Latest papers in fluid mechanics

Transient energy growth in channel flow with compliant walls

Physical Review Fluids - Tue, 04/09/2024 - 11:00

Author(s): Frédéric Alizard, Benoît Pier, and Smail Lebbal

Shear flows in contact with compliant boundaries exhibit a rich dynamics involving traveling-wave-flutter, Tollmien-Schlichting, as well as divergence instabilities. In this context, maximum transient growth effects are the result of optimal energy exchanges during the fluid-structure interaction process. The present investigation studies the detailed contribution of the different interacting modes. In particular, it is found that the optimal gain may be associated with a large-amplitude oscillatory behavior and that wall-compliance enhances this phenomenon.

[Phys. Rev. Fluids 9, 043905] Published Tue Apr 09, 2024

Lagrangian coherent structures control solute dispersion in heterogeneous poroelastic media

Physical Review Fluids - Tue, 04/09/2024 - 11:00

Author(s): Junhong Wu, Daniel Lester, Michael G. Trefry, and Guy Metcalfe

This study focuses on how Lagrangian coherent structures (LCSs) control solute dispersion in heterogeneous poroelastic media (HPM). We show how interactions between medium compressibility, conductivity heterogeneity, and periodic forcing give rise to complex flows and diverse LCS types (KAM islands, chaotic saddles, etc) that have profound impacts on diffusive solute transport (main image) that do not arise in the steady counterpart (inset). Strongly anomalous transport impacts both spatial moments and residence time distributions and persists at low Péclet numbers. This study reveals the complex transport phenomena that can arise in HPM and shows how LCSs govern solute dispersion.

[Phys. Rev. Fluids 9, 044501] Published Tue Apr 09, 2024

Lagrangian modeling of a nonhomogeneous turbulent shear flow: Molding homogeneous and isotropic trajectories into a jet

Physical Review Fluids - Tue, 04/09/2024 - 11:00

Author(s): Bianca Viggiano, Thomas Basset, Mickaël Bourgoin, Raúl Bayoán Cal, Laurent Chevillard, Charles Meneveau, and Romain Volk

We propose a novel approach to accurately model complex flow, ultimately predicting the behavior of a turbulent jet by molding a set of velocity signals input from an idealized flow (readily available from numerical databases online). The model uses fundamental properties of the jet, such as velocity means and standard deviations, easily accessible from textbooks, experiments, or low-order simulations (RANS, LES). The modeled jet reproduces many subtle and intricate properties of the turbulent flow, including the intermittent extreme events known to exist in turbulent flows, which have been typically thought of as not capable of being captured with current modeling techniques.

[Phys. Rev. Fluids 9, 044604] Published Tue Apr 09, 2024

Experimental study of the turbulence ingestion noise of rotor blades

Physical Review Fluids - Tue, 04/09/2024 - 11:00

Author(s): Han Wu, Yuhong Li, Xin Zhang, Siyang Zhong, and Xun Huang

In this work, we experimentally investigate turbulence ingesting rotor noise under various thrusting states. The broadband noise caused by turbulence ingestion is found to dominate at the normalized frequency range of fR/U∞ = 20 to 80 when the rotor is under low-thrusting conditions. Results also suggest that the turbulence ingestion broadband noise can be scaled by Mach number scaling of M∞2Mc4, where M∞ is the freestream Mach number, and Mc is the corresponding blade tip Mach number.

[Phys. Rev. Fluids 9, 044801] Published Tue Apr 09, 2024

Internally heated and fully compressible convection: Flow morphology and scaling laws

Physical Review Fluids - Tue, 04/09/2024 - 11:00

Author(s): Whitney T. Powers, Evan H. Anders, and Benjamin P. Brown

In stars and planets natural processes heat convective flows in the bulk of a convective region rather than at hard boundaries. Internally heated convection has been studied extensively in incompressible fluids, but the effects of stratification and compressibility have not been examined in detail. In this work, we study fully compressible convection driven by a spatially uniform heating source in a suite of two- and three-dimensional Cartesian, hydrodynamic simulations. We characterize how Mach, Reynolds, and Nusselt numbers scale with the characteristic strength of the internal heat source. We also measure kinetic energy power spectra and discuss the flow morphologies.

