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Vortex shedding behind porous flat plates normal to the flow J. Fluid Mech. (IF 3.7) Pub Date : 2024-04-25 M.M. Cicolin, S. Chellini, B. Usherwood, B. Ganapathisubramani, Ian P. Castro
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Adjoint-accelerated Bayesian inference applied to the thermoacoustic behaviour of a ducted conical flame J. Fluid Mech. (IF 3.7) Pub Date : 2024-04-25 Matthew Yoko, Matthew P. Juniper
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Air-blast atomization of a liquid film J. Fluid Mech. (IF 3.7) Pub Date : 2024-04-24 Ippei Oshima, Akira Sou
Air-blast atomizers are extensively used for a variety of purposes. Due to its complexity, the atomization mechanism has not been elucidated. In this study, a mechanistic model is proposed to predict the droplet diameter distribution based on the atomization process of a planar liquid film with co-current gas flows, and its validity is examined by comparing the estimated and measured droplet diameters
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Heavy tails and probability density functions to any nonlinear order for the surface elevation in irregular seas J. Fluid Mech. (IF 3.7) Pub Date : 2024-04-24 Mathias Klahn, Yanyan Zhai, David R. Fuhrman
The probability density function (PDF) for the free surface elevation in an irregular sea has an integral formulation when based on the cumulant generating function. To leading order, the result is Gaussian, whereas nonlinear extensions have long been limited to Gram–Charlier series approximations. As shown recently by Fuhrman et al. (J. Fluid Mech., vol. 970, 2023, A38), however, the second-order
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Lagrangian dynamics and regularity of the spin Euler equation J. Fluid Mech. (IF 3.7) Pub Date : 2024-04-24 Zhaoyuan Meng, Yue Yang
We derive the spin Euler equation for ideal flows by applying the spherical Clebsch mapping. This equation is based on the spin vector, a unit vector field encoding vortex lines, instead of the velocity. The spin Euler equation enables a feasible Lagrangian study of fluid dynamics, as the isosurface of a spin-vector component is a vortex surface and material surface in ideal flows. We establish a non-blowup
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Density-contrast induced inertial forces on particles in oscillatory flows J. Fluid Mech. (IF 3.7) Pub Date : 2024-04-23 Siddhansh Agarwal, Gaurav Upadhyay, Yashraj Bhosale, Mattia Gazzola, Sascha Hilgenfeldt
Oscillatory flows have become an indispensable tool in microfluidics, inducing inertial effects for displacing and manipulating fluid-borne objects in a reliable, controllable and label-free fashion. However, the quantitative description of such effects has been confined to limit cases and specialized scenarios. Here we develop an analytical formalism yielding the equation of motion of density-mismatched
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Experiments on symmetry breaking of azimuthal combustion instabilities and their analysis combining acoustic energy balance and flame describing functions J. Fluid Mech. (IF 3.7) Pub Date : 2024-04-23 V. Latour, D. Durox, A. Renaud, S. Candel
Combustion instabilities in annular systems raise fundamental issues that are also of practical importance to aircraft engines and ground-based gas turbine combustors. Recent studies indicate that the injector plays a significant role in the stability of combustors by defining the flame dynamical response and setting the inlet impedance of the system. The present investigation examines the effects
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Elasto-inertial instability in torsional flows of shear-thinning viscoelastic fluids J. Fluid Mech. (IF 3.7) Pub Date : 2024-04-23 Rishabh V. More, R. Patterson, E. Pashkovski, G.H. McKinley
It is well known that inertia-free shearing flows of a viscoelastic fluid with curved streamlines, such as the torsional flow between a rotating cone and plate or the flow in a Taylor–Couette geometry, can become unstable to a three-dimensional time-dependent instability at conditions exceeding a critical Weissenberg ( $Wi$ ) number. However, the combined effects of fluid elasticity, shear thinning
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Arbitrary-order sensitivities of the incompressible base flow and its eigenproblem J. Fluid Mech. (IF 3.7) Pub Date : 2024-04-23 S.J. Knechtel, T.L. Kaiser, A. Orchini, K. Oberleithner
