui Yang, Christopher J. Howland, Hao-Ran Liu, Roberto Verzicco, Detlef Lohse
Summary: The presence of salt affects the melt rate and shape evolution of ice in seawater. Numerical simulations and experiments are used to study ice melting in saline water. The melt rate of ice decreases and then increases with increasing salt concentration due to the competition between salinity-driven and temperature-driven buoyancy. A theoretical model based on force balance predicts the minimal salt concentration for ice melt rate, consistent with the data. Interplay between phase transitions and double-diffusive convective flows is revealed.
JOURNAL OF FLUID MECHANICS
(2023)
Article
Physics, Fluids & Plasmas
Pallav Kant, Cesar Pairetti, Youssef Saade, Stephane Popinet, Stephane Zaleski, Detlef Lohse
Summary: We use experiments and numerical computations to study the fluid mechanical processes involved in the generation of bioaerosols during forceful respiratory maneuvers like coughing or sneezing. By performing analogous experiments on a cough machine, we observe the disintegration of a thin liquid film into small droplets and identify that aerosol generation is mediated by the formation of inflated baglike structures. The breakup of these bags is triggered by retracting holes on the surface, and the dynamics and stability of the liquid rims bounding these holes play a key role in the cascade from inflated bags to droplets. The viscosity of the fluid also affects the fragmentation process, with more viscous films producing smaller droplets.
PHYSICAL REVIEW FLUIDS
(2023)
Article
Mechanics
Qi Wang, David Goluskin, Detlef Lohse
Summary: Two-dimensional horizontally periodic Rayleigh-Benard convection between stress-free boundaries can exhibit two distinct types of states: roll states and windy states. Roll states consist of pairs of counter-rotating convection rolls, while windy states are dominated by a strong horizontally sheared wind that suppresses convection rolls. Windy states only occur when the Rayleigh number is sufficiently above the onset of convection.
JOURNAL OF FLUID MECHANICS
(2023)