The variation in the wrinkling of a flame burning down inside a vertical Hele-Shaw cell is related to flexure modes of the walls of the cell and a Faraday-like instability of the the flame front.

An asymptotic solution for convective flows driven by internal heating and cooling is derived. The solution is stable and realized by 2D direct numerical simulations at very high Rayleigh numbers. Even more surprisingly, it corresponds to heat transport enhancement beyond the mixing-length scaling regime.

When squirmer type swimmers sediment on a flat surface, the near field hydrodynamic interactions lead to the formation of small spinners at low concentrations. Higher surface coverage results in a polar order of the swimmers and a particle vortex is observed when confined by a circular wall.

Experiments show that the solid-liquid transition of yield stress fluids (emulsions, gels, foams, suspensions, etc.) is associated with the breakage (collapse) of a basic elastic network for a critical deformation, while progressively larger additional elastoplastic deformations take place in the system up to yielding.

Nonequilibrium and equilibrium classical molecular dynamics simulations of the linear viscoelastic response of water are performed. Comparison with available measurements are reported. Anomalous behavior for frequencies above 2 THz is observed, which is yet to be understood.

The effects of surface roughness on accommodation coefficients are studied using the direct simulation Monte-Carlo (DSMC) approach. DSMC simulations are carried out by varying the roughness parameters. An empirical relationship between surface roughness and accommodation coefficients is established.

Finite dilatational effects in wall-bounded compressible turbulence are investigated. We find that finite correlation between the solenoidal and the dilatational parts of the velocity field account for a nonnegligible fraction of the turbulent shear stress near walls.

An integral model is developed to predict the mixing of multiple forced plumes evenly spaced around a circle in a stratified environment, e.g., buoyant plumes in nature. The model reasonably captures the significant plume boundary distortion caused by plume interactions at the touching height.

Direct observation of the liquid film binding buoyant Bretherton bubbles reveals a van-der-Waals-stabilized thickness.

In binary drop impact, in addition to reflexive separation and stretching separation, which occur at low and high impact angles ($B$), respectively, rotational separation is found at intermediate $B$. A generic model is developed to examine the scenarios and the interplay of various factors.

Experiments show that the addition of polymers in droplets enhances the droplet rebound effect when bouncing on a thin film of air.

The short-term falling dynamics of a dripping water drop is studied by simulation and experiment. The pinching dynamics introduces a nonlinear multimode oscillation. A complex transient flow around the drop is induced by the interaction between the falling motion and the shape oscillation.

Experiments show that prior to impact upon a solid surface, a droplet compresses the air beneath it into a nanometer-scale film. This air film is destroyed by the local initiation of liquid-solid contact, forming capillary bridges. A capillary wave leads the advancing wetting front, limiting its speed.

A simulation of deflated vesicles in linear flows finds that their shape stability is unaffected by moderately rotational flows, where the results collapse to those of extensional flow by a simple scaling factor. Vesicles in near shear flows develop an asymmetrical shape that increases their critical capillary number.

The role of electrohydrodynamics on the generation of atmospheric turbulence is studied theoretically and numerically. A nonlinear feedback loop is identified whereby charged aerosols self-induce an electric field, resulting in a body force on the ionized air, augmenting the atmospheric turbulence.

Mechanical heart valves have been linked to the production of unphysiological turbulent blood flow. As a first step toward a model for laminar-turbulent transition in this flow, an absolute instability in the impinging leading-edge vortices that develop between the valve leaflets is identified.

A study of mechanisms of noise radiation from airfoils at high angles of attack (partial to full separation) identifies four different noise generation flow regimes. The relationship between noise, surface pressure, and shear layer turbulence is explored.

Using analytical and numerical methods we examine a solid substrate withdrawn from a liquid bath. After withdrawal the substrate may be macroscopically dry or coated homogeneously by a liquid film. We show that a regular liquid ridge pattern oriented parallel to the meniscus can also be deposited.

We show that the shape and stability of any static liquid bridge can be solved from a master problem obtained from a model of a pressure-controlled experiment.

A foam film is prepared in a controlled way, so that the top part of the film is much thicker than the bottom part. This situation is unstable under gravity and Rayleigh-Taylor-like fingers grow.The wavelength and the growth rate depend on the effective gravity and on the thick-film width.

The Stokes flow of a submerged jet directed toward a free interface is investigated theoretically. The presence of a minute amount of surface-active agents drastically modifies the hydrodynamic response of the interface.

The relaxation process of an elastic sheet supported by a thin viscous film is studied. Asymptotic leveling regimes are identified as a function of the supporting layer thickness when the dynamics is driven either by elastic bending or by thermal fluctuations.

