Latest papers in fluid mechanics

Towards uncovering the structure of power fluctuations of wind farms

Physical Review E - Tue, 12/26/2017 - 10:00

Author(s): Huiwen Liu, Yaqing Jin, Nicolas Tobin, and Leonardo P. Chamorro

The structure of the turbulence-driven power fluctuations in a wind farm is fundamentally described from basic concepts. A derived tuning-free model, supported with experiments, reveals the underlying spectral content of the power fluctuations of a wind farm. It contains two power-law trends and osc...


[Phys. Rev. E 96, 063117] Published Tue Dec 26, 2017

Experimental quantification of nonlinear time scales in inertial wave rotating turbulence

Physical Review Fluids - Tue, 12/26/2017 - 10:00

Author(s): Ehud Yarom, Alon Salhov, and Eran Sharon

The width of the spectrum of the velocities is observed in inertial wave rotating turbulence to be linearly related (at small widths) to Uksin(θ), indicating nonlinear interactions with the mean flow are the main cause of the broadening of the spectrum.


[Phys. Rev. Fluids 2, 122601(R)] Published Tue Dec 26, 2017

Thermally induced rarefied gas flow in a three-dimensional enclosure with square cross-section

Physical Review Fluids - Tue, 12/26/2017 - 10:00

Author(s): Lianhua Zhu, Xiaofan Yang, and Zhaoli Guo

Under rarefied conditions, gas flow can be induced by nonuniform temperatures on bounded walls. Thermally induced flow in an enclosure with nonisothermal walls is analyzed by directly solving the gas kinetic equation via a discrete velocity method with a memory-reduction technique.


[Phys. Rev. Fluids 2, 123402] Published Tue Dec 26, 2017

Disproportionate entrance length in superfluid flows and the puzzle of counterflow instabilities

Physical Review Fluids - Tue, 12/26/2017 - 10:00

Author(s): J. Bertolaccini, E. Lévêque, and P.-E. Roche

A turbulent wake retains a memory of upstream disturbances which fades over a longer distance for lower viscosity. For a zero-viscosity superfluid, numerical simulations find a subtle memory effect that explains a number of contradictory experimental observations.


[Phys. Rev. Fluids 2, 123902] Published Tue Dec 26, 2017

Active aerodynamic drag reduction on morphable cylinders

Physical Review Fluids - Tue, 12/26/2017 - 10:00

Author(s): M. Guttag and P. M. Reis

Inspired by the axial grooves of the Saguaro cactus, active aerodynamic drag on morphable cylinders, whose topography can be tuned pneumatically, is studied. The active samples are controlled, on demand, to obtain drag coefficients that are significantly lower than for samples with fixed morphologies.


[Phys. Rev. Fluids 2, 123903] Published Tue Dec 26, 2017

Effect of Reynolds number and saturation level on gas diffusion in and out of a superhydrophobic surface

Physical Review Fluids - Tue, 12/26/2017 - 10:00

Author(s): Hangjian Ling, Joseph Katz, Matthew Fu, and Marcus Hultmark

Gas diffusion rates in and out of superhydrophobic surfaces in transitional and turbulent boundary layers are observed and measured at varying Reynolds numbers, pressures, and dissolved gas concentrations. Results show a power-law correlation between the Sherwood and friction Reynolds number.


[Phys. Rev. Fluids 2, 124005] Published Tue Dec 26, 2017

Prediction of the low-velocity distribution from the pore structure in simple porous media

Physical Review Fluids - Fri, 12/22/2017 - 10:00

Author(s): Pietro de Anna, Bryan Quaife, George Biros, and Ruben Juanes

Fluid flow through porous media is determined by the underlying pore structure. An analytical relationship is proposed between the distribution of the width of small openings and the distribution of low fluid velocities in the medium, which control the statistics of fluid transport and mixing.


[Phys. Rev. Fluids 2, 124103] Published Fri Dec 22, 2017

Isotropic stochastic rotation dynamics

Physical Review Fluids - Fri, 12/22/2017 - 10:00

Author(s): Sebastian Mühlbauer, Severin Strobl, and Thorsten Pöschel

In stochastic rotation dynamics the cubic interaction volumes induce artificial anisotropy, which can become significant in the vicinity of boundaries. A new study shows that this anisotropy can be avoided by employing randomly distributed, spherical interaction volumes instead of Cartesian grid cells.


[Phys. Rev. Fluids 2, 124204] Published Fri Dec 22, 2017

Rayleigh-Taylor instability in accelerated elastic-solid slabs

Physical Review E - Thu, 12/21/2017 - 10:00

Author(s): S. A. Piriz, A. R. Piriz, and N. A. Tahir

We develop the linear theory for the asymptotic growth of the incompressible Rayleigh-Taylor instability of an accelerated solid slab of density ρ2, shear modulus G, and thickness h, placed over a semi-infinite ideal fluid of density ρ1<ρ2. It extends previous results for Atwood number AT=1 [B. J...


[Phys. Rev. E 96, 063115] Published Thu Dec 21, 2017

Bundling of elastic filaments induced by hydrodynamic interactions

Physical Review Fluids - Thu, 12/21/2017 - 10:00

Author(s): Yi Man, William Page, Robert J. Poole, and Eric Lauga

Bacteria swim in viscous fluids by rotating helical flagellar filaments which dynamically bundle around each other. We derive and study a bundling model whereby straight rotating elastic filaments in viscous fluid induce rotational flows which tend to bend and wrap the filaments around each other.


