Latest papers in fluid mechanics
Revisiting amplitude modulation in non-canonical wall-turbulence through high-Reynolds number experimental data
Author(s): Mitchell Lozier, Ivan Marusic, and Rahul Deshpande
We revisit the amplitude modulation phenomena, as defined by Mathis et al. (J Fluid Mech. 628, 311-337; 2009), in the context of non-canonical wall-turbulence. A unique set of published, high-Reynolds number turbulent boundary layer datasets, from the same experimental facility are considered. It is found that nonlinear interactions, across the turbulence scale hierarchy, may become significant with the introduction of various non-canonical perturbations, in contrast to previous observations for canonical flows. The implications of these findings on the interpretation of amplitude modulation effects, and near-wall flow prediction models, for non-canonical wall-turbulence are discussed.
[Phys. Rev. Fluids 9, 124602] Published Mon Dec 16, 2024
Fractal dimension of non-Newtonian Hele-Shaw flow subject to Saffman-Taylor instability
Author(s): J. Adriazola, B. Gu, L. J. Cummings, and L. Kondic
We introduce a discrete numerical method based on the diffusion-limited aggregation (DLA) approach to simulate two-fluid Hele-Shaw flow subject to the Saffman-Taylor interfacial instability, in the case where the displaced fluid is non-Newtonian. Focusing on fluids for which the most relevant non-Ne…
[Phys. Rev. E 110, 065107] Published Mon Dec 16, 2024
Semianalytical model of optothermal fluidics in a confinement
Author(s): Tetsuro Tsuji, Shun Saito, and Satoshi Taguchi
Elaborating micro- and nanoscale heat using lasers is an emerging experimental technique to induce fluid flows and to control nanomaterial motions; this paper provides a theoretical tool to explore them. When focused lasers are irradiated to microfluidic systems, we can heat up, selectively and locally, fluids, channels, and/or such as thin-metal films. This localized heat generates various thermally-induced transport of fluids and dispersed objects. Considering that flow computation requires a decent amount of training cost, the easy-access instant analytical tool developed here is helpful for researchers without a fluid-mechanics background to explore complex phenomena in their own fields.
[Phys. Rev. Fluids 9, 124202] Published Fri Dec 13, 2024
Heat transfer in a near-critical fluid saturated porous medium: Piston effect and viscous slowing down
Author(s): Didier Lasseux, Bernard Zappoli, Samuel Marre, and Yves Garrabos
Coupled heat and momentum transfer in a porous medium saturated by a near (super) critical fluid is shown to take place under three different regimes depending on the distance to the critical point (CP). Far enough from the CP, transfer is governed by the classical piston effect (PE). While nearing the CP, the PE is hindered by a pressure gradient that builds up in the bulk of the medium. Exceedingly close to the CP, viscous effects are present in the whole domain, including the boundary layer close to the heated boundary, so that the PE is faded away and heat transfer takes place in a diffusive regime.
[Phys. Rev. Fluids 9, 124402] Published Fri Dec 13, 2024
Dynamically relevant recurrent flows obtained via a nonlinear recurrence function from two-dimensional turbulence
Author(s): Edward M. Redfern, Andrei L. Lazer, and Dan Lucas
When searching for recurrence in turbulent flows a well-known issue is an inability of simple distance measures to identify solutions exhibiting high dissipation bursting behaviour. By constructing novel recurrence functions based on the nonlinearity of the governing equations, recurrent flows (unstable periodic and relative periodic orbits) are now able to be computed which cover the full range of turbulent dynamics. This has enabled much improved reconstructions of the flow statistics and indicated simple heuristic weightings of the individual solutions.
[Phys. Rev. Fluids 9, 124401] Published Thu Dec 12, 2024
Flows, self-organization, and transport in living cells
Author(s): Michael J. Shelley
The movement and placement of cellular components is crucial for the proper development of egg cells and embryos. These transport processes take place within the fluidic interior of the cell and can yield surprisingly complex fluid-structure interactions. Fortunately, advances in mathematical modeling, multiscale coarse-graining, and the large-scale simulation of fluid-structure interactions have all helped in the understanding of this fundamental cellular biology. This paper discusses how simulations of immersed mobile structures and load-bearing biopolymers within cells helped show how the mitotic spindle finds its proper place inside an embryo approaching its very first cell division. Also discussed is the role played by coarse-grained porous medium models, stability analyses, and large-scale fluid-structure simulation, in revealing the self-organized processes that may underlie large-scale transport flows in developing egg cells.
