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New insights into head-on bouncing of unequal-size droplets on a wetting surface J. Fluid Mech. (IF 3.7) Pub Date : 2024-03-18 Saroj Ray, Yu Han, Zongyu Yue, Hengjie Guo, Christopher Yu Hang Chao, Song Cheng
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Swing and reverse swing of a cricket ball: laminar separation bubble, secondary vortex and wing-tip-like vortices J. Fluid Mech. (IF 3.7) Pub Date : 2024-03-18 Aman Parekh, Daksh Chaplot, Sanjay Mittal
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Local flow topology of a polymer-laden turbulent boundary layer J. Fluid Mech. (IF 3.7) Pub Date : 2024-03-18 Lucas Warwaruk, Sina Ghaemi
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Evidence for layered anisotropic stratified turbulence in a freely evolving horizontal shear flow J. Fluid Mech. (IF 3.7) Pub Date : 2024-03-18 Samuel F. Lewin, Colm-cille P. Caulfield
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Self-tuning model predictive control for wake flows J. Fluid Mech. (IF 3.7) Pub Date : 2024-03-18 Luigi Marra, Andrea Meilán-Vila, Stefano Discetti
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Mass transport at gas-evolving electrodes J. Fluid Mech. (IF 3.7) Pub Date : 2024-03-18 Farzan Sepahi, Roberto Verzicco, Detlef Lohse, Dominik Krug
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Eulerian discrete kinetic framework in comoving reference frame for hypersonic flows J. Fluid Mech. (IF 3.7) Pub Date : 2024-03-18 Y. Ji, S.A. Hosseini, B. Dorschner, K.H. Luo, I.V. Karlin
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Spontaneous locomotion of a symmetric squirmer J. Fluid Mech. (IF 3.7) Pub Date : 2024-03-18 Richard Cobos, Aditya S. Khair, Ory Schnitzer
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Breaking bubbles across multiple time scales in turbulence J. Fluid Mech. (IF 3.7) Pub Date : 2024-03-18 Yinghe Qi, Xu Xu, Shiyong Tan, Shijie Zhong, Qianwen Wu, Rui Ni
The familiar process of bubbles generated via breaking waves in the ocean is foundational to many natural and industrial applications. In this process, large pockets of entrained gas are successively fragmented by the ambient turbulence into smaller and smaller bubbles. The key question is how long it takes for the bubbles to reach terminal sizes for a given system. Despite decades of effort, the reported
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Impulsive impact of a twin hull J. Fluid Mech. (IF 3.7) Pub Date : 2024-03-15 B.-Y. Ni, Y.A. Semenov
An impulsively starting motion of two cylindrical bodies floating on a free liquid surface is considered. The shape of the cross-section of each body and the distance between them are arbitrary. The integral hodograph method is advanced to derive the complex velocity potential defined in a rectangular parameter region in terms of the elliptic quasi-doubly periodic Jacobi theta functions. A system of
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Modulations of turbulent/non-turbulent interfaces by particles in turbulent boundary layers J. Fluid Mech. (IF 3.7) Pub Date : 2024-03-15 Qingqing Wei, Ping Wang, Xiaojing Zheng
A spatially developing flat-plate boundary layer free from and two-way coupled with inertial solid particles is simulated to investigate the interaction between particles and the turbulent/non-turbulent interface. Particle Stokes numbers based on the outer scale are $St=2$ (low), 11 (moderate) and 53 (high). The Eulerian–Lagrangian point-particle approach is deployed for the simulation of particle-laden
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Turbulent wake characteristics for a circular cylinder in proximity to a moving wall J. Fluid Mech. (IF 3.7) Pub Date : 2024-03-15 Hongyi Jiang, Xiaoying Ju, Zhen Guo, Lizhong Wang
This study investigates the scenario of flow past a circular cylinder in proximity to a moving wall (or equally a body translating in still fluid parallel to a stationary wall). Fifty high-fidelity three-dimensional direct numerical simulations are performed over a parameter space of turbulent Reynolds numbers (Re) of 300 to 1000 combined with gap-to-diameter ratios (G/D) of 0.2 to 3. The flow, hydrodynamic
