New Papers in Fluid Mechanics

Author(s): Rory T. Cerbus and Tom Mullin

The Moody diagram is a well-known engineering plot of friction factor versus flow rate which shows definite relationships over the majority of parameter space. However, in the transitional regime between laminar and turbulent flows where the relationships are deemed indefinite the region is shown hatched. We investigate the transitional regime using a novel method to minimize the influence of initial conditions. This regime is approached from above by reducing the flow speed from a turbulent flow state. We find that flows driven by a constant pressure difference yield a single curve near the maximum of Moody’s hatches, while flows driven by a syringe produce a distinctly different curve.

[Phys. Rev. Fluids 9, 113902] Published Mon Nov 18, 2024

Author(s): Zhaodong Ding, Chengxi Zhao, Kai Mu, and Ting Si

Liquid jets under interfacial shear effects are critical in various scientific and industrial applications. External shear induces axial elastic tension due to velocity gradients across the jet, significantly impacting the linear instability of viscoelastic jets. This study, using slender-jet approximations, reveals that standard models fail to account for the effects of elastic tension. Higher-order approximation models, including parabolic and averaged-parabolic models, are developed to capture these effects accurately, offering a new stabilization mechanism for viscoelastic jets and providing insights for future research.

[Phys. Rev. Fluids 9, 114001] Published Mon Nov 18, 2024

Author(s): Emeka Peter Mazi, Hamad El Kahza, and Pejman Sanaei

In this work, we study the deposition and erosion of solid particles at the microscale level and their direct consequences on the internal structure of porous media with branching structure consisting of axisymmetric channels, undergoing a unidirectional flow. We characterize the evolution of the internal morphology of the porous medium using geometric parameters such as the gradients of initial pore radii and layer thicknesses.

[Phys. Rev. Fluids 9, 114301] Published Mon Nov 18, 2024

Author(s): M. Wasy Akhtar and Rodolfo Ostilla-Mónico

We use numerical simulations to explore how turbulent Plane Couette flow — the flow between two moving plates — responds to modulations in the speed of one plate. We find that the resulting flow behavior, including amplitude and phase response, can largely be predicted using simplified flow models that satisfy linear superposition. The work advances understanding of how turbulent flows react to controlled perturbations, and when do turbulent flows behave in approximately linear fashion.

[Phys. Rev. Fluids 9, 114606] Published Mon Nov 18, 2024

Author(s): Hansol Wee, Ajay Harishankar Kumar, Naresh K. Dhanwani, and Osman A. Basaran

We present a physically based derivation of the slender-jet equations when the jet’s surface is covered with surfactant and surface rheological effects are important. We allow for the possibility that the bulk fluid and the interface may be non-Newtonian, e.g. a bulk phase that is viscoelastic and a surface phase rheology that may not follow the Boussinesq-Scriven model. Theoretical predictions deduced from slender-jet theory are compared with computational results from a fully three-dimensional axisymmetric (3DA) algorithm for a breaking surfactant covered Newtonian jet. For such jets, analytical results are shown to be in excellent accord with ones obtained from 3DA simulations.

[Phys. Rev. Fluids 9, 113602] Published Fri Nov 15, 2024

Author(s): Naili Xu and Ivan Bermejo-Moreno

Fluid flows with partial relaminarization driven by favorable pressure gradients pose significant predictive challenges for equilibrium wall models in large eddy simulations, resulting in an overprediction of the skin friction coefficient. This work introduces a wall modeling approach that smoothly blends equilibrium wall-model and no-slip/laminar boundary conditions based on local flow conditions identified by sensors of acceleration/relaminarization. The proposed modeling approach is applied to the prediction of the flow over a Gaussian-shaped bump at three Reynolds numbers. The results compare favorably with prior experiments and direct numerical simulations across different flow regimes.

[Phys. Rev. Fluids 9, 114605] Published Fri Nov 15, 2024

Author(s): Beverley McKeon, Eric Lauga, Brad Rubin, Arezoo Ardekani, Jackie Chen, Karthik Duraisamy, Sanjiva Lele, Julia Ling, George Rigas, and Peter Schmid

[Phys. Rev. Fluids 9, 110001] Published Thu Nov 14, 2024

Author(s): J. Zhang and S. Perrard

Ned Kahn’s artwork “Kinetic Façade” is composed of thin aluminium plates covering the entire façade of a building. When the wind blows, the panels ripple and form large scale patterns traveling downstream. We perform video analysis and laboratory experiments on a one-dimensional pendulum chain immersed in a turbulent flow. Thanks to our reduced model, we identify the mechanisms that generate the patterns on the facade: the turbulent flow carries pressure fluctuations which actuates each thin plate. Ned Kahn’s original idea, revealing the invisible aspect of the wind, now finds a scientific ground.

[Phys. Rev. Fluids 9, 114604] Published Thu Nov 14, 2024

Author(s): Shiji Lin, Dachuang Shi, Le Zhou, Longquan Chen, and Zhigang Li

Droplet rebound on nonwetting surfaces is a common phenomenon. However, the underlying physics regulating the contact time remains unclear. In this work, we investigate droplet impacts on superamphiphobic surfaces through experiments and theoretical analyses. By analyzing the spreading and retractio…

[Phys. Rev. E 110, L053101] Published Thu Nov 14, 2024

Author(s): Wenbo Li and Dali Kong

Convective dynamics in the interiors of rapidly rotating oblate spheroidal planets are generally marked by extremely small Ekman numbers and moderate Prandtl numbers. In the relevant parameter space, at the onset of thermal convection, the flow structure can be represented by the superposition of multiple inertial modes of the same azimuthal wave number. This paper discusses why such thermal convective motions occur and how the degree of flattening of a planet due to rotation would affect the flows. More importantly, the theory discussed in this paper establishes a necessary foundation for future studies of turbulent convection and MHD dynamo actions.

