Physical Review Fluids

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Updated: 15 hours 13 min ago

Separation regimes of two spheres falling in shear-thinning viscoelastic fluids

Fri, 02/15/2019 - 10:00

Author(s): D. Freire, L. G. Sarasúa, A. Vernet, S. Varela, G. Usera, C. Cabeza, and A. C. Martí

Experiments show that the separation between two spheres settling down in viscoelastic shear-thinning solutions exhibit two different regimes depending on the fluids’ rheological properties. The existence of a previously reported elusive regime is corroborated.

[Phys. Rev. Fluids 4, 023302] Published Fri Feb 15, 2019

Shape factor of the turbulent boundary layer on a flat plate and the Reynolds shear stress in the outer region

Fri, 02/15/2019 - 10:00

Author(s): P. Phani Kumar and J. Dey

From the linear equation for the velocity defect in the outer boundary layer, the product of mean wall normal velocity and free stream velocity is shown to vary linearly with the Reynolds shear stress.

[Phys. Rev. Fluids 4, 024605] Published Fri Feb 15, 2019

Properties of the scalar variance transport equation in turbulent channel flow

Fri, 02/15/2019 - 10:00

Author(s): Ang Zhou, Joseph Klewicki, and Sergio Pirozzoli

We study the total scalar variance equation for fully developed turbulent channel flow subject to uniform scalar generation. We find a total scalar variance leading balance four-layer structure similar to total kinetic energy balance. Differences in the two Karman constants, k and k_θ, are clarified.

[Phys. Rev. Fluids 4, 024606] Published Fri Feb 15, 2019

Dynamics of long gas bubbles rising in a vertical tube in a cocurrent liquid flow

Wed, 02/13/2019 - 10:00

Author(s): M. Magnini, S. Khodaparast, O. K. Matar, H. A. Stone, and J. R. Thome

Long gas bubbles in a vertical tube do not rise in stagnant liquid if Bo < 0.842. An investigation shows that long bubbles rising in co-current liquid flow exhibit different asymptotic regimes at small liquid capillary numbers, as Bo transitions across this critical value.

[Phys. Rev. Fluids 4, 023601] Published Wed Feb 13, 2019

Sharp-edged geometric obstacles in microfluidics promote deformability-based sorting of cells

Wed, 02/13/2019 - 10:00

Author(s): Zunmin Zhang, Wei Chien, Ewan Henry, Dmitry A. Fedosov, and Gerhard Gompper

The application of the deterministic lateral displacement approach in microfluidics to deformability-based sorting of cells is explored. Mesoscale hydrodynamics simulations are employed to show that this requires large flow-induced cell deformation in the trajectory-distinguishing flow region.

[Phys. Rev. Fluids 4, 024201] Published Wed Feb 13, 2019

Wake characteristics of a utility-scale wind turbine under coherent inflow structures and different operating conditions

Tue, 02/12/2019 - 10:00

Author(s): Xiaolei Yang and Fotis Sotiropoulos

Large-eddy simulations show the similarity of turbine wakes for different tip speed ratios and suggest the coexistence of inflow large eddies and wake shear layer instability as the mechanism for the onset of wake meandering.

[Phys. Rev. Fluids 4, 024604] Published Tue Feb 12, 2019

Statistics of incompressible hydrodynamic turbulence: An alternative approach

Mon, 02/11/2019 - 10:00

Author(s): Nahuel Andrés and Supratik Banerjee

Using a recent alternative form of the 4/3 exact relation for fully developed hydrodynamic turbulence, the incompressible energy cascade rate ε is computed. The numerical results show that ε is in clear agreement with the cascade rates computed from the classical 4/3 law.

[Phys. Rev. Fluids 4, 024603] Published Mon Feb 11, 2019

Transition in swimming direction in a model self-propelled inertial swimmer

Fri, 02/08/2019 - 10:00

Author(s): Thomas Dombrowski, Shannon K. Jones, Georgios Katsikis, Amneet Pal Singh Bhalla, Boyce E. Griffith, and Daphne Klotsa

An inertial swimmer comprised of two unequal spheres oscillating in antiphase generates a steady streaming, which propels the swimmer in opposite directions depending on the Reynolds number.

[Phys. Rev. Fluids 4, 021101(R)] Published Fri Feb 08, 2019

Ice wicking

Fri, 02/08/2019 - 10:00

Author(s): Katherine E. Witt, S. Farzad Ahmadi, and Jonathan B. Boreyko

We observe silicone oils wicking across dendritic sheets of frost. The capillary action is found to be dependent upon both the surface orientation and the underlying surface wettability.

[Phys. Rev. Fluids 4, 024002] Published Fri Feb 08, 2019

Buoyant finite-size particles in turbulent duct flow

Fri, 02/08/2019 - 10:00

Author(s): Sagar Zade, Walter Fornari, Fredrik Lundell, and Luca Brandt

Many large spherical particles that sediment and resuspend from the bottom of a duct under fully developed turbulent conditions are studied. Optical experiments and direct numerical simulations are compared and used to investigate turbulence modulation and organization of particles.

