The elastic stress generated moving in a purely viscous flow around a slender cylinder is found to be large near the tips, and larger when the flow is parallel to the axis.

Direct numerical simulations find that rapid head-on collisions of particles mostly occur in regions of straining compared to vortical regions, and that intense vortex tubes conspire with enveloping straining sheets, in the form of vortex-strain worm-rolls, to generate violent collisions.

A study examines wake dynamics for oscillating foils with different trailing edges and relates them to unsteady propulsive performance of the foil. It also connects the main wake features to surface pressure fluctuations on both faces of the foil during an oscillatory period.

We examine the swimming of an elastic helix rotated by a torque at its base, both in free-space and confined to a tube. The image depicts the envelope of an excursion of a filament centerline over one rotation; the blue is the surface of the finite-radius helical filament at one snapshot in time.

The slip velocity of jammed polymer microgels is measured as the wall stress is increased by 4 orders of magnitude. The friction law exhibits a transition in slip regimes, from a nonlinear to a linear scaling, linked to two distinct dissipation mechanisms at the scale of the soft elements.

Supercritical fluids when subjected to vibrations in the direction parallel and normal to the interface lead to Rayleigh-vibrational and parametric instabilities. These instabilities arise in the thermal boundary layer as a result of strong thermomechanical coupling.

The effect of heat-flux conditions on the Rayleigh-Bénard convection in a rarefied gas is investigated, extending instability to higher rarefaction rates compared with the isothermal walls case. The deviation from the Boussinesq limit with increasing compressibility is analyzed.

A study combining direct simulation Monte Carlo simulations with window proper orthogonal decomposition investigates the temporal characteristics of unsteady, laminar shock boundary-layer interactions for different gas mixtures for an Edney type-IV flow.

A state-to-state approach and GPU processors are used to find the nonequilibrium vibrational distributions of O${}_2$ and N${}_2$ in a hypersonic flow past a sphere.

A conventional and high-fidelity direct simulation Monte Carlo approach is applied to a number of hypersonic cases where validation data is available. Changes in the collision model are found to have a small effect on surface properties, with nitrogen recombination being the only notable exception.

A new coherent structure appears on turbulent Rayleigh-Bénard convection in a liquid metal layer; transitions to large-scale cellular structures from oscillatory roll structures occur with Rayleigh numbers. A scaling law describing characteristic length of the structures is suggested.

Compressible thermal convection is experimentally studied. In the large apparent gravity of a rotor centrifuge, using xenon gas, an adiabatic temperature difference of 14 °C over a height equal to 4 cm is obtained. Large Coriolis forces impose a quasigeostrophic regime.

Inspired by the droplet-mediated adhesion of insects, the adhesion between soft and rigid surfaces mediated by a droplet is studied. Deformability allows for enhanced adhesion as well as new routes for “unsticking,” but the dynamics of adhesion also plays a role.

A meniscus formed around a vertical cylinder looks and behaves like a repulsive central potential, deflecting noncoalescent droplets analogous to Rutherford scattering. The scattering behavior is used to probe the potential of the cylindrical meniscus, confirming theoretical models for its shape.

Spreading of liquid on a cold substrate with freezing is investigated. Experimental investigation of the criterion for a solidification-induced pinning of the liquid near the triple line finds that below a temperature-dependent velocity, spreading shows stick-slip dynamics.

Deformation or breakup of a droplet suspended in confined shear flows and subjected to an electric field is investigated numerically. A contrasting behavior of the droplet depending upon the electrical properties of the fluids is reported.

Experiments in a precessing cylinder filled with water show signatures of azimuthally drifting inertial waves. These modes originate from a triadic resonance and their characteristic frequency dependence is explained by a detuning mechanism due to the slowdown of the background flow.

Diffusion between miscible fluids in the viscous-fingering instability produces an unexpected transition into a novel pattern. Usually thought of as a two-dimensional phenomena, this works shows the importance of three-dimensional structure to the patterns that form.

Electric fields and temperature fields significantly modify the stability of dynamic contact lines. Electric fields enhance the growth of transverse perturbations, whereas temperature fields can enhance or suppress growth depending on the direction of the temperature gradient.

Evaporation of a volatile solvent induces solutocapillary Marangoni flows by creating gradients in species concentration and surface tension. These flows are experimentally and theoretically investigated in sub-micron films at dilute solute concentrations where Van der Waals effects are important.

Chemo-hydrodynamic instabilities are investigated in the presence of nano-catalysts. The additional transport mechanism of nano-catalysts as a result of the heat of reaction, called thermophoresis, has affected both the dynamics and the amount of chemical products.

Colloidal particles inside an evaporated droplet on a solid substrate are often preferentially deposited at the droplet contact line, a phenomenon known as the coffee-ring effect. A study shows how this phenomenon is affected by the permeability of the substrate.

A study on the scaling implications of the attached eddy hypothesis and the large deviation theory on the velocity probability distribution function (PDF) concludes that, when scaled properly, the remote tails of the streamwise and spanwise velocity PDF collapse for flows in the logarithmic layer.

