Latest papers in fluid mechanics

Author(s): Cristhian Zárate Evers, Alejandro Gronskis, and Guillermo Artana

We have developed a novel family of self-similar solutions for stress-constrained boundary layer flows over a flat plate. Our work goes beyond previous studies by including power-law stress distributions, creating a complete framework for analyzing boundary layer flows with both increasing and decreasing tangential wall stress. This provides important insights for technologies like magnetic or electric pumping devices.

[Phys. Rev. Fluids 10, 063703] Published Wed Jun 25, 2025

Author(s): Amna Al-Qenae, Javad Shokri, Takshak Shende, Muhammad Sahimi, and Vahid Niasar

Solute transport in porous media is traditionally modeled with constant dispersivity, assuming Newtonian behavior and uniform viscosity. Using high-resolution micromodel experiments with non-Newtonian shear-thinning fluid, this study demonstrates that such assumptions break down when the local viscosity varies with the shear rate. We reveal a nonmonotonic relationship between dispersivity and flow rate and propose a theoretical model that incorporates shear-dependent viscosity to estimate dispersivity in porous media.

[Phys. Rev. Fluids 10, 063802] Published Wed Jun 25, 2025

Author(s): Sedat Tardu and Benjamin Arrondeau

The breaking wave zone of a transitional spot in a Poiseuille flow induces large-scale-outer-layer motions (LSM) that significantly increase the pseudo-turbulent activity. LSM are associated with an intense outer spectral core and a clear scale-separation. The outer spectral core is frozen across the whole layer and the LSM passively penetrates the inner-layer of the spot.

[Phys. Rev. Fluids 10, 063904] Published Wed Jun 25, 2025

Author(s): Daniel Gysbers, Mark A. Levenstein, and Gabriel Juarez

Larvae of sessile marine species must settle in environments with flow velocities that are orders of magnitude faster than their swimming speed. Previous work has indicated that the roughness of benthic substrates may help to facilitate this difficult process, however, systematic studies of larva-flow-substrate interactions are lacking. We modeled short-range larval transport (<10 cm) over a wide range of substrate topographies in wave-like oscillatory flow and found that the transport of larvae to the substrate was aided by recirculatory flow structures generated by millimeter-scale roughness features. Optimal width-to-height ratios were identified that maximized larval settlement.

[Phys. Rev. Fluids 10, 064501] Published Wed Jun 25, 2025

Author(s): Feixiong Rao and Shengqi Zhang

Forced thermal convection in porous media significantly enhances heat transfer, which is a critical requirement in industrial engineering. However, modeling the heat-fluid-solid coupling in turbulent forced convection necessitates further development. In this study, we develop coupled macroscopic models based on the local thermal nonequilibrium model and the pore-scale prevalence hypothesis. Our results demonstrate that the proposed coupled macroscopic models achieve a high level of accuracy and successfully predict both statistically stationary temperature distributions and overall temperature evolutions.

[Phys. Rev. Fluids 10, 064502] Published Wed Jun 25, 2025

Author(s): Sung Min Lee and Jae Hwa Lee

In this study, we perform a direct numerical simulation of a turbulent plane Couette flow over a two-dimensional rod-roughened wall to examine the effect of surface roughness on this type of flow. We find that the surface roughness causes the decreased turbulent activity in the outer layer due to the weakening of the large-scale negative u’-component. An analysis of the large-scale turbulent structures in the outer layer shows that the reduction of the streamwise coherence of the large-scale u’-structure with less energy in the outer layer is due to the suppressed development of a hairpin packet resulting from the weakened roll-cell motions with less influence on the near-wall region.