First-order sensitivities and adjoint analysis are used widely to control the linear stability of unstable flows. Second-order sensitivities have recently helped to increase accuracy. In this paper, a method is presented to calculate arbitrary high-order sensitivities based on Taylor expansions of the incompressible base flow and its eigenproblem around a scalar parameter. For the incompressible Navier–Stokes
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Effect of fluid motions on finite spheres released in turbulent boundary layers J. Fluid Mech. (IF 3.7) Pub Date : 2024-04-23 Yi Hui Tee, Ellen K. Longmire
This paper extends the work in Tee et al. (Intl J. Multiphase Flow, vol. 133, 2020, 103462) to investigate the effect of turbulent fluid motions on the translation and rotation of lifting and wall-interacting spheres in boundary layers. Each sphere was released from rest in smooth-wall boundary layers with $Re_\tau =670$ and 1300 ( $d^+=56$ and 116, respectively) and allowed to propagate with the incoming
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Unravelling the existence of asymmetric bubbles in viscoelastic fluids J. Fluid Mech. (IF 3.7) Pub Date : 2024-04-23 P. Moschopoulos, A. Spyridakis, Y. Dimakopoulos, J. Tsamopoulos
We study the motion and deformation of a single bubble rising inside a cylindrical container filled with a viscoelastic material. We solve numerically the mass and momentum balances along with the constitutive equation for the viscoelastic stresses, without assuming axial symmetry to allow the growth of three-dimensional disturbances. Hence, we may predict the emergence of the notorious knife-edge
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Resolvent analysis of turbulent flow laden with low-inertia particles J. Fluid Mech. (IF 3.7) Pub Date : 2024-04-23 Rasmus Korslund Schlander, Stelios Rigopoulos, George Papadakis
We extend the resolvent framework to two-phase flows with low-inertia particles. The particle velocities are modelled using the equilibrium Eulerian model. We analyse the turbulent flow in a vertical pipe with Reynolds number of $5300$ (based on diameter and bulk velocity), for Stokes numbers $St^+=0-1$ , Froude numbers $Fr_z=-4,-0.4,0.4,4$ and $1/Fr_z = 0$ (gravity omitted). The governing equations
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The effect of permeability on the flow structure of porous square cylinders J. Fluid Mech. (IF 3.7) Pub Date : 2024-04-23 Chansoo Seol, Taewoo Kim, Taehoon Kim
This study experimentally investigates the wake structure of a porous square cylinder in terms of permeability over two decades of $Da$ (i.e. $2.4 \times 10^{-5} < Da < 2.9 \times 10^{-3}$ ). The porous cylinder, featuring a simple cubic lattice structure, was fabricated using an additive manufacturing technique. This unique method, combined with a periodic and scalable lattice structure, effectively
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Influence of the boundary-layer thickness on the generation of tonal noise components by subsonic impinging jets J. Fluid Mech. (IF 3.7) Pub Date : 2024-04-22 Hugo Vincent, Christophe Bogey
The influence of the boundary layer (BL) thickness on the tonal noise generated by subsonic impinging jets is investigated. For that, initially laminar jets at Mach numbers $0.6$ and $0.9$ with BL thicknesses $0.05r_0$ , $0.1r_0$ and $0.2r_0$ , where $r_0$ is the pipe-nozzle radius, impinging on a plate at $6r_0$ from the nozzle, are simulated. For Mach number $0.9$ , acoustic tones due to feedback
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Relaminarization effects in hypersonic flow on a three-dimensional expansion–compression geometry J. Fluid Mech. (IF 3.7) Pub Date : 2024-04-22 Anshuman Pandey, Katya M. Casper, Steven J. Beresh
This experimental work explores the flow field around a three-dimensional expansion–compression geometry on a slender cone at Mach 8 using high-frequency pressure sensors, high-frame-rate schlieren, temperature-sensitive paint, shear-stress measurements and oil-flow visualizations. The $7^\circ$ cone geometry has a hyperbolic slice which acts as an expansion corner and suppresses the disturbances present
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Boundary mixing. Part 2. The impact of ventilation J. Fluid Mech. (IF 3.7) Pub Date : 2024-04-22 Scott W. Li, Andrew W. Woods
Through a combination of laboratory experiments and theoretical models, we investigate the interaction of a mean upwelling through a closed basin with a vertical buoyancy flux. The fluid is mixed by a horizontally oscillating rake, which either traverses the whole basin or which oscillates just near one vertical boundary. We first review the steady state and demonstrate that, in both mixing regimes