[Phys. Rev. Fluids 4, 024303] Published Fri Feb 08, 2019

Flow structure and unsteadiness in a highly confined shock-wave–boundary-layer interaction

Fri, 02/08/2019 - 10:00

Author(s): Jonathan Poggie and Kevin M. Porter

High-fidelity simulations show that the confining effect of sidewalls on a shock-wave/boundary-layer interaction can have a very strong influence on both the mean flow and large-scale unsteadiness, and accurately capturing the sidewall flows is essential in realistic modeling of confined flows.

[Phys. Rev. Fluids 4, 024602] Published Fri Feb 08, 2019

Characterizing vortex tangle properties in steady-state He II counterflow using particle tracking velocimetry

Thu, 02/07/2019 - 10:00

Author(s): Brian Mastracci and Wei Guo

The utility of particle tracking velocimetry for characterizing the quantized vortex tangle in He II thermal counterflow is shown by demonstrating measurements of vortex line spacing, the parameter c2, and vortex reconnection.

[Phys. Rev. Fluids 4, 023301] Published Thu Feb 07, 2019

Application of a self-organizing map to identify the turbulent-boundary-layer interface in a transitional flow

Thu, 02/07/2019 - 10:00

Author(s): Zhao Wu, Jin Lee, Charles Meneveau, and Tamer Zaki

We use the self-organizing map, an unsupervised machine learning method, to find the turbulent/nonturbulent interface in a transitional boundary layer with the help of Johns Hopkins Turbulence Databases. This method separates turbulent regions from vortical streaks and free-stream turbulence.

[Phys. Rev. Fluids 4, 023902] Published Thu Feb 07, 2019

Aerodynamically driven motion of a wall-bounded drop on a smooth solid substrate

Thu, 02/07/2019 - 10:00

Author(s): Patrick M. Seiler, Mark Gloerfeld, Ilia V. Roisman, and Cameron Tropea

The motion of wall-bounded drops moving on solid substrates driven by a fully turbulent channel flow is experimentally investigated. A scaling is found to describe the dimensionless drop velocity in terms of a dimensionless flow attack velocity, taking into account the surface wetting properties.

[Phys. Rev. Fluids 4, 024001] Published Thu Feb 07, 2019

Reconnection of vortex tubes with axial flow

Thu, 02/07/2019 - 10:00

Author(s): P. McGavin and D. I. Pontin

Reconnection of vortex tubes containing twisted vortex lines is studied by numerical simulation, showing that both the sense and strength of the twist affect the topological and geometrical properties of the resulting vortex structures, as well as the timing and rate of the reconnection process.

[Phys. Rev. Fluids 4, 024701] Published Thu Feb 07, 2019

Finite-size Lagrangian coherent structures in a two-sided lid-driven cavity

Wed, 02/06/2019 - 10:00

Author(s): Francesco Romanò, Parvathy Kunchi Kannan, and Hendrik C. Kuhlmann

Finite-size Lagrangian coherent structures can arise in dilute suspensions solely because of the size of the particles. When moving near boundaries, a lubrication-induced drag transfers the particles from the chaotic sea of the unperturbed fluid flow to particular Kolmogorov-Arnold-Moser tori.

[Phys. Rev. Fluids 4, 024302] Published Wed Feb 06, 2019

Fast, thin jets from bubbles expanding and collapsing in extreme vicinity to a solid boundary: A numerical study

Tue, 02/05/2019 - 10:00

Author(s): Christiane Lechner, Werner Lauterborn, Max Koch, and Robert Mettin

Numerical solutions of the compressible Navier-Stokes equation for a bubble collapsing close to a solid boundary find a very thin jet with velocities of 1000m/s.

[Phys. Rev. Fluids 4, 021601(R)] Published Tue Feb 05, 2019

Direct assessment of Kolmogorov's first refined similarity hypothesis

Tue, 02/05/2019 - 10:00

Author(s): John M. Lawson, Eberhard Bodenschatz, Anna N. Knutsen, James R. Dawson, and Nicholas A. Worth

Using 3D averages of energy dissipation rather than a surrogate quantity, high-resolution volumetric measurements and numerical simulations show that velocity increments scale with the local dissipation rate as per Kolmogorov’s 1962 refined similarity hypothesis, supporting small-scale universality.

[Phys. Rev. Fluids 4, 022601(R)] Published Tue Feb 05, 2019

Inertial self-propulsion of spherical microswimmers by rotation-translation coupling

Tue, 02/05/2019 - 10:00

Author(s): Itzhak Fouxon and Yizhar Or

We study inertial spherical squirmers prescribing tangential surface deformations. Breaking axial symmetry induces rotation-translation coupling that overcomes the “scallop theorem”, giving net motion for time-reversible strokes. This swimming mechanism may be relevant for large Volvox colonies.

[Phys. Rev. Fluids 4, 023101] Published Tue Feb 05, 2019

Temperature fluctuations relevant to thermal-plume dynamics in turbulent rotating Rayleigh-Bénard convection

Mon, 02/04/2019 - 10:00

Author(s): Shan-Shan Ding, Hui-Min Li, Wen-Dan Yan, and Jin-Qiang Zhong

Experiments in turbulent rotating Rayleigh-Bénard convection find various statistical properties of the fluctuations of the temperature which can be fit with a model.

[Phys. Rev. Fluids 4, 023501] Published Mon Feb 04, 2019