[Phys. Rev. Fluids 9, 043501] Published Tue Apr 09, 2024

Floquet stability analysis of pulsatile flow in toroidal pipes

Physical Review Fluids - Tue, 04/09/2024 - 11:00

Author(s): J. Simon Kern, Valerio Lupi, and Dan S. Henningson

Unsteady flows in curved pipes are ubiquitous in science and engineering but their stability characteristics are not well understood in most cases of practical interest. We study the linear stability of pulsatile flow in the archetypal configuration of a toroidal pipe, which appears e.g. in aortic blood flow. The Floquet stability analysis of the harmonically forced system reveals that the curvature leads to nonlinear interactions in the baseflow andconsiderable stabilization that can be orders of magnitude larger than in the corresponding planar case. The figure shows a typical snapshot of the streamwise velocity field in a torus subject to a pulsating pressure gradient.

[Phys. Rev. Fluids 9, 043906] Published Tue Apr 09, 2024

Dense fluid transport through nanoporous graphene membranes in the limit of steric exclusion

Physical Review Fluids - Tue, 04/09/2024 - 11:00

Author(s): Runfeng Zhou, Mathew M. Swisher, Akshay Deshmukh, Chengzhen Sun, John H. Lienhard, and Nicolas G. Hadjiconstantinou

We develop a model that describes the permeance of simple fluids as well as small hydrocarbon molecules through nanoporous, atomically thin membranes. The model is in agreement with molecular dynamics simulations for a wide range of pore sizes, including pores approaching the steric exclusion limit, as needed for understanding separation processes using such membranes.

[Phys. Rev. Fluids 9, 044202] Published Tue Apr 09, 2024

Effects of wall conductivities on magnetoconvection in a cube

Physical Review Fluids - Mon, 04/08/2024 - 11:00

Author(s): Hai-Tao Zhu, Long Chen, and Ming-Jiu Ni

This numerical simulation investigates the vertical convection of liquid metal with varying magnetic fields and wall conductivities. The applied horizontal magnetic field alters plume dynamics and topology, leading to a more coherent large-scale flow structure but weakening convection through Joule dissipation. This competition between rectification and magnetic damping determines the magnetic field’s impact on heat transfer, with the quasi-two-dimensional state being the threshold. Our analysis demonstrates that while the plume area remains constant, condensation of coherent structures enhances horizontal heat transport per unit area, significantly improving overall heat transfer.

[Phys. Rev. Fluids 9, 043701] Published Mon Apr 08, 2024

Dynamics of rigid fibers interacting with triangular obstacles in microchannel flows

Physical Review Fluids - Mon, 04/08/2024 - 11:00

Author(s): Zhibo Li, Clément Bielinski, Anke Lindner, Olivia du Roure, and Blaise Delmotte

We combine experiments and numerical simulations to investigate the interaction between a rigid fiber and a triangular obstacle in a microfluidic channel. We find different dynamics depending on the initial position and orientation of the fiber. We show that these dynamics are dictated by the fiber configuration in the vicinity of the obstacle. Some dynamics induce a cross-stream migration which grows with the fiber length. Our findings could in the future be used to design and optimize microfluidic sorting devices to sort rigid fibers by length.

[Phys. Rev. Fluids 9, 044302] Published Mon Apr 08, 2024

Transitional pressure drop in a cavitied microchannel

Physical Review Fluids - Fri, 04/05/2024 - 11:00

Author(s): Yan Yan Liu, Sjouke W. Schekman, Mo Xiao Li, Tian Jian Lu, and Tongbeum Kim

A flow progression from laminar flow slippage to rotational vortices in cavitied microchannels is shown to cause a reversal of flow resistance, i.e. a reduced flow resistance at low Reynolds numbers compared to an unmodified microchannel but a comparatively higher flow resistance at high Reynolds numbers. Furthermore, an earlier transition of initial laminar flow to turbulent flow is suggested to be triggered by instabilities generated along shear layers, formed between the mainstream flow and rotational vortices in each cavity that modifies the sidewalls of microchannels.