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Regressing bubble cluster dynamics as a disordered many-body system J. Fluid Mech. (IF 3.7) Pub Date : 2024-04-22 Kazuki Maeda, Daniel Fuster
The coherent dynamics of bubble clusters are of fundamental and industrial importance, and are elusive due to the complex interactions of disordered bubble oscillations. Here we introduce and demonstrate a method for decomposition of the Lagrangian time series of bubble dynamics data by combining theory and principal component analysis. The decomposition extracts coherent features of bubble oscillations
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Dynamics and active mixing of a droplet in a Stokes trap J. Fluid Mech. (IF 3.7) Pub Date : 2024-04-22 Gesse Roure, Alexander Z. Zinchenko, Robert H. Davis
Particle trapping and manipulation have a wide range of applications in biotechnology and engineering. Recently, a flow-based, particle-trapping device called the Stokes trap was developed for trapping and control of small particles in the intersection of multiple branches in a microfluidic channel. This device can also be used to perform rheological experiments to determine the viscoelastic response
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The effect of flight on a turbulent jet: coherent structure eduction and resolvent analysis J. Fluid Mech. (IF 3.7) Pub Date : 2024-04-19 Igor A. Maia, Liam Heidt, Ethan Pickering, Tim Colonius, Peter Jordan, Guillaume A. Brès
We study coherent structures in subsonic turbulent jets subject to a flight stream. A thorough characterisation of the effects of a flight stream on the turbulent field was recently performed by Maia et al. (Phys. Rev. Fluids, vol. 8, 2023, 063902) and fluctuation energy attenuations were observed over a broad range of frequencies and azimuthal wavenumbers. The Kelvin–Helmholtz, Orr and lift-up mechanisms
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Effects of buoyancy on the dispersion of drugs released intrathecally in the spinal canal J. Fluid Mech. (IF 3.7) Pub Date : 2024-04-19 J. Alaminos-Quesada, C. Gutiérrez-Montes, W. Coenen, A.L. Sánchez
This paper investigates the transport of drugs delivered by direct injection into the cerebrospinal fluid (CSF) that fills the intrathecal space surrounding the spinal cord. Because of the small drug diffusivity, the dispersion of neutrally buoyant drugs has been shown in previous work to rely mainly on the mean Lagrangian flow associated with the CSF oscillatory motion. Attention is given here to
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Spectral proper orthogonal decomposition of time-resolved three-dimensional flow measurements in the turbulent wake of the Ahmed body J. Fluid Mech. (IF 3.7) Pub Date : 2024-04-19 C.W. Chen, S. Wang, S. Ghaemi
This study investigated the turbulent wake flow behind a flat-back Ahmed body using a combination of time-resolved tomographic particle image velocimetry measurements and spectral proper orthogonal decomposition (SPOD). The experiments were conducted at a Reynolds number of ReH = 10 000, which is defined as U∞H/ν, where U∞ represents the free-stream velocity, H is the height of the body and ν represents
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Turbulence over young wind waves dominated by capillaries and micro-breakers J. Fluid Mech. (IF 3.7) Pub Date : 2024-04-19 Jitae Do, Binbin Wang, Kuang-An Chang
We conducted experiments in a laboratory to study turbulent flow over wind generated water waves. The experiments were performed in a wind-wave-current flume with three free stream wind speeds of Uref = 6.0, 8.0 and 10.0 m s−1, corresponding to 10 m equivalent wind speed of U10 = 10.2, 12.2 and 14.1 m s−1 and the root-mean-square wave height of 0.7, 1.1 and 1.7 cm, respectively, at a fetch of 6.2 m
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Steady water waves with arbitrary surface pressure: their recovery from bottom-pressure measurements J. Fluid Mech. (IF 3.7) Pub Date : 2024-04-19 Didier Clamond, Joris Labarbe
Equations relating the pressure at a horizontal seabed, the free-surface profile and the surface pressure are derived for two-dimensional irrotational steady water waves with arbitrary pressure at the free surface. Special cases include gravity, capillary, flexural and wind waves. Without approximations, we show that the free-surface recovery from the bottom pressure requires the resolution of only
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Propagation of a viscous gravity current beneath a granular mush J. Fluid Mech. (IF 3.7) Pub Date : 2024-04-18 Edward M. Hinton, Anja C. Slim
