Physical Review Fluids

Author(s): Jian H. Guan, Saiful I. Tamim, Connor W. Magoon, Howard A. Stone, and Pedro J. Sáenz

This paper is associated with a video winner of a 2024 American Physical Society's Division of Fluid Dynamics (DFD) Gallery of Fluid Motion Award for work presented at the DFD Gallery of Fluid Motion. The original video is available online at the Gallery of Fluid Motion, https://doi.org/10.1103/APS.…

[Phys. Rev. Fluids 10, 110507] Published Thu Nov 20, 2025

Author(s): Pim J. Dekker, Christian Diddens, and Detlef Lohse

This paper is associated with a video winner of a 2024 American Physical Society's Division of Fluid Dynamics (DFD) Milton van Dyke Award for work presented at the DFD Gallery of Fluid Motion. The original video is available online at the Gallery of Fluid Motion, https://doi.org/10.1103/APS.DFD.2024…

[Phys. Rev. Fluids 10, 110508] Published Thu Nov 20, 2025

Author(s): Marcus Lin, Fauzia Wardani, and Dan Daniel

This paper is associated with a video winner of a 2024 American Physical Society's Division of Fluid Dynamics (DFD) Milton van Dyke Award for work presented at the DFD Gallery of Fluid Motion. The original video is available online at the Gallery of Fluid Motion, https://doi.org/10.1103/APS.DFD.2024…

[Phys. Rev. Fluids 10, 110509] Published Thu Nov 20, 2025

Author(s): Umang N. Patel, Jonathan P. Rothstein, and Yahya Modarres-Sadeghi

This paper is associated with a poster winner of a 2024 American Physical Society's Division of Fluid Dynamics (DFD) Gallery of Fluid Motion Award for work presented at the DFD Gallery of Fluid Motion. The original poster is available online at the Gallery of Fluid Motion, https://doi.org/10.1103/AP…

[Phys. Rev. Fluids 10, 110510] Published Thu Nov 20, 2025

Author(s): L. Kahouadji, M. Shams, D. Panda, A. M. Abdal, S. Shin, J. Chergui, D. Juric, and O. K. Matar

This paper is associated with a poster winner of a 2024 American Physical Society's Division of Fluid Dynamics (DFD) Gallery of Fluid Motion Award for work presented at the DFD Gallery of Fluid Motion. The original poster is available online at the Gallery of Fluid Motion, https://doi.org/10.1103/AP…

[Phys. Rev. Fluids 10, 110511] Published Thu Nov 20, 2025

Author(s): Ilya Kolesnichenko and Vladimir Ozernykh

This study examines the parameter region in which a solitary rotating vortex can form in an axial liquid metal flow. For different ratios of azimuthal and axial flow intensities, the flow pattern changes significantly. At high intensity of the axial flow the second vortex is completely suppressed by the first vortex. The rotating vortex has clear-cut boundaries. In the flow regions before and after the vortex generation, the vorticity is close to zero. After switching off electromagnetic forces, the vortex is carried by the axial flow along the channel.

[Phys. Rev. Fluids 10, 113701] Published Thu Nov 20, 2025

Author(s): Clara M. Velte and Preben Buchhave

The omission of time as a parameter in the classical triad interaction analysis is shown to produce a much too simplistic picture of turbulence. Including time into the analysis shows that not only the spatial wave overlap contributes to energy exchanges between wavenumbers, but the temporal overlap is equally important. The phase match condition is thus broadened to also include temporal frequencies. This can explain much of so-called nonequilibrium turbulence. Not least fractal grid generated turbulence, which is a prime example of these effects. Part II investigates the effects on triadic analysis of practical signals with finite temporal and spatial domains and resolutions.

[Phys. Rev. Fluids 10, 114612] Published Thu Nov 20, 2025

Author(s): Preben Buchhave and Clara M. Velte

The inclusion of time as a parameter omitted in the classical triad interaction analysis was introduced in the companion paper Part I. The present work illustrates the effects of practical sampling on the resulting triad interactions. Practical sampling effects include both temporal and spatial digitization (sampling) as well as finite temporal and spatial domains. These effects are seen to broaden the interaction peaks beyond the classically expected delta-functions and the finite domains contribute to a more complex interaction evolution for domains sufficiently small in comparison to the largest scales in the flow under investigation.