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Flow transitions and effective properties in multiphase Taylor–Couette flow J. Fluid Mech. (IF 3.7) Pub Date : 2024-03-15 Arthur B. Young, Abhishek Shetty, Melany L. Hunt
The properties of multiphase flows are challenging to measure, and yet effective properties are fundamental to modelling and predicting flow behaviour. The current study is motivated by rheometric measurements of a gas-fluidized bed using a coaxial rheometer in which the fluidization rate and the rotational speed can be varied independently. The measured torque displays a range of rheological states:
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On the behaviour of the upstream-travelling waves in merging twin-jet systems J. Fluid Mech. (IF 3.7) Pub Date : 2024-03-15 Michael N. Stavropoulos, Eduardo Martini, Daniel M. Edgington-Mitchell, Joel Weightman, Peter Jordan, Petrônio A.S. Nogueira
There is currently considerable interest in the guided-jet mode, as a result of recent works demonstrating it being the upstream component of various resonant systems in high-speed flows. For given jet operating conditions, the mode is known to exist over only a finite-frequency range that, for a twin-jet system, has been observed to vary with both jet separation and solution symmetry. Vortex-sheet
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Stability analysis of electro-osmotic flow in a rotating microchannel J. Fluid Mech. (IF 3.7) Pub Date : 2024-03-15 G.C. Shit, A. Sengupta, Pranab K. Mondal
We investigate the linear stability analysis of rotating electro-osmotic flow in confined and unconfined configurations by appealing to the Debye–Hückel approximation. Pertaining to flow in confined and unconfined domains, the stability equations are solved using the Galerkin method to obtain the stability picture. Both qualitative and quantitative aspects of Ekman spirals are examined in stable and
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Structure and role of the pressure Hessian in regions of strong vorticity in turbulence J. Fluid Mech. (IF 3.7) Pub Date : 2024-03-15 P.-F. Yang, H. Xu, A. Pumir, G.W. He
Amplification of velocity gradients, a key feature of turbulent flows, is affected by the non-local character of the incompressible fluid equations expressed by the second derivative (Hessian) of the pressure field. By analysing the structure of the flow in regions where the vorticity is the highest, we propose an approximate expression for the pressure Hessian in terms of the local vorticity, consistent
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Stability of a photosurfactant-laden viscous liquid thread under illumination J. Fluid Mech. (IF 3.7) Pub Date : 2024-03-14 Michael D. Mayer, Toby L. Kirk, Demetrios T. Papageorgiou
This paper investigates the effects of a light-actuated photosurfactant on the canonical problem of the linear stability of a viscous thread surrounded by a dynamically passive fluid. A model consisting of the Navier–Stokes equations and a set of molar concentration equations is presented that capture light-induced switching between two stable surfactant isomer states, trans and cis. These two states
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A machine learning model for reconstructing skin-friction drag over ocean surface waves J. Fluid Mech. (IF 3.7) Pub Date : 2024-03-14 Kianoosh Yousefi, Gurpreet Singh Hora, Hongshuo Yang, Fabrice Veron, Marco G. Giometto
In order to improve the predictive abilities of weather and climate models, it is essential to understand the behaviour of wind stress at the ocean surface. Wind stress is contingent on small-scale interfacial dynamics typically not directly resolved in numerical models. Although skin friction contributes considerably to the total stress up to moderate wind speeds, it is notoriously challenging to
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Wake of two tandem square cylinders J. Fluid Mech. (IF 3.7) Pub Date : 2024-03-14 Yu Zhou, Jingcheng Hao, Md. Mahbub Alam
The wake of two tandem square cylinders of identical width (d) is experimentally studied, with a view to understanding the dependence of the flow structure, aerodynamics forces and Strouhal number on the centre-to-centre spacing ratio L/d and Reynolds number Re, where L is the distance between the cylinder centres. Extensive measurements are carried out, using hot-wire, particle imaging velocimetry
