A mechanistic model derived from kinetic theory explains how during blood flow in small vessels or microfluidic channels, white blood cells and platelets segregate near the walls. A key result is the existence of a single parameter whose value characterizes segregation of a particular species.

A overview of the coupling between surface roughness, in the form of scales or denticles, and the hydrodynamics of effective swimming is presented.

Subjected to continuous deformation of its wire boundary, a Möbius-strip soap film collapses to a disklike one through a twist singularity at the wire boundary. A simplified model allows further investigation of this process.

An overview of the recently discovered instabilities of drops is presented in this invited paper associated with a lecture given by the author at the 68th Annual Meeting of the APS Division of Fluid Dynamics.

A thorough description of challenges and recent progress in the understanding of flows in planetary molten cores is provided, with particular attention to flow driven by mechanical forcing due to the tugging of one celestial body on another. This case is particularly relevant for the understanding of the reciprocal actions in the Moon/Earth system.

A study of the analogies between elastic and capillary interfacial flows is presented.

Swarms of balloons released into hurricane formation regions can be used to measure meteorological variables and help improve short-term prediction models.

An iterative procedure to calculate pure conductive heat flux in non-Oberbeck-Boussinesq Rayleigh-Bénard convection is presented. Deviations of the conductive heat flux from its Oberbeck-Boussinesq approximation can lead to significant corrections of the experimentally obtained Nusselt numbers.

The enhanced entrainment and mixing of synthetic (pulsed) jets is characterised by a modified effective eddy viscosity.

The decay of kinetic energy is observed over six decades. The azimuthal velocity and its fluctuations are found to decay in a self-similar way, at a rate enhanced by wall friction.

Transient energy growth (TEG) in magnetohydrodynamic flows is shown to play an important role in the emergence of nonlinearity and plausible turbulence in shear flows, which has important astrophysical applications.

3D turbulence leads to the formation of small-scale structures. For moderate Reynolds number, helically forced flows are shown to generate large-scale instabilities. These large-scale instabilities are quantified with a new numeric model using Floquet theory.

A numerical study of the magnetohydrodynamic flow generated in a thin spherical shell in rapid rotation reports, for the first time, the generation of a dynamo magnetic field by the centrifugal instability in a spherical geometry and provides a new explanation for the astrophysical magnetic fields which cannot rely on thermal convection.

Large-eddy simulation combined with a turbine model is used to investigate the effect of vertical wind veer associated with the Coriolis force on the structure and evolution of wind-turbine wakes. The simulation results show that the Coriolis force significantly affects the aerodynamics of the wake, including the mean velocity deficit, turbulence statistics, and wake-meandering characteristics downwind of the turbine.

The dynamics of a thin, incompressible viscous fluid, subject to both van der Waals and Marangoni forces, on a thermally conducting substrate, is theoretically considered in the regime where the temperature field of the film and of the substrate evolve on a comparable time scale. Calculations show that the Marangoni flows have a strong effect on the instability and that the evolution of the temperature field, coupled to the evolving film profile, qualitatively changes the instability.

Thermocapillary induced droplet motion is markedly enhanced when using lubricant impregnated surfaces instead of a solid substrates. These surfaces provide weak pinning, which makes them ideal for droplet transportation, and specifically for water transportation

Drops may coalesce during the fragmentation of a compound liquid jet made of miscible liquids having contrasted viscoelastic properties and submitted to harmonic perturbations. This phenomenon is linked to the spatial development of the capillary instability where velocity fluctuations, arising from the unstable nature of the annular co-flow, are amplified.

An investigation of surfactant-laden multilayer film flow down an inclined plane with an emphasis on flow stability and the computation of traveling waves and their stability is presented. The solutions discussed include solitary pulses propagating in phase on each film surface and traveling waves with capillary-ridge-type and shock-like features.

