Latest papers in fluid mechanics
Self-exploring automated experiments for discovery, optimization, and control of unsteady vortex-dominated flow phenomena
Author(s): Karen Mulleners
This paper discusses the transformative potential of self-exploring automated experiments for the discovery, optimization, and control of unsteady vortex-dominated flow phenomena. By minimizing experimentalists’ input in the actual performance of fluid experiments, the potential for scientific discovery is maximized.
[Phys. Rev. Fluids 9, 124701] Published Wed Dec 04, 2024
Predictability of isotropic turbulence by massive ensemble forecasting
Author(s): Alberto Vela-Martín
Turbulent flows are difficult to predict due to chaos, which amplifies any uncertainty in the initial conditions. The way this uncertainty grows and propagates is key to understanding the emergence of complexity in turbulence and to assessing the reliability of turbulence forecasts. In this Letter, a novel approach based on massive ensembles of simulations reveals that uncertainty propagates in isotropic turbulence following a simple law that depends only on the average properties of the flow. This result opens avenues to improve current forecasting techniques by efficiently and accurately modeling uncertainty propagation.
[Phys. Rev. Fluids 9, L122601] Published Wed Dec 04, 2024
Pore occupancy of gas hydrate
Author(s): David DiCarlo, Zachary W. Murphy, Kehua You, Peter B. Flemings, and Xiaoli Liu
Methane hydrate deposits are one of the largest fractions of hydrocarbons in the Earth's crust. They are found mainly in ocean sediments, and the configuration of the deposits—at the largest (kilometer) and smallest (micrometer) scales—determines how and when gaseous methane is released. Here, using…
[Phys. Rev. E 110, 065102] Published Wed Dec 04, 2024
Numerical study of thermal nonequilibrium effects on Richtmyer-Meshkov flow driven by a heavy forward-triangular bubble
Author(s): Salman Saud Alsaeed and Satyvir Singh
This paper investigates the thermal nonequilibrium effects on Richtmyer-Meshkov (RM) flow driven by a heavy forward-triangular bubble. Numerical laminar simulations are performed by utilizing the compressible dimensionless Navier-Fourier equations obtained from the Boltzmann-Curtiss transport equati…
[Phys. Rev. E 110, 065103] Published Wed Dec 04, 2024
Particle-in-liquid compound drops impact on solid wall: Spreading and retraction
Author(s): Rui Wang and Chun-Yu Zhang
When a particle-laden droplet impacts a flat surface, the presence of the particles inhibits its maximum spreading and reduces the rebound time.
[Phys. Rev. Fluids 9, 123601] Published Tue Dec 03, 2024
Self-similar and universal dynamics in drainage of mobile soap films
Author(s): Antoine Monier, François-Xavier Gauci, Cyrille Claudet, Franck Celestini, Christophe Brouzet, and Christophe Raufaste
We experimentally investigated the drainage of vertical rectangular soap films as they thin under gravity. Drainage dynamics were measured by tracking isothickness interference fringes. We showed that the downward motion of these fringes is self-similar with a power-law time evolution, or equivalently, that the thickness profiles exhibit space-time separation. By combining our data with previous studies, we collapsed all profiles onto a single curve, demonstrating the universality of this phenomenon. These findings are important for studying liquid foams and marginal regeneration instability.
[Phys. Rev. Fluids 9, 124001] Published Tue Dec 03, 2024
Shock-induced instability of dual-layer dilute gas-particle mixture
Author(s): Yifeng He, Baoqing Meng, Baolin Tian, and Yue Yang
We report the mechanism and modeling for the two-dimensional shock-induced instability of a dual-layer gas-particle mixture. In the mixture, the instability is triggered by the pressure perturbation near the perturbed interface instead of the baroclinic vorticity. The velocity difference of gas induced by the pressure perturbation drives the particle interface to grow via drag coupling effects. Inspired by this interfacial instability mechanism, we estimate the growth of the particle interface in the linear stage.