[Phys. Rev. Fluids 9, 044201] Published Fri Apr 05, 2024

Machine-learning-augmented domain decomposition method for near-wall turbulence modeling

Physical Review Fluids - Fri, 04/05/2024 - 11:00

Author(s): Shiyu Lyu, Jiaqing Kou, and Nikolaus A. Adams

In this work, we developed a novel framework for incorporating the near-wall non-overlapping domain decomposition (NDD) method with the machine learning technique. It allows the solution to be calculated with a Robin-type (slip) wall boundary condition on a relatively coarse mesh and then be corrected in the near-wall region by solving the thin boundary-layer equations on a fine subgrid. Through an estimated turbulent viscosity profile provided by a neural network, the proposed method can be easily extended to different turbulence models and achieve commendable accuracy for the test cases of turbulent wall-bounded flows at various Reynolds numbers.

[Phys. Rev. Fluids 9, 044603] Published Fri Apr 05, 2024

Breaking the symmetry of a wavy channel alters the route to chaotic flow

Physical Review E - Thu, 04/04/2024 - 11:00

Author(s): Mohammad Hossein Doranehgard, Nader Karimi, Iman Borazjani, and Larry K. B. Li

We numerically explore the two-dimensional, incompressible, isothermal flow through a wavy channel, with a focus on how the channel geometry affects the routes to chaos at Reynolds numbers between 150 and 1000. We find that (i) the period-doubling route arises in a symmetric channel, (ii) the Ruelle…

[Phys. Rev. E 109, 045103] Published Thu Apr 04, 2024

Microcontinuum approach to multiscale modeling of multiphase reactive flow during mineral dissolution

Physical Review Fluids - Thu, 04/04/2024 - 11:00

Author(s): Zhiying Liu (刘志颖), Qianghui Xu (许强辉), Junyu Yang (杨君宇), Kai H. Luo (罗开红), and Lin Shi (史琳)

The existing hybrid-scale micro-continuum approach faces difficulties in numerical diffusion issues at the gas-liquid interface and the solid boundary. This article proposes a multiscale compressive Continuum Species Transfer (MC-CST) scheme and a concentration extrapolation algorithm to improve the accuracy of two-phase reactive flow simulations. Furthermore, a case study simulating calcite dissolution in a porous medium is presented to underscore the importance of multiscale fluid-rock interactions for an in-depth comprehension of the dissolution regime.

[Phys. Rev. Fluids 9, 043801] Published Thu Apr 04, 2024

Learning in two dimensions and controlling in three: Generalizable drag reduction strategies for flows past circular cylinders through deep reinforcement learning

Physical Review Fluids - Thu, 04/04/2024 - 11:00

Author(s): Michail Chatzimanolakis, Pascal Weber, and Petros Koumoutsakos

We present the automated discovery of control strategies for drag reduction in cylinder flows. Reinforcement Learning algorithms discover control strategies for two-dimensional configurations that generalize to three dimensional flows. We discuss the physical processes involved in the drag reduction mechanisms along with their generalization capabilities. This work demonstrates a practical approach to handling the computationally intensive task of deploying Reinforcement Leaning for bluff body flow control problems: namely train in 2D and control in 3D.

[Phys. Rev. Fluids 9, 043902] Published Thu Apr 04, 2024

Passive stabilization of crossflow instabilities by a reverse lift-up effect

Physical Review Fluids - Thu, 04/04/2024 - 11:00

Author(s): Jordi Casacuberta, Stefan Hickel, and Marios Kotsonis

A physical mechanism has been identified through which a small surface add-on to a swept (angled-back) aircraft wing can delay the development of turbulent disorganized airflow. To reduce the aerodynamic drag of an aicraft, it is important to maximize the extent of smooth laminar airflow around its wings. The mechanism, termed “reverse lift-up effect”, dampens out the critical instability waves leading to turbulent airflow over swept aircraft wings under certain conditions. This may be achieved through particular design of a surface pattern on the aicraft wings. Overall, the present findings aim to contribute to novel design methodologies for future generations of laminar aicraft wings.

