Latest papers in fluid mechanics

Author(s): Ao Xu, Ben-Rui Xu, and Heng-Dong Xi

Through high-resolution pore-scale simulations, we uncover that impermeable solid porous matrices significantly influence the heat and fluid flow within these materials. We discover that as porosity decreases, temperature fluctuations increase; unlike porous materials with matrices being permeable to heat flux, impermeable ones cause less organized flow patterns. Furthermore, intense thermal energy dissipation mainly occurs near the surfaces of the porous material, and exhibits more intermittency compared to traditional convection systems.

[Phys. Rev. Fluids 8, 093504] Published Mon Sep 18, 2023

Author(s): Dana Harvey and Justin C. Burton

During the Leidenfrost effect, a stable vapor film separates a hot solid from an evaporating liquid. As the solid cools, the vapor layer is metastable, and can undergo a violent collapse accompanied by explosive boiling of the liquid. We provide insight into this failure mechanism using a computational model with hydrodynamics, thermodynamics, and rapid evaporation of the liquid phase. By varying both liquid and solid properties, we find that inertial forces, which are typically ignored in theoretical treatments of the vapor layer, are likely responsible for initiating the instability leading to failure.

[Phys. Rev. Fluids 8, 094003] Published Mon Sep 18, 2023

Author(s): Nathan Coppin, Michel Henry, Miguel Cabrera, Emilien Azéma, Frédéric Dubois, Vincent Legat, and Jonathan Lambrechts

The collapse of a granular column is a benchmark case for the study of granular materials. In this work, the collapse dynamics of two-dimensional columns of elongated grains are numerically investigated in dry and immersed conditions. The focus is set on the orientation of the grains and its influence on the behavior of the column. An energy-based approach suggests the influence of grain shape on mobility is limited to the prefactor of a power-law.

[Phys. Rev. Fluids 8, 094303] Published Mon Sep 18, 2023

Author(s): L. Talon, R. Bouguemari, A. Yiotis, and D. Salin

We study experimentally the dynamics of non-wetting blobs flowing simultaneously with a wetting fluid in a quasi-two-dimensional porous medium consisting of random obstacles. The blobs continuously merge forming larger ones (coalescence) and breakup into smaller ones (fragmentation) leading to an overall dynamic equilibrium between the two processes. In this work, we analyze the probability functions for coalescence and breakup as a function of blob sizes and total flow rate.

[Phys. Rev. Fluids 8, 093602] Published Fri Sep 15, 2023

Author(s): J. John Soundar Jerome, Yohann Bachelier, Delphine Doppler, Christoph Lehmann, and Nicolas Rivière

Mechanical structures in nature and in applications are often very flexible and also, are exposed to vortex-laden flows. While vortex-induced-vibration is one of the most commonly studied fluid-structure interactions, we explore what can be called vortex-forced-vibrations of a flexible sheet to provide physical insights on the average reconfiguration, vibration amplitude, and frequency response of a thin sheet forced by von Karman vortices.

[Phys. Rev. Fluids 8, 093801] Published Fri Sep 15, 2023

Author(s): Seunghwan Shin, Filippo Coletti, and Nicholas Conlin

In forced two-dimensional flows, the energy input is not only balanced by viscous dissipation within the fluid, but also by friction along the boundaries. In this study, we investigate the classic experimental realization of quasi-2D turbulence in electromagnetically driven layers of conducting fluids and confirm that friction dominates over viscous dissipation in such systems. The emergence of fully developed turbulence is governed by the frictional Reynolds number (Reα) rather than the commonly used viscous Reynolds number (Re), as evidenced by the fact that descriptors from 58 cases of different forcing in five layer configurations collapse onto master curves when plotted against Reα.