[Phys. Rev. Fluids 9, 124301] Published Tue Dec 03, 2024
Interface-induced turbulence in viscous binary fluid mixtures
Author(s): Nadia Bihari Padhan, Dario Vincenzi, and Rahul Pandit
We uncover interface-induced turbulence, a striking nonequilibrium statistically steady state with spatiotemporal chaos, emerging from interfacial fluctuations in low-Reynolds-number binary-fluid mixtures. Using direct numerical simulations of the Cahn-Hilliard-Navier-Stokes equations, we reveal a power-law energy spectrum indicative of turbulence without a conventional inertial cascade.
[Phys. Rev. Fluids 9, L122401] Published Tue Dec 03, 2024
Rayleigh-Taylor instability in multiple finite-thickness fluid layers
Author(s): Prashant Sharma
We develop a general transfer-matrix formalism for determining the growth rate of the Rayleigh-Taylor instability in a fluid system with spatially varying density and viscosity. We use this formalism to analytically and numerically treat the case of a stratified heterogeneous fluid. We introduce the…
[Phys. Rev. E 110, L063101] Published Tue Dec 03, 2024
Melancholia states of the Atlantic Meridional Overturning Circulation
Author(s): Johannes Lohmann and Valerio Lucarini
A dynamically unstable state of the Atlantic ocean circulation in a global ocean model is constructed via an edge tracking algorithm. Such an unstable state is relevant as it mediates the potential future tipping point of the meridional overturning circulation from its present-day state to a collapsed state as a result of climate change. We identify the physical characteristics of the unstable state, which gives insights into the physical mechanisms necessary to induce a collapse, as well as potential fingerprints and early-warning signals of the tipping point.
[Phys. Rev. Fluids 9, 123801] Published Mon Dec 02, 2024
Pattern formation of freezing infiltration in porous media
Author(s): Nathan D. Jones, Adrian Moure, and Xiaojing Fu
Gravity-driven flow of water into unsaturated porous media can form preferential pathways due to the gravity fingering instability. Here, we consider this process in a subfreezing porous medium using numerical simulations. We find that the macroscopic infiltration rate can be well predicted by the freezing Damköhler number. In contrast to the classical instability, the introduction of freezing in this problem gives rise to a new flow regime in which secondary flow pathways form in between the initial channels. This secondary instability homogenizes the otherwise channelized flow field and decreases the effective infiltration velocity.
[Phys. Rev. Fluids 9, 123802] Published Mon Dec 02, 2024
Dynamics of two-dimensional water flow in angstrom-scale mono and hybrid channels
Author(s): Chengzhen Sun, Qiyuan Wang, Mehdi Neek-Amal, Runfeng Zhou, and Bofeng Bai
In angstrom-scale channels, where water forms a two-dimensional (2D) monolayer, interlayer shear force decreases, making traditional viscosity definitions unsuitable. Our findings demonstrate that in channels below 1 nm, water flow does not follow conventional viscosity-driven principles; instead, friction between water molecules and channel walls governs flow behavior. We extend the Hagen-Poiseuille equation by excluding viscosity and emphasizing friction, providing a more accurate model for flow in ultra-narrow 2D spaces. This approach improves understanding of water flow in angstrom-scale channels, with applications in desalination and energy conversion.
[Phys. Rev. Fluids 9, 124201] Published Mon Dec 02, 2024
Reversible logic with a nanofluidic memristor
Author(s): Sergio Portillo, Javier Cervera, Salvador Mafe, and Patricio Ramirez
A multipore membrane with current-rectifying nanofluidic diodes exhibits memristive properties based on the surface-charge-regulated ionic transport. The neuromorphiclike potentiation of the conductance by voltage pulses provides different functionalities that can be modulated not only by the amplit…
[Phys. Rev. E 110, 065101] Published Mon Dec 02, 2024
Contrasting flow dynamics between stationary and moving clapping bodies
Author(s): Suyog V. Mahulkar and Jaywant H. Arakeri
Flow dynamics of pulse-jetting aquatic animals are often studied with apparatus kept stationary. This paper examines whether the stationary configuration captures the mechanics of the swimming animal. A clapping body, simulating a pulse-jet animal, is tested in freely propelled (dynamic) and forward motion constrained (stationary) conditions. Significant differences are observed in body motion and wake structure: clapping motion is nearly twice as fast in dynamic cases, while mean thrust coefficient and vortex circulation are higher in stationary cases, varying with body depth but which remain constant in dynamic cases. Care is needed in extrapolating data from stationary to swimming bodies.
