New Papers in Fluid Mechanics

Author(s): Prem Chand Chandolu and Balachandra Suri

Horizontally driven shallow electrolyte flows are widely employed laboratory analogs of oceanic and two-dimensional flows. Although previous studies investigated the presence of three-dimensional circulations within the bulk of turbulent shallow flows, relatively little attention was paid to whether the fluid layer thickness itself remains spatiotemporally uniform. In this study, we report experimental measurements of free-surface deformations in shallow flows. For certain Reynolds number and fluid layer height combinations that characterize the flow, we show that the free surface undergoes significant deformation, thereby rendering an otherwise shallow flow geometrically three-dimensional.

[Phys. Rev. Fluids 11, 044801] Published Mon Apr 06, 2026

Author(s): Qiwei Chen and C. Ricardo Constante-Amores

Rayleigh–Bénard convection is a canonical system for studying turbulent heat transport, yet controlling it at high Rayleigh numbers remains computationally prohibitive. Here, we combine data-driven manifold dynamics with reinforcement learning to construct a reduced-order environment that enables efficient training of control policies. When deployed in direct numerical simulations, the learned strategies achieve up to 23% reduction in heat transfer by stabilizing near-wall dynamics and suppressing plume emission. This work establishes a scalable and physically interpretable route to controlling high-dimensional turbulent flows.

[Phys. Rev. Fluids 11, 044903] Published Mon Apr 06, 2026

Author(s): Githin Tom Zachariah and Harry E. A. Van den Akker

The Lattice Boltzmann Method (LBM) exploits its nearly incompressible nature to relate local density to pressure, avoiding iterative Poisson solvers. However, this pressure–density coupling makes robust extension of LBM to the Two-Fluid equations particularly challenging. In this work, we propose two complementary approaches to address this problem: a mixture model for dilute suspensions prioritizing computational efficiency, and a well-balanced formulation employing a pressure-free LBM with an explicit Poisson solver for maximum accuracy. Both methods are validated on standard benchmarks and isotropic turbulent flows, demonstrating accuracy and robustness across challenging flow regimes.

[Phys. Rev. Fluids 11, 044904] Published Mon Apr 06, 2026

Author(s): Marco Raiola and Jochen Kriegseis

Advective flows are often characterized by wavepackets. Hilbert proper orthogonal decomposition (HPOD) extracts these coherent structures from flow field data by exploiting their representation as modulated traveling waves. HPOD is a complex valued extension of proper orthogonal decomposition, where the analytic signal is obtained via a Hilbert transform applied either in time (conventional HPOD) or along the advection direction (space-only HPOD). Both HPOD formulations yield equivalent decompositions for advecting wavepackets. The resulting modes exhibit amplitude and frequency modulation in space and time, enabling instantaneous, local flow analysis.

[Phys. Rev. Fluids 11, 044905] Published Mon Apr 06, 2026

Author(s): Ankit Gautam and Tim Berk

The decay of turbulent kinetic energy is strongly influenced by large-scale coherent structures. Using a synthetic-jet-driven turbulence facility and the Proper Orthogonal Decomposition (POD) method, we show that slowly decaying modes persistent across repeated experiments bias the observed decay rates. Removing these modes reveals a stochastic turbulence field with decay consistent with classical theory. This framework helps resolve discrepancies in reported decay rates and distinguishes whether variations arise from specific coherent modes or changes in the underlying stochastic turbulence.

[Phys. Rev. Fluids 11, 044906] Published Mon Apr 06, 2026

Author(s): Niccolò Tonioni, Lionel Agostini, Franck Kerhervé, Laurent Cordier, and Ricardo Vinuesa

Sparse-sensing reconstruction of turbulent flows remains challenging due to high sensor requirements and poor fidelity near solid interfaces. VIVALDy, a machine learning framework, addresses these limitations through a hybrid β-Variational Autoencoder-Generative Adversarial Network (β-VAE-GAN) and a bidirectional transformer to compress flow fields into a compact latent space and predict temporal evolution from minimal inputs. Masked convolutions are used to enhance fidelity at solid boundaries. Validated against experimental data for a moving cylinder, the framework reconstructs diverse fluid-structure interaction regimes using only cylinder displacement.