Pattern formation of a two-layer thin liquid film system subjected to vertical oscillations is studied with an integrated boundary layer model. Squares, hexagons, or quasiperiodic patterns, as well as localized states, are found. For a Rayleigh-Taylor unstable layer, vibrations can delay or completely suppress film rupture.

A two-phase microfluidic drop dilution system driven by coalescence-induced mass transfer between a moving plug and stationary droplets is modeled. Results show that gutter flows make pass-through streamlines possible where there would otherwise be closed circulation, thereby increasing the rate of mass transfer.

Surface roughness can play a critical role in dynamic wetting processes like imbibition and drainage of capillaries. In the presence of nanoscale roughness, The shear-driven drainage of microscale capillary grooves exhibits regimes that cannot be described by solely considering hydrodynamic and capillary effects. Thermal motion and nanoscale surface roughness “characterized by AFM” induce drainage rates predicted by Kramers theory of thermally activated transitions.

Experiments show, for the first time, two water droplets coalescing and jumping on a superhydrophobic surface. Adhesion, contact angle hysteresis, and initial wetting behavior governed by the surface structure morphology and length scale, are all shown to play a role in droplet jumping.

The effect of particle size segregation in an upslope propagating, bidisperse granular bore is investigated and experimental observations agree with recent progress that upwards and downwards segregation of large and small particles, respectively, is asymmetric.

A study of gas exchange between a bubble and the surrounding liquid, in the limit of small radial velocities, reveals that history effects are important in determining the threshold conditions.

Particle accumulation dynamics in vibrated nonisothermal monodisperse suspensions of solid spheres (in a liquid) are investigated. The diversity of particle agglomerates when the direction of the imposed temperature gradient is changed results from the different roles played by (curved or straight) boundaries in constraining particles and from the different topology of the resulting thermovibrational flow.

A scaling analysis elucidates how interfacial slip modifies the variation of drainage time with the capillary number. It also improves the understanding of coalescence in sheared polymer blends.

The existence of a new regime in convective instabilities when the wavelength of the instability becomes smaller than the pore size is demonstrated. A theory, adapted from classical linear stability analyses, accompanies experimental characterizations of the new regime.

The turbulent flow in thermal convection is expected to be strongly anisotropic. However, new numerical results show that the flow is nearly isotropic. The ring spectrum $E(k,\theta )$, which is essentially energy of a Fourier mode at a wavenumber $k$ and polar angle $\theta$, is almost independent of $\theta$. The energy flux and shell-to-shell transfers in turbulent convection are also quite similar to isotropic hydrodynamic turbulence.

The Reynolds-dependent scaling of the outer peak in the streamwise turbulence intensity in wall-bounded turbulent flows is explained with the discovery of the inner-scaling nature of the outer structure in the near-wall region. Theoretical generalization further reveals that this feature indicates incomplete self-similarity of the wall-parallel velocity components of the log-layer motions in the region close to the wall.

Two novel particle image velocimetry arrangements are used to make true spatial comparisons between high Reynolds number smooth- and rough-wall boundary layer flows across a very wide range of streamwise scales.

Finite Reynolds number contributions from the unsteady and viscous terms to the inertial range solution of the third-order structure functions are examined.

The original interacting particle representation model (IPRM) is a stochastic Lagrangian model that focuses on turbulent structures to improve prediction of Reynolds stresses. A deterministic Eulerian formulation of the IPRM that increases the rate of statistical convergence is introduced.

A numerical analysis shows that when both the vorticity vector and the strain-rate tensor are obtained from a filtered velocity field, the alignment statistics between $\omega$ and the eigenvectors of ${\tilde{s}}_{ij}$ do not vary in response to changing the length-scale of the filter, or in the absence of filtering.

An experimental particle tracking is used to distinguish two sources of Lagrangian unsteadiness in turbulent thermal convection. The first one, induced by the large-scale circulation inhomogeneity, can be suppressed by separating the mean flow and the turbulent fluctuations. This provides a subtle way to study the second unsteadiness, which is linked to the large-scale circulation sloshing.