[Phys. Rev. Fluids 10, 064617] Published Wed Jun 25, 2025

Author(s): Shawan Kumar Jha, Mahendra K. Verma, S. I. Mistakidis, and Pankaj Kumar Mishra

Successive nucleation of a large number of vortices is observed in the wake of the impenetrable barrier accompanied by the emergence of sound waves. A coarsening stage follows where vortices interact with a portion of them being annihilated eventually yielding turbulent response. Depending on the strength and velocity of the stirring potential, different vortex configurations emerge, ranging from vortex dipoles, to vortex clusters, and randomly distributed vortex-antivortex pairs. The dipole and clustered configurations exhibit Kolmogorov-like scaling in the incompressible kinetic energy spectrum, whereas the random vortex-antivortex configurations are characterized by Vinen-like scaling.

[Phys. Rev. Fluids 10, 064618] Published Wed Jun 25, 2025

Author(s): Tong Wang and Li-Hao Feng

The unsteady load caused by gusts (time-varying atmospheric wind disturbances) is an essential factor affecting flight safety. To mitigate gust loads, various flow control methods have been used. However, these methods are effective only in limited ranges, and a full theory of gust load reduction has been elusive. Here we propose a theoretical method for gust load reduction which we have validated through experiments for a certain range of gust amplitudes and frequencies. Our results show that the method reduces lift fluctuations by up to 90%, and provides insight into the relevant flow mechanism.

[Phys. Rev. Fluids 10, 064902] Published Wed Jun 25, 2025

Author(s): S. Paolucci

Continuum mechanics principles are used to obtain the complete linear constitutive equations of a fluid. We obtain the Cauchy stress tensor and entropy that contain additional terms that are missing in the conventional equations. All new terms are due to the relative time rate of change of local temperature. This leads to a new definition of the bulk viscosity. When the results are applied to an ideal gas, the new terms appear to be due to the local time relaxation of intramolecular vibrational energy and when applied to dense gases and liquids they appear to be related to the time relaxation of intermolecular potential energy. Image source: https://stock.adobe.com/images/abstract-background-with-3d-molecules-in-blue-and-red-floating-against-a-blurred-backdrop/919699165

[Phys. Rev. Fluids 10, L061401] Published Wed Jun 25, 2025

Author(s): Sergio Hoyas, Nils Benedikt, Andres Cremades, and Ricardo Vinuesa

Shapley Additive Explanations (SHAP) values are employed to identify high-importance structures. The influence of various coherent structures is assessed in terms of velocity evolution and friction drag generation. While ejections and low-velocity streaks mainly drive the velocity evolution, sweeps emerge as the dominant contributors to friction drag.

[Phys. Rev. Fluids 10, L062601] Published Wed Jun 25, 2025

Author(s): X. Meng, L. Zhao, and Z. You

The threshold Froude number associated with instability onset in grain-water mixture flows has not been well defined. In this study, we conduct a temporal stability analysis, perform periodic box numerical simulations, and construct a traveling-wave solution within a debris flow model that incorporates distinct basal friction laws for grains and water. The coupled fluid–particle dynamics reveals an instability onset and subsequent roll wave coarsening behavior which differs from previous findings. The approach is applied to the debris flow event in the Illgraben torrent, Switzerland. The results lead to insights into roll wave initiation and evolution as observed in the field.

[Phys. Rev. Fluids 10, 064303] Published Tue Jun 24, 2025

Author(s): Yu Chen, Deheng Wei, Si Suo, Mingrui Dong, and Yixiang Gan

This study reveals the onset of a nearly complete segregation regime in submerged granular mixtures rotated in a drum, distinct from dry systems. By introducing an effective density ratio and tracking emergent vortex structures, both experiments and numerical simulations reveal transitions from homogeneous to asymmetrical multi-vortex states. The findings offer predictive capability and mechanistic insights into density-driven segregation in fluid-grain systems.

