New Papers in Fluid Mechanics

Morphodynamics of a sediment bed in a fluid-filled cylinder during spin-down: An experimental study

Physical Review Fluids - Thu, 12/20/2018 - 10:00

Author(s): A. S. González-Vera, M. Duran-Matute, and G. J. F. van Heijst

Laboratory experiments on the evolution of a sediment bed under a spin-down flow show the emergence of diverse types of patterns. The net radially inward sediment transport is quantified and explained through an analytical derivation of the total radial force exerted on the bed.


[Phys. Rev. Fluids 3, 124306] Published Thu Dec 20, 2018

Gradual multifractal reconstruction of time-series: Formulation of the method and an application to the coupling between stock market indices and their Hölder exponents

Sheffield - Thu, 12/20/2018 - 08:22
Author(s):Keylock, C.J.
Publication year: 2018
Journal / Book title: Physica D: Nonlinear Phenomena

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Magnetic structure, dipole reversals, and $1/f$ noise in resistive MHD spherical dynamos

Physical Review Fluids - Wed, 12/19/2018 - 10:00

Author(s): M. Fontana, P. D. Mininni, and P. Dmitruk

A parametric study of dynamos in a rotating sphere shows a rich space of dynamic solutions, with stationary, aperiodic, and small-scale dynamo regimes controlled by Ekman and Reynolds numbers. Magnetic reversals are observed, displaying 1/f noise and statistics reminiscent of geodynamo observations.


[Phys. Rev. Fluids 3, 123702] Published Wed Dec 19, 2018

Film coating on a small sphere crossing an oil-water interface

Physical Review Fluids - Wed, 12/19/2018 - 10:00

Author(s): Haosheng Chen (陈皓生), Qinda Xu (徐勤达), Shuaishuai Liang (梁帅帅), and Jiang Li (李疆)

Experiments show that small spheres can pass through an oil-water interface and be coated with a predictable oil film when the Bond number is between 1.5 and 7.5. The film thickness is approximately proportional to the Bond number, which makes it a convenient method to coat particles with a designed film thickness.


[Phys. Rev. Fluids 3, 124003] Published Wed Dec 19, 2018

Influence of particle dynamics on the instability for pattern formation in shallow pulsed beds

Physical Review Fluids - Wed, 12/19/2018 - 10:00

Author(s): Lilian de Martín

Standing wave patterns can occur both in vibrated granular layers and pulsed fluidized beds. Although the different type of excitation results in a different definition of the driving parameters and instability curve, a theoretical study shows that the instability criterion in both systems is similar.


[Phys. Rev. Fluids 3, 124304] Published Wed Dec 19, 2018

Drag on pairs of square section obstacles in free-surface flows

Physical Review Fluids - Tue, 12/18/2018 - 10:00

Author(s): Francis H. Robertson and Gregory F. Lane-Serff

The effect of one obstacle on the drag on a second obstacle is measured for square obstacles in subcritical open channel flow. The lowest drag occurs when one obstacle is shielded directly behind another, and the largest drag occurs on a slightly upstream obstacle in near side-by-side arrangements.


[Phys. Rev. Fluids 3, 123802] Published Tue Dec 18, 2018

Post-pinch-off relaxation of two-dimensional droplets in a Hele-Shaw cell

Physical Review Fluids - Tue, 12/18/2018 - 10:00

Author(s): Dhirendra Tiwari, Lionel Mercury, Marcel Dijkstra, Himanshu Chaudhary, and José Federico Hernández-Sánchez

The relaxation of a liquid drop in a Hele-Shaw cell is observed experimentally and then modeled successfully.


[Phys. Rev. Fluids 3, 124202] Published Tue Dec 18, 2018

Unsteady motion of a long bubble or droplet in a self-rewetting system

Physical Review Fluids - Mon, 12/17/2018 - 10:00

Author(s): B. R. Duffy, S. K. Wilson, J. J. A. Conn, and K. Sefiane

The evolution of the shape (but not the position) of a long bubble or droplet in a self-rewetting system in a nonuniformly heated tube is shown to be driven entirely by Marangoni effects: a wide droplet widens (and ultimately fills the cross section of the tube), whereas a narrow droplet narrows.


[Phys. Rev. Fluids 3, 123603] Published Mon Dec 17, 2018

Hierarchical random additive model for the spanwise and wall-normal velocities in wall-bounded flows at high Reynolds numbers

Physical Review Fluids - Mon, 12/17/2018 - 10:00

Author(s): X. I. A. Yang, R. Baidya, Yu Lv, and I. Marusic

Both the spanwise and the vertical velocity components in high-Reynolds-number wall-bounded flows may be modeled via a random additive process. Evidence shows that a hierarchical, treelike structure exists for the spanwise velocity component.


[Phys. Rev. Fluids 3, 124606] Published Mon Dec 17, 2018

Cascade leading to the emergence of small structures in vortex ring collisions

Physical Review Fluids - Mon, 12/17/2018 - 10:00

Author(s): Ryan McKeown, Rodolfo Ostilla-Mónico, Alain Pumir, Michael P. Brenner, and Shmuel M. Rubinstein

A novel breakdown mechanism is observed during the head-on collision of two vortex rings. The interacting cores locally flatten into extremely thin vortex sheets and split into smaller daughter filaments iteratively over two generations, leading to the rapid emergence of fine-scale vortices.