The two-dimensional gravity-driven motion of a relatively dense viscous liquid at the base of a granular mush is investigated using a model that exploits the relative shallowness of the flow. The granular mush obeys a $\mu (I)$ -rheology, and we assume that the two phases are segregated throughout the motion. The viscous liquid spreads under gravity, carrying the granular mush above and transporting
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Viscoelastic wetting: Cox–Voinov theory with normal stress effects J. Fluid Mech. (IF 3.7) Pub Date : 2024-04-18 Minkush Kansal, Vincent Bertin, Charu Datt, Jens Eggers, Jacco H. Snoeijer
The classical Cox–Voinov theory of contact line motion provides a relation between the macroscopically observable contact angle, and the microscopic wetting angle as a function of contact-line velocity. Here, we investigate how viscoelasticity, specifically the normal stress effect, modifies the wetting dynamics. Using the thin film equation for the second-order fluid, it is found that the normal stress
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Excitation and evolution of radiating modes in supersonic boundary layers. Part 2. Back effect of spontaneously radiated Mach waves J. Fluid Mech. (IF 3.7) Pub Date : 2024-04-18 Fufeng Qin, Xuesong Wu
This paper investigates the linear and nonlinear evolution of radiating modes under the influence of the spontaneously emitted Mach waves in a simple set-up of the supersonic boundary layers that develop in the entry region of a channel formed by two parallel semi-infinite flat plates. Two scenarios are considered. The first occurs in the boundary layers having identical wall conditions, where the
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Excitation and evolution of radiating modes in supersonic boundary layers. Part 1. Fundamental resonance with impinging sound waves J. Fluid Mech. (IF 3.7) Pub Date : 2024-04-18 Fufeng Qin, Xuesong Wu
This paper investigates the linear and nonlinear evolution of radiating modes in supersonic boundary layers under the influence of impinging sound waves. It is found that the ensuing boundary-layer response is extraordinarily large for a subset of the sound frequency and incident angle, and the resonant over-reflection, corresponding to the reflection coefficient becoming infinite, occurs at a particular
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Equilibrium distributions under advection–diffusion in laminar channel flow with partially absorbing boundaries J. Fluid Mech. (IF 3.7) Pub Date : 2024-04-18 Tomás Aquino
Advective–diffusive transport in Poiseuille flow through a channel with partially absorbing walls is a classical problem with applications to a broad range of natural and engineered scenarios, ranging from solute and heat transport in porous and fractured media to absorption in biological systems and chromatography. We study this problem from the perspective of transverse distributions of surviving
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Dimensional homogeneity constrained gene expression programming for discovering governing equations J. Fluid Mech. (IF 3.7) Pub Date : 2024-04-18 Wenjun Ma, Jun Zhang, Kaikai Feng, Haoyun Xing, Dongsheng Wen
Data-driven discovery of governing equations is of great significance for helping us understand intrinsic mechanisms and build physical models. Recently, numerous highly innovative algorithms have emerged, aimed at inversely discovering the underlying governing equations from data, such as sparse regression-based methods and symbolic regression-based methods. Along this direction, a novel dimensional
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Interaction between a uniform current and a submerged cylinder in a marginal ice zone J. Fluid Mech. (IF 3.7) Pub Date : 2024-04-17 Y.F. Yang, G.X. Wu, K. Ren
The interaction between a uniform current with a circular cylinder submerged in a fluid covered by a semi-infinite ice sheet is considered analytically. The ice sheet is modelled as an elastic thin plate, and the fluid flow is described by the linearised velocity potential theory. The Green function or the velocity potential due to a source is first obtained. As the water surface is divided into two
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Enhanced recovery caused by nonlinear dynamics in the wake of a floating offshore wind turbine J. Fluid Mech. (IF 3.7) Pub Date : 2024-04-16 Thomas Messmer, Michael Hölling, Joachim Peinke
An experimental study in a wind tunnel is presented to explore the wake of a floating wind turbine subjected to harmonic side-to-side and fore–aft motions under laminar inflow conditions. The wake recovery is analysed as a function of the frequency of motion $f_p$ , expressed by the rotor-based Strouhal number, $St = f_p D / U_{\infty }$ ( $D$ is the rotor diameter, $U_{\infty }$ the inflow wind speed)