[Phys. Rev. Fluids 11, 044902] Published Fri Apr 03, 2026

Author(s): Haojun Zhao, Wei Wang, Sheng Xu, and Bing Wang

When a cylindrical droplet containing a solid particle rod interacts with a planar shock wave, a complex evolution of its internal wave structure ensues. We simulate the interaction numerically, and the ray analysis method is specifically adopted to analyze the evolution of the wave structure in detail. The results show that the particle rod separates negative pressure regions more distinctly, raises the droplet’s minimum pressure, leads to cavitation at high shock wave intensity, and that particle eccentricity influences wave structure and cavitation. These findings are expected to contribute to advancements in fuel atomization and biomedical applications.

[Phys. Rev. Fluids 11, 044301] Published Thu Apr 02, 2026

Author(s): Santiago J. Benavides and Miguel D. Bustamante

The transfer of energy and other conserved quantities across scales is a central aspect of out-of-equilibrium systems such as turbulent hydrodynamic flows. Despite its role in the few predictive theories that exist, a dynamical understanding of what determines said transfer (and its direction in scale) has yet to be established. In this study, we investigate how the dynamics of complex Fourier velocity phases influence the flux of conserved quantities in simplified (“shell”) models of hydrodynamic turbulence. We develop an analytically tractable model for the statistics of the phases, validate the model using simulations, and use the model to predict properties of the energy cascade.

[Phys. Rev. Fluids 11, 044601] Published Thu Apr 02, 2026

Author(s): Jun-Yang Li, Dong Sun, Si-Wei Dong, Peng-Xin Liu, and Xian-Xu Yuan

This study examines interscale energy transfer, conventionally denoted as the “energy cascade,” in forced homogeneous isotropic turbulence. By employing spatial filtering techniques, the turbulent kinetic energy is decomposed into distinct large- and small-scale components, as well as local- and sub…

[Phys. Rev. E 113, 045101] Published Wed Apr 01, 2026

Author(s): Alireza Khoshnood, Vedad Dzanic, Zhongzheng Wang, and Emilie Sauret

Viscoelastic natural convection differs from its purely Newtonian analogue due to polymer-induced elastic stresses and shear-dependent viscosity. When coupled to buoyancy-driven flow, these viscoelastic effects modify velocity and thermal boundary layers. We examine the role of cavity aspect ratio in governing the spatial distribution of elastic stresses. Coupled effects of cavity aspect ratio and viscoelasticity determine whether polymer forces enhance or suppress convection, thus affecting local and overall heat transfer performance. These insights offer guidance for controlling heat transfer under low-inertia, with implications for thermal management and process design in polymeric flows.

[Phys. Rev. Fluids 11, 043501] Published Wed Apr 01, 2026

Author(s): Yasushi Mino, Hazuki Tanaka, Koichi Nakaso, Kuniaki Gotoh, and Rei Tatsumi

Numerical simulations of sheared particle suspensions often require large domains to avoid wall effects. We implement Lees–Edwards boundary conditions in particle-resolved Lattice Boltzmann Method–Discrete Element Method (LBM–DEM) simulations to model homogeneous shear flows without physical boundaries. The method enables computationally efficient simulations while resolving particle-scale hydrodynamic interactions. It provides a practical tool for studying suspension rheology quantitatively by capturing how particles interact with the surrounding fluid and with each other across a range of concentrations.

[Phys. Rev. Fluids 11, 044901] Published Wed Apr 01, 2026

Author(s): Reza Azadi and David S. Nobes

While drag reduction in fully developed viscoelastic flows is widely studied, the combined influence of polymer additives and strong spatial acceleration remains largely unexplored. This study employs high-resolution velocimetry to examine near-wall turbulence in semidilute polymer solutions subjected to varying favorable pressure gradients. The results demonstrate that the interplay of viscoelasticity and acceleration profoundly suppresses Reynolds shear stresses, driving the boundary layer toward a distinct quasi-relaminarized state dominated by elastic effects.