[Phys. Rev. Fluids 3, 124702] Published Mon Dec 17, 2018

Viscous damping of gravity-capillary waves: Dispersion relations and nonlinear corrections

Physical Review Fluids - Mon, 12/17/2018 - 10:00

Author(s): Andrea Armaroli, Debbie Eeltink, Maura Brunetti, and Jérôme Kasparian

An envelope equation to model the propagation of surface waves in deep viscous fluids is proposed. The dispersion relation comprising viscosity and surface tension is expressed as an operator and used to generalize the universal nonlinear Schrödinger equation and quantify nonlinear damping.


[Phys. Rev. Fluids 3, 124803] Published Mon Dec 17, 2018

Relative velocities in bidisperse turbulent aerosols: Simulations and theory

Physical Review E - Thu, 12/13/2018 - 10:00

Author(s): Akshay Bhatnagar, K. Gustavsson, B. Mehlig, and Dhrubaditya Mitra

We perform direct numerical simulations of a bidisperse suspension of heavy spherical particles in forced, homogeneous, and isotropic three-dimensional turbulence. We compute the joint distribution of relative particle distances and longitudinal relative velocities between particles of different ine...


[Phys. Rev. E 98, 063107] Published Thu Dec 13, 2018

Apparent slip and drag reduction for the flow over superhydrophobic and lubricant-impregnated surfaces

Physical Review Fluids - Thu, 12/13/2018 - 10:00

Author(s): Edoardo Alinovi and Alessandro Bottaro

The flow within microscopic indentations filled with a lubricant fluid is studied by varying viscosity ratio, surface tension, and lubricant-to-working-fluid volume fraction. This yields protrusion heights that readily quantify the drag reduction of a lubricant-impregnated microstructured surface.


[Phys. Rev. Fluids 3, 124002] Published Thu Dec 13, 2018

Data-assimilated low-order vortex modeling of separated flows

Physical Review Fluids - Thu, 12/13/2018 - 10:00

Author(s): Darwin Darakananda, André Fernando de Castro da Silva, Tim Colonius, and Jeff D. Eldredge

This works shows for the first time that an inexpensive ensemble of low-order vortex models can accurately capture the aerodynamics of a low Reynolds number separated flow, even when disturbed by gusts, when it assimilates measured surface pressures.


[Phys. Rev. Fluids 3, 124701] Published Thu Dec 13, 2018

An amplitude equation for surface gravity wave-topography interactions

Physical Review Fluids - Thu, 12/13/2018 - 10:00

Author(s): Jim Thomas and Ray Yamada

A new amplitude equation that captures the effect of arbitrary topography on surface waves is presented. It can be integrated more quickly than the fully nonlinear equations, while accurately capturing the wave dynamics.


[Phys. Rev. Fluids 3, 124802] Published Thu Dec 13, 2018

Role of symmetry in driven propulsion at low Reynolds number

Physical Review E - Wed, 12/12/2018 - 10:00

Author(s): Johannes Sachs, Konstantin I. Morozov, Oded Kenneth, Tian Qiu, Nico Segreto, Peer Fischer, and Alexander M. Leshansky

We theoretically and experimentally investigate low-Reynolds-number propulsion of geometrically achiral planar objects that possess a dipole moment and that are driven by a rotating magnetic field. Symmetry considerations (involving parity P̂ and charge conjugation Ĉ) establish correspondence betwe...


[Phys. Rev. E 98, 063105] Published Wed Dec 12, 2018

Experimental modulation and theoretical simulation of zonal oscillation for electrostatically levitated metallic droplets at high temperatures

Physical Review E - Wed, 12/12/2018 - 10:00

Author(s): H. P. Wang, M. X. Li, P. F. Zou, X. Cai, L. Hu, and B. Wei

The second- and third-order zonal oscillations of metallic droplets at high temperatures beyond 2000 K were experimentally achieved by electrostatic levitation. To quantitatively describe the suspension stability of different metallic droplets, a stability factor model was proposed as a function of ...


[Phys. Rev. E 98, 063106] Published Wed Dec 12, 2018

Childhood of turbulent spots in a shear flow

Physical Review Fluids - Wed, 12/12/2018 - 10:00

Author(s): M. Couliou and R. Monchaux

We numerically investigate temporal aspects of turbulent spot spreading in plane Couette flow for transitional Reynolds numbers, focusing on streamwise spreading. From the topology of turbulent spots and associated large-scale flows, we propose a decomposition of the streamwise growth rate.


[Phys. Rev. Fluids 3, 123901] Published Wed Dec 12, 2018

Investigation of the phenomena occurring near the liquid–vapor interface during evaporation of water at low pressures

Physical Review Fluids - Wed, 12/12/2018 - 10:00

Author(s): Mohammad Amin Kazemi, David S. Nobes, and Janet A. W. Elliott

The three-dimensional flow generated below a liquid-vapor meniscus during low-pressure water evaporation is quantified with experiments using scanning particle image velocimetry and compared with an extensive numerical model. Results show how buoyancy effects in the liquid may suppress thermocapillary flows at the interface.


[Phys. Rev. Fluids 3, 124001] Published Wed Dec 12, 2018

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