Latest papers in fluid mechanics

Mixing by squirmers in stratified fluids

Physical Review Fluids - Mon, 02/24/2025 - 10:00

Author(s): Vaseem A. Shaik and Gwynn J. Elfring

We analyze the mixing induced by a model swimmer, the spherical squirmer, in density stratified fluids. Our findings indicate that the mixing by a squirmer is much larger than that caused by a point-sized swimmer (like force-dipole), although still small in weak stratification relevant to the ocean. Equivalent results are also obtained for a homogeneous dilute suspension of noninteracting squirmers.


[Phys. Rev. Fluids 10, 024102] Published Mon Feb 24, 2025

Mixing by squirmers in stratified fluids

Physical Review Fluids - Mon, 02/24/2025 - 10:00

Author(s): Vaseem A. Shaik and Gwynn J. Elfring

We analyze the mixing induced by a model swimmer, the spherical squirmer, in density stratified fluids. Our findings indicate that the mixing by a squirmer is much larger than that caused by a point-sized swimmer (like force-dipole), although still small in weak stratification relevant to the ocean. Equivalent results are also obtained for a homogeneous dilute suspension of noninteracting squirmers.


[Phys. Rev. Fluids 10, 024102] Published Mon Feb 24, 2025

Gas flow regimes and transition criteria in porous media

Physical Review Fluids - Mon, 02/24/2025 - 10:00

Author(s): Mingbao Zhang, Zhiguo Tian, Yunfan Huang, and Moran Wang

This study examines gas flow in porous media, finding four regimes: slip, Darcy, inertia, and turbulence. After scaling the Forchheimer equation, we introduce a dimensionless number, Rd, which provides a more physically grounded criterion for the transition to the inertia regime. Through experimental validations, the new mechanism also shows how gas slip effects influence flow at low permeability. These insights contribute to advancing both theoretical frameworks and experimental studies of gas flow in porous systems.


[Phys. Rev. Fluids 10, 024303] Published Mon Feb 24, 2025

Following marginal stability manifolds in quasilinear dynamical reductions of multiscale flows in two space dimensions

Physical Review E - Mon, 02/24/2025 - 10:00

Author(s): Alessia Ferraro, Gregory P. Chini, and T. M. Schneider

We derive a two-dimensional (2D) extension of a recently developed formalism for slow-fast quasilinear (QL) systems subject to fast instabilities. The emergent dynamics of these systems is characterized by a slow evolution of (suitably defined) mean fields coupled to marginally stable, fast fluctuat…


[Phys. Rev. E 111, 025105] Published Mon Feb 24, 2025

Similarity learning with neural networks

Physical Review E - Mon, 02/24/2025 - 10:00

Author(s): G. Sanfins, F. Ramos, and D. Naiff

In this work, we introduce a neural network algorithm designed to automatically identify similarity relations from data. By uncovering these similarity relations, our network approximates the underlying physical laws that relate dimensionless quantities to their dimensionless variables and coefficie…


[Phys. Rev. E 111, 025106] Published Mon Feb 24, 2025

Recovery towards self-similarity in Rayleigh-Taylor instability under stepwise and sinusoidal acceleration reversals

Physical Review E - Mon, 02/24/2025 - 10:00

Author(s): Nicholas Pak, Elise Theriot, Denis Aslangil, Andrew Lawrie, and Arindam Banerjee

The dynamic properties of an interfacial flow between heavy and light incompressible fluids that are initially Rayleigh-Taylor unstable and are subjected to an external acceleration field oriented in opposition to the density gradient are studied. Rayleigh-Taylor instability occurs in nature with a …


[Phys. Rev. E 111, 025107] Published Mon Feb 24, 2025

Large eddy simulation of droplet breakup in turbulent flow with adaptive mesh refinement

Physical Review Fluids - Fri, 02/21/2025 - 10:00

Author(s): Xiaoqiang Sun, Hong Yan, and Fuzhen Chen

A series of turbulence-droplet interactions with realistic density ratios encountered in an aeroengine combustor are simulated and the effect of droplet size is investigated. It is shown that droplets present periphery shedding at the initial stage of breakup and are stretched into a disk-like shape before final breakup. The vortical turbulence helps to deform and break up the interface. The general turbulent characteristics are similar to single-phase flow and more perturbations are introduced by the gas-liquid interactions.