[Phys. Rev. Fluids 9, 113502] Published Wed Nov 13, 2024

Author(s): Rajaram Lakkaraju, Dinesh Kumar Chandraker, and Gautam Biswas

The hydrodynamic and thermal interactions between neighboring vapor bubbles on hot surfaces play a crucial role in heat transport and flow characteristics. To investigate these interactions, we conducted numerical simulations of saturated vapor bubbles in a two-dimensional square enclosure filled wi…

[Phys. Rev. E 110, 055103] Published Wed Nov 13, 2024

Author(s): Jason Olsthoorn

Seasonally ice-covered lakes cool during the Fall season due to a loss of heat through their exposed surface. This heat loss drives convection within the lake, which warms the surface. A balance between the heat lost to the atmosphere and the convective warming creates a dynamic equilibrium between the surface water temperature and the convection below. We identified the three convective regimes in this system and predict the transitions between them. Understanding these transitions is essential for predicting the time of ice formation in lakes.

[Phys. Rev. Fluids 9, 113501] Published Tue Nov 12, 2024

Author(s): Chuhan Wang, Le Fang, Zhan Wang, and Chunxiao Xu

We propose a “frozen-phase” experiment to reveal the effect of Fourier phase dynamics on the energy transfer in three-dimensional turbulence. The method employed to freeze the phases can be considered as a designed forcing term in the spectral space that only acts on the evolution equation of Fourier phases. The results from this experiment demonstrate the necessity of phase dynamics in sustaining a standard forward energy cascade but also the possibility of developing an attenuated cascade without phase dynamics. These findings provide novel insights for modeling the nonlinear triadic interaction in realistic fluid flows.

[Phys. Rev. Fluids 9, 114603] Published Tue Nov 12, 2024

Author(s): Léo-Paul Euvé, Kim Pham, Philippe Petitjeans, Vincent Pagneux, and Agnès Maurel

In this work, we provide experimental evidence of negative refraction using a locally resonant metamaterial with hyperbolic dispersion, supported by a theoretical model. By characterizing both elliptical and hyperbolic regimes, our results demonstrate the potential of metamaterials in controlling water waves, opening up new possibilities in wave manipulation technologies.

[Phys. Rev. Fluids 9, L112801] Published Tue Nov 12, 2024

Author(s): Yufei Ma and Haibo Huang

Although the scaling law We1/2 where We is the Weber number for describing the maximum spreading of an impacting drop in the capillary regime has been validated by subsequent works, the We1/4 scaling persists in the literature. We found not only viscous dissipation but also the initial diameter result in the gap. Taking the initial diameter and wettability into account, a generalized scaling for the drop’s maximum spreading is established, showing excellent agreement with data for both low and relatively high We.

[Phys. Rev. Fluids 9, 113601] Published Fri Nov 08, 2024

Author(s): Yuke Li and Victor Steinberg

This study explores non-modal elastic instability in low-inertia viscoelastic channel flow with a smoothed inlet, revealing how reduced perturbations affect flow behavior. The transition from laminar to chaotic flow is captured by universal scaling laws for velocity fluctuations and friction, independent of perturbation intensity. Most notably, the study presents a critical scaling relation between the onset of instability and the intensity of inlet perturbations characteristic of non-modal instability with onset of elastic waves, offering a new understanding of the conditions leading to elastic instability and turbulence in inertialess viscoelastic channel flow.

[Phys. Rev. Fluids 9, 113302] Published Thu Nov 07, 2024

Author(s): D. Paulovics, T. Frisch, C. Raufaste, and F. Celestini

A sub-millimetric jet impinges on a substrate heated above the boiling point of the liquid. Under specific conditions - determined by the jet radius, substrate temperature, and the impinging angle - a “Leidenfrost jet” can be observed, bouncing off the surface. Surfing on its own vapor layer, this jet rebounds without making any contact with the heated substrate.

[Phys. Rev. Fluids 9, L112001] Published Tue Nov 05, 2024

Author(s): Seunghyeon Baek and Sung-Ik Sohn

This study investigates the Rayleigh-Taylor instability in the magnetic field applied parallel to the interface. The motion of the interface is described using a current-vortex-sheet model. The growth rate of the interface is obtained from a linear stability analysis of the model. The interface of a…

[Phys. Rev. E 110, 055102] Published Tue Nov 05, 2024

Author(s): P.-T. Brun

This paper explores the intricate dynamics of interfacial flows, focusing on the dual role of surface tension in shaping and destabilizing interfaces within solidifying polymer melts. It reviews recent developments in the experimental characterization and rationalization of these complex flows, emphasizing key challenges and opportunities. The insights presented aim to inform the strategic harnessing of interfacial effects to advance soft material technologies.

[Phys. Rev. Fluids 9, 110501] Published Mon Nov 04, 2024

Author(s): Daniel J. Coxe, Yulia T. Peet, and Ronald J. Adrian

Turbulent drag reduction by spanwise wall oscillations has been understood through reducing skin friction and manipulation of Reynolds stress and stress producing events. This work aims to contextualize spanwise wall oscillations around the optimal frequency in terms of Fourier spectra in streamwise and spanwise directions along with the wall normal distributions of coefficients spectra. Analysis of where drag reduction occurs and potential physical mechanisms is provided by determining scale contributions of the Reynolds stress to the bulk mean velocity via the scale dependent Fukagata-Iwamoto-Kasagi (FIK) identity and vorticity contribution to the gradient of turbulent Reynolds’ stresses.

[Phys. Rev. Fluids 9, 114601] Published Mon Nov 04, 2024