New Papers in Fluid Mechanics

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

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

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

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

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

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

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

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

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

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

Author(s): Karen Mulleners

This paper discusses the transformative potential of self-exploring automated experiments for the discovery, optimization, and control of unsteady vortex-dominated flow phenomena. By minimizing experimentalists’ input in the actual performance of fluid experiments, the potential for scientific discovery is maximized.

[Phys. Rev. Fluids 9, 124701] Published Wed Dec 04, 2024

Author(s): Alberto Vela-Martín

Turbulent flows are difficult to predict due to chaos, which amplifies any uncertainty in the initial conditions. The way this uncertainty grows and propagates is key to understanding the emergence of complexity in turbulence and to assessing the reliability of turbulence forecasts. In this Letter, a novel approach based on massive ensembles of simulations reveals that uncertainty propagates in isotropic turbulence following a simple law that depends only on the average properties of the flow. This result opens avenues to improve current forecasting techniques by efficiently and accurately modeling uncertainty propagation.

[Phys. Rev. Fluids 9, L122601] Published Wed Dec 04, 2024

Author(s): David DiCarlo, Zachary W. Murphy, Kehua You, Peter B. Flemings, and Xiaoli Liu

Methane hydrate deposits are one of the largest fractions of hydrocarbons in the Earth's crust. They are found mainly in ocean sediments, and the configuration of the deposits—at the largest (kilometer) and smallest (micrometer) scales—determines how and when gaseous methane is released. Here, using…

[Phys. Rev. E 110, 065102] Published Wed Dec 04, 2024

Author(s): Salman Saud Alsaeed and Satyvir Singh

This paper investigates the thermal nonequilibrium effects on Richtmyer-Meshkov (RM) flow driven by a heavy forward-triangular bubble. Numerical laminar simulations are performed by utilizing the compressible dimensionless Navier-Fourier equations obtained from the Boltzmann-Curtiss transport equati…

[Phys. Rev. E 110, 065103] Published Wed Dec 04, 2024

Author(s): Rui Wang and Chun-Yu Zhang

When a particle-laden droplet impacts a flat surface, the presence of the particles inhibits its maximum spreading and reduces the rebound time.

[Phys. Rev. Fluids 9, 123601] Published Tue Dec 03, 2024

Author(s): Antoine Monier, François-Xavier Gauci, Cyrille Claudet, Franck Celestini, Christophe Brouzet, and Christophe Raufaste

We experimentally investigated the drainage of vertical rectangular soap films as they thin under gravity. Drainage dynamics were measured by tracking isothickness interference fringes. We showed that the downward motion of these fringes is self-similar with a power-law time evolution, or equivalently, that the thickness profiles exhibit space-time separation. By combining our data with previous studies, we collapsed all profiles onto a single curve, demonstrating the universality of this phenomenon. These findings are important for studying liquid foams and marginal regeneration instability.

[Phys. Rev. Fluids 9, 124001] Published Tue Dec 03, 2024

Author(s): Yifeng He, Baoqing Meng, Baolin Tian, and Yue Yang

We report the mechanism and modeling for the two-dimensional shock-induced instability of a dual-layer gas-particle mixture. In the mixture, the instability is triggered by the pressure perturbation near the perturbed interface instead of the baroclinic vorticity. The velocity difference of gas induced by the pressure perturbation drives the particle interface to grow via drag coupling effects. Inspired by this interfacial instability mechanism, we estimate the growth of the particle interface in the linear stage.

[Phys. Rev. Fluids 9, 124301] Published Tue Dec 03, 2024

Author(s): Nadia Bihari Padhan, Dario Vincenzi, and Rahul Pandit

We uncover interface-induced turbulence, a striking nonequilibrium statistically steady state with spatiotemporal chaos, emerging from interfacial fluctuations in low-Reynolds-number binary-fluid mixtures. Using direct numerical simulations of the Cahn-Hilliard-Navier-Stokes equations, we reveal a power-law energy spectrum indicative of turbulence without a conventional inertial cascade.

[Phys. Rev. Fluids 9, L122401] Published Tue Dec 03, 2024

Author(s): Prashant Sharma

We develop a general transfer-matrix formalism for determining the growth rate of the Rayleigh-Taylor instability in a fluid system with spatially varying density and viscosity. We use this formalism to analytically and numerically treat the case of a stratified heterogeneous fluid. We introduce the…

[Phys. Rev. E 110, L063101] Published Tue Dec 03, 2024

Author(s): Johannes Lohmann and Valerio Lucarini

A dynamically unstable state of the Atlantic ocean circulation in a global ocean model is constructed via an edge tracking algorithm. Such an unstable state is relevant as it mediates the potential future tipping point of the meridional overturning circulation from its present-day state to a collapsed state as a result of climate change. We identify the physical characteristics of the unstable state, which gives insights into the physical mechanisms necessary to induce a collapse, as well as potential fingerprints and early-warning signals of the tipping point.

[Phys. Rev. Fluids 9, 123801] Published Mon Dec 02, 2024