Physical Review Fluids

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Complexity of the laminar-turbulent boundary in pipe flow

Wed, 05/30/2018 - 11:00

Author(s): Nazmi Burak Budanur and Björn Hof

Numerical experiments demonstrate that the laminar-turbulent boundary in pipe flow exhibits qualitatively different regions whose dynamics resemble that of the nearby unstable invariant solutions. In addition, various different state space paths to turbulence from this boundary are illustrated.

[Phys. Rev. Fluids 3, 054401] Published Wed May 30, 2018

Evolution of wave patterns and temperature field in shock-tube flow

Tue, 05/29/2018 - 11:00

Author(s): A. D. Kiverin and I. S. Yakovenko

The gas-dynamical mechanism of ignition kernels formation in shock tubes is formulated on the basis of numerical analysis of the flow pattern developed behind the shock wave propagating in the rectangular tube filled with a reactive gaseous mixture.

[Phys. Rev. Fluids 3, 053201] Published Tue May 29, 2018

Hexagonal convection patterns and their evolutionary scenarios in electroconvection induced by a strong unipolar injection

Tue, 05/29/2018 - 11:00

Author(s): Kang Luo, Jian Wu, Hong-Liang Yi, Lin-Hua Liu, and He-Ping Tan

Various flow patterns and their evolutionary scenarios in three-dimensional electroconvection are numerically investigated. Specifically, a careful comparison of the hexagonal pattern is made to the previous semianalytical stability analysis results.

[Phys. Rev. Fluids 3, 053702] Published Tue May 29, 2018

Instability waves and transition in adverse-pressure-gradient boundary layers

Tue, 05/29/2018 - 11:00

Author(s): Rikhi Bose, Tamer A. Zaki, and Paul A. Durbin

The role of instability waves (IW) in free-stream turbulence (FST) induced boundary-layer transition in an adverse pressure gradient is studied with direct simulations. IW are found relevant even at moderate FST intensity of 2%. The effect of FST spectrum and intensity on transition are explored.

[Phys. Rev. Fluids 3, 053904] Published Tue May 29, 2018

Scalewise invariant analysis of the anisotropic Reynolds stress tensor for atmospheric surface layer and canopy sublayer turbulent flows

Thu, 05/24/2018 - 11:00

Author(s): Peter Brugger, Gabriel G. Katul, Frederik De Roo, Konstantin Kröniger, Eyal Rotenberg, Shani Rohatyn, and Matthias Mauder

The return-to-isotropy of turbulence across scales is studied for different thermal stratification and surface roughness regimes from measurements in the atmospheric boundary layer and it is compared with predictions of a homogenous model.

[Phys. Rev. Fluids 3, 054608] Published Thu May 24, 2018

Vortex line topology during vortex tube reconnection

Wed, 05/23/2018 - 11:00

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

The evolving topology of vortex lines during reconnection of vortex tubes is addressed. New features of the reconnection process are revealed, such as the generation of many small flux rings, and of vorticity null points. Methods to measure changes in flux connectivity are discussed.

[Phys. Rev. Fluids 3, 054701] Published Wed May 23, 2018

Thermally activated vapor bubble nucleation: The Landau-Lifshitz–Van der Waals approach

Tue, 05/22/2018 - 11:00

Author(s): Mirko Gallo, Francesco Magaletti, and Carlo Massimo Casciola

A continuum model embedding thermal fluctuations, capillarity, and hydrodynamic effects is proposed to investigate bubble cavitation. The simulations, validated against molecular dynamics, access multibubble nucleation statistics and long-time dynamics in unprecedentedly large domains.

[Phys. Rev. Fluids 3, 053604] Published Tue May 22, 2018

Wake meandering of a model wind turbine operating in two different regimes

Tue, 05/22/2018 - 11:00

Author(s): Daniel Foti, Xiaolei Yang, Filippo Campagnolo, David Maniaci, and Fotis Sotiropoulos

We present wind tunnel and numerical experiments of the flow behind a model wind turbine in optimal and sub-optimal regimes. Spatio-temporal filtering and dynamic mode decomposition reveal that the onset and amplitude of wake meandering are affected by both the operating regime and the nacelle.

[Phys. Rev. Fluids 3, 054607] Published Tue May 22, 2018

Basal melting driven by turbulent thermal convection

Mon, 05/21/2018 - 11:00

Author(s): Babak Rabbanipour Esfahani, Silvia C. Hirata, Stefano Berti, and Enrico Calzavarini

The evolution of heat flux through an initially solid pure substance that is heated from below and that undergoes both phase-change and natural convection is studied numerically and contrasted with the dynamics of the Rayleigh-Bénard system in laminar and turbulent regimes.

[Phys. Rev. Fluids 3, 053501] Published Mon May 21, 2018

Real-time feedback control of three-dimensional Tollmien-Schlichting waves using a dual-slot actuator geometry

Mon, 05/21/2018 - 11:00

Author(s): SH. S. Vemuri, R. Bosworth, J. F. Morrison, and E. C. Kerrigan

Tollmien-Schlichting (TS) waves are attenuated experimentally using a single-input and single-output feedback control system in real time. On implementing the controller, TS wave growth rates are shown to be suppressed significantly over a noticeably large domain.