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Short-wavelength instabilities in a finite-amplitude plane inertial wave J. Fluid Mech. (IF 3.7) Pub Date : 2024-03-13 D.S. Abhiram, Manikandan Mathur
We perform a linear stability analysis of a finite-amplitude plane inertial wave (of frequency $\omega$ in the range $0\le \omega \le f$ , where $f$ is the Coriolis frequency) by considering the inviscid evolution of three-dimensional (3-D), small-amplitude, short-wavelength perturbations. Characterizing the base flow plane inertial wave by its non-dimensional amplitude $A$ and the angle $\varPhi$
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Pore-scale study on the effect of heterogeneity on evaporation in porous media J. Fluid Mech. (IF 3.7) Pub Date : 2024-03-13 Linlin Fei, Dominique Derome, Jan Carmeliet
The evaporation process in porous media typically experiences three main periods, among which the first period, named the constant rate period (CRP), performs most efficiently in removing liquid. We aim to prolong the CRP to very low degrees of saturation (S) and increase its evaporation rate by playing with heterogeneity in wettability and pore size. First, we show that a porous medium with a smaller
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On the development and analysis of coupled surface–subsurface models of catchments. Part 3. Analytical solutions and scaling laws J. Fluid Mech. (IF 3.7) Pub Date : 2024-03-12 Piotr Morawiecki, Philippe H. Trinh
The objective of this three-part work is to formulate and rigorously analyse a number of reduced mathematical models that are nevertheless capable of describing the hydrology at the scale of a river basin (i.e. catchment). Coupled surface and subsurface flows are considered. In this third part, we focus on the development of analytical solutions and scaling laws for a benchmark catchment model that
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Wave scattering and radiation by a surface-piercing vertical truncated metamaterial cylinder J. Fluid Mech. (IF 3.7) Pub Date : 2024-03-12 S. Zheng, H. Liang, D. Greaves
In this paper, we study wave scattering and radiation by a surface-piercing vertical truncated metamaterial cylinder composed of a closely spaced array of thin vertical barriers, between which fluid can flow. A theoretical model is developed under full depth-dependent linearised water wave theory, where an effective medium equation and effective boundary conditions are employed, respectively, to describe
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The conditional Lyapunov exponents and synchronisation of rotating turbulent flows J. Fluid Mech. (IF 3.7) Pub Date : 2024-03-12 Jian Li, Mengdan Tian, Yi Li, Wenwen Si, Huda Khaleel Mohammed
The synchronisation between rotating turbulent flows in periodic boxes is investigated numerically. The flows are coupled via a master–slave coupling, taking the Fourier modes with wavenumber below a given value $k_m$ as the master modes. It is found that synchronisation happens when $k_m$ exceeds a threshold value $k_c$ , and $k_c$ depends strongly on the forcing scheme. In rotating Kolmogorov flows
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Stationary dimpled drops under linear flow J. Fluid Mech. (IF 3.7) Pub Date : 2024-03-12 Sumit Malik, Olga M. Lavrenteva, Moshe Idan, Avinoam Nir
The axially symmetric deformation of a drop in a viscous fluid, under the influence of an externally imposed flow having simultaneous rotating and compressional or extensional components, is addressed. In the previous studies, two families of stationary drop shapes were constructed by simulating the dynamics of drop deformation: stable singly connected shapes with respect to axisymmetric disturbances
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Modelling the unsteady lift of a pitching NACA 0018 aerofoil using state-space neural networks J. Fluid Mech. (IF 3.7) Pub Date : 2024-03-12 Luca Damiola, Jan Decuyper, Mark C. Runacres, Tim De Troyer
The development of simple, low-order and accurate unsteady aerodynamic models represents a crucial challenge for the design optimisation and control of fluid dynamical systems. In this work, wind tunnel experiments of a pitching NACA 0018 aerofoil conducted at a Reynolds number $Re = 2.8 \times 10^5$ and at different free-stream turbulence intensities are used to identify data-driven nonlinear state-space
