Latest papers in fluid mechanics

Shear-triggered coalescence

Physical Review Fluids - Thu, 02/08/2024 - 10:00

Author(s): Alireza Mashayekhi, Coralie Vazquez, Hongying Zhao, Michael Gattrell, James F. Gilchrist, and John M. Frostad

In prior work, it was observed that some bitumen droplets coalesced faster when colliding in shear than colliding head-on. Inspired by this observation, we aimed to reproduce the same behavior in a simpler system composed of pure oil, water, and surfactants/particles. Using a cantilevered-capillary force apparatus we observed this phenomenon for droplets stabilized by cellulose nanocrystals and coined the term “shear-triggered coalescence” to describe it.


[Phys. Rev. Fluids 9, 023602] Published Thu Feb 08, 2024

Instability and rupture of sheared viscous liquid nanofilms

Physical Review Fluids - Thu, 02/08/2024 - 10:00

Author(s): Vira Dhaliwal, Christian Pedersen, Kheireddin Kadri, Guillaume Miquelard-Garnier, Cyrille Sollogoub, Jorge Peixinho, Thomas Salez, and Andreas Carlson

Liquid nanofilms are subject to rupture due to intermolecular forces triggered by surface perturbations arising from thermal fluctuations. When a shear stress is imposed at the free surface it becomes stable in the direction of shear, but perturbations can still grow in the perpendicular direction to the shear.


[Phys. Rev. Fluids 9, 024201] Published Thu Feb 08, 2024

Turbulent puffs in transitional pulsatile pipe flow at moderate pulsation amplitudes

Physical Review Fluids - Thu, 02/08/2024 - 10:00

Author(s): Daniel Morón and Marc Avila

Pulsatile pipe flow, or the flow in a pipe with a mean and one or more harmonic bulk velocity components, is a benchmark to study unsteady driven flows in industrial and biological applications. We study the transitional regime of pulsatile pipe flow at moderate-to-high amplitudes and intermediate pulsation frequencies. We show that, as in steady driven pipe flow, the first long-lived turbulent structures are localized. We combine direct numerical simulations, causal analysis and turbulence modeling to describe the behavior of these turbulent patches in pulsatile pipe flow, and to determine the physical mechanisms by which they survive the pulsation.


[Phys. Rev. Fluids 9, 024601] Published Thu Feb 08, 2024

Laser-induced thermocapillary flows on a flowing soap film

Physical Review Fluids - Thu, 02/08/2024 - 10:00

Author(s): Yu Zhao and Haitao Xu

We propose a focused laser heating method to study wave properties of flowing soap films. The laser-induced thermocapillary flows lead to symmetric disturbances in film thickness. The shock waves originating from the propagating symmetric elastic waves, which have remained elusive despite considerable experimental efforts, are thus stimulated on flowing soap films with low surfactant concentrations, or appreciable elasticities. Interestingly, on soap films with high surfactant concentrations, or vanishingly small elasticities, the laser-induced disturbances in film thickness remain unchanged and flow with the film without propagating, creating “laser-engraving” on free liquid films.


[Phys. Rev. Fluids 9, L022001] Published Thu Feb 08, 2024

Electrowetting dynamics of sessile droplets in a viscous medium

Physical Review Fluids - Wed, 02/07/2024 - 10:00

Author(s): Juan S. Marin Quintero, Butunath Majhy, and Prashant R. Waghmare

This work analyzes the transient wetting dynamics of droplets in viscous media with appropriate governing parameters and examines the drop’s transient response immediately after the actuation, the drop’s retraction and resultant dynamics, and the effect of multiple wave actuation on the droplet transition.


[Phys. Rev. Fluids 9, 024001] Published Wed Feb 07, 2024

Reversal of the transverse force on a spherical bubble rising close to a vertical wall at moderate-to-high Reynolds numbers

Physical Review Fluids - Tue, 02/06/2024 - 10:00

Author(s): Pengyu Shi

Bubbles rising near a vertical wall are known to bounce repeatedly when the Reynolds number (Re) exceeds about 65. This behavior contradicts potential flow theory, which suggests a consistently attractive transverse force. In this study, we demonstrate through numerical simulations that below a critical Re-dependent separation, the transverse force decreases with decreasing separation, potentially reversing from attractive to repulsive. We believe this reversal is responsible for the bouncing motion observed in freely near-wall rising bubbles.


[Phys. Rev. Fluids 9, 023601] Published Tue Feb 06, 2024

Near-critical behavior of the Zhong-Zhang model

Physical Review E - Mon, 02/05/2024 - 10:00

Author(s): J. H. Lowenstein

The Zhong-Zhang (ZZ) model is a one-degree-of-freedom dynamical system describing the motion of an insulating plate of length d floating on the upper surface of a convecting fluid, with locking at the boundaries. In the absence of noise, the system away from the boundaries is described by linear dif…


[Phys. Rev. E 109, 025102] Published Mon Feb 05, 2024

Electroosmotic mixing of viscoplastic fluids in a microchannel

Physical Review Fluids - Mon, 02/05/2024 - 10:00

Author(s): Sumit Kumar Mehta and Pranab Kumar Mondal

This work finds that the yield stress (YS) of electrically actuated viscoplastic fluids significantly influences mixing and aggregation phenomena. When shear force is applied below the YS limit, these fluids exhibit solid-like behavior due to their viscoplasticity. This is commonly observed in biological fluids like blood used in applications where rapid mixing is crucial. The local modulation of electrical forcing is achievable due to the ionic interaction between the solid and liquid phases. This leads to the observation of distinct flow structures, found to be influenced by the YS. Additionally, the likelihood of constituent particles aggregating is strongly correlated with YS.