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Langmuir turbulence in suspended kelp farms J. Fluid Mech. (IF 3.7) Pub Date : 2024-04-16 Tong Bo, James C. McWilliams, Chao Yan, Marcelo Chamecki
This study investigates the influence of suspended kelp farms on ocean mixed layer hydrodynamics in the presence of currents and waves. We use the large eddy simulation method, where the wave effect is incorporated by solving the wave-averaged equations. Distinct Langmuir circulation patterns are generated within various suspended farm configurations, including horizontally uniform kelp blocks and
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Reactive control of velocity fluctuations using an active deformable surface and real-time PIV J. Fluid Mech. (IF 3.7) Pub Date : 2024-04-16 Findlay McCormick, Bradley Gibeau, Sina Ghaemi
This study demonstrates an experimental realization of turbulence control strategies previously explored by Choi et al. (J. Fluid Mech., vol. 262, 1994, pp. 75–110) through numerical simulations. To conduct the experiments, a deformable surface with a streamwise array of 16 independently controlled actuators was developed. A real-time particle image velocimetry (RT-PIV) system was also created for
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The structure of turbulence in unsteady flow over urban canopies J. Fluid Mech. (IF 3.7) Pub Date : 2024-04-16 Weiyi Li, Marco G. Giometto
The topology of turbulent coherent structures is known to regulate the transport of energy, mass and momentum in the atmospheric boundary layer (ABL). While previous research has primarily focused on characterizing the structure of turbulence in stationary ABL flows, real-world scenarios frequently deviate from stationarity, giving rise to nuanced and poorly understood changes in the turbulence geometry
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Characterization of partial wetting by CMAS droplets using multiphase many-body dissipative particle dynamics and data-driven discovery based on PINNs J. Fluid Mech. (IF 3.7) Pub Date : 2024-04-16 Elham Kiyani, Mahdi Kooshkbaghi, Khemraj Shukla, Rahul Babu Koneru, Zhen Li, Luis Bravo, Anindya Ghoshal, George Em Karniadakis, Mikko Karttunen
The molten sand that is a mixture of calcia, magnesia, alumina and silicate, known as CMAS, is characterized by its high viscosity, density and surface tension. The unique properties of CMAS make it a challenging material to deal with in high-temperature applications, requiring innovative solutions and materials to prevent its buildup and damage to critical equipment. Here, we use multiphase many-body
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Interplay of scales during the spatial evolution of energy-containing motions in wall-bounded turbulent flows J. Fluid Mech. (IF 3.7) Pub Date : 2024-04-16 Ezhilsabareesh Kannadasan, Callum Atkinson, Julio Soria
This article extends the previous investigation of the spatial evolution of energy-containing motions in wall-bounded turbulent flows (Kannadasan et al., J. Fluid Mech., vol. 955, 2023, R1) by examining their scale-interactions through spectral analysis based on the spanwise scale decomposition of turbulent kinetic energy and the Reynolds stress transport equation. The energy-containing motions located
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Cylinder flow and noise control by active base blowing J. Fluid Mech. (IF 3.7) Pub Date : 2024-04-16 Reza Maryami, Yu Liu
An extensive experimental investigation was undertaken to control the flow and noise characteristics influenced by vortex shedding from a circular cylinder by implementing air blowing at the base of the cylinder. The study synchronised near-field pressure and far-field noise measurements with the wake velocity field to understand the noise reduction mechanism of base blowing. Surface pressure fluctuations
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Mechanism for axial pattern formation of concentrated suspension in a horizontal rotating cylinder J. Fluid Mech. (IF 3.7) Pub Date : 2024-04-16 Sudarshan Konidena, Bernhard Vowinckel, Ryohei Seto, K. Anki Reddy, Anugrah Singh
We have performed numerical simulations to investigate the phenomenon of axial pattern formation exhibited by a non-neutrally buoyant concentrated suspension. Continuum modelling of the concentrated suspension is done using the suspension balance model to identify the underlying mechanism of the phenomenon. We demonstrate that axial concentration variations become amplified to axial bands owing to