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Life on the edge: subcritical pipe flow transition as a spectral submanifold J. Fluid Mech. (IF 3.7) Pub Date : 2024-03-12 Peter J. Schmid
Subcritical pipe flow transition has received a great deal of attention over the past decades, as it constitutes a quintessential bifurcation process between two metastable fluid states: the laminar and turbulent solutions. Coherent lower-branch structures, forming flow states that facilitate between these two attracting equilibria, have been proposed that together form an edge manifold in phase space
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Beyond optimal disturbances: a statistical framework for transient growth J. Fluid Mech. (IF 3.7) Pub Date : 2024-03-12 Peter Frame, Aaron Towne
The theory of transient growth describes how linear mechanisms can cause temporary amplification of disturbances even when the linearized system is asymptotically stable as defined by its eigenvalues. This growth is traditionally quantified by finding the initial disturbance that generates the maximum response at the peak time of its evolution. However, this can vastly overstate the growth of a real
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Prandtl number effects on extreme mixing events in forced stratified turbulence J. Fluid Mech. (IF 3.7) Pub Date : 2024-03-12 Nicolaos Petropoulos, Miles M.P. Couchman, Ali Mashayek, Stephen M. de Bruyn Kops, Colm-cille P. Caulfield
Relatively strongly stratified turbulent flows tend to self-organise into a ‘layered anisotropic stratified turbulence’ (LAST) regime, characterised by relatively deep and well-mixed density ‘layers’ separated by relatively thin ‘interfaces’ of enhanced density gradient. Understanding the associated mixing dynamics is a central problem in geophysical fluid dynamics. It is challenging to study LAST
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Stable production of fluid jets with vanishing diameters via tip streaming J. Fluid Mech. (IF 3.7) Pub Date : 2024-03-12 M. Rubio, J.M. Montanero, J. Eggers, M.A. Herrada
We study numerically the microjetting mode obtained when a fluid is injected through a tube submerged in a uniaxial extensional flow. The steady solution to the full nonlinear Navier–Stokes equations is calculated. We obtain the linear global modes determining the linear stability of the steady solution. For sufficiently large outer viscosity, the flow remains stable for infinitely small values of
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Surface corrugations induce helical near-surface flows and transport in microfluidic channels J. Fluid Mech. (IF 3.7) Pub Date : 2024-03-11 Christina Kurzthaler, Danielle L. Chase, Howard A. Stone
We study theoretically and experimentally pressure-driven flow between a flat wall and a parallel corrugated wall, a design used widely in microfluidics for low-Reynolds-number mixing and particle separation. In contrast to previous work, which focuses on recirculating helicoidal flows along the microfluidic channel that result from its confining lateral walls, we study the three-dimensional pressure
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On the development and analysis of coupled surface–subsurface models of catchments. Part 1. Analysis of dimensions and parameters for UK catchments J. Fluid Mech. (IF 3.7) Pub Date : 2024-03-11 Piotr Morawiecki, Philippe H. Trinh
The objective of this three-part work is to formulate and rigorously analyse a number of reduced mathematical models that are nevertheless capable of describing the hydrology at the scale of a river basin (i.e. catchment). Coupled surface and subsurface flows are considered. In this first part, we identify and analyse the key physical parameters that appear in the governing formulations used within
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On the development and analysis of coupled surface–subsurface models of catchments. Part 2. A three-dimensional benchmark model and its properties J. Fluid Mech. (IF 3.7) Pub Date : 2024-03-11 Piotr Morawiecki, Philippe H. Trinh