[Phys. Rev. Fluids 10, 064304] Published Tue Jun 24, 2025

Author(s): Haozhe Geng, Wen-Li Chen, Hui Li, and Donglai Gao

Gravity-driven collapses such as landslides, avalanches, and mudslides have garnered increasing attention, and understanding their complex dynamics is a key concern for risk assessment. In this paper, we design a laboratory experiment to investigate the dry granular column collapse from a rough slop…

[Phys. Rev. Fluids 10, 063801] Published Mon Jun 23, 2025

Author(s): Junnan Cui, Qunbin Chen, Jingsong He, Liu Yang, and Xingya Feng

This study studies the generation of extreme waves in a physical wave flume and in a numerical wave tank based on the higher order Peregrine solutions to the Schrodinger equation. Higher harmonics of the wave elevations during modulation and demodulation are extracted and analyzed. Through spectral analysis, the nonlinear energy transfer characteristics of Peregrine solutions are identified.

[Phys. Rev. Fluids 10, 064802] Published Mon Jun 23, 2025

Author(s): Xuke Zhu, Yubin Song, Peng Zhang, Xiaoshuo Yang, Yongchao Ji, and Zhenhua Xia

Despite decades of research on compressible turbulent channel flows (CTCFs), studies inconsistently employ either spatially uniform or density-weighted body forces. We conduct direct numerical simulations of CTCFs with symmetric (cold) and asymmetric (cold/quasi-adiabatic) thermal walls to systematically assess the impact of these two forcing strategies on turbulence statistics. While differences are minimal in symmetric cases, strong compressibility or large wall temperature differences lead to notable discrepancies, highlighting the importance of force selection in high-Mach or thermally asymmetric flows.

[Phys. Rev. Fluids 10, 064616] Published Fri Jun 20, 2025

Author(s): Daniel Wälchli, Pascal Weber, Michail Chatzimanolakis, Robert Katzschmann, and Petros Koumoutsakos

This paper introduces inverse reinforcement learning to discover objectives in fish schooling. The methodology is not specific to fish schools and applicable across other natural systems. It provides a new path to bioinspired optimization by analyzing data to infer goals rather than a-priori specifying them.

[Phys. Rev. Fluids 10, 064901] Published Wed Jun 18, 2025

Author(s): Nandita Pan and Supratik Banerjee

Below critical temperature, turbulence prevents the spontaneous phase separation of binary mixtures, resulting in a phase arrested state of emulsion. The current study explores if a Kolmogorov-like energy cascade exists in fully developed binary fluid turbulence. Using exact relations and direct numerical simulations with up to 10243 grid points, we show that the combined kinetic and interfacial energy exhibits a cascade with a constant transfer rate across the inertial scales. In addition, the cascade rates computed from the three exact laws in divergence, alternative and correlator forms show excellent agreement, thus confirming the equivalence between the three formulations.

[Phys. Rev. Fluids 10, 064615] Published Tue Jun 17, 2025

Author(s): Ramadan Abu-Rjal, Zuzanna S. Siwy, and Yoav Green

Nanofluidic systems subject to viscosity gradients are ubiquitous to technology and nature, including desalination and energy harvesting systems that utilize fresh water and seawater, thermoionics that leverage large temperature gradients of an electrolyte, and even ion channels that are sandwiched …

[Phys. Rev. E 111, 065105] Published Mon Jun 16, 2025

Author(s): Aaditya U. Joshi, Osman A. Basaran, and David S. Corti

Drop coalescence plays a crucial role in nature and industry. In continuum theory, after the two drops are taken to touch at a point at the onset of coalescence, two scaling regimes for the temporal growth of the bridge connecting the drops have been identified. Coalescence, however, is initiated a…

[Phys. Rev. E 111, 065106] Published Mon Jun 16, 2025

Author(s): Fernando Alonso-Marroquin and Martin P. Andersson

A computationally efficient method to calculate the capillary pressure-saturation relations of immiscible multiphase flow on two-dimensional pore morphologies is presented. The method is an extension of the porous morphology method that includes the wetting angle and trapped mechanism of the displac…

[Phys. Rev. E 111, 065107] Published Mon Jun 16, 2025