Physical Review Fluids

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): 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): 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): Bapan Mondal, Shubhra Sahu, and Somnath Bhattacharyya

Present continuum based modified electrokinetic model capture the nonclassical pattern of the electric double layer arises in the strong coupling regime i.e., layered structure of ions, counterion saturation, overscreening of surface charge, and reversal in electroosmotic flow. Based on the present modified model we have established qualitative agreement with several experimental observations, which the mean-field based models fails to envisage. The short-range effects on ion transport and their impact on membrane polarization are quantified in this study, which has not been addressed in previous studies. It may provide useful insights on tuning the electroosmosis and particle trapping.

[Phys. Rev. Fluids 11, 034202] Published Tue Mar 24, 2026

Author(s): Pritpal Matharu, Bartosz Protas, and Tsuyoshi Yoneda

A key open question in turbulence research concerns the nature of fluid motions that can produce a self-similar energy cascade consistent with Kolmogorov’s statistical theory of turbulence. We approach this problem by considering the one-dimensional viscous Burgers equation as a toy model, and frame the question in terms of a family of partial-differential-equation-constrained optimization problems which are solved numerically. Our results represent a successful effort to construct time-dependent solutions of this model characterized by self-similar energy transfers, providing a framework that may be used to search for self-similar behavior in three-dimensional turbulence.

[Phys. Rev. Fluids 11, 034608] Published Mon Mar 23, 2026

Author(s): Yicong Fu, Zhengyang Liu, Samir Tandon, Jake Gelfand, and Sunghwan Jung

Flexible vortex generators enhance heat and mass transport, but most studies focus on solid, non-porous panels or passive flexible reeds. Inspired by porous, compliant fish-gill filaments, we demonstrate the mixing benefit of pitching flexible perforated panels. Pitching drives unsteady entrainment; perforation yields spatially discretized vortices without a conventional leading-edge contribution, while chord-wise flexibility sustains mixing via wake-mode transitions. We examined the Lagrangian coherent structures to link vortex dynamics to convective–diffusive transport, and proposed three indices to quantify mixing by uniformity, mean increase, and spatial dispersion.

[Phys. Rev. Fluids 11, 034703] Published Mon Mar 23, 2026

Author(s): A. Roccon, G. Amati, L. Brandt, D. Calhoun, P. Costa, W. Lu, S. Pirozzoli, D. Richter, M. Umair, D. You, T. Zahtila, and C. Marchioli

Resolving turbulent flows pushes both computations and algorithms to their limits. As a result, high-fidelity turbulence simulations increasingly rely on GPU-accelerated solvers that adapt to massive parallelism and memory constraints to overcome the computational limits of CPU-based solvers. This review maps the rapidly expanding ecosystem of GPU-accelerated DNS and LES codes for single- and multiphase turbulence for both compressible and incompressible flow, analyzing algorithmic strategies, porting challenges, and performance bottlenecks. By linking numerical methods to hardware evolution and memory constraints, we outline the path toward efficient, exascale turbulence simulations.

[Phys. Rev. Fluids 11, 034905] Published Mon Mar 23, 2026

Author(s): Rahul Chajwa, C. Rajarshi, Rama Govindarajan, and Sriram Ramaswamy

When the worldlines of inertial particles in background flows cross, they generate low-dimensional structures with diverging particle number-density, formally similar to optical caustics. We show that orientable motile particles in flows can form caustics even when their mechanical inertia is neglected. Singular perturbation analysis of self-propelled particles around a point vortex and numerical simulations of their motion in a turbulent flow uncover the various regimes of caustics, demarcating the necessary conditions for their formation. Active caustics greatly enhance encounters between Stokesian swimmers, and an order-of-magnitude estimate points to their ecological relevance.

[Phys. Rev. Fluids 11, 033104] Published Fri Mar 20, 2026

Author(s): Zhicheng Kai, Peter Frame, and Aaron Towne

The transient growth of disturbances is typically investigated using the matrix exponential of the linearized Navier-Stokes operator. We introduce a data-driven algorithm that computes optimal initial conditions, response modes, and their associated energy growth directly from snapshots of flow data. Our method simplifies and broadens the application of transient growth analysis, eliminating the need for access to the linearized operator and enabling application to experimental data. We demonstrate the method, including a regularization to mitigate the sensitivity to noise, using a Ginzburg-Landau equation, Poiseuille flow, and a transitional boundary layer.

[Phys. Rev. Fluids 11, 034904] Published Fri Mar 20, 2026

Author(s): Hanbing Zou, Xin Jin, Haotian Chen, Wei Wang, Sheng Xu, and Bing Wang

Understanding droplet dynamics under detonation loading is vital for advanced propulsion technologies like rotating detonation engines. This study reveals fundamental differences between detonation and shock wave interactions with water droplets using high-resolution simulations. We demonstrate that the rapid post-wave pressure attenuation in detonations accelerates cavitation collapse and suppresses the Rayleigh-Taylor forward jet typical of shock impacts, leading instead to unique leeward-side flattening.

[Phys. Rev. Fluids 11, 034303] Published Wed Mar 18, 2026

Author(s): B. Kaoui, A. Bou Orm, P. Navet, J. Baish, and L. L. Munn

Bicuspid valves with crescent-shaped leaflets in veins and lymphatics ensure unidirectional flow to the heart by preventing reflux. While longer leaflets increase hydrodynamic resistance and excessive stiffness hinders proper valve closure, a key question remains: why is the leaflet crescent-shaped, and to what extent should it be creased to optimize performance? This study isolates geometry by varying only leaflet length under backward flow, revealing a transition from reflux to full blockage. The threshold and, thus, valve competency depend strongly on cusp shape, explaining reflux in short, immature, or abnormal valves.

[Phys. Rev. Fluids 11, 033103] Published Tue Mar 17, 2026

Author(s): Maxim Nikitin, Xiyu Xie, Qinrong Yu, and Dmitry Pashchenko

Classical pressure-drop correlations for packed beds often yield inconsistent predictions across different geometric scales and flow rates. By applying a residual-driven sensitivity analysis to an extensive experimental dataset, this work reveals that while geometric wall effects initially dominate prediction errors, the superficial velocity overwhelmingly dictates residual behavior once these are minimized. This finding indicates that future model improvements should prioritize flow-regime-dependent corrections over further geometric refinement.

[Phys. Rev. Fluids 11, 034302] Published Tue Mar 17, 2026

Author(s): Sagar Chaudhary, Dimitrios Fraggedakis, and Charles M. Schroeder

Capillary suspensions are defined by liquid-bound particle clusters, yet despite decades of study, their stability in strong flows remains incompletely understood. Here, we establish a universal set of stability criteria for a liquid-bound particle doublet in extensional flow. A critical capillary number governing stability is identified through a combination of analytical theory and experiments. Below this threshold, stability depends sensitively on initial particle separation, whereas above it, clusters are unconditionally unstable. These results provide a quantitative framework for predicting and controlling flow-induced breakup in capillary suspensions.

[Phys. Rev. Fluids 11, L032301] Published Tue Mar 17, 2026