[Phys. Rev. Fluids 9, 120501] Published Wed Dec 11, 2024
Pathways from nucleation to raindrops
Author(s): F. Poydenot and B. Andreotti
How does rain initiate from cloud droplets? Drops above 100 μm have large enough inertia to fall, allowing them to grow by capturing smaller droplets during descent. However, rain formation needs to overcome a gap of very low collision rate for droplet sizes between 3-30 μm, where this mechanism is inefficient. We investigate four pathways to rain: the coalescence pathway; the mixing pathway driven by the creation of supersaturated conditions from mixing of cloud and drop-free air; the electrostatic pathway arising from these attractive forces; and the turbulence pathway. Rainfall begins when the drop size distribution broadens enough for a few droplets to create efficient collisions.
[Phys. Rev. Fluids 9, 123602] Published Mon Dec 09, 2024
Adjoint-based full-order and reduced-order approaches for gust mitigation
Author(s): Bolun Xu, Mingjun Wei, and John T. Hrynuk
Adjoint-based approaches were developed for full-order and reduced-order models to mitigate a streamwise or transverse gust and maintain the lift performance of a heaving-pitching wing. Simultaneous optimization of multiple parameters in flow control becomes feasible by solving both the physical model and its adjoint model. With a head-on streamwise gust, adjoint-based optimization suggests reducing the wing oscillation to maintain the original lift force; with a transverse gust, besides the reduced oscillation, the optimal wing motion shows an overall pitching-down motion towards the gust to balance out the additional lift generated by the gust.
[Phys. Rev. Fluids 9, 123901] Published Mon Dec 09, 2024
Hydrodynamic density-functional theory for the moving contact-line problem reveals fluid structure and emergence of a spatially distinct pattern
Author(s): Andreas Nold, Benjamin D. Goddard, David N. Sibley, and Serafim Kalliadasis
The almost 60-year-old moving contact line problem has generated and driven an abundance of research. A variety of models have been proposed to alleviate the singularity at the three-phase conjunction. However, by design they are phenomenological and fall short of identifying the nanoscale effects that determine the fluid structure and compete to resolve the singularity. Here we put forward an inherently multiscale continuum model founded on first principles that bridges the micro- to the macroscale while retaining all fundamental microscopic information. It unravels the underlying physics of moving contact lines showing that it is much more intricate than previous models suggest.
[Phys. Rev. Fluids 9, 124003] Published Mon Dec 09, 2024
Influence of freestream turbulence and porosity on porous disk-generated wakes
Author(s): M. Bourhis and O. R. H. Buxton
This paper uncovers how freestream turbulence (FST) affects the wakes of porous discs with varying porosities, often used as wind turbines surrogates in wind tunnel studies. Low-porosity disks behave similarly to solid bodies in terms of entrainment behavior and scaling laws. FST reduces both wake growth and entrainment rates in the far wake, with turbulence intensity and length scale playing distinct roles. Intriguingly, as porosity increases, these “solid body” FST effects gradually diminish and are reversed above a critical porosity. This study also sheds light on the influence of disc porosity and FST on the presence of equilibrium and nonequilibrium turbulence in the wakes.
[Phys. Rev. Fluids 9, 124501] Published Mon Dec 09, 2024
Axisymmetric internal wave tunneling
Author(s): S. Boury, B. R. Sutherland, S. Joubaud, T. Peacock, and P. Odier
Though internal waves cannot propagate vertically through weakly stratified fluid, if the depth of the weak stratification is sufficiently shallow, these waves can partially transmit through it. This paper quantitatively extends previous results on Cartesian internal wave tunneling to the case of axisymmetric wave fields and proposes a simple three-layer model. We show that there exists a smooth transition between the fully propagating and the tunneling regimes. We further reflect on the challenges set by the measurement of internal wave mode amplitudes in confined domains, and we discuss an innovative method to measure said amplitudes in this experimental and numerical context.
[Phys. Rev. Fluids 9, 124801] Published Mon Dec 09, 2024
Microscale transport of ${\mathrm{CO}}_{2}$ and ${\mathrm{H}}_{2}$ storage in shale gas formations
Author(s): Lingfu Liu and Saman A. Aryana
This work focuses on microscale transport behavior of binary mixtures in the context of CO2 and H2 storage in shale gas formations. To this end, a multiple relaxation time lattice Boltzmann (LB) model is implemented to simulate microscale transport behavior. In the LB model, a combined boundary sche…
[Phys. Rev. E 110, 065105] Published Mon Dec 09, 2024
Rare, noise-induced, bypass transition in plane Couette flow can bypass instantons
Author(s): Joran Rolland
This paper presents a study of rare noise-induced transitions from stable laminar flow to transitional turbulence in plane Couette flow, which we will term buildup. We wish to study forced paths that go all the way from laminar to turbulent flow and to focus the investigation on whether these paths …
[Phys. Rev. E 110, 065106] Published Mon Dec 09, 2024
Dry granular collapse into a liquid: Role of viscous dissipation on granular flow regimes and associated waves
Author(s): Alexis Bougouin, Sylvain Viroulet, Laurent Lacaze, Olivier Roche, and Raphaël Paris
During the generation of free-surface waves in landslide-tsunami modeling, the importance of grain-fluid interaction is still not well identified. To clarify this, the present study examines experimentally the role of viscous dissipation on the dynamics of dry granular masses collapsing into a liquid pool, by varying both the grain size and liquid viscosity. The experiments reveal a richness in granular collapse regimes, from dilute- and dense-inertial to dense-viscous regimes, that significantly influence the entire wave train, while having limited impact on the leading and largest wave.