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Peeling fingers in an elastic Hele-Shaw channel J. Fluid Mech. (IF 3.7) Pub Date : 2024-04-16 João V. Fontana, Callum Cuttle, Draga Pihler-Puzović, Andrew L. Hazel, Anne Juel
Using experiments and a depth-averaged numerical model, we study instabilities of two-phase flows in a Hele-Shaw channel with an elastic upper boundary and a non-uniform cross-section prescribed by initial collapse. Experimentally, we find increasingly complex and unsteady modes of air-finger propagation as the dimensionless bubble speed $Ca$ and level of collapse are increased, including pointed fingers
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Simulating the rheology of dense suspensions using pairwise formulation of contact, lubrication and Brownian forces J. Fluid Mech. (IF 3.7) Pub Date : 2024-04-15 Xuan Li, John R. Royer, Christopher Ness
Dense suspensions of solid particles in viscous liquid are ubiquitous in both industry and nature, and there is a clear need for efficient numerical routines to simulate their rheology and microstructure. Particles of micron size present a particular challenge: at low shear rates, colloidal interactions control their dynamics while at high rates, granular-like contacts dominate. While there are established
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Low-order modelling of three-dimensional surface waves in liquid film flow on a rotating disk J. Fluid Mech. (IF 3.7) Pub Date : 2024-04-15 Dong Ju Kim, Daegyoum Kim
Using low-dimensional numerical simulations, we investigate the characteristics of complex and three-dimensional surface waves in a liquid film flowing over a rotating disk, focusing on large flow rates from a nozzle. Existing integral boundary layer (IBL) models, which are based on spatially averaged variables along the direction normal to the disk surface, have primarily focused on the formation
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On the dynamics and wakes of a freely settling Platonic polyhedron in a quiescent Newtonian fluid J. Fluid Mech. (IF 3.7) Pub Date : 2024-04-15 Guodong Gai, Anthony Wachs
We investigate systematically the free settling of a single Platonic polyhedron in an unbounded domain filled with an otherwise quiescent Newtonian fluid. We consider a particle–fluid density mimicking a rock in water. Five Platonic polyhedrons of increasing sphericity are studied for a range of Galileo numbers $10 \leqslant \mathcal {G}a \leqslant 300$ . We construct a regime map in the parameter
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Aeroacoustics of a ducted fan ingesting an adverse pressure gradient boundary layer J. Fluid Mech. (IF 3.7) Pub Date : 2024-04-15 Feroz Ahmed, Ismaeel Zaman, Djamel Rezgui, Mahdi Azarpeyvand
The aeroacoustics of a boundary layer ingesting (BLI) ducted fan is investigated experimentally. The study examines a ducted fan immersed in an adverse streamwise pressure gradient turbulent boundary layer developed over a curved wall. Aeroacoustics measurements indicate that the noise from the BLI ducted fan results from a complex interaction among the fan, duct and the incoming boundary layer. The
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Different scenarios in sloshing flows near the critical filling depth J. Fluid Mech. (IF 3.7) Pub Date : 2024-04-12 A. Bardazzi, C. Lugni, O.M. Faltinsen, D. Durante, A. Colagrossi
In the present paper, the sloshing flow in a cuboid tank forced to oscillate horizontally is investigated with both experimental and numerical approaches. The filling depth chosen is $h/L=0.35$ (with h the water depth and L the tank height), which is close to the critical depth. According to Tadjbakhsh & Keller (J. Fluid Mech., vol. 8, issue 3, 1960, pp. 442–451), as the depth passes through this critical
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Electromagnetically driven flow in unsupported electrolyte layers: lubrication theory and linear stability of annular flow J. Fluid Mech. (IF 3.7) Pub Date : 2024-04-12 Andrey Pototsky, Sergey A. Suslov
We consider a thin horizontal layer of a non-magnetic electrolyte containing a bulk solution of salt and carrying an electric current. The layer is bounded by two deformable free surfaces loaded with an insoluble surfactant and is placed in a vertical magnetic field. The arising Lorentz force drives the electrolyte in the plane of the layer. We employ the long-wave approximation to derive general two-dimensional
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The dynamics of fibres dispersed in viscoelastic turbulent flows J. Fluid Mech. (IF 3.7) Pub Date : 2024-04-12 M.S. Aswathy, Marco Edoardo Rosti
