As a capillary bridge of a viscoelastic fluid breaks to form beads-on-a-string, diameter-space-time diagrams are used to reproduce the position of the minimum diameter on the filament, the asymmetric satellite drop distribution and the movement of the filament in the direction of drop coalescence. Further, the size of the largest drop and the number of drops formed are quantified as a function of polymer concentration.

The strength of the activity of polar particles is varied in two-dimensional Lattice Boltzmann simulations of a liquid crystal model of active material. The simulations find phase separation and then mixing in the chaotic flow.

High-resolution measurements of velocity fields reveal the fine structure of vortices and indicate flow-regime transition in rapidly rotating Rayleigh-Bénard convection.

Using a high-speed camera, three types of splashing are identified as drops impact on a surface; the types of splashing depend on the surface roughness and on the ambient gas pressure.

The fate of total mechanical energy during flow separation is visualized through energy transport lines. A spiral node attractor inside the separation bubble and three segments of the wall are identified as attracting sets.

Experiments are conducted to explore the flow of Carbopol past obstacles in a narrow slot, and they are compared with model predictions. Flow patterns markedly lack the fore-aft symmetry expected theoretically, which suggests this results from rheological hysteresis near the yield point.

Flow pattern and apparent complex viscosity are derived explicitly for viscoelastic flow induced by an oscillatory colloid in polymer solutions, with depletion effect taken into account. Within the linear regime, the model can be used to interpret active and passive microrheological measurements.

The response of thixotropic fluids to applied forces depends not just on the instantaneous forces but on how they change over time. A model of thixotropic flow in a pipe illustrates how this can lead to the net transport of fluid under oscillatory forcing at intermediate Deborah numbers and that the effect vanishes in the limit of either a small or a large Deborah number (i.e., very slow or very fast forcing).

The world’s largest free-floating soap bubbles can encompass a small automobile and span nearly 100 square meters, despite being only microns thick. Experiments show that long, polydisperse polymer chains provide extensional properties during bubble formation and reduce gravitational drainage at high concentrations. However, too many polymers inhibit bubble formation, leading to an ideal concentration well below the characteristic overlap concentration for polymers in solution.

Three-dimensional dynamics of a spherical drop pair rising side-by-side in a surrounding, denser, fluid is investigated. We show that two liquid drops move away from each other when a single drop would have risen vertically. Interesting drop trajectories without large shape deformations are found.

Different breakup regimes of bubbles and droplets caused by a sudden channel expansion in a microfluidic device are investigated. Without modifying the geometry and by only tuning several dimensionless parameters related to the fluid flow, a microchannel expansion region can produce mono-, bi-, or tri-disperse bubble or droplet populations.

In vitro experiments with red blood cells (RBCs) indicate that at high velocities RBCs take both symmetric parachute and asymmetric slipper shapes, while unconfined computations indicate only symmetric parachute shapes are observed. How do we resolve this anomaly?

For a drop rising in a linearly density-stratified fluid, the drag acting on the drop, the drop deformation, and the drift volume induced are calculated. It is found that the stratification enhances the drag and reduces the drift volume, but it does not deform the drop.

In density-matched suspensions of Quincke particles, macroscopic flow arises due to the synchronization of their rotations at electric-field values smaller than the threshold field for the spontaneous rotation of a single particle.

Extant theories for induced-charge electrokinetics (ICEK) sometimes fail to predict even the correct direction of flow. By combining the recently discovered phenomenon of asymmetric rectified electric fields with a generalized form of ICEK, this long-standing dilemma is explained.

The multiphysics problem of a liquid film wetting an inclined substrate under the influence of a stabilizing electric field is considered. The use of a spatial stability analysis to predict the threshold of dripping suppression is assessed via reduced-order modeling and direct numerical simulation.

Time-resolved synchrotron x-ray microtomography combined with pressure measurements during two-phase displacement in porous media identifies three flow regimes. Intermittent occupancy creates temporary high-conductivity connections, leading to a power-law trend of pressure gradient with flow rate.

Particles that descend from a buoyant current are carried back toward the source resulting in a sediment deposit whose depth decreases linearly with distance from the source beyond a recirculation zone. The experimental results are used to predict the deposit of sediments from glacial plumes occurring around Antarctica.

Surface waves in the ocean surface boundary layer can create Langmuir turbulence which has structure distinct from shear turbulence in a conventional boundary layer. We show that the distinctive structure of Langmuir turbulence is quickly lost away from the surface, so that near the boundary layer base it becomes indistinguishable from turbulence in the absence of surface waves. This has important implications for modeling the effect of ocean surface waves on the boundary layer entrainment and improving ocean surface boundary layer parameterizations in Earth system models.

An experimental study explores the dynamics of lock-in and quasiperiodicity phenomena associated with upstream shear layer instabilities for a gaseous transverse jet exposed to axisymmetric excitation. Various dynamical responses are dependent on the jet-to-crossflow momentum flux ratio.

Transient growth in thermocapillary liquid layers is examined by nonmodal stability theory. Rather large transient growth occurs in subcritical flows at small Prandtl numbers. The growth decreases with Prandtl number but increases with Biot number, while its energy comes from the basic flow.

A theoretical and numerical analysis of the rupture of a nonwetting, ultrathin liquid film placed on a solid substrate reveals that the lubrication description experiences a crossover to a universal self-similar solution of the Stokes equations prior to the singularity.

Ballistic impact can be used to induce dynamic wrinkling in a floating elastic sheet. A mathematical model is developed and analyzed to describe the resulting dynamics: an elastocapillary wave propagates out from the point of impact, and the evolving wrinkle wavelength is dictated by fluid inertia.