[Phys. Rev. Fluids 9, 124302] Published Fri Dec 06, 2024
Tail length influences swimming speed of helical swimmers in granular media
Author(s): Rogelio Valdés, Elsa de la Calleja, Roberto Zenit, and Francisco A. Godínez
We experimentally investigate the effects of helical tail length on the swimming efficiency of artificial robots in granular matter. Using magnetically driven swimmers, we found that longer tails boost forward velocity, challenging the traditional behavior observed in Newtonian fluids. We reveal the crucial role of head size in these dynamics through a modified Resistive Force Theory model. Our results demonstrate the intricate relationship between head drag and tail morphology, showing long-range effects linked to force chain formation and buckling. This important discovery broadens our understanding of locomotion in granular systems, an area where current theories are limited.
[Phys. Rev. Fluids 9, 124303] Published Fri Dec 06, 2024
Granular flows over normally vibrated inclined bases
Author(s): Prasad Sonar, Ashish Bhateja, and Ishan Sharma
We investigate granular flows over an inclined, normally vibrated rigid base using the discrete element method, systematically varying the inclination angle (θ), vibration frequency (f), and amplitude (A). Our findings demonstrate that vibrated bases can amplify the mass flow rate (Q) by 25–100 times compared to fixed bases depending upon the choice of parameters and, further, it is possible to find conditions that maintain Q nearly constant. Finally, Q is characterized by a dimensionless parameter S, also known as the shaking strength, which represents the ratio of vibrational to gravitational energies.
[Phys. Rev. Fluids 9, 124304] Published Fri Dec 06, 2024
Numerical analysis of binary fluid convection with thermal and solutal lateral gradients
Author(s): Juan Sánchez Umbría and Marta Net
This paper analyzes the influence of laterally enforced solutal gradients on the steady and bifurcated periodic dynamics in binary fluids contained in horizontally heated slots, taking into account the Soret and Dufour effects. Numerical Newton-Krylov continuation techniques to follow the primary an…
[Phys. Rev. E 110, 065104] Published Fri Dec 06, 2024
Effects of wall groove misalignment on viscoplastic flow dynamics in superhydrophobic channels
Author(s): A. Joulaei, H. Rahmani, and S. M. Taghavi
In viscoplastic Poiseuille flows over superhydrophobic surfaces, misalignment between lower and upper grooves alters flow characteristics. Adjusting groove misalignment along with key dimensionless parameters—offset number, Bingham number, slip number, groove periodicity, and slip area fraction—affects velocity distributions, plug morphology, and yielded/unyielded zones. Misalignment intensifies velocity and strain rate deviations, leading to plug deformation, asymmetry, and potential breakage. Four distinct regimes of center plug morphology emerge, highlighting the complex interplay between misalignment and viscoplastic flow behavior.
[Phys. Rev. Fluids 9, 123301] Published Wed Dec 04, 2024
Combined parabolic and elliptic velocity profile-based low-dimensional model in falling film
Author(s): Arghya Samanta
Based on the assumption of a combined parabolic and elliptic velocity profile, the simplified second-order depth-averaged equations are derived. As the parameter A relating to the eccentricity of the ellipse increases, new results adequately capture available findings. However, A = 2.23219 provides a relatively more accurate result. Maximum amplitude and speed of the steady-state traveling wave increase with rising values of A. The backflow phenomenon occurs in the capillary regime. Interestingly, the combined velocity profile detects the point of inflection in the capillary region at A = 2.23219, but it disappears at higher values of A, signaling a strong influence of the elliptic part.
[Phys. Rev. Fluids 9, 124002] Published Wed Dec 04, 2024
Flows over backward-facing steps with different spanwise widths
Author(s): Ke Zheng, Heri Setiawan, Jimmy Philip, Junghoon Lee, and Jason P. Monty
The effect of spanwise aspect ratio (AR) on flow characteristics over backward-facing steps with extended streamwise length and external corners is investigated experimentally. For intermediate AR, a unique wake pattern is observed, where there is no separation bubble, and the flow after reattachment ejects from, rather than impinging on, the central plane bottom floor, leading to intensified fluctuations and a broader region of high turbulence. This flow feature may be attributed to strong interactions of separated flows from all open edges with possible contributions from corner vortices that develop alongside the step. We also discuss the influence of these corner vortices for varying AR.
[Phys. Rev. Fluids 9, 124601] Published Wed Dec 04, 2024
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