This study explores the dynamics of finite-size fibres suspended freely in a viscoelastic turbulent flow. For a fibre suspended in Newtonian flows, two different flapping regimes were identified by Rosti et al. (Phys. Rev. Lett., vol. 121, issue 4, 2018, 044501): one dominated by time scales from the flow, and another dominated by time scales associated with its natural frequency. We explore in this
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Departure from the statistical equilibrium of large scales in forced three-dimensional homogeneous isotropic turbulence J. Fluid Mech. (IF 3.7) Pub Date : 2024-04-12 Mengjie Ding, Jin-Han Xie, Jianchun Wang
We study the statistically steady states of the forced dissipative three-dimensional homogeneous isotropic turbulence at scales larger than the forcing scale in real separation space. The probability density functions (p.d.f.s) of longitudinal velocity difference at large separations are close to, but deviate from, Gaussian, measured by their non-zero odd parts. The analytical expressions of the third-order
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Turbulence induced by a swarm of rising bubbles from coarse-grained simulations J. Fluid Mech. (IF 3.7) Pub Date : 2024-04-12 Rémi Zamansky, Florian Le Roy De Bonneville, Frédéric Risso
We performed numerical simulations of a homogeneous swarm of bubbles rising at large Reynolds number, $Re=760$ , with volume fractions ranging from 1 % to 10 %. We consider a simplified model in which the interfaces are not resolved, but which allows us to simulate flows with a large number of bubbles and to emphasize the interactions between bubble wakes. The liquid phase is described by solving,
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On the low-frequency flapping motion in flow separation J. Fluid Mech. (IF 3.7) Pub Date : 2024-04-12 Xingjun Fang, Zhan Wang
Transitional separating flow induced by a rectangular plate subjected to uniform incoming flow at Reynolds number (based on the incoming velocity and half plate height) 2000 is investigated using direct numerical simulation. The objective is to unveil the long-lasting mystery of low-frequency flapping motion (FM) in flow separation. At a fixed streamwise-vertical plane or from the perspective of previous
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Emergence of a hexagonal pattern in shear-thickening suspensions under orbital oscillations J. Fluid Mech. (IF 3.7) Pub Date : 2024-04-12 Li-Xin Shi, Meng-Fei Hu, Song-Chuan Zhao
A dense particle suspension under shear may lose its uniform state to large local density and stress fluctuations, which challenge the mean-field description of the system. Here, we explore the novel dynamics of a non-Brownian suspension under orbital oscillations, where localized density waves along the flow direction appear beyond an excitation frequency threshold and self-organize into a hexagonal
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Inertial coalescence of drops with some viscosity J. Fluid Mech. (IF 3.7) Pub Date : 2024-04-12 Edward Beaty, John R. Lister
When two fluid drops touch, they coalesce due to surface tension. At early times, there is only a relatively small fluid bridge joining the drops. An asymptotic solution is presented for an inertial regime of early-time coalescence, in which inertial forces balance surface tension at leading order. It is demonstrated that viscosity nevertheless has a leading-order effect. Radial momentum is created
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Wave front perturbation effect on the variability of monopile wave impact loads J. Fluid Mech. (IF 3.7) Pub Date : 2024-04-12 Arefhossein Moalemi, Henrik Bredmose, Trygve Kristiansen, Fabio Pierella
The slamming wave force and pressure variabilities for monopile wave impacts are studied as functions of wave breaking shape and transverse perturbations on the breaking wave front. The impacting wave topology is characterized as slosh, flip-through, $\varOmega$ , overturning and fully broken. Fifty test repetitions are conducted for each type of wave impact to assess the variability of force impulse
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Stable three-dimensional vortex families consistent with Jovian observations including the Great Red Spot J. Fluid Mech. (IF 3.7) Pub Date : 2024-04-12 Aidi Zhang, Philip S. Marcus
Detailed observations of the velocities of Jovian vortices exist at only one height in the atmosphere, so their vertical structures are poorly understood. This motivates this study that computes stable three-dimensional, long-lived planetary vortices that satisfy the equations of motion. We solve the anelastic equations with a high-resolution pseudo-spectral method using the observed Jovian atmospheric