[Phys. Rev. Fluids 2, 123101] Published Thu Dec 21, 2017

Bounds on poloidal kinetic energy in plane layer convection

Physical Review Fluids - Thu, 12/21/2017 - 10:00

Author(s): A. Tilgner

Upper bounds E for the poloidal kinetic energy in thermal convection are derived from known bounds on the Nusselt number, and are improved by solving a separate optimization problem. The same procedure leads to a bound on the dissipation due to non poloidal velocity components.


[Phys. Rev. Fluids 2, 123502] Published Thu Dec 21, 2017

Analyte preconcentration in nanofluidic channels with nonuniform zeta potential

Physical Review Fluids - Thu, 12/21/2017 - 10:00

Author(s): A. Eden, C. McCallum, B. D. Storey, S. Pennathur, and C. D. Meinhart

A simulation of analyte preconcentration in a gated nanofluidic device finds that local field-effect control of surface properties can generate tunable ion concentration polarization regions in which anionic analytes are predicted to significantly accumulate if the electric double layers overlap.


[Phys. Rev. Fluids 2, 124203] Published Thu Dec 21, 2017

Chaotic versus stochastic behavior in active-dissipative nonlinear systems

Physical Review Fluids - Thu, 12/21/2017 - 10:00

Author(s): Hiroshi Gotoda, Marc Pradas, and Serafim Kalliadasis

Time-series tools are used to analyze how chaotic dynamics interacts with noise in the generalized Kuramoto-Sivashinsky equation, a prototype for falling films. The critical value of the noise intensity for the chaotic-stochastic transition is quantified in terms of the system control parameter.


[Phys. Rev. Fluids 2, 124401] Published Thu Dec 21, 2017

Hierarchical micro- and nanofabrication by pattern-directed contact instabilities of thin viscoelastic films

Physical Review Fluids - Wed, 12/20/2017 - 10:00

Author(s): Abir Ghosh, Dipankar Bandyopadhyay, Jayati Sarkar, and Ashutosh Sharma

We propose that strategic use of an array of periodic patterns on a debonding contactor during elastic contact lithography can transform a flat polymer surface into a biomimetic super-hydrophobic surface having high-aspect ratio hierarchical patterns with tuneable adhesive properties.


[Phys. Rev. Fluids 2, 124004] Published Wed Dec 20, 2017

Brownian dynamics of elongated particles in a quasi-two-dimensional isotropic liquid

Physical Review Fluids - Wed, 12/20/2017 - 10:00

Author(s): Christoph Klopp, Ralf Stannarius, and Alexey Eremin

An experimental exploration of diffusive translational and rotational motions of elongated particles confined in a quasi-two-dimensional fluid is presented. Data obtained over 3 orders of magnitude in particle length demonstrate crossovers between hydrodynamical regimes determined by characteristic length scales.


[Phys. Rev. Fluids 2, 124202] Published Wed Dec 20, 2017

Dense, layered, inclined flows of spheres

Physical Review Fluids - Wed, 12/20/2017 - 10:00

Author(s): James T. Jenkins and Michele Larcher

In dense, inclined flows of spheres, particles are often observed to translate in layers. The forces and rate of momentum transfer associated with a process of rub, lift, fall, and bump are calculated, and a relation between the ratio of shear stress to normal stress and the rate of strain is determined.


[Phys. Rev. Fluids 2, 124301] Published Wed Dec 20, 2017

Dynamic fluid sloshing in a one-dimensional array of coupled vessels

Physical Review Fluids - Wed, 12/20/2017 - 10:00

Author(s): Y. H. Huang and M. R. Turner

An investigation of an N-vessel coupled sloshing system determines the existence of regions of parameter space where the (N+1)-fold 1:⋯:1 resonance can occur. These internal resonances are the precursors to the interesting dynamics in the nonlinear regime.


[Phys. Rev. Fluids 2, 124801] Published Wed Dec 20, 2017

Boundary conditions for a one-sided numerical model of evaporative instabilities in sessile drops of ethanol on heated substrates

Physical Review E - Tue, 12/19/2017 - 10:00

Author(s): Sergey Semenov, Florian Carle, Marc Medale, and David Brutin

The work is focused on obtaining boundary conditions for a one-sided numerical model of thermoconvective instabilities in evaporating pinned sessile droplets of ethanol on heated substrates. In the one-sided model, appropriate boundary conditions for heat and mass transfer equations are required at ...


[Phys. Rev. E 96, 063113] Published Tue Dec 19, 2017

Control of viscous fingering by nanoparticles

Physical Review E - Tue, 12/19/2017 - 10:00

Author(s): Nasser Sabet, Hassan Hassanzadeh, and Jalal Abedi

A substantial viscosity increase by the addition of a low dose of nanoparticles to the base fluids can well influence the dynamics of viscous fingering. There is a lack of detailed theoretical studies that address the effect of the presence of nanoparticles on unstable miscible displacements. In thi...


[Phys. Rev. E 96, 063114] Published Tue Dec 19, 2017

Rotating Hele-Shaw cell with a time-dependent angular velocity

Physical Review Fluids - Tue, 12/19/2017 - 10:00

Author(s): Pedro H. A. Anjos, Victor M. M. Alvarez, Eduardo O. Dias, and José A. Miranda

Most rotating Hele-Shaw cell studies assume a constant cell angular velocity and neglect inertial effects. This work considers a time-dependent angular velocity and includes inertia. These two new elements introduce important changes in the linear and weakly nonlinear dynamics of the problem.


[Phys. Rev. Fluids 2, 124003] Published Tue Dec 19, 2017

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