Using magnetic levitation, we measure the dispersion relationship for a 3-layer (semi-infinite oil / aqueous / semi-infinite oil) fluid system as a function of the height of the middle layer. The experimental results are compared with predictions of linear stability theory.

Forcing by spanwise opposing jets centered around $y^{+}=30$ produces drag reduction of more than 10% at Re${}_{\tau }$=550.

A map is proposed for the different regimes of turbulent convection through a channel—hard turbulence, soft turbulence, and Batchelor regimes—in agreement with all the published data.

Dumbbell formation for elastic capsules in extensional Stokes flows where velocity is a nonlinear function of position, with pressure decreased at particle edges and increased in the middle, is studied computationally. The strong stability of strain-hardening capsules contrasts with droplet behavior.

Hydrodynamic interaction between soft particles is studied in a confined system under a parabolic flow. Both vesicles and drops exhibit the same qualitative phase diagram regarding their clustering, highlighting a universal character, independent of the nature and shape of the deformable entities.

The hydrodynamic force on a sphere sedimenting in a viscoelastic shear flow depends, in a complicated fashion, on both magnitude and orientation of the shear relative to gravity. Drag and lift forces are calculated perturbatively for weak elasticity, for any orientation.

Thermal convection in an internally heated horizontal layer with stress-free boundaries is analyzed numerically. The work is related to liquid metal batteries, where convection is caused by Joule heating of electrolyte. Three-dimensional convection cells are found at subcritical Rayleigh numbers.

A study is presented of the role of van der Waals interactions on the thin-film dynamics of a long bubble that advances at uniform speed in a cylindrical capillary tube, with focus on conditions that lead to film rupture.

The radial trajectory of isoconcetration contours of dissolved CO${}_2$ from a cylindrical bubble are tracked with planar laser-induced fluorescence. The unsteady CO${}_2$ concentration field is characterized via two simple analytical diffusion models, validated against experiments and numerical simulations.

Experiments show that a pair of droplets in an alternating electric field coalesce through a repeated sequence: dipole-dipole attraction, the formation of liquid bridge, the repulsion of equipotential droplets, the elongation and breakup of the bridge.

Interfacial bubbles are formed when a ring holding a thin liquid film is plunged into a pool of the same liquid. Their formation is explained by competition between the pressure exerted by the air flow under a plunging film and the Laplace pressure needed to generate film dimpling and air entrapment.

The method of weighted residuals is used to derive a highly accurate model for flow down an inclined plane under the effect of electric fields. The model is shown to compare well with direct numerical simulations. The flow is studied parametrically in two and three dimensions.

When a magnetic field pervades a turbulent conducting fluid, energy dissipates by Joule heating. Here we show that rather than damping turbulence, the field promotes large, nearly two-dimensional structures minimising dissipation. The net effect can increase the intensity of turbulence.

A linear global stability analysis is performed for an axisymmetric boundary layer formed on a circular cone. The combined effect of transverse curvature and favorable pressure gradient has been studied. The increase in semicone angle makes the flow temporally stable and convectively unstable.

The effect of evaporation and condensation on the Rayleigh-Taylor instability is studied with a rigorous approach, finding that phase change induces an additional flow that affects heating of the interphase boundary. This reduces the ratio of the phase change rate to the interface position deviation.

A model is presented to investigate the hydrodynamics of an elastic sheet lubricated by a thin film on a wetting substrate, with focus on elastic effects that lead to different film profiles, contact angles, and spreading dynamics.

Drift volume quantifies fluid volume entrained by a translating body and is important in heat and mass transfer. In a detailed analysis, drift volume is computed as the time-integrated flux through a streamtube. Leading-order expressions are derived as a function of Reynolds number, upon which drift volume is shown to be critically dependent.

An electrohydrodynamic instability excited by light is experimentally demonstrated in Au-PVP plasmonic nanoparticles suspended in isopropanol and water. The nanoparticles become charged by the light and the resulting electrical oscillations are measured.

Intense microscale convection is produced by single cavitation bubbles. Ring vortices can be formed by bubbles collapsing near solid surfaces. Such unsteady flow fields are measured with a high-speed particle imaging velocimetry (µPIV) setup. Net liquid displacement is tracked and visualized by synthesized Lagrangian ink maps.