[Phys. Rev. Fluids 8, 094601] Published Fri Sep 15, 2023

Author(s): Francesco Carbone, Mirko Piersanti, Fabio Lepreti, Leonardo Primavera, Christian N. Gencarelli, Nicola Pirrone, and Roberto Battiston

The upper portions of the Earth's atmospheric layer, e.g., the ionospheric plasma layer, can be significantly affected by perturbations generated in the lower layers. In fact, all perturbations formed within the troposphere can easily propagate, not only horizontally within the layer but also vertic…

[Phys. Rev. E 108, 035105] Published Thu Sep 14, 2023

Author(s): Imogen G. Cresswell, Evan H. Anders, Benjamin P. Brown, Jeffrey S. Oishi, and Geoffrey M. Vasil

We study force balances in two-dimensional Rayleigh-Benard simulations with a large range of imposed background magnetic fields. We find two main regimes, a magnetically constrained regime where the linear Lorentz force dominates, and a magnetically influenced regime where the nonlinear Lorentz force heavily influences dynamics, meaning that classic hydrodynamical flow patterns are not achieved at the highest Rayleigh number studied in this work. Despite the impact of the nonlinear Lorentz force on the dynamics, we find classical hydrodynamic scaling of the Nusselt number and also derive scaling laws for the magnetic field in both of these regimes.

[Phys. Rev. Fluids 8, 093503] Published Thu Sep 14, 2023

Author(s): Jinyu Yao, Harry B. Bingham, and Xinshu Zhang

Mini-tsunamis are generated when a ship travels through a depth change and can cause significant coastline erosion. It is found that the amplitude of mini-tsunami and wavelength are increased by the higher order bottom and free-surface nonlinearities, and those effects are more significant for a fast-traveling ship in a narrow channel. Our work can shed light on nonlinear effects in the generation of mini-tsunamis, and advance the development of warning systems for coastal erosion owing to the ship-generated waves.

[Phys. Rev. Fluids 8, 094801] Published Thu Sep 14, 2023

Author(s): Fabio Ramos and Gabriel Sanfins

We introduce similarity relations and symmetry groups for the analysis of laminar Bingham fluid flows, presenting a valuable new expression for calculating the friction factor, particularly when pressure gradient data are available. Notably, we highlight the significance of friction coordinates as the most suitable framework for unraveling the complexities of Bingham plastic fluids.

[Phys. Rev. Fluids 8, L091301] Published Thu Sep 14, 2023

Author(s): Morteza Dejam and Hassan Hassanzadeh

We extend the Taylor-Aris dispersion theory to upscale the gas absorption into a viscous incompressible liquid flowing along an inclined surface. A reduced-order model of advection-dispersion-reaction is developed with the aid of Reynolds decomposition and cross-sectional averaging techniques. The u…

[Phys. Rev. E 108, 035104] Published Wed Sep 13, 2023

Author(s): Alessio Roccon, Francesco Zonta, and Alfredo Soldati

Phase-field modeling of drop dynamics and direct numerical simulation of drop-laden turbulent flow are used to examine the complex topological changes of the dispersed phase — breakage and coalescence — and to determine the evolving drop size distribution. Potentials and perspectives for further development of the phase-field method to model mass transfer, heat transfer, and Marangoni effects due to thermocapillarity and surfactants are also discussed.

[Phys. Rev. Fluids 8, 090501] Published Tue Sep 12, 2023

Author(s): Tobias G. Oliver, Adrienne S. Jacobi, Keith Julien, and Michael A. Calkins

We investigate the most turbulent simulations to date for rapidly rotating convection in a plane layer geometry. The results show that the flow remains viscously controlled across the investigated parameter space, and that the length scales present within the flow remain comparable to those predicted by linear theory.

[Phys. Rev. Fluids 8, 093502] Published Tue Sep 12, 2023

Author(s): Aminur Rahman

Damped-driven systems are ubiquitous in science, however, the damping and driving mechanisms are often quite convoluted. This paper presents an experimental and theoretical investigation of a fluidic droplet on a vertically vibrating fluid bath as a damped-driven system. We study a fluidic droplet i…

[Phys. Rev. E 108, 035103] Published Mon Sep 11, 2023

Author(s): James E. Sprittles, Jingbang Liu, Duncan A. Lockerby, and Tobias Grafke

The rupture of thin liquid films on solid surfaces is conventionally assumed to be driven by intermolecular forces, in the so-called spinodal regime. Here, a theoretical framework is created for the experimentally observed thermal regime, in which fluctuation-induced nanowaves rupture films. Fluctuating hydrodynamics is able to capture this regime and its predictions are verified by molecular simulations. Rare-event theory is then applied to this field for the first time to reveal a novel picture of how and when rogue nanowaves create rupture.