Depending on the value of the Péclet number, a chemical reaction decreasing the viscosity locally may either reduce or enhance a viscous fingering instability. The stabilization and destabilization at low and high Péclet numbers, respectively, are related to changes in viscosity gradients that develop around the miscible interface due to the reaction. In particular, at low values of the Péclet number, the buildup of a local viscosity minimum improves the sweep efficiency in comparison to the nonreactive case, paving the way to a chemical control of viscous fingering.

The friction opposing drops moving on liquid-infused surfaces is experimentally characterized in various configurations (drops sliding down an incline, drops confined in Hele-Shaw cells, bubbles rising on immersed materials). It is found that viscous resistance mainly takes place in the oil meniscus surrounding the drop, which leads to a universal scaling law for the friction, in agreement with the observations.

The dynamics of a confined, elastic interface magnetic fluid drop subjected to a magnetic field is studied. A mode-coupling model shows how magnetoelastic effects affect the shape of the patterns. These structures differ from those in which surface tension replaces bending rigidity at the interface.

The effective anisotropic hydrodynamic slip of a channel wall decorated by superhydrophobic grooves is shown to alter the equilibrium positions of neutrally buoyant particles and to generate their motion transverse to the pressure gradient.

Direct numerical simulations and the immersed boundary method show that finite-size particles greatly enhance small-scale motions. Enstrophy and dissipation become similar in this augmented small-scale turbulence, as manifest in statistical relations and spatial distributions. This kind of similarity also exists in single-phase high-Reynolds-number turbulence but not in low-Reynolds-number turbulence.

Simultaneous three-dimensional measurement of the velocity of beads and the surrounding flow is carried out in a turbulent channel flow. The results show that the quasi-steady drag is not sufficient to model the dynamics of the beads in the near-wall region.

An experimental investigation of the settling velocity of solid particles in homogeneous isotropic turbulence finds that for different shapes of particles, the settling is slowed down by the turbulence. A relationship between modified settling velocity and turbulence intensity is obtained.

Sedimentation of a particle pair in a shear-thinning fluid is studied for varying generalized Archimedes number. Unlike in the Newtonian fluid, one more group of multiple stable states is identified, and the drafting-kissing-tumbling state disappears when the shear-thinning effect is strong enough.

Large-eddy simulations of interactions between shock waves and particle clouds show that lower particle Reynolds numbers result in stronger shock wave attenuation and a stronger reflected shock wave. Velocity fluctuations are found to be most intense at moderate Reynolds numbers, while particle forces vary most at the highest Reynolds numbers.

Experiments are conducted to investigate the motion of single particles with particle Reynolds number less than 10 in the viscous sublayer of turbulent shear flows. The flow field is measured with laser doppler velocimetry. We find that particle motion closely follows fluid fluctuations with velocity statistics scaling with the viscous velocity. Thus, for the conditions studied, particles roll and slide without taking off, in contrast to viscous laminar flow where the lift force may exceed the immersed particle weight.

A dynamic pore network model is developed for evaporation in porous media with continuous and discontinuous corner films. The continuous corner films can be interrupted into discontinuous ones by the capillary scissors effect due to the local convex topology of the solid matrix in porous media.

Cooling of the flow induced by a spark plasma discharge is found to occur at two different rates: an initially fast cooling regime followed by a slow cooling regime. Convective cooling in the fast regime contributes to 30–50% of the total cooling and occurs within the first millisecond of the induced flow.

An investigation shows that 5/3 and -7/3 frequency spectra of turbulent energy and pressure, respectively, appear along shear layers in the very near-field of grid turbulence via interactions between vortices due to shedding and shear-layer instability.

The effects of wall thermal conditions on the canonical case of an impinging shock wave interacting with a turbulent boundary layer is a topic that remains under explored. Direct numerical simulations are used to study the flow properties of hypersonic-shock–boundary-layer interactions with distinct wall thermal conditions and shock angles.

Coarse-grained superfluid dynamics are investigated through detailed numerical simulation at the level of individual quantized vortex lines. Simulations show a strong correlation between the formation of quantized vortex bundles and the production of extreme negative pressure regions in excess of 3 standard deviations. This motivates the use of experimental pressure measurements for probing superfluid turbulence at low temperatures.

Direct numerical simulation shows that the anisotropy in a certain class of passive scalar fields is frozen in the sense that under certain conditions, the large-scale anisotropy remains almost unchanged irrespective of the growth of the anisotropy of the turbulent flows convecting the scalar.

A subfilter-scale model for large-eddy simulation is devised using proper orthogonal decomposition, assuming self-similarity among the finest resolved and subfilter scales. The model naturally manifests the forward and backward transfer of interscale energy as well as the correct near-wall scaling.

Several families of two-dimensional instabilities exhibiting maximal growth rates at low Reynolds numbers are observed in a frozen Lamb-Oseen vortex dipole. Despite their damping due to base-flow unsteadiness, these unstable modes are able to grow in the time-evolving aircraft wake by taking advantage of transient growth based on the Orr mechanism.

The two-mode quasigeostrophic model and associated turbulence phenomenology is a holy grail of geophysical fluid dynamics. An illustration of how wind-generated near-inertial waves in the ocean modify the quasigeostrophic turbulence phenomenology is presented.

Flow structures and the kinetic-potential energy exchange in rotating stratified turbulence are studied by simulations. Differences of cyclonic and anticyclonic vortices are shown. The intense kinetic-potential energy exchange is found to be associated with the cyclonic structures.

A weakly nonlinear model is developed that accounts for viscous dissipation in the reflection of an internal wave beam from a uniform slope. The theoretical predictions compare favorably with Navier-Stokes simulations and also explain the poor quantitative agreement of earlier inviscid models with laboratory experiments.

Experiments show that inertial modes generate a system of averaged vortices in viscous boundary layers of a rotating cavity.