Latest papers in fluid mechanics

Author(s): Paolo Botticini, Davide Picchi, Santanu Sinha, and Alex Hansen

We characterize the nonlinear pressure drop–flow rate relation of elongated bubble trains in capillary tubes by incorporating thin-film hydrodynamics at low capillary numbers. We show that pore-scale statistical heterogeneity in capillary bundles induces systematic deviations from the single-phase limit, controlled by both the pore-size distribution and flow parameters. We identify a crossover between sublinear regimes with exponents ranging from 2/3 to 1, connecting the Bretherton and Darcy limits and in qualitative agreement with values reported for immiscible two-phase flow in porous media.

[Phys. Rev. Fluids 11, 073601] Published Mon Jul 06, 2026

Author(s): Linsheng Zhang (张林生), Weixing Zhou (周伟星), and Robert J. Poole

We revisit the classical homogeneous shear assumption in cone-and-plate rheometry over a slip boundary condition, and resolve inconsistencies between two slip boundary formulations. Our results show that a fixed slip-length model induces radial shear-rate non-uniformity, whereas a constant wall-stress formulation restores homogeneous shear via a radius-dependent slip length. Extending our work to shear-thinning Carreau fluids, we demonstrate a strong shear-rate dependence of drag reduction and effective slip length. Despite distinct local flow structures, both models yield consistent area-averaged slip from torque measurements, providing a unified framework for slip quantification.

[Phys. Rev. Fluids 11, 074001] Published Mon Jul 06, 2026

Author(s): George Lucas S. Torres, Ashok Gopalarathnam, and Flávio D. Marques

Unsteady thin-airfoil theory is a straightforward reduced-order framework for arbitrary airfoil motions and geometries. However, an inconsistency appears when recovering classical unsteady problems: Glauert’s bound-vorticity expansion is not uniformly convergent at the trailing edge in unsteady motion. Revisiting Wagner’s problem through the unsteady Kutta condition, this work derives a recurrence for the bound-vorticity coefficients and builds a uniformly convergent bound vortex-sheet formulation with a discrete-vortex equivalent. With few terms, the method ensures bound-wake continuity, zero trailing-edge loading, and smooth transient predictions for Wagner’s indicial problem

[Phys. Rev. Fluids 11, 074701] Published Mon Jul 06, 2026