The objective of this three-part work is to formulate and rigorously analyse a number of reduced mathematical models that are nevertheless capable of describing the hydrology at the scale of a river basin (i.e. catchment). Coupled surface and subsurface flows are considered. In this second part, we construct a benchmark catchment scenario and investigate the effects of parameters within their typical
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Electrolubrication in liquid mixtures between two parallel plates J. Fluid Mech. (IF 3.7) Pub Date : 2024-03-08 Roni Kroll, Yoav Tsori
We describe theoretically ‘electrolubrication’ in liquid mixtures: the phenomenon whereby an electric field applied transverse to the confining surfaces leads to concentration gradients that alter the flow profile significantly. When the more polar liquid is the less viscous one, the stress in the liquid falls on two electric-field-induced thin lubrication layers. The thickness of the lubrication layer
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Evaporation from a cylindrical cavity: effect of gravity on the vapour cloud J. Fluid Mech. (IF 3.7) Pub Date : 2024-03-08 Senthil Kumar Parimalanathan, Sam Dehaeck, Metin Hatipogullari, Alexey Y. Rednikov, Hatim Machrafi, Pierre Colinet
We examine the vapour cloud of a pure liquid evaporating from a millimetric cylindrical well/cavity/aperture. This is accomplished by injecting the liquid up a vertical pipe towards its outlet onto a horizontal substrate. The injection is halted before the liquid surpasses the substrate level. The resulting final state is a meniscus at or near the pipe's end. The analysis is realised by vapour interferometry
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The sub-microscale dynamics of double-diffusive convection J. Fluid Mech. (IF 3.7) Pub Date : 2024-03-07 Timour Radko
This study investigates the dynamics of fingering convection on scales much smaller than the typical size of individual salt fingers. On such scales, salinity patterns exhibit the spontaneous emergence of sharp fronts induced by finger-scale strain. In contrast, velocity and temperature fields are largely devoid of sub-microscale variability, which is attributed to the rapid molecular dissipation of
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Detailed characterization of extreme clustering at near-contact scales in isotropic turbulence J. Fluid Mech. (IF 3.7) Pub Date : 2024-03-07 Danielle R. Johnson, Adam L. Hammond, Andrew D. Bragg, Hui Meng
Recent measurements of inertial particles in isotropic turbulence (Hammond & Meng, J. Fluid Mech., vol. 921, 2021, A16) revealed surprising extreme clustering of particles at near-contact separations $(r)$ , whereby the radial distribution function, $g(r)$ , grows from $O(10)$ to $O(10^3)$ with a $(r/a)^{-6}$ scaling (where $a$ is the particle radius), and a surprising upturn of the mean inward particle-pair
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Effect of bulk viscosity on the hypersonic compressible turbulent boundary layer J. Fluid Mech. (IF 3.7) Pub Date : 2024-03-07 Chaoyu Zheng, Yongliang Feng, Xiaojing Zheng
The impact of bulk viscosity is unclear with considering the increased dilatational dissipation and compressibility effects in hypersonic turbulence flows. In this study, we employ direct numerical simulations to conduct comprehensive analysis of the effect of bulk viscosity on hypersonic turbulent boundary layer flow over a flat plate. The results demonstrate that the scaling relations remain valid
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Turbulent–turbulent transient concept in pulsating flows J. Fluid Mech. (IF 3.7) Pub Date : 2024-03-07 P.S. Taylor, M. Seddighi
The turbulence behaviour of current-dominated pulsating flows has been investigated. Direct numerical simulations have been carried out for Stokes lengths over a range of $l_s^+=5\unicode{x2013}26$ , and amplitudes spanning 90 % of the current-dominated regime, about a mean flow of $\overline {Re}=6275$ . The results show that the turbulence response in intermediate and low-frequency pulsations is
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Influence of immersed particles on the stability of the liquid–liquid interface in a two-layer channel flow J. Fluid Mech. (IF 3.7) Pub Date : 2024-03-07 Désirée Ruiz-Martín, Javier Rivero-Rodríguez, Mario Sánchez-Sanz