[Phys. Rev. Fluids 10, 024004] Published Fri Feb 21, 2025

Large eddy simulation of droplet breakup in turbulent flow with adaptive mesh refinement

Physical Review Fluids - Fri, 02/21/2025 - 10:00

Author(s): Xiaoqiang Sun, Hong Yan, and Fuzhen Chen

A series of turbulence-droplet interactions with realistic density ratios encountered in an aeroengine combustor are simulated and the effect of droplet size is investigated. It is shown that droplets present periphery shedding at the initial stage of breakup and are stretched into a disk-like shape before final breakup. The vortical turbulence helps to deform and break up the interface. The general turbulent characteristics are similar to single-phase flow and more perturbations are introduced by the gas-liquid interactions.


[Phys. Rev. Fluids 10, 024004] Published Fri Feb 21, 2025

Route to turbulence in magnetohydrodynamic square duct flow

Physical Review Fluids - Thu, 02/20/2025 - 10:00

Author(s): Mattias Brynjell-Rahkola, Yohann Duguet, and Thomas Boeck

The transition route from laminar to turbulent flow in a magnetohydrodynamic duct with a square cross-section is investigated in the limit of low magnetic Reynolds number. In the presence of a transverse magnetic field, Hartmann and Shercliff layers are present on the walls orthogonal and parallel to the field direction, respectively. Independently of the initial location of a finite perturbation in either Shercliff or Hartmann layers, transition relies on a tripping of the Shercliff layer by perturbations, while the Hartmann layer plays a passive role. This is explained, using a dynamical systems interpretation, by the spatial localization of the edge states in the Shercliff layer.


[Phys. Rev. Fluids 10, 023903] Published Thu Feb 20, 2025

Route to turbulence in magnetohydrodynamic square duct flow

Physical Review Fluids - Thu, 02/20/2025 - 10:00

Author(s): Mattias Brynjell-Rahkola, Yohann Duguet, and Thomas Boeck

The transition route from laminar to turbulent flow in a magnetohydrodynamic duct with a square cross-section is investigated in the limit of low magnetic Reynolds number. In the presence of a transverse magnetic field, Hartmann and Shercliff layers are present on the walls orthogonal and parallel to the field direction, respectively. Independently of the initial location of a finite perturbation in either Shercliff or Hartmann layers, transition relies on a tripping of the Shercliff layer by perturbations, while the Hartmann layer plays a passive role. This is explained, using a dynamical systems interpretation, by the spatial localization of the edge states in the Shercliff layer.


[Phys. Rev. Fluids 10, 023903] Published Thu Feb 20, 2025

Manipulation on a heavy fluid layer with dual-mode perturbations via reverberating waves

Physical Review Fluids - Thu, 02/20/2025 - 10:00

Author(s): Ning Zhou, Zhigang Zhai, and Xisheng Luo

The growth of a shock-induced heavy fluid layer with dual-mode perturbations is investigated. Processes of the disturbed reverberating waves interacting with the layer are modeled theoretically. By considering the reverberating waves, growth of the heavy fluid layer can be well manipulated.


[Phys. Rev. Fluids 10, 023904] Published Thu Feb 20, 2025

Flow structure around a vertical cylinder placed in an open channel under combined wave-current flows

Physical Review Fluids - Thu, 02/20/2025 - 10:00

Author(s): Wen-Yi Chang and George Constantinescu

Surface mounted cylinders in combined wave-current flow generate a wide range of coherent structures that include vortex tubes (VT), wake billow vortices (VW), and horseshoe vortices observed in steady flow. Additionally, horizontal near-bed vortices are sometimes generated on the wake side of the cylinder. The formation of these vortices and the forces acting on the cylinder are a function of the ratio between the steady current velocity and the oscillatory velocity (0≤Us/Um≤1.4) and of the Keulegan-Carpenter number, KC=UmT/D (1.5≤KC≤30.8), where T is the period of the oscillatory flow.


[Phys. Rev. Fluids 10, 024804] Published Thu Feb 20, 2025

Flow structure around a vertical cylinder placed in an open channel under combined wave-current flows

Physical Review Fluids - Thu, 02/20/2025 - 10:00

Author(s): Wen-Yi Chang and George Constantinescu

Surface mounted cylinders in combined wave-current flow generate a wide range of coherent structures that include vortex tubes (VT), wake billow vortices (VW), and horseshoe vortices observed in steady flow. Additionally, horizontal near-bed vortices are sometimes generated on the wake side of the cylinder. The formation of these vortices and the forces acting on the cylinder are a function of the ratio between the steady current velocity and the oscillatory velocity (0≤Us/Um≤1.4) and of the Keulegan-Carpenter number, KC=UmT/D (1.5≤KC≤30.8), where T is the period of the oscillatory flow.


[Phys. Rev. Fluids 10, 024804] Published Thu Feb 20, 2025

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