[Phys. Rev. Fluids 10, 114613] Published Thu Nov 20, 2025

Author(s): Lekha Sharma, Mayank Pathak, Harshit Tiwari, and Mahendra K. Verma

We investigate the influence of Prandtl number (Pr) on turbulent compressible convection by performing extensive numerical simulations in both two- and three-dimensions. We find that the bulk remains adiabatic across all Pr, while the global heat and momentum transport exhibits scalings similar to the incompressible Rayleigh-Bénard convection (RBC). In contrast, the boundary layers exhibit distinct scalings near the top and bottom boundaries, unlike RBC, accounting the effects of compressibility. The key image shows the flow structures at two different Pr’s.

[Phys. Rev. Fluids 10, 114611] Published Wed Nov 19, 2025

Author(s): John C. Sentmanat, Peter A. Kottke, and Andrei G. Fedorov

In vacuum nanoelectrospray, a stream of electrically charged nanoliter droplets moving at high speed through a rarefied space at sub-atmospheric pressure. A supersonic gas microjet in crossflow can effectively redirect the nanodroplets to control their destination. The fundamental theory predicts the droplet fate to enable applications such as high-resolution inkjet printing, trust vectoring for precise satellite control, and biochemical imaging using desorption electrospray ionization.

[Phys. Rev. Fluids 10, 114303] Published Tue Nov 18, 2025

Author(s): Chunlai Wu, Rudie P. J. Kunnen, Ziqi Wang, Xander M. de Wit, Federico Toschi, and Herman J. H. Clercx

We report an experimental technique that fully resolves the three-dimensional angular velocity of magnetic particles, suspended in turbulence and actuated by an oscillating magnetic field, using only single-camera two-dimensional imaging. The particles, smaller than the Taylor microscale of the turbulent flow and less dense than water, are tracked with high accuracy to reveal their magnetically driven rotational dynamics affected by turbulence-induced hydrodynamic torque. This method to measure the rotational dynamics of small particles overcomes a key experimental limitation and the experimental apparatus enables active modulation of turbulence through external magnetic fields.

[Phys. Rev. Fluids 10, 114903] Published Tue Nov 18, 2025

Author(s): Manikandan Balasubramaniyan, Haiqing Wang, Peijin Liu, Yu Guan, Bo Yin, and Larry K. B. Li

Turbulent premixed bluff-body flames can host both hydrodynamic and self-excited thermoacoustic modes, yet their coupling remains unclear. By fixing the Reynolds number and equivalence ratio while sweeping only the combustor length, we map the route from desynchronization to two-frequency quasiperiodicity and ultimately to 1:2 mutual synchronization, accompanied by strong pressure and heat-release-rate (HRR) oscillations. Spatiotemporal analyses reveal the recirculation zone as the dominant energy-injection site. We also identify two blow-off pathways with clear, local HRR precursors.

[Phys. Rev. Fluids 10, 113201] Published Mon Nov 17, 2025

Author(s): Leon Li and R. Jason Hearst

This study examines the effects of freestream turbulence on the wakes of circular and square cylinders, with a particular focus on the streamwise evolution of the wake properties. Four different inflow conditions are created by an active grid and are good approximations of homogeneous, isotropic turbulence, thus enabling us to isolate its effects on the wakes. Contiguous high resolution PIV data is gathered up to 1 m downstream of the cylinders. The results reveal that increasing turbulence intensity promotes early transition to self-similarity of the wake velocity deficit, and the earlier breakdown of coherent structures, leading to a reduced average number of vortices in the wake.