The current study investigates the global linear stability of a two-layer channel flow with a train of solid particles flowing near the liquid–liquid interface. Three different mechanisms of instability (shear, interfacial and migration modes) are identified, and their interactions are examined. The interfacial instability, associated with the viscosity jump at the liquid–liquid interface, is found
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Exploring slip effects of ferrofluid film flow over a slanted rough surface J. Fluid Mech. (IF 3.7) Pub Date : 2024-03-05 Anupam Bhandari, K.P.S. Parmar
We examined the influences of slip parameters on the velocity and thermal characteristics of a ferrofluid film of fixed thickness. The flow is generated on a rough and inclined whirling surface that is positioned in an external magnetic (dipole) field. The similarity transformation reduces the model equations (continuity, momentum, energy and concentration), and the solution of the normalized coupled
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Velocity gradient analysis of a head-on vortex ring collision J. Fluid Mech. (IF 3.7) Pub Date : 2024-03-05 Rahul Arun, Tim Colonius
We simulate the head-on collision between vortex rings with circulation Reynolds numbers of 4000 using an adaptive, multiresolution solver based on the lattice Green's function. The simulation fidelity is established with integral metrics representing symmetries and discretization errors. Using the velocity gradient tensor and structural features of local streamlines, we characterize the evolution
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Consistent outer scaling and analysis of adverse pressure gradient turbulent boundary layers J. Fluid Mech. (IF 3.7) Pub Date : 2024-03-04 Mingze Han, Mingze Ma, Chao Yan
Under adverse pressure gradient (APG) conditions, the outer regions of turbulent boundary layers (TBLs) are characterized by an increased velocity defect $U_{e}-U$ , an outwards shift of the peak value of the Reynolds shear stress $-\langle uv\rangle$ and an appearance of the outer peak value of the Reynolds normal stress $\langle uu\rangle$ . Here $U_{e}$ is the TBL edge velocity. Scaling APG TBLs
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Regimes in rotating Rayleigh–Bénard convection over rough boundaries J. Fluid Mech. (IF 3.7) Pub Date : 2024-03-04 Vinay Kumar Tripathi, Pranav Joshi
The present work focuses on the effect of rough horizontal boundaries on the heat transfer in rotating Rayleigh–Bénard convection. We measure the non-dimensional heat transfer, the Nusselt number $Nu$ , for various strengths of the buoyancy forcing characterized by the Rayleigh number $Ra$ ( ${10^5}\mathrm{\ \mathbin{\lower.3ex\hbox{$\buildrel< \over {\smash{\scriptstyle\sim}\vphantom{_x}}$}}\ }Ra\mathrm{\
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Optimising subgrid-scale closures for spectral energy transfer in turbulent flows J. Fluid Mech. (IF 3.7) Pub Date : 2024-03-04 Miralireza Nabavi, Jeonglae Kim
Subgrid-scale (SGS) modelling is formulated using a local transport of spectral kinetic energy estimated by a wavelet multiresolution analysis. Using a spectrally and spatially local decomposition by wavelet, the unresolved inter-scale energy transfer and modelled SGS dissipation are evaluated to enforce explicitly and optimally their balance a priori over a range of large-eddy simulation (LES) filter
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Inertia and slip effects on the instability of a liquid film coated on a fibre J. Fluid Mech. (IF 3.7) Pub Date : 2024-03-04 Chengxi Zhao, Ran Qiao, Kai Mu, Ting Si, Xisheng Luo
To investigate the influence of inertia and slip on the instability of a liquid film on a fibre, a theoretical framework based on the axisymmetric Navier–Stokes equations is proposed via linear instability analysis. The model reveals that slip significantly enhances perturbation growth in viscous film flows, whereas it exerts minimal influence on flows dominated by inertia. Moreover, under no-slip
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Spatial discretization effects in spanwise forcing for turbulent drag reduction J. Fluid Mech. (IF 3.7) Pub Date : 2024-03-01 Emanuele Gallorini, Maurizio Quadrio
