An experimental and numerical study of the consequences of varying the strength of hydrodynamic coupling between model cilia finds traveling waves, steady chevrons, and periodic phase defects.

New direct numerical simulations find that the control strategy of Schoppa and Hussain fails to deliver drag reduction due to a failure to penetrate the near-wall region.

A theoretical model with a common set of parameters is presented to quantitatively describe the mean and variance temperature profiles in turbulent Rayleigh-Benard convection. This model is thoroughly tested in a specially designed quasi-two-dimensional convection cell, and the experimental results agree well with the theoretical predictions.

The mean velocity normal to the wall in a laminar and in a turbulent boundary layer with zero pressure gradient is investigated in experiments and in numerical simulations. Unlike the mean streamwise velocity and the turbulent shear stress, the mean wall-normal velocity is found to scale with its maximum and the boundary layer thickness.

The bending dynamics of trimers depends strongly on whether the flow is laminar or turbulent and, in the latter case, is sensitive to the flow dimension. Trimers are found to be mainly fully extended in 3D turbulence and either fully extended or fully folded in 2D turbulence.

Direct numerical simulations with 12,288${}^3$ grid points up to $R_{\lambda }=2300$ finds small systematic differences from Kolmogorov’s $k^{-5/3}$ scaling of the inertial range of the energy spectrum.

Modification of the forces due to abnormal motions of the wall are analyzed in a model left ventricle, showing that loss of temporal synchrony is more relevant than loss of spatial uniformity. A relatively simple integral model is then introduced, it is able to capture the main properties of the global hemodynamic force balance.

Energy transfer in viscoelastic homogeneous isotropic turbulence is investigated based on direct numerical simulations using the FENE-P model.

Experiments are conducted to investigate the interplay between surface tension effect, viscous dissipation, and elasticity in the free expansion of fluid sheets of viscous liquid and viscoelastic gels, produced thanks to the impact of a drop on a small solid target.

The flow topology distributions in different regimes of premixed turbulent combustion are investigated using DNS data of statistically planar turbulent H${}_2$-air premixed flames with equivalence ratio $\varphi =0.7$.

A new set of continuum breakdown parameters, rigorously derived from Generalized Chapman-Enskog theory, to capture regions of strong thermal and chemical nonequilibrium for high speed, chemically reacting flows is presented. Detailed analysis shows that chemical reactions can indirectly contribute to continuum breakdown via strong diffusion fluxes.

A possible bypass transition scenario in a Mach 3 flat plate boundary layer is proposed and investigated numerically.

Noise amplifier flows, such as the flow above a backward facing step, are characterized by a large amplification to external stochastic perturbations. These perturbations, however, quickly loose their randomness: the response to inlet white noise undergoes a selective process promoting a response structure with an approximately single frequency active in the whole domain.

A linear stability analysis is conducted on the inclined flow of heated binary liquid mixtures. The variation in the density of the liquid with temperature and solutal concentration is found to augment the Marangoni and Soret effects and have a significant impact on interfacial instability.

A weighted residual model is developed and implemented to carry out a nonlinear stability analysis of the gravity-driven flow of heated binary liquids with variable mass density.

An elegant study shows the existence of low-Rossby-number, low-magnetic-Prandtl-number kinematic dynamos driven by turbulent rotating convection.

A turbulent spread rate within a linear modeling framework is used to compute the aerodynamic sound from supersonic mixing layers with heat release. The focus is on radiation from outer-mode-dominated mixing layers, which show different characteristics when compared to the classical Kelvin-Helmholtz mode based radiated sound.

Optical measurements with micrometer vertical resolution are performed to study the very first surface deformations produced by a turbulent wind over a viscous liquid. Varying the liquid viscosity over three decades provides new insight into surface deformations for wind velocity below the onset of wave amplification.

The stability of thin viscous films coated on the inside of a horizontal cylindrical substrate is investigated by means of an optimal transient growth analysis. Despite the asymptotic stability of the system, the large algebraic growth of interfacial disturbances can result in dripping droplets.

A general three-field gradient dynamics model for the dynamics of liquid films covered by soluble surfactant is developed. Extending or amending the underlying energy functional results in a variety of thermodynamically consistent dynamical models.

Vortical structures form in an enclosed fluid within transverse grooves along a laminar flow in a microchannel, and act as fluid bearings on the boundary for lubrication. The fluid bearings generated from low-viscosity fluids can be used to transport high-viscosity fluids for drag reduction.

The impact of nonideal diffusion on the structure of supercritical cryogenic binary mixing layers is investigated. Nonideal diffusion has a dramatic impact near chemical thermodynamic stability limits where the components become quasi-immiscible and ultimately form a nonmixing layer.

Any liquid deposited on a solid moving quickly enough can remain in levitation above the surface. An analysis shows how the air flowing below and around the liquid sets the thickness of the air gap between the drop and the solid, and creates an aerodynamic force that gives control over the drop movement.

Numerical simulations elucidate the motion of rigid and deformable capsules in vector chromatography microfluidic devices.

A comprehensive analytical and numerical analyses of the flow generated in a thin slab by instantaneous thermal insulation of the walls is presented.

Raman and fluorescence imaging are used to investigate the drying of a confined drop of a charged colloidal dispersion. The experiments provide estimates of the collective diffusion coefficient of the dispersion, and they evidence both drying-induced buoyancy flows at low concentrations and homogeneous drying of a gel at higher concentrations.

Clouds of inertial particles released in a turbulent flow experience deformation. By analytical characterizing of this deformation, a relationship is provided for the clustering of inertial particles that is applicable to a wide range of Stokes numbers.

Singular perturbation theory calculations of the effect of fluid inertia on the angular velocity of a small spheroid in a shear flow show how weak fluid inertia reduces the angular velocity in an unbounded shear, and how this reduction depends upon the shape of the spheroid.

An experimental study of rotating Rayleigh-Benard convection investigates the role of the thermal boundary conditions.

Laboratory experiments and a theoretical model shed light on the dynamical phenomena observed in turbulent Rayleigh-Bénard convection with modulated rotations, including phase lags in convection roll movement and nonlinear amplitude responses of the circulation strength.

Thermal and viscous boundary layers in a series of turbulent convection flows at a very low Prandtl number are analyzed. After the removal of the large-scale motion, a Rayleigh number beyond which the viscous boundary layer will become fully turbulent is predicted.

Direct numerical simulations reveal that the wall temperature has a strong effect on shock-wave/turbulent boundary layer interactions.

Two coaxial helical vortices undergo recurrent motion without reconnecting, resembling the leapfrogging of two vortex rings.

A new calculation of the thrust forces and the efficiency of an airfoil undergoing small heaving and pitching motions is presented.

Could velocity fields form infinite gradients in high Reynolds number flows? A proposed iterative mechanism, which involves transformation of vortex tubes to sheets and back to tubes, is analyzed using elementary fluid mechanics.