Physical Review Fluids

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Physics of nanoscale immiscible fluid displacement

Wed, 12/11/2019 - 10:00

Author(s): Gerald J. Wang, Angelo Damone, Francesco Benfenati, Pietro Poesio, Gian Paolo Beretta, and Nicolas G. Hadjiconstantinou

At the nanoscale, and in particular in the presence of slip, hydrodynamic bending of interfaces between immiscible liquids becomes negligible. The dynamic contact angle is then governed by the Molecular Kinetic Theory (MKT) of Blake and collaborators.


[Phys. Rev. Fluids 4, 124203] Published Wed Dec 11, 2019

Mass transfer from a cylindrical body in a linear ambient velocity distribution

Wed, 12/11/2019 - 10:00

Author(s): Ehud Yariv

Asymptotic methods and conformal mappings are used to study mass or heat transport from a particle that is subject to a weak flow.


[Phys. Rev. Fluids 4, 124503] Published Wed Dec 11, 2019

Forced dynamic dewetting of structured surfaces: Influence of surfactants

Mon, 12/09/2019 - 10:00

Author(s): Franziska Henrich, Dorota Linke, Hans Martin Sauer, Edgar Dörsam, Steffen Hardt, Hans-Jürgen Butt, and Günter K. Auernhammer

The interaction of pinning and surfactant-induced changes of dynamic contact angles on receding contact lines is studied. With increasing surfactant concentration the surfactant-induced effects dominate over pinning effects. This behavior is correlated to the emptying of the surface structures.


[Phys. Rev. Fluids 4, 124202] Published Mon Dec 09, 2019

Role of large-scale advection and small-scale turbulence on vertical migration of gyrotactic swimmers

Mon, 12/09/2019 - 10:00

Author(s): C. Marchioli, H. Bhatia, G. Sardina, L. Brandt, and A. Soldati

The role of large-scale motions and small-scale turbulence on rising of small bottom-heavy swimmers is examined via high Reynolds number direct numerical simulation of turbulent free-surface flow. The swimmers’ rising efficiency is quantified via a new timescale that combines the stability number and the Kolmogorov timescale.


[Phys. Rev. Fluids 4, 124304] Published Mon Dec 09, 2019

Potential-core closing of temporally developing jets at Mach numbers between 0.3 and 2: Scaling and conditional averaging of flow and sound fields

Mon, 12/09/2019 - 10:00

Author(s): Christophe Bogey and Pierre Pineau

Using direct numerical simulation, the potential-core closing of temporally developing round jets at Mach numbers between 0.3 and 2 is shown to radiate strong axisymmetric acoustic waves in the downstream direction. The Mach number dependence and the generation mechanism of these waves are revealed.


[Phys. Rev. Fluids 4, 124601] Published Mon Dec 09, 2019

Turbulent flows around side-by-side cylinders with regular and multiscale arrangements

Mon, 12/09/2019 - 10:00

Author(s): Shancong Tao and Yi Zhou

A numerical study confirms that by using multiscale structures, turbulence with a wider range of scales can be generated. However, the multiscale-generated turbulence may not have a long-lasting memory and can eventually forget its multiscale initial conditions.


[Phys. Rev. Fluids 4, 124602] Published Mon Dec 09, 2019

Absolute instability of impinging leading edge vortices in a submodel of a bileaflet mechanical heart valve

Fri, 12/06/2019 - 10:00

Author(s): Hadi Zolfaghari and Dominik Obrist

Mechanical heart valves have been linked to the production of unphysiological turbulent blood flow. As a first step toward a model for laminar-turbulent transition in this flow, an absolute instability in the impinging leading-edge vortices that develop between the valve leaflets is identified.


[Phys. Rev. Fluids 4, 123901] Published Fri Dec 06, 2019

Mechanisms of airfoil noise near stall conditions

Fri, 12/06/2019 - 10:00

Author(s): Giovanni Lacagnina, Paruchuri Chaitanya, Tim Berk, Jung-Hoon Kim, Phillip Joseph, Bharathram Ganapathisubramani, Seyed Mohammad Hasheminejad, Tze Pei Chong, Oksana Stalnov, Kwing-So Choi, Muhammad Farrukh Shahab, Mohammad Omidyeganeh, and Alfredo Pinelli

A study of mechanisms of noise radiation from airfoils at high angles of attack (partial to full separation) identifies four different noise generation flow regimes. The relationship between noise, surface pressure, and shear layer turbulence is explored.


[Phys. Rev. Fluids 4, 123902] Published Fri Dec 06, 2019

Mitigation of turbophoresis in particle-laden turbulent channel flows by using incident electric fields

Fri, 12/06/2019 - 10:00

Author(s): M. Di Renzo, P. L. Johnson, M. Bassenne, L. Villafañe, and J. Urzay

The influence of electric forces on inertial particles in turbulent channel flows is explored using direct numerical simulations. It is found that the near-wall buildup of particle concentration due to turbophoresis can be reduced up to 2 orders of magnitude by imposing an ac electric field.