Wall-based spanwise forcing has been experimentally used with success by Auteri et al. (Phys. Fluids, vol. 22, 2010, 115103) to obtain large reductions of turbulent skin-friction drag and considerable energy savings in a pipe flow. The spatial distribution of the azimuthal wall velocity used in the experiment was not continuous, but piecewise constant. The present study is a numerical replica of the
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Unsteady large-scale wake structure behind levitated free-stream-aligned circular cylinder J. Fluid Mech. (IF 3.7) Pub Date : 2024-03-01 Sho Yokota, Taku Nonomura
The relationships between characteristic large-scale wake structures appearing behind a free-stream-aligned circular cylinder are investigated and discussed from the velocity field obtained by wind tunnel tests. The tests were conducted under a supportless condition using a magnetic suspension and balance system and stereo PIV measurements at a Reynolds number of $3.46\times 10^4$ . The velocity fields
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A controllable sliding law for thin-film flows over slippery fluid-saturated substrates: theory and experiments J. Fluid Mech. (IF 3.7) Pub Date : 2024-03-01 Zihan Yan, Katarzyna N. Kowal
We develop a theoretical and experimental framework for generating slip underneath thin-film flows of viscous fluids in the laboratory, with the ability to control slip as desired. Such a framework is useful for large-scale fluid-mechanical experiments in which basal sliding is important. In particular, we consider the flow of a thin film of viscous fluid spreading over a structured, slippery substrate
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Vortex line entanglement in active Beltrami flows J. Fluid Mech. (IF 3.7) Pub Date : 2024-03-01 Nicolas Romeo, Jonasz Słomka, Jörn Dunkel, Keaton J. Burns
Over the last decade, substantial progress has been made in understanding the topology of quasi-two-dimensional (2-D) non-equilibrium fluid flows driven by ATP-powered microtubules and microorganisms. By contrast, the topology of three-dimensional (3-D) active fluid flows still poses interesting open questions. Here, we study the topology of a spherically confined active flow using 3-D direct numerical
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Interface coupling effect and multi-mode Faraday instabilities in a three-layer fluid system J. Fluid Mech. (IF 3.7) Pub Date : 2024-03-01 Yi-Fei Huang, Rong-Lin Zhuo, Juan-Cheng Yang, Ming-Jiu Ni
We investigate the Faraday instabilities of a three-layer fluid system in a cylindrical container containing low-viscosity liquid metal, sodium hydroxide solution and air by establishing the Mathieu equations with considering the viscous model derived by Labrador et al. (J. Phys.: Conf. Ser., vol. 2090, 2021, 012088). The Floquet analysis, asymptotic analysis, direct numerical simulation and experimental
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Resonant response of a flexible semi-submersible floating structure: experimental analysis and second-order modelling J. Fluid Mech. (IF 3.7) Pub Date : 2024-03-01 Christine Lynggård Hansen, Henrik Bredmose, Maude Vincent, Stefan Emil Steffensen, Antonio Pegalajar-Jurado, Bjarne Jensen, Martin Dixen
The dynamics and nonlinear wave forcing of a flexible floating structure are investigated experimentally and numerically. The floater was designed to match sub-harmonic rigid-body natural frequencies of typical floating wind turbine substructures, with the addition of a flexible bending mode. Experiments were carried out for three sea states with phase-shifted input signals to allow harmonic separation
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Forced synchronization of self-excited chaotic thermoacoustic oscillations J. Fluid Mech. (IF 3.7) Pub Date : 2024-03-01 Yu Guan, Bo Yin, Zhijian Yang, Larry K.B. Li
We experimentally investigate the forced synchronization of a self-excited chaotic thermoacoustic oscillator with two natural frequencies, $f_1$ and $f_2$ . On increasing the forcing amplitude, $\epsilon _f$ , at a fixed forcing frequency, $f_f$ , we find two different types of synchronization: (i) $f_f/f_1 = 1:1$ or $2:1$ chaos-destroying synchronization (CDS), and (ii) phase synchronization of chaos
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The dynamics of impinging plumes from a moving source J. Fluid Mech. (IF 3.7) Pub Date : 2024-02-29 E.L. Newland, A.W. Woods