[Phys. Rev. Fluids 11, 034611] Published Tue Mar 31, 2026

Author(s): Ankan Biswas, Amal Manoharan, and Ashwin Joy

Topological entropy serves as a viable candidate for quantifying mixing and complexity of a highly chaotic system. Particularly in turbulence, this is determined as the exponential stretching rate of a fluid material line that typically necessitates a Lagrangian description. We extend our recent wor…

[Phys. Rev. E 113, 035107] Published Mon Mar 30, 2026

Author(s): Saideep Pavuluri, Thomas Daniel Seers, Ali Saeibehrouzi, Ran Holtzman, Soroush Abolfathi, Petr Denissenko, and Harris Sajjad Rabbani

Controlling capillary fingering via patterned porous media (PPM) optimizes industrial processes (e.g., fuel cells). We introduce a 2D Zoned Sequential Deposition method to fabricate PPM with tunable porous media features. Direct numerical simulations across varying capillary numbers and heterogeneity factors show that highly heterogeneous PPM (having larger pore-diameter contrasts between different zones) promotes structured drainage: flow follows underlying porous microstructure, draining through large pores with less than 10% occupancy of finer spaces. This coupling of fabricated morphology and flow behavior provides a framework for designing porous materials with predictable flow patterns.

[Phys. Rev. Fluids 11, 034001] Published Thu Mar 26, 2026

Author(s): M. Noseda, B. L. Español, P. D. Mininni, and P. J. Cobelli

Helicity, the volume integral of the velocity-vorticity scalar product, is a key dynamical invariant encoding flow topology; however, measuring it in turbulence is a significant challenge due to the requirement for high-resolution velocity gradients. We introduce chirality tomography, a Lagrangian method that reconstructs three-dimensional helicity maps from the entanglement of particle trajectories. By establishing a robust proxy between trajectory linking and local helicity, we provide the first spatially resolved maps of chiral structures in fully developed turbulence. The approach bridges trajectory-level topology with fundamental physics, with a practical diagnostic for complex flows.

[Phys. Rev. Fluids 11, 034609] Published Wed Mar 25, 2026

Author(s): G. A. Gerolymos and I. Vallet

In turbulent flows of dilute gases, the amplitudes and correlations of the turbulent fluctuations of the thermodynamic variables (pressure, density and temperature), satisfy exact nonlinear compatibility relations and inequalities. These define realizability constraints on the thermodynamic turbulence structure, valid from the quasi-incompressible-flow limit to hypersonic Mach numbers. Furthermore, the ratios between fluctuation intensities define the signs of correlations between the thermodynamic fluctuations, and define bivariate mappings of the thermodynamic turbulence structure.

[Phys. Rev. Fluids 11, 034610] Published Wed Mar 25, 2026

Author(s): Qinran Wei, Suyu Ding, Yang Zhao, Yuanpeng Ma, Dachuan Sang, Dong Zhang, and Xiasheng Guo

Numerical simulations of surface acoustic wave (SAW)-induced acoustic streaming are highly sensitive to the choice of second-order boundary conditions. This study systematically compares the no-slip (NS) and Stokes slip (SD) boundary conditions through different numerical approaches. Two- and three-…

[Phys. Rev. E 113, 035105] Published Wed Mar 25, 2026

Author(s): Lachezar S. Simeonov

We derive the quantum potential directly from the material derivative of the osmotic velocity and formulate a two-fluid model that reproduces the Madelung equations. Interactions between the two fluids are included but remain secondary. The framework is generalized to incorporate electromagnetic fie…

[Phys. Rev. E 113, 035106] Published Wed Mar 25, 2026

Author(s): Írio M. Coutinho and José A. Miranda

In this work, we investigate the possibility of suppressing injection-driven, viscous fingering instabilities in a radial Hele-Shaw cell, via the action of centrifugal forces. We consider the situation in which an inviscid fluid of negligible density is injected into a viscous and denser one, while …

[Phys. Rev. E 113, 035103] Published Tue Mar 24, 2026

Author(s): Haoyu Liu, Edidiong Michael Umana, and Xiufeng Yang

The interaction between flexible bodies and fluids is very complex, however, studying this mechanism helps us understand how natural plants deform in response to fluid flow to prevent structural damage. Due to the complexity of fluid-structure interaction, there is a lack of methods for quickly and …

[Phys. Rev. E 113, 035104] Published Tue Mar 24, 2026