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Data-driven state-space and Koopman operator models of coherent state dynamics on invariant manifolds J. Fluid Mech. (IF 3.7) Pub Date : 2024-04-12 C. Ricardo Constante-Amores, Michael D. Graham
The accurate simulation of complex dynamics in fluid flows demands a substantial number of degrees of freedom, i.e. a high-dimensional state space. Nevertheless, the swift attenuation of small-scale perturbations due to viscous diffusion permits in principle the representation of these flows using a significantly reduced dimensionality. Over time, the dynamics of such flows evolves towards a finite-dimensional
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Direct numerical simulations of microlayer formation during heterogeneous bubble nucleation J. Fluid Mech. (IF 3.7) Pub Date : 2024-04-12 M. Saini, X. Chen, S. Zaleski, D. Fuster
In this article, we present direct numerical simulation results for the expansion of spherical cap bubbles attached to a rigid wall due to a sudden drop in the ambient pressure. The critical pressure drop beyond which the bubble growth becomes unstable is found to match well with the predictions from classical theory of heterogeneous nucleation imposing a quasi-static bubble evolution. When the pressure
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A comprehensive study on the roles of viscosity and heat conduction in shock waves J. Fluid Mech. (IF 3.7) Pub Date : 2024-04-12 Qingbo Zhu, You Wu, Wenyuan Zhou, Qingchun Yang, Xu Xu
Shock waves are of great interest in many fields of science and engineering, but the mechanisms of their formation, maintenance and dissipation are still not well understood. While all transport processes existing in a shock wave contribute to its compression and irreversibility, they are not of equal importance. To figure out the roles of viscosity and heat conduction in shock transition, the existence
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Evolution of wind-induced wave groups in water of finite depth J. Fluid Mech. (IF 3.7) Pub Date : 2024-04-12 Montri Maleewong, Roger Grimshaw
The generation of water waves by wind is a fundamental and much-studied problem of scientific and operational concern. One mechanism that has obtained a wide degree of acceptance and use is the Miles air shear flow instability theory in which water waves grow due to energy transfer from the air at a critical level where the wave phase speed matches the wind speed. In this paper we revisit and extend
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New momentum integral equation applicable to boundary layer flows under arbitrary pressure gradients J. Fluid Mech. (IF 3.7) Pub Date : 2024-04-11 Tie Wei, Zhaorui Li, Yanxing Wang
By incorporating the traditionally overlooked advective term in the wall-normal momentum equation, a new momentum integral equation is developed for two-dimensional incompressible turbulent boundary layers under arbitrary pressure gradients. The classical Kármán's integral arises as a special instance of the new momentum integral equation when the pressure gradient is weak. The new momentum integral
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Fluid–structure–surface interaction of a flexibly mounted pitching and plunging flat plate in proximity to the free surface J. Fluid Mech. (IF 3.7) Pub Date : 2024-04-11 Hadi Samsam-Khayani, Banafsheh Seyed-Aghazadeh
This experimental study investigates the fluid–structure–surface interactions of a flexibly mounted rigid plate in axial flow, focusing on flow-induced vibration (FIV) response and vortex dynamics of the system within a reduced velocity range of $U^*=0.29\unicode{x2013}8.73$ , corresponding to a Reynolds number range of $Re=518\unicode{x2013}15\,331$ . The plate, with one and two degrees of freedom
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Turbulent flows over porous lattices: alteration of near-wall turbulence and pore-flow amplitude modulation J. Fluid Mech. (IF 3.7) Pub Date : 2024-04-11 Seyed Morteza Habibi Khorasani, Mitul Luhar, Shervin Bagheri
Turbulent flows over porous lattices consisting of rectangular cuboid pores are investigated using scale-resolving direct numerical simulations. Beyond a certain threshold which is primarily determined by the wall-normal Darcy permeability, ${{\mathsf{K}}_y}$ , near-wall turbulence transitions from its canonical regime, marked by the presence of streak-like structures, to another marked by the presence