[Phys. Rev. Fluids 9, 023301] Published Mon Feb 05, 2024

Data-based approach for time-correlated closures of turbulence models

Physical Review E - Thu, 02/01/2024 - 10:00

Author(s): J. Domingues Lemos and A. A. Mailybaev

Developed turbulent motion of fluid still lacks an analytical description despite more than a century of active research. Nowadays, phenomenological ideas are widely used in practical applications, such as small-scale closures for numerical simulations of turbulent flows. In the present paper, we us…


[Phys. Rev. E 109, 025101] Published Thu Feb 01, 2024

Editorial: The 2023 François Naftali Frenkiel Award for Fluid Mechanics

Physical Review Fluids - Wed, 01/31/2024 - 10:00

Author(s): Eric Lauga and Beverley McKeon

[Phys. Rev. Fluids 9, 010001] Published Wed Jan 31, 2024

Autothermotaxis of volatile drops

Physical Review Fluids - Wed, 01/31/2024 - 10:00

Author(s): Pallav Kant, Mathieu Souzy, Nayoung Kim, Devaraj van der Meer, and Detlef Lohse

We present an extraordinary phenomenon that emerges from seemingly simple ingredients: a volatile droplet deposited on a highly wetting and heat-conducting warm substrate. Contrary to prevailing intuition that the deposited droplet would spread more and evaporate faster, we find that the droplet instead undergoes contraction and in addition it spontaneously and erratically moves, for substrate temperatures well below the boiling point of the liquid. We term this remarkable phenomenon “Autothermotaxis” and show that it originates from the thermal Marangoni flow in the droplet which undergoes an instability. The thermal Marangoni flow is also the reason for the contraction of the droplet.


[Phys. Rev. Fluids 9, L012001] Published Wed Jan 31, 2024

Unifying length-scale-based rheology of dense suspensions

Physical Review Fluids - Tue, 01/30/2024 - 10:00

Author(s): Zhuan Ge, Teng Man, Herbert E. Huppert, Kimberly M. Hill, and Sergio Andres Galindo-Torres

Suspensions, comprising particles and fluid, play a crucial role across diverse domains, including in nature, such as submarine landslides, biological systems such as blood flows, as well as industrial materials like concrete. The rheology of these materials is a combination of both fluid and solid properties. This study introduces a dimensionless number derived from the ratio between characteristic length scales, offering a unified perspective on the rheology of dense suspensions across a spectrum from conditions where fluid-like effects dominate to regimes influenced by inertial forces. The derivation contained herein is strict, offering significant physical insight into these systems.


[Phys. Rev. Fluids 9, L012302] Published Tue Jan 30, 2024

Elastic instability in a family of rectilinear viscoelastic channel flows devoid of centerline symmetry

Physical Review Fluids - Mon, 01/29/2024 - 10:00

Author(s): Shailendra Kumar Yadav, Ganesh Subramanian, and V. Shankar

The recently discovered elastic center-mode instability in plane-Poiseuille flow is shown to be present even in base flows devoid of centerline symmetry. This is illustrated using the Couette-Poiseuille family of asymmetric velocity profiles, wherein the instability is present when the maximum of the base flow is present within the channel domain. The predicted instability is potentially relevant to viscoelastic flows in the Taylor-Dean, shallow-cavity, and slider-bearing configurations.


[Phys. Rev. Fluids 9, 013301] Published Mon Jan 29, 2024

Modal and nonmodal stability analysis of turbulent stratified channel flows

Physical Review Fluids - Mon, 01/29/2024 - 10:00

Author(s): Donato Variale, Enza Parente, Jean Christophe Robinet, and Stefania Cherubini

This work aims at studying the modal and nonmodal stability of stably stratified turbulent channel flow, assessing the influence of stratification at fixed friction Reynolds number. When increasing the stratification, the energy gain for streamwise-independent perturbations increases by two orders of magnitude, and the spanwise wavenumber for which the energy gain peaks reaches values comparable to those reported in the direct numerical simulations. Moreover, for nonzero values of the streamwise and spanwise wavenumbers, α and β, the energy gain curve has two peaks, one for shorter target times and α>β, leading to a center-channel temperature peak, and another for α<β at larger target times.


[Phys. Rev. Fluids 9, 013904] Published Mon Jan 29, 2024

Sound waves, diffusive transport, and wall slip in nanoconfined compressible fluids

Physical Review Fluids - Mon, 01/29/2024 - 10:00

Author(s): Hannes Holey, Peter Gumbsch, and Lars Pastewka

In this work we compare long wavelength fluctuations in nanoconfined simple fluids from molecular dynamics simulations with continuum descriptions. Quasi-two-dimensional descriptions of these confined fluids give rise to attenuation behavior of hydrodynamic fluctuations distinct from the bulk. Interactions with the walls introduce additional dissipation and can be related to wall slip and an anomalous dispersion relation for sound.


[Phys. Rev. Fluids 9, 014203] Published Mon Jan 29, 2024

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