[Phys. Rev. Fluids 4, 124303] Published Fri Dec 06, 2019

Dispersion and reaction in random flows: Single realization versus ensemble average

Fri, 12/06/2019 - 10:00

Author(s): Antoine Renaud and Jacques Vanneste

The dispersion and reaction of a scalar patch by a random flow is investigated. A comparison of single realizations to the ensemble average shows explicitly that the two concentrations have very different tails, leading to different reaction front velocities in the fast-reacting problem.


[Phys. Rev. Fluids 4, 124502] Published Fri Dec 06, 2019

Genuine compressibility effects in wall-bounded turbulence

Thu, 12/05/2019 - 10:00

Author(s): Ming Yu, Chun-Xiao Xu, and Sergio Pirozzoli

Finite dilatational effects in wall-bounded compressible turbulence are investigated. We find that finite correlation between the solenoidal and the dilatational parts of the velocity field account for a nonnegligible fraction of the turbulent shear stress near walls.


[Phys. Rev. Fluids 4, 123402] Published Thu Dec 05, 2019

Rayleigh-Taylor-like instability in a foam film

Wed, 12/04/2019 - 10:00

Author(s): Evgenia Shabalina, Antoine Bérut, Mathilde Cavelier, Arnaud Saint-Jalmes, and Isabelle Cantat

A foam film is prepared in a controlled way, so that the top part of the film is much thicker than the bottom part. This situation is unstable under gravity and Rayleigh-Taylor-like fingers grow.The wavelength and the growth rate depend on the effective gravity and on the thick-film width.


[Phys. Rev. Fluids 4, 124001] Published Wed Dec 04, 2019

Micron-sized double emulsions and nematic shells generated via tip streaming

Wed, 12/04/2019 - 10:00

Author(s): Kunyun He, Francisco Campo-Cortés, Martyna Goral, Teresa López-León, and José Manuel Gordillo

The smallest compound droplets reported up to date, with outer diameters comparable with a red blood cell, are produced in a continuous way at frequencies exceeding 10 kHz from the capillary breakup of the coaxial cylindrical jets issued from the tip of the conical drops formed using an outer coflow.


[Phys. Rev. Fluids 4, 124201] Published Wed Dec 04, 2019

Systematic direct simulation Monte Carlo approach to characterize the effects of surface roughness on accommodation coefficients

Tue, 12/03/2019 - 10:00

Author(s): Kishore K. Kammara, Rakesh Kumar, Amit K. Singh, and Arun K. Chinnappan

The effects of surface roughness on accommodation coefficients are studied using the direct simulation Monte-Carlo (DSMC) approach. DSMC simulations are carried out by varying the roughness parameters. An empirical relationship between surface roughness and accommodation coefficients is established.


[Phys. Rev. Fluids 4, 123401] Published Tue Dec 03, 2019

Membrane filtration with multiple fouling mechanisms

Tue, 12/03/2019 - 10:00

Author(s): Pejman Sanaei and Linda J. Cummings

A simplified mathematical model, which characterizes membrane internal pore structure accounts for multiple simultaneous membrane fouling mechanisms (adsorption, blocking, and cake formation) and is able to predict the optimum permeability.


[Phys. Rev. Fluids 4, 124301] Published Tue Dec 03, 2019

Inertial drag in granular media

Tue, 12/03/2019 - 10:00

Author(s): Shivakumar Athani and Pierre Rognon

We find evidence that the granular drag force on an object moving through a granular material is strongly enhanced when the object is accelerating. This effect can be explained by showing that the accelerating object accelerates the grains nearby, inducing an inertial resistance.


[Phys. Rev. Fluids 4, 124302] Published Tue Dec 03, 2019

Bretherton's buoyant bubble

Mon, 12/02/2019 - 10:00

Author(s): Wassim Dhaouadi and John M. Kolinski

Direct observation of the liquid film binding buoyant Bretherton bubbles reveals a van-der-Waals-stabilized thickness.


[Phys. Rev. Fluids 4, 123601] Published Mon Dec 02, 2019

Rotational separation after temporary coalescence in binary droplet collisions

Mon, 12/02/2019 - 10:00

Author(s): Kuo-Long Pan, Kuan-Ling Huang, Wan-Ting Hsieh, and Chi-Ru Lu

In binary drop impact, in addition to reflexive separation and stretching separation, which occur at low and high impact angles (B), respectively, rotational separation is found at intermediate B. A generic model is developed to examine the scenarios and the interplay of various factors.


[Phys. Rev. Fluids 4, 123602] Published Mon Dec 02, 2019

Deep learning of turbulent scalar mixing

Mon, 12/02/2019 - 10:00

Author(s): Maziar Raissi, Hessam Babaee, and Peyman Givi

Based on recent developments in physics-informed deep learning and deep hidden physics models, we put forth a framework for discovering turbulence models from scattered and potentially noisy spatio-temporal measurements of the probability density function.


[Phys. Rev. Fluids 4, 124501] Published Mon Dec 02, 2019

Inverse energy cascade and vortical structure in the near-wall region of turbulent channel flow

Wed, 11/27/2019 - 10:00

Author(s): Fujihiro Hamba

An inverse cascade is found in the energy transfer in scale space of channel flow. The conditional average of the velocity field associated with the inverse cascade or negative subgrid-scale production reveals a long streamwise vortex near the wall with a short vortex in the upstream region.


[Phys. Rev. Fluids 4, 114609] Published Wed Nov 27, 2019

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