A theory of charge dynamics and fluid flow over charge-modulated surfaces is developed, finding nontrivial implications for finite thickness of an electrically charged interfacial layer. The results could be consequential in designing novel electrokinetic devices, including micromixers.

Pulse-burst PIV measurements at a 37.5 kHz repetition rate are presented, examining the gas-phase velocity up- and downstream of a dense particle curtain following interaction with a shock wave. From these data, the unsteady drag imposed on the curtain is estimated using a control volume approach.

Shock interaction with a rigid moving cylinder has been studied. The influences of shock Mach number and cylinder diameter on the shock reflection trajectories, dynamic drag coefficient, and cylinder movement are analyzed. Correlations to predict the peak drag coefficient have been proposed.

Separation by shear flow and by rotating electric field of one type of chiral particle from mirror-image particles in a racemic mixture is studied theoretically.

The slanted snaking bifurcation structure of spatially localized Faraday waves is demonstrated for the first time. A universal model reproduces the observed snaking and relates the observed slant to the effect of a conserved quantity associated with the meniscus dynamics in the experiment.

An Eulerian approach to optimize open-flow mixing with duty-cycled vortical crossflows is developed using general physical principles. For mixers based on microbubble streaming, the formalism identifies optimum mixing protocols that agree with experiments and numerical simulations of mixing.

In a subsonic turbulent jet we find noise at low angles to the downstream jet axis generated mainly by the axisymmetric part of axial velocity fluctuations. Jet noise control should thus focus on this part of the velocity field. A lower bound for noise for a given jet size and velocity is suggested.

Predictions are made of the scalings of the second-order structure function for any of the three velocity components and for the two points in arbitrary positions in the log region according to the attached-eddy hypothesis. Those predictions are then compared with experimental and numerical data.

Direct numerical simulations show that high-Reynolds-number turbulence in a periodic cube is composed of a hierarchy of antiparallel vortex tubes. The hierarchy is sustained by scale-by scale vortex stretching, which leads to scale-by-scale energy cascade and consequent quasicyclic behavior of the turbulence.

The time scale on which fluid particles in two-dimensional turbulence change their direction is presented. The influence of confinement on the directional change is investigated and the statistics obtained from fluid-particle trajectories are compared to those of football players.

Turbulent thermal diffusion results in large-scale clustering of inertial particles in temperature stratified turbulence. A complete theory and the experimental validation of this effect is presented for arbitrary temperature gradients and Stokes numbers.

Combining atmospheric surface layer experimental data and existing laboratory results, spatial scales of large-scale structures show Reynolds number invariance over 3 orders of magnitude change in Re${}_{\tau }$. Universal laws for growth of spatial length scales with wall-normal distance are found.

The impact of jet-free surface interaction is to reduce outward growth of spanwise vorticity in the upper shear layer. Turbulence statistics along the free surface, two-point correlation, and joint probability density function are used to quantify confinement effects on jet-surface interaction.

Hot-wire measurements and DNS data for turbulent boundary layers reveal a nontrivial variation of the skewness and flatness of the longitudinal velocity gradient with distance from the wall and Reλ, casting doubts on the use of atmospheric shear layer data for testing Kolmogorov similarity laws.

A numerical study of flow structure and lift generation on a simplified rotating wing model caused by increasing the distance from the rotational axis is presented. Deterioration in characteristic leading-edge vortex structure and lift force reduction occur as this distance increases.

Turbulent wake dynamics of rectangular cylinders normal to a Re ~ 6600 flow are examined with stereoscopic particle image velocimetry. Three regimes are identified based on wake velocity fluctuations and related to variations in vortex formation.

Initial shape of the release dictates the spreading of a gravity current over inclined non-erodible surfaces with small slope angles (θ ⪅ 10°) during short and long time evolution. For steeper slopes (θ⪆ 10°), initial volume of the release dominates, with the initial shape taking on a secondary one.

The vorticity-based modeling concept for stratified flows is extended to unsteady flow fields that cannot be rendered quasisteady by a change of reference frames. The vorticity model predictions are then compared to direct numerical simulation results for partial-depth lock-exchange flows.

Experiments on waves at the surface of a floating elastic sheet are presented, with implications for ocean and lake ice sheets. The growth of a daughter wave from the interaction between two mother waves at different scales is observed and is well described by weakly nonlinear resonant interaction.