We present the results from a series of experiments investigating the dynamics of gravity currents which form when a dense saline or particle-laden plume issuing from a moving source interacts with a horizontal surface. We define the dimensionless parameter $P$ as the ratio of the source speed, $u_a$ , to the buoyancy speed, $(B_0/z_0)^{1/3}$ , where $B_0$ and $z_0$ are the source buoyancy flux and
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Effect of gas content on cavitation nuclei J. Fluid Mech. (IF 3.7) Pub Date : 2024-02-29 Karim Alamé, Krishnan Mahesh
Cavitation inception originates from nuclei in a liquid. This paper proposes a Gibbs free energy approach that provides a smooth transition from homogeneous to heterogeneous nucleation when gas is present. The impact of gas content on nucleation is explored. It is found that the gas content stabilises nuclei, a phenomenon not present in pure liquid–vapour systems. This reduces the energy barrier over
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A simple prediction of time-mean and wave orbital velocities in submerged canopy J. Fluid Mech. (IF 3.7) Pub Date : 2024-02-29 Xiaoxia Zhang, Chuyan Zhao, Heidi Nepf
Flow within submerged canopies influences the transport of nutrients, sediment, pollutants, plant seeds and the settlement of larvae. To improve our understanding of mass transport within canopies, a simple model is proposed to predict the total time-varying velocity within submerged rigid canopies (representing coral reefs) and flexible canopies (representing seagrasses and saltmarshes). The model
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Vortex dynamics and boundary layer transition in flow around a rectangular cylinder with different aspect ratios at medium Reynolds number J. Fluid Mech. (IF 3.7) Pub Date : 2024-02-29 Jiang-Hua Li, Bo-Fu Wang, Xiang Qiu, Quan Zhou, Shi-Xiao Fu, Yu-Lu Liu
The numerical investigation focuses on the flow patterns around a rectangular cylinder with three aspect ratios ( $L/D=5$ , $10$ , $15$ ) at a Reynolds number of $1000$ . The study delves into the dynamics of vortices, their associated frequencies, the evolution of the boundary layer and the decay of the wake. Kelvin–Helmholtz (KH) vortices originate from the leading edge (LE) shear layer and transform
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Investigation of near-wall particle statistics in CFD-DEM simulations of dense fluidised beds and derivation of an Eulerian particle dynamic wall boundary condition J. Fluid Mech. (IF 3.7) Pub Date : 2024-02-29 Dorian Dupuy, Renaud Ansart, Olivier Simonin
In two-fluid simulations of gas–solid fluidised beds, the gaseous phase and the particulate phase are modelled as continuous media. The stress exerted by the particulate medium on the container walls should be modelled to predict accurately the bed dynamics. This paper addresses the modelling of sliding particle–wall contacts in two-fluid simulations, based on reference simulations coupling computational
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Effects of surface roughness on the propulsive performance of pitching foils J. Fluid Mech. (IF 3.7) Pub Date : 2024-02-29 Rodrigo Vilumbrales-Garcia, Melike Kurt, Gabriel D. Weymouth, Bharathram Ganapathisubramani
The hydrodynamic influence of surface texture on static surfaces ranges from large drag penalties (roughness) to potential performance benefits (shark-like skin). Although it is of wide-ranging research interest, the impact of roughness on flapping systems has received limited attention. In this work, we explore the effect of roughness on the unsteady performance of a harmonically pitching foil through
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Acoustic streaming: insights across Reynolds numbers J. Fluid Mech. (IF 3.7) Pub Date : 2024-02-29 Nitesh Nama
When a fluid system is subjected to an acoustic wave (or another periodic actuation), the response of the fluid is not purely periodic, but is rather characterized by the combination of a periodic flow and a steady Stokes drift component, where the former is, in many cases, an acoustic wave and the latter is commonly referred to as acoustic streaming. Classical theories of acoustic streaming have focused