The steady flow regimes and mixing performances of arrow-like micro-mixers are investigated experimentally and by DNS for varying $Re$ and tilting angles. Arrow-mixers trigger mixing at lower $Re$ than for T-mixers, but for large tilting angles mixing does not increase monotonically with $Re$.

The deformation of a flexible fiber transported perpendicularly in a plug flow in a confining microchannel is studied using experiments and numerical simulations. The fiber deflection, resulting from an inhomogeneous force distribution, is a function of an elastoviscous number and fiber confinement.

Nonspherical particles in the ocean are relevant to phenomena such as microplastics, plankton and sediment. Experimental results of the orientation dynamics of nonspherical particles in waves find competition between the waves and the inertial effects on particle orientation.

Direct numerical simulations are used to study the relative dispersion of settling, bidisperse inertial particles in isotropic turbulence. It is found that gravity can significantly enhance the relative dispersion, not only in the direction parallel, but even in the direction normal to gravity.

Rapid magnetic resonance imaging shows how bubbles collapse in fluidized beds as a result of gas channeling to neighboring bubbles.

Potential flow analysis is used to find the elevation profile of traveling dunes of given volume and locate the brink point where the flow separates without singularity.

Depending on topology of pore space, different patterns of multiphase flow in porous media are observed. By analyzing pore-scale mechanisms, a phase diagram is constructed showing that wettability and structural disorder collectively affect displacement efficiency and fluid-fluid interfacial area.

A solute flowing in a pressure-driven channel flow experiences an enhanced effective axial dispersion coefficient due to the transverse velocity gradients. An investigation shows how this phenomenon, known as Taylor dispersion, is affected by cross flow and mass transfer at the wall.

Static and transient responses of an airfoil to bi-directional flow control actuation at the trailing-edge are investigated in wind tunnel experiments. Flow field measurements elucidate control of aerodynamic loads through regulation of trapped vorticity concentrations upstream of the trailing edge.

A study shows that when trained using channel flow data at just one Reynolds number and informed with known flow physics, the neural network works robustly as a wall model in large-eddy simulation (LES) of channel flow at any Reynolds number. It also outperforms the equilibrium wall model in LES of a 3D boundary layer flow.

Turbulent flows are often bounded by nonturbulent fluid with a sharp interface between the two flow states. Drawing a parallel between this interface and the wall in a wall-bounded flow and similarly, to wall-bounded turbulence, shows the importance of the anisotropy very close to the interface.

We propose a windward bi-frequency control strategy to manipulate experimentally the wake past a yawed car model using pulsed jets. By varying the low frequency value in the actuation, we can provide a complete authority for the manipulation of the mean wake orientation and reduce drag.

Streamline segment statistics are collected from tomographic particle image velocimetry and direct numerical simulation data of a turbulent wavy channel flow. The model equation for such statistics is adapted for inhomogeneous turbulence. The novel formulation is applied to explain the observations and identify the locally acting mechanisms.

A generalized framework of incorporating vortex identifiers into subgrid-scale models for large-eddy simulation is presented. The proposed models can automatically identify the under-resolved vortex stretching process and drain energy from the inertial subrange.

High-resolution, high-frame-rate particle image velocimetry measurements in a refractive index-matched flow facility are used to explore the spatiotemporal signature of outer, large-scale motions influencing near-wall, smaller scales (so-called inner-outer interactions) in a turbulent boundary layer.

We find a novel shedding mode (Alternating-Symmetric) in the vortex-induced vibration response of a cylinder free to oscillate in the inline direction. In this mode, two vortices of opposite sign are shed simultaneously from two sides of the oscillating cylinder, but their sizes alternate per cycle.

Wake characteristics and force production of a flat plate wing starting from rest at high incidence are examined. Circulation production at the wing leading edge is shown to be coupled to wing kinematics and the wake state. Several potential flow models are compared to experiments.

Vortex shedding patterns are examined on a yawed wing pitching in reverse flow. The yawed wing exhibits suppression of its secondary flow structures compared to an unyawed wing. Various physical mechanisms, particularly spanwise flow, are evaluated to explain the shedding pattern of the yawed wing.

Wave scattering on a bathtub vortex in shallow water is studied in the linear approximation. The results obtained are relevant to the interpretation of laboratory experiments and can be considered the hydrodynamic model of wave scattering by a rotating black hole in general relativity.

We report an experimental study of the nonlinear regime of an inertial wave attractor revealing the emergence of a triadic resonance instability with singular features. The attractor properties are shown to be well described by introducing a turbulent viscosity in the linear attractor model.

Inspired by geophysical phenomena, such as storm generated internal waves in the ocean, an experimental study is performed using an axisymmetric internal wave generator. Radial and vertical confinement lead to Bessel-shaped standing waves and resonance effects caused by multiple cavity reflections.

Evanescent regions exist in numerous areas of the deep ocean where the stratification also varies with depth. Using theoretical predictions and experiments, the kinetic energy density in propagating internal waves generated from these evanescent regions is explored.