[Phys. Rev. Fluids 9, 043903] Published Thu Apr 04, 2024

Heat transfer and transport property contrast effects on the compressible Rayleigh-Taylor instability

Physical Review Fluids - Thu, 04/04/2024 - 11:00

Author(s): Kevin Cherng, Sanjiva Lele, and Daniel Livescu

We systematically examine how heat conduction between two fluids at different temperatures, large contrasts in transport properties, and sudden changes in transport properties can affect the fully compressible Rayleigh-Taylor instability (RTI) using direct numerical simulations. These variations cause departures from the classical self-similar development of the RTI, along with misalignment between regions of mixing and regions of most intense turbulent activity. Under certain conditions, dynamical quantities such as vorticity and dissipation appear to depend only on the transport properties and not on past flow history.

[Phys. Rev. Fluids 9, 043904] Published Thu Apr 04, 2024

Revisiting Taylor's hypothesis in homogeneous turbulent shear flow

Physical Review Fluids - Wed, 04/03/2024 - 11:00

Author(s): Frank G. Jacobitz and Kai Schneider

Taylor’s hypothesis of frozen flow is revisited in homogeneous turbulent shear flow by examining the cancellation properties of Eulerian and convective accelerations at different spatial flow scales. The anti-alignment in the joint pdf given in the figure shows that the Eulerian and convective accelerations cancel for small scales of the turbulent motion, indicating that Taylor’s hypothesis holds. This is not so for the large-scale motion of homogeneous turbulent shear flow.

[Phys. Rev. Fluids 9, 044602] Published Wed Apr 03, 2024

Optimal external forces of the lock-in phenomena for flow past an inclined plate in uniform flow

Physical Review E - Tue, 04/02/2024 - 11:00

Author(s): Makoto Iima

We theoretically studied the optimal control, frequency lock-in, and phase lock-in phenomena due to the spatially localized periodic forcing in flow past an inclined plate. Although frequency lock-in is evident in many fluid phenomena, especially fluid-structure interactions, not many researchers ha…

[Phys. Rev. E 109, 045102] Published Tue Apr 02, 2024

Finite speed of sound effects on asymmetry in multibubble cavitation

Physical Review Fluids - Tue, 04/02/2024 - 11:00

Author(s): Mandeep Saini, Youssef Saade, Daniel Fuster, and Detlef Lohse

Cavitation bubbles are present in a plethora of industrial and medical applications, and their understanding proves crucial to the development and tuning processes. In this study, we perform three dimensional direct numerical simulations (DNS) of multiple cavitation bubbles driven by pressure waves. Similarly observed in previously conducted experiments, it is found that these bubbles can exhibit an asymmetry in the direction of wave propagation. We show that this asymmetry is a consequence of the force induced by the wave on the bubbles, due to the finite speed of sound in the liquid medium.

[Phys. Rev. Fluids 9, 043602] Published Tue Apr 02, 2024

Mutual interaction of a collapsing bubble and a nearby viscoelastic solid

Physical Review Fluids - Tue, 04/02/2024 - 11:00

Author(s): Jihoo Moon, Ehsan Mahravan, and Daegyoum Kim

This work investigates the interaction of a viscoelastic solid and a nearby collapsing bubble, using numerical simulations. The Deborah number, which quantifies the relative time scales of solid deformation and bubble dynamics, is found to effectively characterize the bubble-solid interaction. Analyses on the temporal distribution of energy components and the imbalance in pressure distribution surrounding the bubble reveal the rationale behind changes in bubble behaviors with respect to the viscosity and elasticity of the solid. Furthermore, the solid deformation induced by an expanding and collapsing bubble and the shape of the crater formed by a bubble jet are examined.

[Phys. Rev. Fluids 9, 043603] Published Tue Apr 02, 2024


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