[Phys. Rev. Fluids 3, 053903] Published Mon May 21, 2018

Transient deformation of a droplet near a microfluidic constriction: A quantitative analysis

Fri, 05/18/2018 - 11:00

Author(s): Corentin Trégouët, Thomas Salez, Cécile Monteux, and Mathilde Reyssat

Microdroplets are deformed and their transient relaxation in a microchannel is studied. By precisely analyzing the flow-induced stress on the droplets and their deformation, rheological properties are measured in situ.

[Phys. Rev. Fluids 3, 053603] Published Fri May 18, 2018

Erratum: Onset of low Prandtl number thermal convection in thin spherical shells [Phys. Rev. Fluids <b>3</b>, 024801 (2018)]

Fri, 05/18/2018 - 11:00

Author(s): F. Garcia, F. R. N. Chambers, and A. L. Watts

[Phys. Rev. Fluids 3, 059901] Published Fri May 18, 2018

Predictive model for convective flows induced by surface reactivity contrast

Thu, 05/17/2018 - 11:00

Author(s): Scott M. Davidson, Rob G. H. Lammertink, and Ali Mani

Concentration gradients in a fluid due to contrast in surface reactivity generate convective flows. An analytical model predicting the velocity magnitude in such flows is derived and verified against direct numerical simulation data over a wide range of parameters.

[Phys. Rev. Fluids 3, 053701] Published Thu May 17, 2018

Self-similar dynamics of air film entrained by a solid disk in confined space: A simple prototype of topological transitions

Thu, 05/17/2018 - 11:00

Author(s): Hana Nakazato, Yuki Yamagishi, and Ko Okumura

Experimental observations of two-dimensional pinch-off of an air sheet surrounded by viscous liquid lead to an exactly solvable case of self-similar dynamics of a topological transition: Scaling functions for velocity and shape are both analytic and precisely describe experimental observations.

[Phys. Rev. Fluids 3, 054004] Published Thu May 17, 2018

Effective slip over partially filled microcavities and its possible failure

Thu, 05/17/2018 - 11:00

Author(s): Zhouyang Ge, Hanna Holmgren, Martin Kronbichler, Luca Brandt, and Gunilla Kreiss

Liquid-infused surfaces have potential applications for drag reduction. A study of their effective slip length and robustness via a multiscale (nano to micron) numerical framework is presented, relating their performance to various design parameters.

[Phys. Rev. Fluids 3, 054201] Published Thu May 17, 2018

Secondary flow in turbulent ducts with increasing aspect ratio

Thu, 05/17/2018 - 11:00

Author(s): R. Vinuesa, P. Schlatter, and H. M. Nagib

The secondary flow in wide turbulent ducts is characterized by means of high-order direct numerical simulations. New results indicate that ducts or experimental facilities with aspect ratios larger than 10 may, if properly designed, exhibit good agreement with results obtained from spanwise-periodic channel computations.

[Phys. Rev. Fluids 3, 054606] Published Thu May 17, 2018

Variational method enabling simplified solutions to the linearized Boltzmann equation for oscillatory gas flows

Wed, 05/16/2018 - 11:00

Author(s): Daniel R. Ladiges and John E. Sader

Cercignani’s variational principle, originally derived for steady rarefied gas flows, is extended to unsteady flows exhibiting oscillatory time dependence. The utility of this theory is demonstrated by deriving approximate formulas and numerical results for Couette flow and Stokes’ second problem.

[Phys. Rev. Fluids 3, 053401] Published Wed May 16, 2018

Equatorially trapped convection in a rapidly rotating shallow shell

Wed, 05/16/2018 - 11:00

Author(s): Benjamin Miquel, Jin-Han Xie, Nicholas Featherstone, Keith Julien, and Edgar Knobloch

Motivated by the recent discovery of subsurface oceans on planetary moons, convective flows in shallow spherical shells set in rapid rotation are explored. A new equatorial beta-plane convection model that captures trapping of convection at low latitudes due to rotation is investigated.

[Phys. Rev. Fluids 3, 053801] Published Wed May 16, 2018

Non-normality and classification of amplification mechanisms in stability and resolvent analysis

Wed, 05/16/2018 - 11:00

Author(s): Sean Symon, Kevin Rosenberg, Scott T. M. Dawson, and Beverley J. McKeon

Eigenspectra and pseudospectra of the (turbulent) mean-linearized Navier-Stokes operator are used to characterize amplification mechanisms in laminar and turbulent flows in which linear mechanisms are important.

[Phys. Rev. Fluids 3, 053902] Published Wed May 16, 2018

Physics of singularities in pressure-impulse theory

Wed, 05/16/2018 - 11:00

Author(s): R. Krechetnikov

Classical pressure-impulse theory solution for water impact of a flat plate exhibits both singular initial fluid acceleration and a near-plate-edge singularity in the velocity field. Here the singularities are resolved by including effects of compressibility, viscosity, and surface tension.

[Phys. Rev. Fluids 3, 054003] Published Wed May 16, 2018