[Phys. Rev. Fluids 9, 114702] Published Wed Nov 27, 2024
Rayleigh-Taylor unstable flames: The effect of two-mode coupling
Author(s): Mingxuan Liu (刘明轩) and Elizabeth P. Hicks
We explore how adding a reaction to a Rayleigh-Taylor unstable interface affects the way that two short wavelength modes couple to generate longer wavelength modes. Using simulations, we identify five distinct flame growth solution types. Depending on the greatest common divisor of the wavenumbers of the two modes, the flame may stall, develop coherent pulsations, or even become a metastable traveling wave. We also compare our results with two-mode coupling in ablative and classical Rayleigh-Taylor and show that all three systems may follow the same mode coupling dynamics.
[Phys. Rev. Fluids 9, 113203] Published Tue Nov 26, 2024
Giant superhydrophobic slip of shear-thinning liquids
Author(s): Ory Schnitzer and Prasun K. Ray
Recent experiments and simulations have suggested that flows of strongly shear-thinning liquids can be greatly enhanced by superhydrophobicity, above and beyond the enhancements familiar for Newtonian liquids. Using asymptotics and numerics, we illuminate the singular mechanism underlying such enhancement, considering the prototypical problem of shear-driven flow over a grooved superhydrophobic surface. A key finding is that the singular scaling of the effective slip length at small solid fractions transitions from logarithmic to algebraic as the viscosity at infinite shear is reduced relative to its value at zero shear.
[Phys. Rev. Fluids 9, L112201] Published Tue Nov 26, 2024
Aerodynamic bag breakup of a polymeric droplet
Author(s): Navin Kumar Chandra, Shubham Sharma, Saptarshi Basu, and Aloke Kumar
When liquid droplets encounter high-speed gas flows, they fragment through various modes, with bag-mediated breakup mode observed at lower Weber numbers. This study shows that even minute concentrations of long-chain polymer molecules in a Newtonian solvent can drastically modify its fragmentation characteristics. By investigating the role of liquid elasticity, we uncover how polymeric additives control the fragmentation dynamics of a droplet specifically in the bag breakup regime.
[Phys. Rev. Fluids 9, 113303] Published Mon Nov 25, 2024
Bubble oscillation and effects of dynamic behaviors on forces and mass transfer in photoelectrochemical water splitting
Author(s): Yonglu She, Qiang Xu, Tengfei Nie, Xinyi Luo, Mengsha Wang, Xingmiao Ye, Dengwei Jing, and Liejin Guo
The evolution and accumulation of bubbles formed by gas release at the reaction interface present a considerable challenge for improving the efficiency of photoelectrochemical water splitting. Bubble oscillation enhances mass transfer and influences flow dynamics within the system. This study successfully regulates the amplitudes of bubble oscillations by adjusting system temperature and operating voltage and analyzes the mechanism and the mass transfer theory of oscillating bubbles, offering a new approach to managing bubble dynamics.
[Phys. Rev. Fluids 9, 114305] Published Mon Nov 25, 2024
Interaction of an inner-scaled Helmholtz resonator with boundary-layer turbulence
Author(s): Abdelrahman Hassanein, Davide Modesti, Fulvio Scarano, and Woutijn J. Baars
This work provides key insights into the interaction between grazing turbulence and a Helmholtz resonator. By tuning the resonator’s frequency to align with the scales of energetic pressure fluctuations in turbulent boundary layers, the device amplifies small-scale velocity fluctuations while reducing large-scale turbulence energy. This frequency-specific modulation suggests that Helmholtz resonators could serve as scalable, wall-embedded surfaces for targeted turbulence control, offering new pathways in flow control.
[Phys. Rev. Fluids 9, 114610] Published Mon Nov 25, 2024
Contrasting thermodynamic and hydrodynamic entropy
Author(s): Mahendra K. Verma, Rodion Stepanov, and Alexandre Delache
In this paper, using hydrodynamic entropy, we quantify multiscale disorder in Euler and hydrodynamic turbulence. These examples illustrate that the hydrodynamic entropy is not extensive because it is not proportional to the system size. Consequently, we cannot add hydrodynamic and thermodynamic entr…
[Phys. Rev. E 110, 055106] Published Mon Nov 25, 2024
Pages