[Phys. Rev. Fluids 8, L092001] Published Mon Sep 11, 2023

Author(s): Swarnak Ray and Arun Roy

We propose a simple active hydrodynamic model for the self-propulsion of a liquid droplet suspended in micellar solutions. The self-propulsion of the droplet occurs by spontaneous breaking of isotropic symmetry and is studied using both analytical and numerical methods. The emergence of self-propuls…

[Phys. Rev. E 108, 035102] Published Fri Sep 08, 2023

Author(s): I. Rubinstein and B. Zaltzman

Dendrite formation due to morphological instability in cathodic electrodeposition of a metal and related fluid flows are investigated. We show that the electric double layer fine structure and the finite electrode reaction rate regularize the electrodeposition front short-wave singularity and select a range of unstable perturbation modes. The critical wavelength corresponds to the fastest growing mode and scales with the electric double layer width and the reaction-diffusion length. The emerging electroconvective (electroosmotic) flow in the nonequilibrium regime selects the cathodic diffusion layer width as the dominant length scale for morphological instability and emerging dendrites.

[Phys. Rev. Fluids 8, 093701] Published Thu Sep 07, 2023

Author(s): A. F. V. de A. Aquino, S. G. Mallinson, G. D. McBain, G. D. Horrocks, C. M. de Silva, and T. J. Barber

Numerical simulations using the dispersed-phase continuum (DPC) and the particle-in-cell (PinC) models were performed to characterize the onset of instability where the airflow in the print gap of inkjet printers becomes nonuniform in the spanwise direction. The results indicated that the baseflow shifts from a uniform flow field to a standing wave regime at a specific number density, which characterizes a supercritical pitchfork bifurcation. Furthermore, the comparison between both models showed that the DPC technique effectively computed the mean flow field with a reduction of up to 1000x in processing time.

[Phys. Rev. Fluids 8, 094302] Published Thu Sep 07, 2023

Author(s): Saideep Pavuluri, Ran Holtzman, Luqman Kazeem, Malyah Mohammed, Thomas Daniel Seers, and Harris Sajjad Rabbani

The interplay between viscosity ratio and contact angle for viscous-dominated flows in a two-dimensional porous medium is studied with Direct Numerical Simulations. Viscous fingering, intermediate flow, and compact displacement regimes were examined for various viscosity ratios at the sample scale. Even at the pore-scale, various pore filling mechanisms were found. For imbibition and drainage, cooperative filling occurs at large viscosity ratios. At low viscosity ratios, film flow (strong imbibition), and unstable bursts (strong drainage) were seen. Changes in pore filling mechanisms occurring at the same contact angle indicates the viscosity ratio impact on effective wettability variation.

[Phys. Rev. Fluids 8, 094002] Published Wed Sep 06, 2023

Author(s): Haolin Li, Anne Juel, Finn Box, and Draga Pihler-Puzović

An air finger is injected with constant volumetric flow rate into a bifurcating liquid-filled Hele-Shaw channel topped with an elastic sheet, to study airway reopening. Imposing collapsed channel configurations, we observe finger propagation in straight parts of the channel that are reflected in finger morphologies. The mechanics involved also controls recovery of steady states post-bifurcation, and, in some regimes, can lead to multiple reopening scenarios downstream from the bifurcation for experimentally indistinguishable fingers in the main channel. Our results suggest that steady state propagation is unlikely to be recovered between bifurcations in practical networks.

[Phys. Rev. Fluids 8, 094001] Published Tue Sep 05, 2023