[Phys. Rev. Fluids 10, 114610] Published Mon Nov 17, 2025

Author(s): Dana L. O.-L. Lavacot, Jessie Liu, Brandon E. Morgan, and Ali Mani

The Macroscopic Forcing Method (MFM) is a numerical tool for determining closure operators, including turbulent closures, through forced numerical simulations. In this work, we outline and demonstrate the recommended MFM procedure to avoid slow statistical convergence of MFM measurements as well as maintain consistent boundary condition treatment. We apply the method to quantify eddy diffusivity moments in two-dimensional Rayleigh-Taylor instability to improve statistical convergence for analysis.

[Phys. Rev. Fluids 10, 114904] Published Mon Nov 17, 2025

Author(s): Cailei Lu, Zhenze Yao, Mengqi Zhang, Kang Luo, and Hongliang Yi

A linear nonmodal analysis is performed to investigate the transient growth of diffusive convection in the absence/presence of a bounded Couette flow. The results first examine the properties of transient growth of the pure diffusive convection and interpret the mechanism to cause this growth. Then, the transient growth of diffusive convection with a Couette flow is investigated. Three nonmodal instability regimes regarding the transient growth of the mixed convection are identified, and two mechanisms of the double diffusion to enhance the lift-up mechanism are revealed.

[Phys. Rev. Fluids 10, 113902] Published Fri Nov 14, 2025

Author(s): Wangxin Yu, Qingquan Liu, Huaning Wang, Chun Feng, and Xiaoliang Wang

There are a variety of shock waves in fast-moving granular flows colliding with obstacles which crucially shape flow resistance and impact dynamics. This study employs a depth-integrated numerical model to reveal four distinct interaction regimes—oblique, attached bow, detached bow, and runover—depending on the Froude number and wedge geometry. The results also identify a previously unreported transitional attached bow shock that bridges classical regimes, which would be helpful for improving understanding of flow-obstacle interactions relevant to geophysical hazards.

[Phys. Rev. Fluids 10, 114302] Published Fri Nov 14, 2025

Author(s): Valerio Lupi, Daniele Massaro, Adam Peplinski, and Philipp Schlatter

Swirl switching is the temporal rotation of the plane of symmetry of the cross-sectional vortices about the equatorial plane of a curved pipe and can induce considerable structural vibrations. We investigate the effect of bending angle and inflow conditions by performing high-fidelity direct numerical simulations of spatially developing bent pipe flows and extracting spatially coherent structures through proper orthogonal decomposition. Our results show that upstream turbulence is not the primary cause of swirl switching. Instead, the phenomenon likely arises because of a symmetry-breaking instability of the shear layer originating within the curved section.

[Phys. Rev. Fluids 10, 114608] Published Fri Nov 14, 2025

Author(s): Dhananjay Singh, Harshit Tiwari, Lekha Sharma, and Mahendra K. Verma

We present a novel mathematical framework to compute mode-to-mode energy transfers and fluxes for compressible flows. This formalism captures detailed energy conservation within triads and allows decomposition of transfers into rotational, compressive, and mixed components, providing a clear picture of energy exchange among velocity and internal energy modes. The key image shows the decomposed energy fluxes.

[Phys. Rev. Fluids 10, 114609] Published Fri Nov 14, 2025

Author(s): Lei Dong, Wenqiang Zhang, Dandan Xiao, and Xuerui Mao

The modulation frequency exerts a significant effect on the evolution of plasma-induced vortices, giving rise to three distinct flow structures: vortex-free evolution, leapfrogging, and coexistence of multiple vortex pairs. Among them, the formation of leapfrogging enhances the entrainment coefficient of the plasma jet, thereby potentially enabling more effective flow control.

[Phys. Rev. Fluids 10, 114701] Published Fri Nov 14, 2025

Author(s): Patrice Meunier

Precessing flows in cylinders are highly effective for mixing a passive scalar, as illustrated here with the thin streaks of fluorescent dye. The stretching and folding of these streaks results from chaotic advection by the flow which becomes resonant at specific cylinder heights. This paper reviews theoretical, experimental, and numerical studies of the resonances and the instabilities of a precessional flow, as well as their implications for efficient mixing.

[Phys. Rev. Fluids 10, 114803] Published Fri Nov 14, 2025