Asymmetric liquid ligaments typically produced by inkjet printing may recoil or a drop may pinch off. Scaling laws are provided for these two competing processes, and it is shown that long and short ligaments experience different pinch-off regimes.

The smallest compound droplets reported up to date, with outer diameters comparable with a red blood cell, are produced in a continuous way at frequencies exceeding 10 kHz from the capillary breakup of the coaxial cylindrical jets issued from the tip of the conical drops formed using an outer coflow.

The interaction of pinning and surfactant-induced changes of dynamic contact angles on receding contact lines is studied. With increasing surfactant concentration the surfactant-induced effects dominate over pinning effects. This behavior is correlated to the emptying of the surface structures.

At the nanoscale, and in particular in the presence of slip, hydrodynamic bending of interfaces between immiscible liquids becomes negligible. The dynamic contact angle is then governed by the Molecular Kinetic Theory (MKT) of Blake and collaborators.

A theoretical framework based on the method of reflections for Laplace’s and Stokes’ equations is developed to systematically determine multibody chemohydrodynamic interactions of autophoretic colloids. This approach is an efficient alternative to full numerical simulations of suspension dynamics.

A simplified mathematical model, which characterizes membrane internal pore structure accounts for multiple simultaneous membrane fouling mechanisms (adsorption, blocking, and cake formation) and is able to predict the optimum permeability.

We find evidence that the granular drag force on an object moving through a granular material is strongly enhanced when the object is accelerating. This effect can be explained by showing that the accelerating object accelerates the grains nearby, inducing an inertial resistance.

The influence of electric forces on inertial particles in turbulent channel flows is explored using direct numerical simulations. It is found that the near-wall buildup of particle concentration due to turbophoresis can be reduced up to 2 orders of magnitude by imposing an ac electric field.

The role of large-scale motions and small-scale turbulence on rising of small bottom-heavy swimmers is examined via high Reynolds number direct numerical simulation of turbulent free-surface flow. The swimmers’ rising efficiency is quantified via a new timescale that combines the stability number and the Kolmogorov timescale.

Experiments and a two-phase continuum model are used to study how gas flow enhances silo discharge. A modified Hagen-Beverloo law is proposed, taking into account the gas flow rate, the particle size, and the silo and orifice geometry.

Using laboratory experiments, the collapse of a liquid-saturated granular column in air on a horizontal plane is analyzed in light of the “column” Bond number, the grain diameter to capillary length ratio, the initial aspect ratio, the Stokes number, and the initial volume fraction.

Several patterns of inertial particle focusing over a square cross section are experimentally observed for suspension flows through a square duct. A numerical study describes transitions between the focusing patterns in terms of the bifurcation of particle equilibrium positions.

When subject to strong shear, settling particles dispersed at semidilute concentrations may modulate the suspending flow significantly, in a way that enhances or attenuates turbulence. The modulation is enabled by the appearance of clusters and void fraction bubbles in the particle phase.

Based on recent developments in physics-informed deep learning and deep hidden physics models, we put forth a framework for discovering turbulence models from scattered and potentially noisy spatio-temporal measurements of the probability density function.

The dispersion and reaction of a scalar patch by a random flow is investigated. A comparison of single realizations to the ensemble average shows explicitly that the two concentrations have very different tails, leading to different reaction front velocities in the fast-reacting problem.

Asymptotic methods and conformal mappings are used to study mass or heat transport from a particle that is subject to a weak flow.

A forcing technique is devised to generate centerline scalar mixing of round jets in a triply periodic box. It is derived from the scalar transport equation using a Reynolds-like decomposition of the scalar field. The result is a combination of a mean gradient term and a linear scalar term.

Using direct numerical simulation, the potential-core closing of temporally developing round jets at Mach numbers between 0.3 and 2 is shown to radiate strong axisymmetric acoustic waves in the downstream direction. The Mach number dependence and the generation mechanism of these waves are revealed.

A numerical study confirms that by using multiscale structures, turbulence with a wider range of scales can be generated. However, the multiscale-generated turbulence may not have a long-lasting memory and can eventually forget its multiscale initial conditions.

The transport equation for the statistical moments of a passive scalar dispersed in a turbulent flow is solved. The analytical solution for the passive scalar variance is shown to fit wind tunnel data from a neutral turbulent boundary layer.

A detailed analysis of cylinder wake dynamics is presented for characteristic instabilities spanning laminar-to-turbulent transition regimes. A new three-dimensional vortex tracking algorithm is introduced to elucidate the vorticity transport and relate it to structural loads.

We develop an alternate method for investigating the stability of a one-parameter family of periodic solutions of the four-vortex problem known as ‘leapfrogging’ orbits and confirm the value of a bifurcation parameter. This approach could be applied to other related and more general problems.